Disease and injury among participants in the Agricultural Health Study

Assessment of relationship between farmer's syndrome and neurotoxic symptoms in farming couples

The purpose of this study was to evaluate the relationship between farmer’s syndrome and neurotoxic symptoms in farming couples. The study was conducted on 348 farmers (174 couples) in Chungnam Province of South Korea. We obtained information on general and agricultural characteristics, farmer’s syndrome, and neurotoxic symptoms through face-to-face surveys from 2014 to 2019. The Korean version of the diagnostic standard scale was used for farmer’s syndrome, and the Swedish Q16 questionnaire was used for neurotoxic symptoms. Logistic regression analysis was used to identify neurotoxic symptoms affected by farmer’s syndrome. The prevalence of ‘positive’ neurotoxic symptoms was higher in wives (72.4%) than in husbands (56.9%). Compared with husbands with ‘negative and probable’ farmer’s syndrome (reference), husbands with ‘positive’ farmer’s syndrome were more likely to have ‘positive’ neurotoxic symptoms (odds ratio [OR] = 5.37, 95% confidence interval [CI] = 2.01–14.30). Compared with wives with ‘negative and probable’ farmer’s syndrome (reference), wives with ‘positive’ farmer’s syndrome were more likely to have ‘positive’ neurotoxic symptoms (OR = 7.07, 95% CI = 2.58–19.38). Therefore, neurotoxic symptoms in both husbands and wives were significantly associated with farmer’s syndrome. However, wives had a higher risk of neurotoxic symptoms than husbands. The findings of this study might be useful as important data for establishing and training agricultural safety and health policy.

Persistent Organic Pollutant-Mediated Insulin Resistance

Persistent organic pollutants (POPs) such as organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) have become wide-spread environmental contaminants as a consequence of their extensive use, long-range transport, and persistence. Because POPs are highly resistant to metabolic degradation, humans bioaccumulate these lipophilic and hydrophobic pollutants in fatty tissues for many years. Previous studies have demonstrated that POPs including PCBs are involved in the development of diabetes mellitus (DM) type 2 and insulin resistance. Numerous epidemiological studies suggest an association between POP burden and DM type 2/metabolic syndrome. In addition, several experimental studies have provided additional evidence supporting the association between POP exposure and DM type 2 or insulin resistance. Epidemiological and experimental studies have provided compelling evidence indicating that exposure to POPs increases the risk of developing insulin resistance and metabolic disorders. However, the detailed molecular mechanism underlying POP-induced insulin resistance is yet to be elucidated. In this article, we review literature that has reported on the association between POP burden and insulin resistance and the mechanism underlying POP-induced insulin resistance, and discuss implications for public health.

Thyroid Function Disruptors: from nature to chemicals

The modern concept of thyroid disruptors includes man-made chemicals and bioactive compounds from food that interfere with any aspect of the hypothalamus-pituitary-thyroid axis, thyroid hormone biosynthesis and secretion, blood and transmembrane transport, metabolism and local action of thyroid hormones. This review highlights relevant disruptors that effect populations through their diet: directly from food itself (fish oil and polyunsaturated fatty acids, pepper, coffee, cinnamon and resveratrol/grapes), through vegetable cultivation (pesticides) and from containers for food storage and cooking (bisphenol A, phthalates and polybrominated diphenyl ethers). Due to the vital role of thyroid hormones during every stage of life, we review effects from the gestational period through to adulthood, including evidence from in vitro studies, rodent models, human trials and epidemiological studies.

Utah Regional Differences in Respirator Use and Fit Testing among Pesticide Applicators

The purpose of this study was to determine regional differences within Utah in response to piloting a mobile respirator training and fit assessment program for pesticide applicators. The objectives were to describe worker perceptions of respirator use and training experiences. Pilot trainings were offered in two southern counties and two northern counties of Utah. A total of 141 individuals completed the post-training questionnaire regarding use and fit testing experience with respirators as well as perceptions of the benefits to protecting respiratory health. The majority of respondents were male (95.7%, f = 112). The proportion of participants in the southern counties who had respirator training experience (61.0%, f = 25) was not significantly higher (2 = 3.763, df = 1, p = 0.05) than the proportion of participants in the northern counties (43.0%, f = 43). Three-fourths (73.5%, f = 72) of participants in the northern counties agreed that they expect to wear a respirator in dusty conditions, while two-thirds (61.0%, f = 25) of participants in the southern counties agreed that they expect to wear a respirator in dusty conditions. The results indicated that more training should be done to improve perceptions and beliefs about using respirators. A high priority for this population will be identification of comfortable respirator options as well as communicating the importance of proper fit testing.

