The Agricultural Health Study: factors affecting completion and return of self-administered questionnaires in a large prospective cohort study of pesticide applicators

Occupational pesticide use and self-reported olfactory impairment in US farmers

OBJECTIVES

Pesticide exposure may impair human olfaction, but empirical evidence is limited. We examined associations between occupational use of 50 specific pesticides and olfactory impairment, both self-reported, among 20 409 participants in the Agricultural Health Study, a prospective cohort of pesticide applicators (mostly farmers, 97% male).

METHODS

We used logistic regression models to estimate odds ratios (OR) and 95% confidence intervals (CI) for associations between pesticide use at enrolment (1993-1997) and olfactory impairment reported two decades later (2013-2016), adjusting for baseline covariates.

RESULTS

About 10% of participants reported olfactory impairment. The overall cumulative days of any pesticide use at enrolment were associated with a higher odds of reporting olfactory impairment (OR (highest vs lowest quartile): 1.17 (95% CI: 1.02 to 1.34), p-trend = 0.003). In the analyses of 50 specific pesticides, ever-use of 20 pesticides showed modest associations with olfactory impairment, with ORs ranging from 1.11 to 1.33. Of these, higher lifetime days of use of 12 pesticides were associated with higher odds of olfactory impairment compared with never use (p-trend ≤ 0.05), including two organochlorine insecticides (dichlorodiphenyltrichloroethane and lindane), two organophosphate insecticides (diazinon and malathion), permethrin, the fungicide captan and six herbicides (glyphosate, petroleum distillates, 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid and metribuzin), although many of these did not exhibit clear, monotonic exposure-response patterns.

CONCLUSION

Overall, we found relatively broad associations between pesticides and olfactory impairment, involving many individual pesticides and covering several chemical classes, suggesting that pesticides could affect olfaction through multiple pathways. Future epidemiological studies with objective measurement of olfaction are required to confirm these findings.

Exercise attenuates the association between household pesticide exposure and depressive symptoms: Evidence from NHANES, 2005-2014

BACKGROUND

The effect of household pesticide exposure on depressive symptoms in the general population is underexplored, and the role of exercise in the association between pesticide exposure and depressive symptoms is unclear.

OBJECTIVE

The goals of this study are to examine whether the associations between household pesticide exposure and depressive symptoms exist in the general population, and whether exercise can attenuate these associations.

METHODS

We used data from the 2005-2014 National Health and Nutrition Examination Surveys (NHANES), including a total of 14708 US adult participants who were 20 years or older. Depressive symptoms were assessed using the Patient Health Questionnaire (PHQ-9). Exercise information on the recreational physical activity (RPA) and pesticide exposure were self-reported in an interview.

RESULTS

Participants with exposure of household pesticide had a higher odds ratio ([OR]; OR = 1.32, 95% confidence intervals [CI]: 1.12-1.56) for depressive symptoms, compared to those who had not been unexposed. A significant interaction between exercise and pesticide exposure on depressive symptoms was observed (P = 0.038). Stratified analysis showed that household pesticide exposure was associated with a 50% higher risk of depressive symptoms (OR = 1.50, 95% CI: 1.20-1.86) in the population with light RPA. However, we did not find a significant association in the group with moderate + vigorous RPA (P = 0.305).

CONCLUSION

This study further confirms that household pesticide exposure is associated with an elevated risk of depressive symptoms in the general population. More importantly, we for the first time reports that moderate + vigorous RPA attenuates the positive association between household pesticide exposure and depressive symptoms.

Assessing the Potential for Bias From Nonresponse to a Study Follow-up Interview: An Example From the Agricultural Health Study

Prospective cohort studies are important tools for identifying causes of disease. However, these studies are susceptible to attrition. When information collected after enrollment is through interview or exam, attrition leads to missing information for nonrespondents. The Agricultural Health Study enrolled 52,394 farmers in 1993-1997 and collected additional information during subsequent interviews. Forty-six percent of enrolled farmers responded to the 2005-2010 interview; 7% of farmers died prior to the interview. We examined whether response was related to attributes measured at enrollment. To characterize potential bias from attrition, we evaluated differences in associations between smoking and incidence of 3 cancer types between the enrolled cohort and the subcohort of 2005-2010 respondents, using cancer registry information. In the subcohort we evaluated the ability of inverse probability weighting (IPW) to reduce bias. Response was related to age, state, race/ethnicity, education, marital status, smoking, and alcohol consumption. When exposure and outcome were associated and case response was differential by exposure, some bias was observed; IPW conditional on exposure and covariates failed to correct estimates. When response was nondifferential, subcohort and full-cohort estimates were similar, making IPW unnecessary. This example provides a demonstration of investigating the influence of attrition in cohort studies using information that has been self-reported after enrollment.

Sex Steroid Hormone Single-Nucleotide Polymorphisms, Pesticide Use, and the Risk of Prostate Cancer: A Nested Case-Control Study within the Agricultural Health Study

Experimental and epidemiologic investigations suggest that certain pesticides may alter sex steroid hormone synthesis, metabolism or regulation, and the risk of hormone-related cancers. Here, we evaluated whether single-nucleotide polymorphisms (SNPs) involved in hormone homeostasis alter the effect of pesticide exposure on prostate cancer risk. We evaluated pesticide-SNP interactions between 39 pesticides and SNPs with respect to prostate cancer among 776 cases and 1,444 controls nested in the Agricultural Health Study cohort. In these interactions, we included candidate SNPs involved in hormone synthesis, metabolism or regulation (N = 1,100), as well as SNPs associated with circulating sex steroid concentrations, as identified by genome-wide association studies (N = 17). Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Multiplicative SNP-pesticide interactions were calculated using a likelihood ratio test. We translated p-values for interaction into q-values, which reflected the false discovery rate, to account for multiple comparisons. We observed a significant interaction, which was robust to multiple comparison testing, between the herbicide dicamba and rs8192166 in the testosterone metabolizing gene SRD5A1 (p-interaction = 4.0 × 10^-5; q-value = 0.03), such that men with two copies of the wild-type genotype CC had a reduced risk of prostate cancer associated with low use of dicamba (OR = 0.62 95% CI: 0.41, 0.93) and high use of dicamba (OR = 0.44, 95% CI: 0.29, 0.68), compared to those who reported no use of dicamba; in contrast, there was no significant association between dicamba and prostate cancer among those carrying one or two copies of the variant T allele at rs8192166. In addition, interactions between two organophosphate insecticides and SNPs related to estradiol metabolism were observed to result in an increased risk of prostate cancer. While replication is needed, these data suggest both agonistic and antagonistic effects on circulating hormones, due to the combination of exposure to pesticides and genetic susceptibility, may impact prostate cancer risk.

Strategies for biological monitoring of exposure for contemporary-use pesticides

Pesticides are used on a massive scale in the United States. The widespread use of these pesticides has made it virtually impossible for the average person to avoid exposure at some level. Generally, it is believed that low-level exposure to these pesticides does not produce acute toxic effects; however, various cancers and other noncancer health endpoints have been associated with chronic exposure to several groups of pesticides. Therefore, it is imperative that well-designed studies investigate the potential relationship between contemporary pesticide exposure and health effects. For these studies to be accurate, reliable methods for determining individual exposure must be used. Biological monitoring is a useful tool for assessing exposure to some contemporary pesticides. As with any analytical method, biological monitoring entails many difficulties, but, in many instances, they can be overcome by the logical use of available information and information acquired in carefully designed studies. At the Centers for Disease Control and Prevention (CDC), we have acquired extensive experience in the development and application of specific techniques for biological monitoring of a variety of toxicants, including many of the contemporary-use pesticides. We have used these methods to measure the internal dose of pesticides received by people in acute and chronic incidents resulting from both environmental and industrial exposure. Additionally, we have established normative values, or reference ranges, of several pesticides based on measurements of their metabolites in the urine of randomly selected adults in the US population. These data have been successfully used to distinguish overt exposures from `background' exposure. In this paper, we present several examples of the usefulness of biological monitoring in urine and blood and describe the difficulties involved with developing methods in these matrices. We also present a general strategy, considerations, and recommendations for developing biological monitoring techniques for measuring the internal dose of contemporary-use pesticides.

Use of Dieselized Farm Equipment and Incident Lung Cancer: Findings from the Agricultural Health Study Cohort

BACKGROUND

Diesel exhaust is a known lung carcinogen. Farmers use a variety of dieselized equipment and thus may be at increased risk of lung cancer, but farm exposures such as endotoxins may also be protective for lung cancer.

OBJECTIVES

We evaluated the relative risk of incident lung cancer, including histological subtype, from enrollment (1993-1997) to 2010-2011 in relation to farm equipment use in the Agricultural Health Study (AHS), a prospective cohort study of pesticide applicators and spouses in Iowa and North Carolina, USA.

METHODS

Farm equipment use was reported by 21,273 farmers and 29,840 spouses. Rate ratios (RRs) were estimated separately for farmers and spouses with Poisson regression models adjusted for smoking and other confounders. We conducted stratified analyses by exposure to animals or stored grain, a surrogate for endotoxin exposure.

RESULTS

Daily diesel tractor use (vs. no use) was positively associated with lung cancer in farmers (RR = 1.48; 95% CI: 0.87, 2.50; 35 exposed, 32 unexposed cases), particularly adenocarcinoma (RR = 3.39; 95% CI: 1.23, 9.33; 12 exposed, 7 unexposed cases). The association of adenocarcinoma with daily (vs. low/no) use of diesel tractors was stronger for farmers with no animal or stored grain exposures (RR = 6.23; 95% CI: 2.25, 17.25; 5 exposed, 18 unexposed cases) than among farmers with these exposures (RR = 1.19; 95% CI: 0.51, 2.79; 7 exposed, 27 unexposed cases) (p-interaction = 0.05).

CONCLUSIONS

This study provides preliminary evidence of an increased risk of lung adenocarcinoma among daily drivers of diesel tractors and suggests that exposure to endotoxins may modify the impact of diesel exposure on lung cancer risk. Confirmation of these findings with more exposed cases and more detailed exposure information is warranted.

CITATION

Tual S, Silverman DT, Koutros S, Blair A, Sandler DP, Lebailly P, Andreotti G, Hoppin JA, Beane Freeman LE. 2016. Use of dieselized farm equipment and incident lung cancer: findings from the Agricultural Health Study Cohort. Environ Health Perspect 124:611-618; http://dx.doi.org/10.1289/ehp.1409238.

Pesticide Exposures and Body Mass Index (BMI) of Pesticide Applicators From the Agricultural Health Study

Endocrine-disrupting chemicals, including pesticides, may be associated with weight gain. This is the first longitudinal study to examine a potential association between weight gain and pesticides using data on 8,365 male pesticide applicators from the Agricultural Health Study (AHS) cohort established in 1993. The relationship between total cumulative days of exposure to pesticide functional/chemical classes and to the four most frequently used individual pesticides was studied in relation to body mass index (BMI) at the time of 5-yr follow-up (beginning in 1998) with the length of the exposure period dating back to age 20 yr. Multiple regression, Spearman correlation, ordinal logistic regression, and logistic regression models all utilized a Bonferroni-adjusted p value, were adjusted for relevant covariates, and were stratified by state of residence (Iowa/North Carolina) and presence/absence of weight-related health conditions. Adjusted multiple regression yielded statistically significant positive parameter estimates for the study sample and Iowa subgroups with consistent findings for triazine herbicides and atrazine: Change in BMI per 100 cumulative pesticide exposure days ranged from 0.07 to 0.11 for triazine herbicides and from 0.10 to 0.19 for atrazine. Ordinal logistic regression compared normal weight with overweight and with obese using the zero exposure category as referent. Statistically significant adjusted odds ratios identified for the study sample and both state subgroups for the highest level of atrazine exposure ranged from 1.4 to 1.7. Further investigation is warranted to evaluate the associations identified here.

Pesticide use and risk of end-stage renal disease among licensed pesticide applicators in the Agricultural Health Study

OBJECTIVES

Experimental studies suggest a relationship between pesticide exposure and renal impairment, but epidemiological evidence is limited. We evaluated the association between exposure to 39 specific pesticides and end-stage renal disease (ESRD) incidence in the Agricultural Health Study, a prospective cohort study of licensed pesticide applicators in Iowa and North Carolina.

METHODS

Via linkage to the US Renal Data System, we identified 320 ESRD cases diagnosed between enrolment (1993-1997) and December 2011 among 55 580 male licensed pesticide applicators. Participants provided information on use of pesticides via self-administered questionnaires. Lifetime pesticide use was defined as the product of duration and frequency of use and then modified by an intensity factor to account for differences in pesticide application practices. Cox proportional hazards models, adjusted for age and state, were used to estimate associations between ESRD and: (1) ordinal categories of intensity-weighted lifetime use of 39 pesticides, (2) poisoning and high-level pesticide exposures and (3) pesticide exposure resulting in a medical visit or hospitalisation.

RESULTS

Positive exposure-response trends were observed for the herbicides alachlor, atrazine, metolachlor, paraquat, and pendimethalin, and the insecticide permethrin. More than one medical visit due to pesticide use (HR=2.13; 95% CI 1.17 to 3.89) and hospitalisation due to pesticide use (HR=3.05; 95% CI 1.67 to 5.58) were significantly associated with ESRD.

CONCLUSIONS

Our findings support an association between ESRD and chronic exposure to specific pesticides, and suggest pesticide exposures resulting in medical visits may increase the risk of ESRD.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov NCT00352924.

Informed consent for biobanking research: cancer patient recruitment from rural communities in Maine

Biobanking research seeks to improve the diversity, availability, and quality of human specimens critical for translational research, including biospecimen collections from disadvantaged minorities. American rural whites are seldom represented in such initiatives as geographic isolation makes obtaining informed consent challenging. We report a case series of 83 newly diagnosed cancer patients, attending a rural community medical center, who consented to participate in cancer research. To enable pooling with population studies, we created a BioGeoBank using 2007 NCI and ISBER Best Practices, after a protocol approval by Eastern Maine Medical Center (EMMC) IRB and OHP HRPO. Informed consent forms were at Flesch-Kincaid 8th Grade reading level, supplemented by NCI educational brochures. Of 108 patients identified, 85 were eligible. Of these, 83 patients (49 lung cancer, 21 breast cancer, and 13 other cancers) consented to donate data, blood, and tissue specimens for future research, and maintained eligibility. Two years later, we executed a legacy protocol to transfer specimens to NCI's biorepository. Of the 69 surviving patients, 9 patients could not be contacted. All those contacted (60) agreed to provide additional data on environmental risks, and consented to specimen transfer. Self-organizing map analyses showed no evidence that age, education, income, familial susceptibility, or lifestyle factors were associated with consent to donate data or biospecimens. Cancer cases reported 1-3 co-morbid chronic diseases (mostly cardiovascular), near lifetime smoking and/or alcohol consumption; familial cancer risks, and many had a prior cancer history. Anecdotally, willingness to consent was based on altruistic hopes that research would generate knowledge to reduce cancer incidence. Our study shows that cancer patients from disadvantaged white rural communities with health disparities associated with geographic isolation are motivated to consent to participate and support biobank research.

Pesticide exposure and depression among male private pesticide applicators in the agricultural health study

BACKGROUND

Pesticide exposure may be positively associated with depression. Few previous studies have considered the episodic nature of depression or examined individual pesticides.

OBJECTIVE

We evaluated associations between pesticide exposure and depression among male private pesticide applicators in the Agricultural Health Study.

METHODS

We analyzed data for 10 pesticide classes and 50 specific pesticides used by 21,208 applicators enrolled in 1993-1997 who completed a follow-up telephone interview in 2005-2010. We divided applicators who reported a physician diagnosis of depression (n = 1,702; 8%) into those who reported a previous diagnosis of depression at enrollment but not follow-up (n = 474; 28%), at both enrollment and follow-up (n = 540; 32%), and at follow-up but not enrollment (n = 688; 40%) and used polytomous logistic regression to estimate odds ratios (ORs) and 95% CIs. We used inverse probability weighting to adjust for potential confounders and to account for the exclusion of 3,315 applicators with missing covariate data and 24,619 who did not complete the follow-up interview.

RESULTS

After weighting for potential confounders, missing covariate data, and dropout, ever-use of two pesticide classes, fumigants and organochlorine insecticides, and seven individual pesticides-the fumigants aluminum phosphide and ethylene dibromide; the phenoxy herbicide (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T); the organochlorine insecticide dieldrin; and the organophosphate insecticides diazinon, malathion, and parathion-were all positively associated with depression in each case group, with ORs between 1.1 and 1.9.

CONCLUSIONS

Our study supports a positive association between pesticide exposure and depression, including associations with several specific pesticides.

Lifetime and current pesticide exposure among Latino farmworkers in comparison to other Latino immigrants

BACKGROUND

Pesticide exposure poses a health risk for farmworkers. This analysis documents lifetime and current pesticide exposure of North Carolina Latino migrant farmworkers, with comparison to non-farmworker Latino immigrants.

METHODS

During May to October 2012, 235 Latino farmworkers and 212 Latino non-farmworkers completed interviews with items to construct measures of lifetime, current residential and occupational pesticide exposure.

RESULTS

Farmworkers experience levels of lifetime and residential pesticide exposure that are consistently greater than among non-farmworkers. Farmworkers report a large number of occupational pesticide exposures. Lifetime exposure and current residential pesticide exposure are related to social determinants. Education is inversely related to lifetime pesticide exposure for farmworkers and non-farmworkers; farmworkers with H-2A visas report greater residential pesticide exposure than those without H-2A visas.

CONCLUSIONS

Occupational safety policy needs to consider these patterns of lifetime exposure when setting standards. Health care providers should be aware of the lifetime and current exposure of this vulnerable population.

Long-term exposure to fine particulate matter: association with nonaccidental and cardiovascular mortality in the agricultural health study cohort

BACKGROUND

Few studies have examined the relationship between long-term exposure to ambient fine particulate matter (PM2.5) and nonaccidental mortality in rural populations.

OBJECTIVE

We examined the relationship between PM2.5 and nonaccidental and cardiovascular mortality in the U.S. Agricultural Health Study cohort.