Dermal exposure associated with occupational end use of pesticides and the role of protective measures

BACKGROUND

Occupational end users of pesticides may experience bodily absorption of the pesticide products they use, risking possible health effects. The purpose of this paper is to provide a guide for researchers, practitioners, and policy makers working in the field of agricultural health or other areas where occupational end use of pesticides and exposure issues are of interest.

METHODS

This paper characterizes the health effects of pesticide exposure, jobs associated with pesticide use, pesticide-related tasks, absorption of pesticides through the skin, and the use of personal protective equipment (PPE) for reducing exposure.

CONCLUSIONS

Although international and national efforts to reduce pesticide exposure through regulatory means should continue, it is difficult in the agricultural sector to implement engineering or system controls. It is clear that use of PPE does reduce dermal pesticide exposure but compliance among the majority of occupationally exposed pesticide end users appears to be poor. More research is needed on higher-order controls to reduce pesticide exposure and to understand the reasons for poor compliance with PPE and identify effective training methods.

Mortality in the California Farmer Health Study cohort

Western agriculture, in comparison with Midwestern and Eastern, is more diverse, with a drier climate, mild winters, and different exposures. This randomly selected cohort of 1947 Californian farmers confirmed the usual finding: a lower mortality rate than general population (by 50%). A low smoking prevalence and healthy worker effect are likely contributors. Although farmers were more likely to die from injuries and skin cancer, death was less likely from Alzheimer's and cerebrovascular diseases. Within the cohort, disability and persistent wheeze were associated with increased mortality. The 200 deaths were insufficient to determine the significance of rare diseases.

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.

Thyroid function tests in persons with occupational exposure to fipronil

BACKGROUND

Fipronil represents a chemical class of insecticides acting at the γ-aminobutyric acid receptor in pests. [corrected] Fipronil has been associated with a significant increase in the incidence of thyroid gland tumors concomitant with prolonged exposure to thyroid-stimulating hormone (TSH) in rats. An association between human TSH concentration and thyroid cancer has been also reported. The primary objective of this study was to test the hypothesis that chronic occupational fipronil exposure may be associated with abnormal thyroid function tests.

METHODS

In 2008, 159 workers of a factory manufacturing fipronil-containing veterinary drugs were assessed. Serum concentrations of TSH, total thyroxine, free thyroxine, fipronil, and fipronil sulfone were measured.

RESULTS

A positive and significant correlation was observed between serum fipronil or fipronil sulfone levels and duration of fipronil exposure. Serum fipronil sulfone concentration was negatively correlated with TSH concentration in fipronil-exposed workers, but with no significant increase in thyroid function test abnormalities.

CONCLUSION

This study did not show that chronic fipronil exposure was associated with an increase of thyroid function test abnormalities. But, despite the fact that fipronil exposure in rats has been associated with increased serum TSH, fipronil sulfone concentrations were negatively correlated with serum TSH concentrations in fipronil-exposed workers, raising the possibility that fipronil has a central inhibitory effect on TSH secretion in humans. Close occupational medical surveillance, therefore, appears to be required in factory workers manufacturing fipronil-containing veterinary drugs. Larger epidemiological studies as well as investigations on possible thyroid-disrupting mechanisms of fipronil are also required.

DNA adduct variations in non-smoking crop farmers: potential relationship with occupational exposure to pesticides?

Genotoxic impact of the occupational exposure was measured in farmers from Normandy, France. White blood cell DNA-adduct levels were measured for 116 non-smoking French crop farmers, using the (32)P-postlabelling method. A single blood sample was collected per farmer, at a randomised period of the year. Significantly higher bulky DNA-adduct levels were observed for samples collected from April to July, compared with samples collected during the other months. Agricultural practices were not significantly different between these two groups of farmers, but interestingly, the mean and the median duration without exposure to pesticides were significantly shorter for farmers sampled between April and July. These data, obtained in a homogeneous population of farmers, indicate a genotoxic impact for a sub-group, with a potential association with the use of pesticides. From the rest of the group, this study also gives for the first time additional information on the background fluctuations of this biomarker over the year.