METHODS

The cohort (n = 83,378) included farmers, their spouses, and commercial pesticide applicators residing primarily in Iowa and North Carolina. Deaths occurring between enrollment (1993-1997) and 30 December 2009 were identified by record linkage. Six-year average (2001-2006) remote-sensing derived estimates of PM2.5 were assigned to participants' residences at enrollment, and Cox proportional hazards models were used to estimate hazard ratios (HR) in relation to a 10-μg/m(3) increase in PM2.5 adjusted for individual-level covariates.

RESULTS

In total, 5,931 nonaccidental and 1,967 cardiovascular deaths occurred over a median follow-up time of 13.9 years. PM2.5 was not associated with nonaccidental mortality in the cohort as a whole (HR = 0.95; 95% CI: 0.76, 1.20), but consistent inverse relationships were observed among women. Positive associations were observed between ambient PM2.5 and cardiovascular mortality among men, and these associations were strongest among men who did not move from their enrollment address (HR = 1.63; 95% 0.94, 2.84). In particular, cardiovascular mortality risk in men was significantly increased when analyses were limited to nonmoving participants with the most precise exposure geocoding (HR = 1.87; 95% CI: 1.04, 3.36).

CONCLUSIONS

Rural PM2.5 may be associated with cardiovascular mortality in men; however, similar associations were not observed among women. Further evaluation is required to explore these sex differences.

Hypothyroidism and pesticide use among male private pesticide applicators in the agricultural health study

OBJECTIVE

Evaluate the association between thyroid disease and use of insecticides, herbicides, and fumigants/fungicides in male applicators in the Agricultural Health Study.

METHODS

We examined the association between use of 50 specific pesticides and self-reported hypothyroidism, hyperthyroidism, and "other" thyroid disease among 22,246 male pesticide applicators.

RESULTS

There was increased odds of hypothyroidism with ever use of the herbicides 2,4-D (2,4-dichlorophenoxyacetic acid), 2,4,5-T (2,4,5-trichlorophenoxyacetic acid), 2,4,5-TP (2,4,5-trichlorophenoxy-propionic acid), alachlor, dicamba, and petroleum oil. Hypothyroidism was also associated with ever use of eight insecticides: organochlorines chlordane, dichlorodiphenyltrichloroethane (DDT), heptachlor, lindane, and toxaphene; organophosphates diazinon and malathion; and the carbamate carbofuran. Exposure-response analysis showed increasing odds with increasing level of exposure for the herbicides alachlor and 2,4-D and the insecticides aldrin, chlordane, DDT, lindane, and parathion.

CONCLUSION

There is an association between hypothyroidism and specific herbicides and insecticides in male applicators, similar to previous results for spouses.

Exacerbation of symptoms in agricultural pesticide applicators with asthma

PURPOSE

Exacerbation is a critical event in asthma management. We investigated whether exacerbation of symptoms is associated with farming exposures among agricultural pesticide applicators with asthma.

METHODS

Participants were pesticide applicators with active asthma (wheezing and breathing problems in past 12 months) who completed enrollment questionnaires for the Agricultural Health Study (AHS). Exacerbation of asthma was defined as having visited a hospital emergency room or doctor for an episode of wheezing or whistling in the past 12 months. Exposures of interest were using 36 specific pesticides in the past 12 months and conducting various agricultural activities. Adjusted odds ratios (ORs) were estimated by logistic regression while controlling for potential confounders.

RESULTS

The 926 AHS adult pesticide applicators with active asthma included 202 (22%) with exacerbation. Inverse associations with exacerbation were observed for two herbicides [glyphosate, odds ratio (OR) = 0.5, 95% confidence interval (CI) 0.3, 0.8, and paraquat, OR = 0.3, 95% CI 0.1, 0.9] and several agricultural activities (repairing engines, grinding metal, driving diesel tractors, and performing veterinary procedures). Only asthma cases with allergies (i.e., doctor-diagnosed hay fever or eczema, 46%) had positive exacerbation-pesticide associations, with OR = 2.1 (95% CI 1.1, 4.1) for the herbicide pendimethalin and OR = 10.2 (95% CI 1.9, 55) for the insecticide aldicarb.

CONCLUSIONS

The inverse associations with two pesticides and specific farm activities are consistent with the possibility that asthma cases prone to exacerbation may avoid exposures that trigger symptoms. Although limited by small sample size and a cross-sectional design, our study suggests that use of specific pesticides may contribute to exacerbation of asthma among individuals with allergies.

Risk of total and aggressive prostate cancer and pesticide use in the Agricultural Health Study

Because pesticides may operate through different mechanisms, the authors studied the risk of prostate cancer associated with specific pesticides in the Agricultural Health Study (1993-2007). With 1,962 incident cases, including 919 aggressive prostate cancers among 54,412 applicators, this is the largest study to date. Rate ratios and 95% confidence intervals were calculated by using Poisson regression to evaluate lifetime use of 48 pesticides and prostate cancer incidence. Three organophosphate insecticides were significantly associated with aggressive prostate cancer: fonofos (rate ratio (RR) for the highest quartile of exposure (Q4) vs. nonexposed = 1.63, 95% confidence interval (CI): 1.22, 2.17; P(trend) < 0.001); malathion (RR for Q4 vs. nonexposed = 1.43, 95% CI: 1.08, 1.88; P(trend) = 0.04); and terbufos (RR for Q4 vs. nonexposed = 1.29, 95% CI: 1.02, 1.64; P(trend) = 0.03). The organochlorine insecticide aldrin was also associated with increased risk of aggressive prostate cancer (RR for Q4 vs. nonexposed = 1.49, 95% CI: 1.03, 2.18; P(trend) = 0.02). This analysis has overcome several limitations of previous studies with the inclusion of a large number of cases with relevant exposure and detailed information on use of specific pesticides at 2 points in time. Furthermore, this is the first time specific pesticides are implicated as risk factors for aggressive prostate cancer.

Lifetime organophosphorous insecticide use among private pesticide applicators in the Agricultural Health Study

Organophosphorous insecticides (OPs) are the most commonly used insecticides in US agriculture, but little information is available regarding specific OP use by individual farmers. We describe OP use for licensed private pesticide applicators from Iowa and North Carolina in the Agricultural Health Study (AHS) using lifetime pesticide use data from 701 randomly selected male participants collected at three time periods. Of 27 OPs studied, 20 were used by >1%. Overall, 95% had ever applied at least one OP. The median number of different OPs used was 4 (maximum=13). Malathion was the most commonly used OP (74%) followed by chlorpyrifos (54%). OP use declined over time. At the first interview (1993-1997), 68% of participants had applied OPs in the past year; by the last interview (2005-2007), only 42% had. Similarly, median annual application days of OPs declined from 13.5 to 6 days. Although OP use was common, the specific OPs used varied by state, time period, and individual. Much of the variability in OP use was associated with the choice of OP, rather than the frequency or duration of application. Information on farmers' OP use enhances our ability to characterize and understand the potential health effects of multiple OP exposures.

Using multiple imputation to assign pesticide use for non-responders in the follow-up questionnaire in the Agricultural Health Study

The Agricultural Health Study (AHS), a large prospective cohort, was designed to elucidate associations between pesticide use and other agricultural exposures and health outcomes. The cohort includes 57,310 pesticide applicators who were enrolled between 1993 and 1997 in Iowa and North Carolina. A follow-up questionnaire administered 5 years later was completed by 36,342 (63%) of the original participants. Missing pesticide use information from participants who did not complete the second questionnaire impedes both long-term pesticide exposure estimation and statistical inference of risk for health outcomes. Logistic regression and stratified sampling were used to impute key variables related to the use of specific pesticides for 20,968 applicators who did not complete the second questionnaire. To assess the imputation procedure, a 20% random sample of participants was withheld for comparison. The observed and imputed prevalence of any pesticide use in the holdout dataset were 85.7% and 85.3%, respectively. The distribution of prevalence and days/year of use for specific pesticides were similar across observed and imputed in the holdout sample. When appropriately implemented, multiple imputation can reduce bias and increase precision and can be more valid than other missing data approaches.

Pesticide use and fatal injury among farmers in the Agricultural Health Study

PURPOSE

To assess whether pesticide use practices were associated with injury mortality among 51,035 male farmers from NC and IA enrolled in the Agricultural Health Study.

METHODS

We used Cox proportional hazards models adjusted for age and state to estimate fatal injury risk associated with self-reported use of 49 specific pesticides, personal protective equipment, specific types of farm machinery, and other farm factors collected 1-15 years preceding death. Cause-specific mortality was obtained through linkage to mortality registries.

RESULTS

We observed 338 injury fatalities over 727,543 person-years of follow-up (1993-2008). Fatal injuries increased with days/year of pesticide application, with the highest risk among those with 60+ days of pesticide application annually [hazard ratio (HR) = 1.87; 95% confidence interval (CI) = 1.10, 3.18]. Chemical-resistant glove use was associated with decreased risk (HR = 0.73; 95% CI = 0.58, 0.93), but adjusting for glove use did not substantially change estimates for individual pesticides or pesticide use overall. Herbicides were associated with fatal injury, even after adjusting for operating farm equipment, which was independently associated with fatal injury. Ever use of five of 18 herbicides (2,4,5-T, paraquat, alachlor, metribuzin, and butylate) were associated with elevated risk. In addition, 2,4-D and cyanazine were associated with fatal injury in exposure-response analyses. There was no evidence of confounding of these results by other herbicides.

CONCLUSION

The association between application of pesticides, particularly certain herbicides, and fatal injuries among farmers should be interpreted cautiously but deserves further evaluation, with particular focus on understanding timing of pesticide use and fatal injury.

A review of pesticide exposure and cancer incidence in the agricultural health study cohort

We reviewed epidemiologic evidence related to occupational pesticide exposures and cancer incidence in the Agricultural Health Study (AHS) cohort. Studies were identified from the AHS publication list available on a Medline/PubMed database search in March 2009. Findings related to lifetime-days and/or intensity-weighted lifetime-days of pesticide use are the primary focus of this review, because these measures allow for the evaluation of potential exposureresponse relationships. Most of the 32 pesticides examined were not strongly associated with cancer incidence in pesticide applicators. Increased rate ratios and positive exposureresponse patterns were reported for 12 pesticides currently registered in Canada and/or the United States. Exposure misclassification is also a concern in the AHS and may limit the analysis of exposureresponse patterns. Epidemiologic evidence outside the AHS remains limited with respect to most of the observed associations, but animal toxicity data support the biological plausibility of relationships observed six pesticides. Continued follow-up is needed to clarify associations reported to date. In particular, further evaluation of registered pesticides is warranted.

Genetic variation in base excision repair pathway genes, pesticide exposure, and prostate cancer risk

BACKGROUND

Previous research indicates increased prostate cancer risk for pesticide applicators and pesticide manufacturing workers. Although underlying mechanisms are unknown, evidence suggests a role of oxidative DNA damage.

OBJECTIVES

Because base excision repair (BER) is the predominant pathway involved in repairing oxidative damage, we evaluated interactions between 39 pesticides and 394 tag single-nucleotide polymorphisms (SNPs) for 31 BER genes among 776 prostate cancer cases and 1,444 male controls in a nested case-control study of white Agricultural Health Study (AHS) pesticide applicators.

METHODS

We used likelihood ratio tests from logistic regression models to determine p-values for interactions between three-level pesticide exposure variables (none/low/high) and SNPs (assuming a dominant model), and the false discovery rate (FDR) multiple comparison adjustment approach.

RESULTS

The interaction between fonofos and rs1983132 in NEIL3 [nei endonuclease VIII-like 3 (Escherichia coli)], which encodes a glycosylase that can initiate BER, was the most significant overall [interaction p-value (pinteract) = 9.3 × 10-6; FDR-adjusted p-value = 0.01]. Fonofos exposure was associated with a monotonic increase in prostate cancer risk among men with CT/TT genotypes for rs1983132 [odds ratios (95% confidence intervals) for low and high use compared with no use were 1.65 (0.91, 3.01) and 3.25 (1.78, 5.92), respectively], whereas fonofos was not associated with prostate cancer risk among men with the CC genotype. Carbofuran and S-ethyl dipropylthiocarbamate (EPTC) interacted similarly with rs1983132; however, these interactions did not meet an FDR < 0.2.

CONCLUSIONS

Our significant finding regarding fonofos is consistent with previous AHS findings of increased prostate cancer risk with fonofos exposure among those with a family history of prostate cancer. Although requiring replication, our findings suggest a role of BER genetic variation in pesticide-associated prostate cancer risk.

Genetic variation in nucleotide excision repair pathway genes, pesticide exposure and prostate cancer risk

Previous research demonstrates increased prostate cancer risk for pesticide applicators and pesticide manufacturing workers. Although underlying mechanisms are unknown, human biomonitoring studies indicate increased genetic damage (e.g. chromosomal aberrations) with pesticide exposure. Given that the nucleotide excision repair (NER) pathway repairs a broad range of DNA damage, we evaluated interactions between pesticide exposure and 324 single-nucleotide polymorphisms (SNPs) tagging 27 NER genes among 776 prostate cancer cases and 1444 male controls in a nested case-control study of white Agricultural Health Study pesticide applicators. We determined interaction P values using likelihood ratio tests from logistic regression models and three-level pesticide variables (none/low/high) based on lifetime days of use weighted to an intensity score. We adjusted for multiple comparisons using the false discovery rate (FDR) method. Of the 17 interactions that met FDR <0.2, 3 displayed a monotonic increase in prostate cancer risk with increasing exposure in one genotype group and no significant association in the other group. Men carrying the variant A allele at ERCC1 rs2298881 exhibited increased prostate cancer risk with high versus no fonofos use [odds ratio (OR) 2.98; 95% confidence interval (CI) 1.65-5.39; P(interact) = 3.6 × 10(-4); FDR-adjusted P = 0.11]. Men carrying the homozygous wild-type TT genotype at two correlated CDK7 SNPs, rs11744596 and rs2932778 (r(2) = 1.0), exhibited increased risk with high versus no carbofuran use (OR 2.01; 95% CI 1.31-3.10 for rs11744596; P(interact) = 7.2 × 10(-4); FDR-adjusted P = 0.09). In contrast, we did not observe associations among men with other genotypes at these loci. While requiring replication, our findings suggest a role for NER genetic variation in pesticide-associated prostate cancer risk.

Paraquat and Parkinson's disease: an overview of the epidemiology and a review of two recent studies

OBJECTIVE

This paper reviews and evaluates two recent epidemiologic studies focused on pesticides, and in particular, paraquat as a cause of PD. Both studies are derived primarily from the Agricultural Health Study (AHS). A review and evaluation is also provided on the AHS and several additional studies of paraquat and PD.

METHODS

The methods used to design and conduct the studies and analyze the data are described and evaluated.

RESULTS

Studies were inadequately designed and often underpowered with very few exposed individuals. They were not population-based, failed to distinguish incident from prevalent cases, relied on multiple comparisons, and may have reported results selectively. The results across the studies are inconsistent.

CONCLUSIONS

The inherent difficulties of studying Parkinson's disease in relation to paraquat or other pesticides are well illustrated by these studies. A conclusion regarding these relationships cannot be reached based on the current literature. Further research with higher methodological standards is needed to reach a definitive conclusion.

Neurologic symptoms associated with raising poultry and swine among participants in the Agricultural Health Study

OBJECTIVE

Guillain-Barré Syndrome (GBS) is the leading cause of acute peripheral neuropathy worldwide, often associated with recent foodborne infection with Campylobacter jejuni. In this cross-sectional analysis of data from the Agricultural Health Study, we tested whether swine and poultry exposure were associated with increased prevalence of GBS-like neurologic symptoms.

METHODS

Using multivariate analysis, we tested the symptoms such as numbness and weakness, relevant to inflammatory peripheral neuropathies, among farmers with self-reported occupational poultry or swine exposure compared with farmers who reported no occupational animal exposure.

RESULTS

Among swine farmers/workers, prevalence of weakness and numbness were increased (P < 0.05). Among poultry farmers/workers, prevalence of weakness and numbness were increased, but increased prevalence of weakness was not statistically significant.

CONCLUSIONS

Occupational contact with live poultry or swine, potentially related to C. jejuni exposure, was associated with increased reporting of GBS-like symptoms.

Telomere length in myelodysplastic syndromes

The relationship between telomere length (TL) and predisposition to myelodysplastic syndromes (MDS) remains unclear. We compared peripheral blood leukocyte (PBL) TL among cases of histologically confirmed MDS (n = 65) who were treatment-naive with no prior cancer history to age-matched controls (n = 63). Relative TL was measured in PBLs and saliva by quantitative polymerase chain reaction (PCR) and in CD15+ and CD19+ cells by flow cytometry-fluorescence in situ hybridization (flow-FISH). Human telomerase reverse transcriptase gene (hTERT) mutations were assessed by PCR. After adjustment for age and sex, relative TLs were reduced in PBLs (p = 0.02), CD15+ (p = 0.01), CD19+ (p = 0.25), and saliva (p = 0.13) in MDS cases versus controls, although only the PBL and CD15+ results were statistically significant. Among MDS cases, CD15+ and CD19+ cell TLs were positively correlated (p = 0.03). PBL TL was reduced among those occupationally exposed to paints and pesticides, but was not associated with hTERT genotype. Future studies are needed to further investigate constitutional telomere attrition as a possible predisposing factor for MDS.

Recruitment and retention of farm owners and workers for a six-month prospective injury study in New Zealand: a feasibility study

Background

Agricultural workers experience high rates of occupational injury. There is a lack of analytic studies which provide detailed occupational exposure information to inform intervention development.

Methods

A feasibility study simulating a six month prospective cohort study was designed and undertaken. The levels of farm and worker participation and retention were analysed to determine the feasibility of the methods for wider deployment.

Results

Recruitment levels were comparable with other studies, with 24% of farms and 36% of non-owner workers participating. Once recruited, retention was high at 85% and 86% respectively.

Conclusions

The main challenges identified were in the recruitment process. Once recruited, farms and workers tended to complete the study, indicating that prospective studies in this the agricultural workforce may be feasible. Issues encountered and potential solutions for future studies are discussed.