Pesticide exposure and lymphohaematopoietic cancers: a case-control study in an agricultural region (Larissa, Thessaly, Greece)

BACKGROUND

The causality of lymphohaematopoietic cancers (LHC) is multifactorial and studies investigating the association between chemical exposure and LHC have produced variable results. The aim of this study was to investigate the relationships between exposure to pesticides and LHC in an agricultural region of Greece.

METHODS

A structured questionnaire was employed in a hospital-based case control study to gather information on demographics, occupation, exposure to pesticides, agricultural practices, family and medical history and smoking. To control for confounders, backward conditional and multinomial logistic regression analyses were used. To assess the dose-response relationship between exposure and disease, the chi-square test for trend was used.

RESULTS

Three hundred and fifty-four (354) histologically confirmed LHC cases diagnosed from 2004 to 2006 and 455 sex- and age-matched controls were included in the study. Pesticide exposure was associated with total LHC cases (OR 1.46, 95% CI 1.05-2.04), myelodysplastic syndrome (MDS) (OR 1.87, 95% CI 1.00-3.51) and leukaemia (OR 2.14, 95% CI 1.09-4.20). A dose-response pattern was observed for total LHC cases (P = 0.004), MDS (P = 0.024) and leukaemia (P = 0.002). Pesticide exposure was independently associated with total LHC cases (OR 1.41, 95% CI 1.00 - 2.00) and leukaemia (OR 2.05, 95% CI 1.02-4.12) after controlling for age, smoking and family history (cancers, LHC and immunological disorders). Smoking during application of pesticides was strongly associated with total LHC cases (OR 3.29, 95% CI 1.81-5.98), MDS (OR 3.67, 95% CI 1.18-12.11), leukaemia (OR 10.15, 95% CI 2.15-65.69) and lymphoma (OR 2.72, 95% CI 1.02-8.00). This association was even stronger for total LHC cases (OR 18.18, 95% CI 2.38-381.17) when eating simultaneously with pesticide application.

CONCLUSIONS

Lymphohaematopoietic cancers were associated with pesticide exposure after controlling for confounders. Smoking and eating during pesticide application were identified as modifying factors increasing the risk for LHC. The poor pesticide work practices identified during this study underline the need for educational campaigns for farmers.

Risk factors of thyroid tumors: role of environmental and occupational exposures to chemical pollutants

BACKGROUND

The rising incidence of thyroid cancer observed during the last few decades in most western countries is explained in large part by increasing numbers of diagnoses due to changes in medical screening practices. However, beside radiation exposure, exposure to environmental chemicals may also play a role in thyroid cancer etiology and in the increased incidence. This paper presents the main chemicals suspected to induce thyroid tumorigenesis, and epidemiological results on the association between chemical exposure and thyroid tumors.

METHODS

We reviewed experimental studies to identify the main chemicals possibly involved in thyroid tumorigenesis. We also reviewed the main epidemiological studies investigating the association between environmental chemical exposure and thyroid neoplasm in humans.

RESULTS

Environmentally abundant chemicals may disrupt thyroid function and/or play a role in tumorigenesis through a variety of mechanisms. Epidemiological results provide insufficient evidence of a causal link between exposure to environmental chemicals and thyroid tumors, but raise the hypothesis of an increased risk of thyroid neoplasm for workers in the leather, wood, and paper industries, and those exposed to certain solvents and pesticides.

CONCLUSION

This paper highlights the need for large epidemiological studies evaluating the exposure to various groups of environmental chemicals and its impact on the thyroid gland.

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.

Ensuring long-term sustainability of existing cohorts remains the highest priority to inform cancer prevention and control

The case for continued follow-up of existing cohorts arises from the key attributes of cohorts that are already meeting the goals proposed by Potter for the creation of a new cohort. These attributes include the basic nature of ongoing cohorts in that they are, by design, hypothesis-driven and must adapt to emerging technologies over time. Importantly, cohort investigators must identify and address gaps in knowledge that will inform public health strategies and clinical practices. Above all, cohorts must capitalize on their unique features to address public health priorities and inform our prevention strategies. Continued follow-up adds substantial return on investment to guide cancer prevention.