Body mass index, agricultural pesticide use, and cancer incidence in the Agricultural Health Study cohort

Obesity is associated with increased risks of several cancers including colon and female breast. Pesticide use in agricultural populations has also been linked with higher risks of various cancers. However, the interaction between obesity and pesticide use on cancer risk has not been well studied. Using data from the Agricultural Health Study, we examined the association between body mass index (BMI) and the risk of cancer at 17 sites and the interaction between BMI and pesticide use. Pesticide applicators residing in Iowa and North Carolina and their spouses were enrolled between 1993 and 1997 and given a self-administered questionnaire to obtain pesticide use and other information. This analysis included 39,628 men and 28,319 women with height and weight data who were cancer-free at enrollment. Among these participants, 4,432 were diagnosed with cancer between enrollment and 2005 and 64% were overweight or obese. BMI (per 1 kg/m(2)) was positively associated with colon cancer in men (hazard ratio (HR) 1.05, 95% confidence interval (CI) 1.02-1.09) and breast cancer in postmenopausal women (HR 1.03, 95% CI 1.01-1.06). In contrast, BMI was inversely associated with lung cancer in men, with a significant association in ever smokers (HR 0.92, 95% CI 0.88-0.97) and a null association in never smokers. The positive association between BMI and colon cancer in men was significant in those who ever used carbofuran (HR = 1.10, 95% CI 1.04-1.17; p-interaction = 0.04) or metolachlor (HR = 1.09, 95% CI 1.04-1.15; p-interaction = 0.02) but was null in non-users of these pesticides. Among male ever smokers, the inverse association between BMI and lung cancer was significant in non-users of carbofuran (HR = 0.87, 95% CI = 0.82-0.92) but was null in users of carbofuran (p-interaction = 0.02). These findings suggest that certain pesticides may modify the effects of BMI on the risks of colon and lung cancers.

A review of pesticide exposure and cancer incidence in the Agricultural Health Study cohort

OBJECTIVE

We reviewed epidemiologic evidence related to occupational pesticide exposures and cancer incidence in the Agricultural Health Study (AHS) cohort.

DATA SOURCES

Studies were identified from the AHS publication list available at http://aghealth.nci.nih.gov as well as through a Medline/PubMed database search in March 2009. We also examined citation lists. Findings related to lifetime-days and/or intensity-weighted lifetime-days of pesticide use are the primary focus of this review, because these measures allow for the evaluation of potential exposure-response relationships.

DATA SYNTHESIS

We reviewed 28 studies; most of the 32 pesticides examined were not strongly associated with cancer incidence in pesticide applicators. Increased rate ratios (or odds ratios) and positive exposure-response patterns were reported for 12 pesticides currently registered in Canada and/or the United States (alachlor, aldicarb, carbaryl, chlorpyrifos, diazinon, dicamba, S-ethyl-N,N-dipropylthiocarbamate, imazethapyr, metolachlor, pendimethalin, permethrin, trifluralin). However, estimates of association for specific cancers were often imprecise because of small numbers of exposed cases, and clear monotonic exposure-response patterns were not always apparent. Exposure misclassification is also a concern in the AHS and may limit the analysis of exposure-response patterns. Epidemiologic evidence outside the AHS remains limited with respect to most of the observed associations, but animal toxicity data support the biological plausibility of relationships observed for alachlor, carbaryl, metolachlor, pendimethalin, permethrin, and trifluralin.

CONCLUSIONS

Continued follow-up is needed to clarify associations reported to date. In particular, further evaluation of registered pesticides is warranted.

Identification of Iowa live births in the Agricultural Health Study

In the Agricultural Health Study, information on participant live births was largely provided by female partners of male private applicators. At the Iowa site, such information was available for 13,599 (42.9%) of 31,707 applicators. To improve identification of live births among Iowa participants, we used a probabilistic and deterministic approach to link available demographic data from 31,707 households and information on live births from 13,599 households with 1,014,916 Iowa birth certificates. Record linkage identified 16,611 (93.7%) of 17,719 reported live births and 17,883 additional live births, most (14,411 or 80.6%) not reported due to nonresponse by female partners. This record linkage produced an expanded cohort of live-born children among Iowa participants, which will facilitate improved study of the effects of agricultural exposures, including pesticides, on selected birth outcomes and childhood disease.

Pesticide use and cutaneous melanoma in pesticide applicators in the agricultural heath study

BACKGROUND

Melanoma rates continue to increase; however, few risk factors other than sun sensitivity and ultraviolet radiation (including sun exposure) have been identified. Although studies of farmers have shown an excess risk of melanoma and other skin cancers, it is unclear how much of this is related to sun exposure compared with other agricultural exposures.

METHODS

We examined dose-response relationships for 50 agricultural pesticides and cutaneous melanoma incidence in the Agricultural Health Study cohort of licensed pesticide applicators, along with ever use of older pesticides that contain arsenic. Logistic regression was used to examine odds ratios (ORs) and 95% confidence intervals (CIs) associated with pesticide exposure adjusted for age, sex, and other potential confounders.

RESULTS

We found significant associations between cutaneous melanoma and maneb/mancozeb (>or= 63 exposure days: OR = 2.4; 95% CI, 1.2-4.9; trend p = 0.006), parathion (>or= 56 exposure days: OR = 2.4; 95% CI, 1.3-4.4; trend p = 0.003), and carbaryl (>or= 56 exposure days: OR = 1.7; 95% CI, 1.1-2.5; trend p = 0.013). Other associations with benomyl and ever use of arsenical pesticides were also suggested.

CONCLUSIONS

Most previous melanoma literature has focused on host factors and sun exposure. Our research shows an association between several pesticides and melanoma, providing support for the hypotheses that agricultural chemicals may be another important source of melanoma risk.

Rhinitis associated with pesticide use among private pesticide applicators in the agricultural health study

Farmers commonly experience rhinitis but the risk factors are not well characterized. The aim of this study was to analyze cross-sectional data on rhinitis in the past year and pesticide use from 21,958 Iowa and North Carolina farmers in the Agricultural Health Study, enrolled 1993-1997, to evaluate pesticide predictors of rhinitis. Polytomous and logistic regression models were used to assess association between pesticide use and rhinitis while controlling for demographics and farm-related exposures. Sixty-seven percent of farmers reported current rhinitis and 39% reported 3 or more rhinitis episodes. The herbicides glyphosate [odds ratio (OR) = 1.09, 95% confidence interval (95% CI) = 1.05-1.13] and petroleum oil (OR = 1.12, 95% CI = 1.05-1.19) were associated with current rhinitis and increased rhinitis episodes. Of the insecticides, four organophosphates (chlorpyrifos, diazinon, dichlorvos, and malathion), carbaryl, and use of permethrin on animals were predictors of current rhinitis. Diazinon was significant in the overall polytomous model and was associated with an elevated OR of 13+ rhinitis episodes (13+ episodes OR = 1.23, 95% CI = 1.09-1.38). The fungicide captan was also a significant predictor of rhinitis. Use of petroleum oil, use of malathion, use of permethrin, and use of the herbicide metolachlor were significant in exposure-response polytomous models. Specific pesticides may contribute to rhinitis in farmers; agricultural activities did not explain these findings.

Cancer incidence among pesticide applicators exposed to butylate in the Agricultural Health Study (AHS)

Although limited, epidemiologic studies suggest possible associations between butylate use and cancer risk, specifically prostate cancer and non-Hodgkin lymphoma (NHL). We examined butylate use and cancer risk more broadly in the AHS, a cohort of licensed pesticide applicators in Iowa and North Carolina. Pesticide use information was collected using self-administered questionnaires. Poisson regression was used to calculate rate ratios (RR) and 95% confidence intervals (CI). Two exposure metrics were used: lifetime exposure days (LD) and intensity-weighted lifetime exposure days (IWLD). We used two referent groups: unexposed to butylate and the lowest butylate usage category. This analysis included 19,655 applicators with complete butylate use information; 5297 applicators were exposed to butylate, making this the largest study of butylate to date. The mean follow-up time since enrollment was 9 years. Prostate cancer risk was significantly elevated among applicators in the highest LD category in both referent groups (low-exposed referent: RR(LD)=2.09, 95% CI=1.27-3.44). We observed a significantly elevated joint effect of prostate cancer family history and high butylate usage across both exposure metrics and both referent groups (low-exposed referent: RR(LD)=2.00, 95% CI=1.07-3.74), and a non-significant, elevated interaction between butylate use and prostate cancer family history, similar to a previous AHS finding. Statistically significant increased risks and exposure-response trends were seen for all lymphohematopoietic cancers (AL) and NHL for both exposure metrics and referent groups (low-exposed referent: AL:RR(LD)=2.27, 95% CI=1.18-4.37; NHL: RR(LD)=3.44, 95% CI=1.29-9.21). Our analysis did not find meaningful associations for other cancers analyzed. Further study is warranted for AL, NHL and prostate cancers.

Cancer incidence among paraquat exposed applicators in the agricultural health study: prospective cohort study

Paraquat (1,1'-dimethyl-4, 4'-bipyridinium dichloride) is a nonselective herbicide that is extremely toxic after acute exposure. It was once widely used in North America and is still used in some countries, including the United States. Although there is little firm evidence that paraquat is a carcinogen, previous studies have suggested a potential relationship with some cancers. This prospective cohort study was performed to evaluate the association between lifetime paraquat exposure and cancer incidence among licensed pesticide applicators with 9.1 years of median follow-up. The lifetime ever-use of paraquat was evaluated in 56,224 subjects at baseline and exposure-response relationship was evaluated in 24,667 subjects (44%) who provided detailed information on total life-time paraquat exposure in a second questionnaire. Among the total subjects, the risk for non-Hodgkin's lymphoma (NHL) in the exposed group was marginally elevated (Relative risk [RR], 1.47; 95% confidence interval [CI], 0.97-2.23) compared to the non-exposed group. However, among the 24,667 applicators who supplied total life-time exposure days, the highest tertile of lifetime exposure-days (LE) and intensity-weighted lifetime exposure-days (IWLE) was not significantly associated with NHL risk (RR, 1.57; 95%CI, 0.57-4.23 for LE; RR, 1.42; 95%CI, 0.40-4.71 for IWLE, respectively) and there was no significant exposure-response trend (p-trend > 0.1). There was some suggestion of a possible link between paraquat exposure and NHL risk in humans, but the inconsistency in exposure level trend suggests that this could be a chance finding.

Pesticide use and adult-onset asthma among male farmers in the Agricultural Health Study

Although specific pesticides have been associated with wheeze in farmers, little is known about pesticides and asthma. Data from 19,704 male farmers in the Agricultural Health Study were used to evaluate lifetime use of 48 pesticides and prevalent adult-onset asthma, defined as doctor-diagnosed asthma after the age of 20 yrs. Asthma cases were categorised as allergic (n = 127) and nonallergic (n = 314) based on their history of eczema or hay fever. Polytomous logistic regression, controlling for age, state, smoking and body mass, was used to assess pesticide associations. High pesticide exposure events were associated with a doubling of both allergic and nonallergic asthma. For ever-use, 12 individual pesticides were associated with allergic asthma and four with nonallergic asthma. For allergic asthma, coumaphos (OR 2.34; 95% CI 1.49-3.70), heptachlor (OR 2.01; 95% CI 1.30-3.11), parathion (OR 2.05; 95% CI 1.21-3.46), 80/20 mix (carbon tetrachloride/carbon disulfide) (OR 2.15; 95% CI 1.23-3.76) and ethylene dibromide (OR 2.07; 95% CI 1.02-4.20) all showed ORs of >2.0 and significant exposure-response trends. For nonallergic asthma, DDT (dichlorodiphenyltrichloroethane) showed the strongest association (OR 1.41; 95% CI 1.09-1.84), but with little evidence of increasing asthma with increasing use. Current animal handling and farm activities did not confound these results. There was little evidence that allergy alone was driving these associations. In conclusion, pesticides may be an overlooked contributor to asthma risk among farmers.

Occupational exposure to metribuzin and the incidence of cancer in the Agricultural Health Study

PURPOSE

Little is known about the potential carcinogenicity of the triazinone herbicide metribuzin. We evaluated the association between metribuzin use and cancer risk in the Agricultural Health Study, a prospective cohort study of licensed pesticide applicators in Iowa and North Carolina.

METHODS

Applicators (N=23,072) provided information on metribuzin use on a self-administered questionnaire at enrollment (1993-1997). Among metribuzin users (n=8,504), there were 554 incident cancer cases. We used multivariable Poisson regression to evaluate potential associations between metribuzin use and cancer incidence by using two quantitative exposure metrics, lifetime days and intensity-weighted lifetime days.

RESULTS

Using intensity-weighted lifetime days, the rate ratio (RR) and 95% confidence interval (CI) for the highest exposed tertile for lymphohematopoietic malignancies were 2.09 (95% CI: 0.99-4.29), p trend=0.02 and 2.42 (95% CI: 0.82-7.19), p trend=0.08 for leukemia. For non-Hodgkin lymphoma, the RR was 2.64 (95% CI: 0.76-9.11), p trend=0.13 for lifetime days and 2.52 (95% CI: 0.66-9.59), p trend=0.13 for intensity-weighted lifetime days. Patterns of association were similar for both exposure metrics, but associations were generally weaker than for intensity-weighted days.

CONCLUSIONS

The results from this study suggest a potential association between metribuzin use and certain lymphohematopoietic malignancies; however, having not been observed previously, caution should be used in interpretation.

Agricultural pesticide use and pancreatic cancer risk in the Agricultural Health Study Cohort

Pancreatic cancer is a rapidly fatal disease that has been linked with pesticide use. Previous studies have reported excess risks of pancreatic cancer with organochlorines such as DDT, however, many other commonly used pesticides have not been examined. To further examine the potential associations between the use of a number of pesticides and pancreatic cancer, we conducted a case-control analysis in the Agricultural Health Study, one of the largest prospective cohorts with over 89,000 participants including pesticide applicators and their spouses in Iowa and North Carolina. This analysis included 93 incident pancreatic cancer cases (64 applicators, 29 spouses) and 82,503 cancer-free controls who completed an enrollment questionnaire providing detailed pesticide use, demographic and lifestyle information. Ever use of 24 pesticides and intensity-weighted lifetime days [(lifetime exposure days) x (exposure intensity score)] of 13 pesticides was assessed. Risk estimates were calculated using unconditional logistic regression controlling for age, smoking, and diabetes. Among pesticide applicators, 2 herbicides (EPTC and pendimethalin) of the 13 pesticides examined for intensity-weighted lifetime use showed a statistically significant exposure-response association with pancreatic cancer. Applicators in the top half of lifetime pendimethalin use had a 3.0-fold (95% CI 1.3-7.2, p-trend = 0.01) risk compared with never users, and those in the top half of lifetime EPTC use had a 2.56-fold (95% CI = 1.1-5.4, p-trend = 0.01) risk compared with never users. Organochlorines were not associated with an excess risk of pancreatic cancer in this study. These findings suggest that herbicides, particularly pendimethalin and EPTC, may be associated with pancreatic cancer.

Keokuk County rural health study: self-reported use of agricultural chemicals and protective equipment

The Keokuk County Rural Health Study is a population-based study of an agricultural community in Iowa. The study includes in-depth evaluations of respiratory disease, injury, and other health outcomes in relation to environmental and occupational exposures. This article reports descriptive findings on pesticide use from among the 1191 participants completing occupational surveys. Fifty-one percent (612) of respondents (farmers and non-farmers) had applied insecticides including lawn and garden chemicals at home during the past year. Thirty-three percent (395) of respondents had personally mixed or applied farm chemicals during their life. One-hundred and four had a current pesticide applicator's license. Information on the specific types of pesticides and protective measures used was obtained for the 144 individuals who had mixed or applied pesticides on farms within the previous year. Of these individuals, 67% worked with fertilizers, 49% used herbicides, 48% used crop insecticides, 28% used crop storage insecticides, 45% applied livestock insecticides, and 9% worked with fungicides. The use of personal protective equipment such as gloves, aprons, and respirators varied depending on the chemical. A substantial proportion did not use gloves even for mixing. Thirty-five percent reported at least one suspected work-related symptom after working with pesticides during the previous year. The lack of differences in protective equipment use between applicators who have completed pesticide applicator training courses and those who have not suggests a need to develop more effective training methods. The increased use of protective equipment when applying odorous agrochemicals suggests that addition of an odorant to more toxic pesticides may be a successful intervention strategy.

Depression and pesticide exposures among private pesticide applicators enrolled in the Agricultural Health Study

BACKGROUND

We evaluated the relationship between diagnosed depression and pesticide exposure using information from private pesticide applicators enrolled in the Agricultural Health Study between 1993 and 1997 in Iowa and North Carolina.

METHODS

There were 534 cases who self-reported a physician-diagnosed depression and 17,051 controls who reported never having been diagnosed with depression and did not feel depressed more than once a week in the past year. Lifetime pesticide exposure was categorized in three mutually exclusive groups: low (< 226 days, the reference group), intermediate (226-752 days), and high (> 752 days). Two additional measures represented acute high-intensity pesticide exposures: an unusually high pesticide exposure event (HPEE) and physician-diagnosed pesticide poisoning. Logistic regression analyses were performed relating pesticide exposure to depression.

RESULTS

After adjusting for state, age, education, marital status, doctor visits, alcohol use, smoking, solvent exposure, not currently having crops or animals, and ever working a job off the farm, pesticide poisoning was more strongly associated with depression [odds ratio (OR) = 2.57; 95% confidence interval (CI), 1.74-3.79] than intermediate (OR = 1.07; 95% CI, 0.87-1.31) or high (OR = 1.11; 95% CI, 0.87-1.42) cumulative exposure or an HPEE (OR = 1.65; 95% CI, 1.33-2.05). In analysis of a subgroup without a history of acute poisoning, high cumulative exposure was significantly associated with depression (OR = 1.54; 95% CI, 1.16-2.04).

CONCLUSION

These findings suggest that both acute high-intensity and cumulative pesticide exposure may contribute to depression in pesticide applicators. Our study is unique in reporting that depression is also associated with chronic pesticide exposure in the absence of a physician-diagnosed poisoning.

Hearing loss among licensed pesticide applicators in the agricultural health study

OBJECTIVE

We evaluated self-reported hearing loss and pesticide exposure in licensed private pesticide applicators enrolled in the Agricultural Health Study in 1993 to 1997 in Iowa and North Carolina.

METHODS

Among 14,229 white male applicators in 1999 to 2003, 4926 reported hearing loss (35%). Logistic regression was performed with adjustment for state, age, and noise, solvents, and metals. We classified pesticides by lifetime days of use.