The cytotoxic effects of the organophosphates chlorpyrifos and diazinon differ from their immunomodulating effects

Some organophosphate insecticides have immunomodulating capacities, but it is unknown whether different compounds within this class affect the immune system to the same extent. In this in vitro study, human immortalized T-lymphocytes or bronchial epithelial cells were treated with diazinon or chlorpyrifos in the absence or presence of cellular stress factors, thereby mimicking a stimulated immune system. Cytotoxicity was determined and cytokine release or cytokine-promoter studies were performed to study immunomodulatory effects of these chemicals, whereby the same concentrations of chlorpyrifos and diazinon were used. Results showed that chlor- pyrifos was cytotoxic at concentrations >/= 250 muM, whereas diazinon was not toxic at concentrations up to 1 mM. The immunomodulatory effects of these two compounds were similar for most cytokine promoters tested and induction of cellular stress enhanced these effects. The results were compared to data obtained with blood mononuclear cells, which confirmed the results of stably transfected cell lines, but refer to a higher sensitivity of primary cells. In conclusion, these two pesticides act in a different manner on cell viability and on some immune parameters, but cell viability was not linked to immunomodulation. The results also imply that healthy and diseased individuals are differentially affected by these pollutants.

Associations of common variants in genes involved in metabolism and response to exogenous chemicals with risk of multiple myeloma

BACKGROUND

We examined risk of multiple myeloma (MM) associated with variants in genes involved in metabolism and response to exogenous chemicals [cytochrome P450 enzymes (CYP1B1, CYP2C9), epoxide hydrolase (EPHX1), paraoxonase 1 (PON1), arylhydrocarbon hydroxylase receptor (AHR), and NAD(P)H:quinone oxidoreductase (NQO1)].

METHODS

This study included 279 MM cases and 782 controls in a pooled analysis of two population-based case-control studies. One common variant from each candidate gene was genotyped using DNA from blood or buccal cells. We estimated risk of MM associated with each genotype, controlling for race, gender, study site, and age, using odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Evaluations of the CYP1B1 V432L variant (rs1056836) suggested increased risk of MM among persons with the CG and GG genotypes compared to the CC genotype [OR (95% CI)=1.4 (1.0-2.0)]. Similar results were seen in analyses stratified by race and gender. We did not find any associations between MM and the CYP2C9, EPHX1, NQO1, or PON1 genes.

CONCLUSIONS

CYP1B1 activates chemicals such as polycyclic aromatic hydrocarbons and dioxins to create oxidized, reactive intermediates, and higher gene activity has been shown for the G allele. We conducted the largest analysis to date on MM and these genetic variants and our results provide preliminary evidence that variation in CYP1B1 may influence susceptibility to MM.

Performance of different work clothing types for reducing skin exposure to pesticides during open field treatment

The aim of this study was to estimate the performance of different work clothing types for reducing skin exposure to five pesticides (azinphos-methyl, terbutylazine, alachlor, dimethoate, and dicamba) in field distribution by tractor equipped with boom sprayer. Performance was assessed by measuring the penetration factors of different types of work clothing. The results show that the protection offered by personal protective equipment (PPE) was always >97%, whereas the performance of cotton garments ranged from 84.1% to 92.5%. The different cotton garments differed significantly in their permeability, and the upper part of the body was the anatomical region showing the greatest values of the penetration factors. These results confirm the necessity of using PPE properly to minimise dermal exposure to pesticides.

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.

Depression and pesticide exposures in female spouses of licensed pesticide applicators in the agricultural health study cohort

OBJECTIVE

This nested case-control study evaluated the association between depression and pesticide exposure among women.

METHODS

The study population included 29,074 female spouses of private pesticide applicators enrolled in the Agricultural Health Study between 1993 and 1997. Cases were women who had physician-diagnosed depression requiring medication. Lifetime pesticide use was categorized as never mixed/applied pesticides, low exposure (up to 225 days), high exposure (>225 days), and a history of diagnosed pesticide poisoning.

RESULTS

After adjustment for state, age, race, off-farm work, alcohol, cigarette smoking, physician visits, and solvent exposure, depression was significantly associated with a history of pesticide poisoning (odds ratio [OR] = 3.26; 95% confidence interval [CI] = 1.72-6.19) but not low (OR = 1.09; CI = 0.91-1.31) or high (OR = 1.09; 95% CI = 0.91-1.31) cumulative pesticide exposure.

CONCLUSION

Pesticide poisoning may contribute to risk of depression.