RESULTS

Compared with no exposure, the odds ratio (95% confidence interval) for the highest quartile of exposure was 1.19 (1.04 to 1.35) for insecticides and 1.17 (1.03 to 1.31) for organophosphate insecticides. Odds of hearing loss were elevated for high pesticide exposure events (1.38, 1.25 to 1.54), pesticide-related doctor visits (1.38, 1.17 to 1.62) or hospitalization (1.81, 1.25 to 2.62), and diagnosed pesticide poisoning (1.75, 1.36 to 2.26).

CONCLUSIONS

Although control for exposure to noise or other neurotoxicants was limited, this study extends previous reports suggesting that organophosphate exposure increases risk of hearing loss.

Cutaneous melanoma and obesity in the Agricultural Health Study

PURPOSE

To describe the risk of cutaneous melanoma in the Agricultural Health Study (AHS), a cohort of pesticide applicators and their spouses, according to baseline characteristics related to obesity along with sun exposure and sun sensitivity.

METHODS

The AHS cohort was enrolled in Iowa and North Carolina during 1993-1997 and followed up through 2003 for cancer incidence. We identified 315 cases of cutaneous melanoma, which reduced to 168 incident cases among subjects reporting height, weight, sun sensitivity, and sun exposure information (on the spouse questionnaire or take-home applicator questionnaire; N = 44,086). Unconditional multiple logistic regression models were used to obtain adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs).

RESULTS

The results were consistent with those of prior studies of melanoma that indicate an association with measures of sun sensitivity. The highest category of body surface area (BSA; OR = 2.6; 95% CI, 1.5-4.4) and body mass index (BMI; OR = 2.5; 95% CI, 1.5-4.3) at age 20 were significantly associated with melanoma. There was some evidence for an association with BSA, but not BMI, at enrollment.

CONCLUSIONS

Obesity was associated with an increased risk of melanoma, indicating strategies to control obesity may result in risk reduction for melanoma.

Meat and meat mutagens and risk of prostate cancer in the Agricultural Health Study

Meats cooked at high temperatures, such as pan-frying or grilling, are a source of carcinogenic heterocyclic amines and polycyclic aromatic hydrocarbons. We prospectively examined the association between meat types, meat cooking methods, meat doneness, and meat mutagens and the risk for prostate cancer in the Agricultural Health Study. We estimated relative risks and 95% confidence intervals (95% CI) for prostate cancer using Cox proportional hazards regression using age as the underlying time metric and adjusting for state of residence, race, smoking status, and family history of prostate cancer. During 197,017 person-years of follow-up, we observed 668 incident prostate cancer cases (613 of these were diagnosed after the first year of follow-up and 140 were advanced cases) among 23,080 men with complete dietary data. We found no association between meat type or specific cooking method and prostate cancer risk. However, intake of well or very well done total meat was associated with a 1.26-fold increased risk of incident prostate cancer (95% CI, 1.02-1.54) and a 1.97-fold increased risk of advanced disease (95% CI, 1.26-3.08) when the highest tertile was compared with the lowest. Risks for the two heterocyclic amines 2-amino-3,4,8-trimethylimidazo-[4,5-f]quinoxaline and 2-amino-3,8-dimethylimidazo-[4,5-b]quinoxaline were of borderline significance for incident disease [1.24 (95% CI, 0.96-1.59) and 1.20 (95% CI, 0.93-1.55), respectively] when the highest quintile was compared with the lowest. In conclusion, well and very well done meat was associated with an increased risk for prostate cancer in this cohort.

Pesticide use and chronic bronchitis among farmers in the Agricultural Health Study

BACKGROUND

Farmers have increased risk for chronic bronchitis. Few investigators have considered pesticides.

METHODS

We evaluated pesticides as risk factors for chronic bronchitis using the Agricultural Health Study enrollment data on lifetime pesticide use and history of doctor-diagnosed chronic bronchitis from 20,908 private pesticide applicators, primarily farmers.

RESULTS

A total of 654 farmers (3%) reported chronic bronchitis diagnosed after age 19. After adjustment for correlated pesticides as well as confounders, 11 pesticides were significantly associated with chronic bronchitis. Heptachlor use had the highest odds ratio (OR=1.50, 95% Confidence Interval (CI)=1.19, 1.89). Increased prevalence for chronic bronchitis was also seen for individuals who had a history of a high pesticide exposure event (OR=1.85, 95% CI=1.51, 2.25) and for those who also applied pesticides in off-farm jobs (OR=1.40, 95% CI=1.04, 1.88). Co-morbid asthma and current farm activities did not explain these results.

CONCLUSIONS

These results provide preliminary evidence that pesticide use may increase chronic bronchitis prevalence.

Pesticide use and colorectal cancer risk in the Agricultural Health Study

We investigated the relationship between agricultural pesticides and colorectal cancer incidence in the Agricultural Health Study. A total of 56,813 pesticide applicators with no prior history of colorectal cancer were included in this analysis. Detailed pesticide exposure and other information were obtained from self-administered questionnaires completed at the time of enrollment (1993-1997). Cancer incidence was determined through population-based cancer registries from enrollment through December 31, 2002. A total of 305 incident colorectal cancers (212 colon, 93 rectum) were diagnosed during the study period, 1993-2002. Although most of the 50 pesticides studied were not associated with colorectal cancer risk, chlorpyrifos use showed significant exposure response trend (p for trend = 0.008) for rectal cancer, rising to a 2.7-fold (95% confidence interval: 1.2-6.4) increased risk in the highest exposure category. Aldicarb was associated with a significantly increased risk of colon cancer (p for trend = 0.001), based on a small number of exposed cases, with the highest exposure category resulting in a 4.1-fold increased risk (95% confidence interval: 1.3-12.8). In contrast, dichlorophenoxyacetic acid showed a significant inverse association with colon cancer but the association was not monotonic. Our findings should be interpreted cautiously since the literature suggesting that pesticides are related to colorectal cancer is limited. Nonetheless the possibility of an association between exposure to certain pesticides and incidence of colorectal cancer among pesticide applicators deserves further evaluation.

Neurologic symptoms in licensed pesticide applicators in the Agricultural Health Study

Exposure to high levels of many pesticides has both acute and long-term neurologic consequences, but little is known about the neurotoxicity of chronic exposure to moderate pesticide levels. We analysed cross-sectional data from 18 782 Caucasian, male, licensed pesticide applicators, enrolled in the Agricultural Health Study from 1993 to 1997. Applicators provided information on lifetime pesticide use, and 23 neurologic symptoms typically associated with pesticide intoxication. Increased risk of experiencing >/=10 symptoms during the year before enrollment was associated with cumulative pesticide use, personally mixing or applying pesticides, pesticide-related medical care, diagnosed pesticide poisoning, and events involving high personal pesticide exposure. Greatest risk was associated with use of organophosphate and organochlorine insecticides. Results were similar after stratification by pesticide use during the year before enrollment, or exclusion of applicators with a history of pesticide poisoning, or high-exposure events. Use of pesticide application methods likely to involve high personal exposure was associated with greater risk. Groups of symptoms reflecting several neurologic domains, including affect, cognition, autonomic and motor function, and vision, were also associated with pesticide exposure. These results suggest that neurologic symptoms are associated with cumulative exposure to moderate levels of organophosphate and organochlorine insecticides, regardless of recent exposure or history of poisoning.

Pesticides and other agricultural factors associated with self-reported farmer's lung among farm residents in the Agricultural Health Study

BACKGROUND

Farmer's lung, or hypersensitivity pneumonitis, is an important contributor to respiratory morbidity among farmers.

METHODS

Using the 1993-7 enrolment data from the Agricultural Health Study, we conducted a cross-sectional study of occupational risk factors for farmer's lung among 50,000 farmers and farm spouses in Iowa and North Carolina using hierarchical logistic regression controlling for age, state, and smoking status. Participants provided information on agricultural exposures, demographic characteristics, and medical history via self-administered questionnaires. Approximately 2% of farmers (n = 481) and 0.2% of spouses (n = 51) reported doctor-diagnosed farmer's lung during their lifetime. We assessed farmers and spouses separately due to different information on occupational exposure history. Only pesticide exposures represented lifetime exposure history, all other farm exposures represented current activities at enrolment.

RESULTS

Among farmers, handling silage (OR = 1.41, 95% CI 1.10 to 1.82), high pesticide exposure events (OR = 1.75, 95% CI 1.39 to 2.21), and ever use of organochlorine (OR = 1.34, 95% CI 1.04 to 1.74) and carbamate pesticides (OR = 1.32, 95% CI 1.03 to 1.68) were associated with farmer's lung in mutually-adjusted models. The insecticides DDT, lindane, and aldicarb were positively associated with farmer's lung among farmers. Current animal exposures, while not statistically significant, were positively associated with farmer's lung, particularly for poultry houses (OR = 1.55, 95% CI 0.93 to 2.58) and dairy cattle (OR = 1.28, 95% CI 0.86 to 1.89). The occupational data were more limited for spouses; however, we saw similar associations for dairy cattle (OR = 1.50, 95% CI 0.72 to 3.14) and organochlorine pesticides (OR = 1.29, 95% CI 0.64 to 2.59).

CONCLUSION

While historic farm exposures may contribute to the observed associations with pesticides, these results suggest that organochlorine and carbamate pesticides should be further evaluated as potential risk factors for farmer's lung

Occupational exposure to organochlorine insecticides and cancer incidence in the Agricultural Health Study

Organochlorine (OC) insecticides have been regulated as possible human carcinogens primarily on the basis of animal studies. However, the epidemiologic evidence is inconsistent. We investigated the relationship between cancer incidence and OC insecticide use among pesticide applicators enrolled in the Agricultural Health Study, a prospective cohort study of 57,311 licensed applicators in Iowa and North Carolina enrolled between 1993 and 1997. Information on ever use of 7 OC insecticides (aldrin, chlordane, DDT, dieldrin, heptachlor, lindane, toxaphene) was collected from a self-administered questionnaire at enrollment. Lifetime exposure-days to OC insecticides were calculated using additional data from a take-home questionnaire completed by 25,291 participants (44% of total). We found no clear evidence of an association between use of OC insecticides and incident cancers (N = 1,150) ascertained through December, 2002. When we focused on individual insecticides and structurally similar groups (aldrin and dieldrin; chlordane and heptachlor), significantly increased relative risks of some cancers were observed for use of some chemicals (rectal cancer and chlordane, lung cancer and dieldrin, non-Hodgkin lymphoma (NHL) and lindane, melanoma and toxaphene, leukemia and chlordane/heptachlor). Some significant decreased relative risks were also observed (colon cancer and aldrin; overall cancer and heptachlor). In conclusion, we did not observe any clear relationship between cancer risk and the use of OC insecticides. Our chemical-specific findings are based on small numbers and multiple comparisons, and should be interpreted with caution; however, some observed associations (lindane and NHL, chlordane/heptachlor and leukemia) are supported by previous evidence.

Carbaryl exposure and incident cancer in the Agricultural Health Study

Carbaryl is a carbamate insecticide with a broad spectrum of uses in agricultural, commercial and household settings. It has previously been linked with non-Hodgkin lymphoma (NHL) but studies of cancer risk in humans are limited. We examined occupational carbaryl use and risk of all cancers in the Agricultural Health Study, a prospective study of a cohort of pesticide applicators in North Carolina and Iowa. This analysis included 21,416 subjects (1,291 cases) enrolled from 1993-1997 and followed for cancer incidence through 2003. Pesticide exposure and other data were collected using self-administered questionnaires. Poisson regression was used to calculate rate ratios (RRs) and 95% confidence intervals (CIs) while controlling for potential confounders. Carbaryl was not associated with cancer risk overall. Relative to subjects who never used carbaryl, melanoma risk was elevated with >175 lifetime exposure-days (RR = 4.11; 95%CI, 1.33-12.75; p-trend = 0.07), >10 years of use (RR = 3.19; 95%CI, 1.28-7.92; p-trend = 0.04), or >or=10 days of use per year (RR = 5.50; 95%CI, 2.19-13.84; p-trend < 0.001). Risk remained after adjusting for sunlight exposure. Although not significant, there appeared to be a trend of decreasing prostate cancer risk with increasing level of exposure. A small increase in NHL risk was observed using some, but not all, exposure measures. No associations were observed with other examined cancer sites. Because the observed results were not hypothesized a priori and because of limited study of their biological plausibility, they should be interpreted with caution.

Pesticides and adult respiratory outcomes in the agricultural health study

In the 1700s, Bernardino Ramazzini was among the first to describe respiratory disease among agricultural workers. Since then, farmers continue to have higher rates of respiratory illnesses, even as changes occur in occupational and environmental exposures on farms. While grain and animal exposures have been well studied for their role in agricultural lung diseases, pesticide exposures have not. Using the Agricultural Health Study, a prospective cohort study of approximately 89,000 licensed pesticide applicators and their spouses in Iowa and North Carolina, we are currently assessing the association of pesticides with respiratory outcomes, including wheeze, adult asthma, farmer's lung, and chronic bronchitis. At enrollment (1993-1997), 19% of farmers and 22% of commercial pesticide applicators reported wheeze in the previous year. Using logistic regression models adjusted for age, state, smoking status, and body mass index, we evaluated the association of 40 individual pesticides with wheeze within these two groups separately. In both groups, we observed strong evidence of an association of organophosphates with wheeze. For farmers, the organophosphates chlorpyrifos, malathion, and parathion were positively associated with wheeze; for the commercial applicators, the organophosphates chlorpyrifos, dichlorvos, and phorate were positively associated with wheeze. Chlorpyrifos was strongly associated with wheeze in a dose-dependent manner in both groups; use of chlorpyrifos for at least 20 days per year had an odds ratio of 1.48 (95% confidence interval [CI] = 1.00-2.19) for farmers and 1.96 (95% CI = 1.05-3.66) for commercial applicators. Our wheeze results are consistent with recent animal models that support a role for organophosphates and respiratory outcomes.

Reduced fertility among overweight and obese men

BACKGROUND

Overweight and obese men have been reported to have lower sperm counts and hormonal changes, but data are lacking regarding effects on couple fertility.

METHODS

We examined the relationship between male body mass index (BMI) and infertility in couples enrolled in the Agricultural Health Study in the United States. The analysis sample was limited to couples (wife <40 years old) with an attempt at pregnancy in the last 4 years based on pregnancy and fertility data provided by wives. Infertility was defined as not conceiving a pregnancy after at least 12 months of unprotected intercourse regardless of whether or not a pregnancy ultimately occurred. Self-reported weight and height were used to calculate BMI (kg/m). Adjusted odds ratios (aORs) for infertility associated with increases in male BMI were calculated with logistic regression.

RESULTS

Adjusting for potential confounders, a 3-unit increase in male BMI was associated with infertility (aOR = 1.12; 95% confidence interval = 1.01-1.25; n = 1329). There was a dose-response relationship, and the BMI effect was stronger when the data were limited to couples with the highest-quality infertility data. The association between BMI and infertility was similar for older and younger men, suggesting that erectile dysfunction in older men does not explain the association.

CONCLUSIONS

This report of lower fertility in overweight and obese men needs replication. If the findings are robust, programs to prevent obesity may improve men's reproductive health and save medical costs for infertility treatment.

Cancer incidence among pesticide applicators exposed to cyanazine in the agricultural health study

BACKGROUND

Cyanazine is a common pesticide used frequently in the United States during the 1980s and 1990s. Animal and human studies have suggested that triazines may be carcinogenic, but results have been mixed. We evaluated cancer incidence in cyanazine-exposed pesticide applicators among the 57,311 licensed pesticide applicators in the Agricultural Health Study (AHS).

METHODS

We obtained detailed pesticide exposure information from a self-administered questionnaire completed at enrollment (1993-1997). Cancer incidence was followed through January 2002. Over half of cyanazine-exposed applicators had >or=6 years of exposure at enrollment, and approximately 85% had begun using cyanazine before the 1990s. We used adjusted Poisson regression to calculate rate ratios (RRs) and 95% confidence intervals (CIs) of multiple cancer sites among cyanazine-exposed applicators. We calculated ptrend values, and all statistical tests were two-sided. Two exposure metrics were used: tertiles of lifetime days of exposure (LD) and intensity-weighted LD.

RESULTS

A total of 20,824 cancer-free AHS applicators reported ever using cyanazine at enrollment. Cancer incidence comparisons between applicators with the lowest cyanazine exposure and those with the highest exposure yielded the following for the LD metric: all cancers, RR=0.99 (95% CI, 0.80-1.24); prostate cancer, RR=1.23 (95% CI, 0.87-1.70); all lymphohematopoietic cancers, RR=0.92 (95% CI, 0.50-1.72); non-Hodgkin lymphoma, RR=1.25 (95% CI, 0.47-3.35); lung cancer, RR=0.52 (95% CI, 0.22-1.25).

CONCLUSIONS

We did not find any clear, consistent associations between cyanazine exposure and any cancer analyzed. The number of sites was small for certain cancers, limiting any conclusion with regard to ovarian, breast, and some other cancers.

Phorate exposure and incidence of cancer in the agricultural health study

BACKGROUND

We recently reported a link between use of the organophosphate pesticide phorate and risk of prostate cancer among applicators with a family history of prostate cancer in the Agricultural Health Study (AHS).

OBJECTIVE

This finding, together with findings of associations between other organophosphate pesticides and cancer more broadly, prompted us to examine phorate exposure and overall cancer incidence in the AHS. Adding 3 years of follow-up and using more detailed exposure information allowed us to see whether the prostate cancer finding held.

METHODS

The AHS is a prospective study of licensed restricted-use pesticide applicators from North Carolina and Iowa. To our knowledge, this is the largest examination of workers occupationally exposed to phorate. Pesticide exposure and other information was collected using two self-administered questionnaires completed from 1993 to 1997. Poisson regression was used to calculate rate ratios (RR) and 95% confidence intervals (CI), adjusting for potential confounders.

RESULTS

Phorate use was not related to the incidence of all cancers combined or to any individual cancer, although we had insufficient numbers to study non-Hodgkin lymphoma or leukemia, which have been linked to organophosphates in other studies. Although prostate cancer risk was not significantly related to phorate use overall or among those without a family history, the risk tended to increase among applicators with a family history of prostate cancer. The interaction RR was 1.53 (95% CI, 0.99-2.37).

CONCLUSION

The observed statistical interaction suggests a gene-environment interaction between family history and phorate exposure in the incidence of prostate cancer, but other explanations are also possible.