The role of agricultural pesticide use in the development of non-Hodgkin's lymphoma in women

Occupational Cancers among Employed Women: A Narrative Review

The facts that occupational cancer in women is under-investigated, with few in-depth analyses are well known. In recent decades the workforce has changed, with an increasing number of women employed. Therefore, the inclusion of women in occupational cancer studies has become more urgent and feasible than in the past decades. The difficulties to evaluate occupational causes of female gynecologic tumors in most past cohorts and the potential variation in outcome responses between men and women must be taken into consideration. This narrative review discusses women's occupational cancer as a current area of research, focusing on three groups of workers characterized by peculiar exposure to occupational carcinogens and where women are often employed: beauticians and hairdressers; farmers; and healthcare workers. We discuss the most relevant cancers in each working category, with a particular focus on female breast cancer. In the three industries reviewed in detail, there are some risk factors which may affect primarily women, inducing breast cancer and cervical cancer, as well as risk factors that are carcinogenic in both genders, but whose effects are less well known in women.

Why We Will Continue to Lose Our Battle with Cancers If We Do Not Stop Their Triggers from Environmental Pollution

Besides our current health concerns due to COVID-19, cancer is a longer-lasting and even more dramatic pandemic that affects almost a third of the human population worldwide. Most of the emphasis on its causes has been posed on genetic predisposition, chance, and wrong lifestyles (mainly, obesity and smoking). Moreover, our medical weapons against cancers have not improved too much during the last century, although research is in progress. Once diagnosed with a malignant tumour, we still rely on surgery, radiotherapy, and chemotherapy. The main problem is that we have focused on fighting a difficult battle instead of preventing it by controlling its triggers. Quite the opposite, our knowledge of the links between environmental pollution and cancer has surged from the 1980s. Carcinogens in water, air, and soil have continued to accumulate disproportionally and grow in number and dose, bringing us to today's carnage. Here, a synthesis and critical review of the state of the knowledge of the links between cancer and environmental pollution in the three environmental compartments is provided, research gaps are briefly discussed, and some future directions are indicated. New evidence suggests that it is relevant to take into account not only the dose but also the time when we are exposed to carcinogens. The review ends by stressing that more dedication should be put into studying the environmental causes of cancers to prevent and avoid curing them, that the precautionary approach towards environmental pollutants must be much more reactionary, and that there is an urgent need to leave behind the outdated petrochemical-based industry and goods production.

Residential Proximity to Intensive Animal Agriculture and Risk of Lymphohematopoietic Cancers in the Agricultural Health Study

BACKGROUND

Although occupational exposure to animals has been associated with lymphohematopoietic malignancies, to our knowledge no studies have evaluated adult cancer risks associated with living near intensive animal agriculture.

METHODS

We linked participants in the prospective Agricultural Health Study to permitted animal feeding operations in Iowa. We created metrics reflecting the intensity of animal exposures within 2 and 5 km of participants' residences, enumerating both total and inverse distance-weighted animal units (AUs), standardized by animal size and manure production. We estimated risk of lymphohematopoietic malignancies and subtypes [hazard ratio (HR), 95% confidence interval (95% CI)], adjusting for demographic and farming-related factors, including occupational pesticide exposure. We stratified associations by animal type and animal-related work activities.

RESULTS

We observed 519 cases (1993-2015) among 32,635 pesticide applicators and 211 cases among 19,743 spouses. Among applicators, no associations were evident within 2 km, but risk of any lymphohematopoietic cancer was elevated across quintiles of weighted AUs within 5 km. Risk of non-Hodgkin lymphoma (NHL) was elevated for the second (HR = 1.5; 95% CI, 1.1, 2.1), third (HR = 1.6; 95% CI, 1.1, 2.2), and fourth (HR = 1.7; 95% CI, 1.3, 2.4) highest quintiles of weighted AUs within 5 km (Ptrend = 0.52) and increased with dairy cattle AUs (Ptrend = 0.04). We found positive trends for leukemia and some NHL subtypes with increasing numbers of both beef and dairy cattle. Risks did not vary by animal-related work (Pinteraction = 0.61). Associations were similar using the total exposure metric and inconsistent among spouses.

CONCLUSION

Residential proximity to intensive animal agriculture was positively associated with risk of NHL and leukemia, even after consideration of occupational animal and pesticide exposures.

Organochlorine and organophosphorus pesticides and bladder cancer: A case-control study

BACKGROUND

Exposure to pesticides is associated with an increase in the incidence of cancer. We aimed to investigate the association of serum organochlorine pesticides (OCPs) and organophosphorus pesticides (OPs) levels and GSTM1/GSTT1 gene polymorphism with bladder cancer (BC).

METHODS

This study was performed on 57 patients with BC and 30 controls (C). Acetylcholinesterase (AChE) activity, arylesterase activity of paraoxonase-1 (ARE), total antioxidant capacity (TAC), and malondialdehyde (MDA) levels were determined in serums of all participants. Genomic DNA was extracted using the salting out method and GSTM1/GSTT1 gene polymorphisms were examined by multiplex polymerase chain reaction assay. Measurement of OCPs (α-hexachlorocyclohexane [α-HCH], β-HCH, γ-HCH, 2,4-dichlorodiphenyltrichloroethane [2,4-DDT], 4,4-DDT, 2,4- dichlorodiphenyldichloroethylene [2,4-DDE], and 4,4-DDE) in serum was carried out using an FID-equipped gas-chromatography system.

RESULTS

AChE activity was significantly lower, ARE activity and TAC were declined but it was not statistically significant, however, α-HCH, γ-HCH, 4,4-DDE, 2,4-DDT, and 4,4-DDT pesticides, and MDA were significantly higher in BC patients compared with the control subjects. Also, a positive correlation was found between the number of smoked cigarettes and the years of smoking with BC development. There was no association between GSTM1/GSTT1 gene polymorphisms and OCPs in BC patients.

CONCLUSION

Due to the higher levels of some OCPs in the BC patients, along with the reduction in AChE activity and increased MDA levels, it may be concluded that OCPs and OPs play an important role in the induction of BC in southeastern Iran.

The association between non-Hodgkin lymphoma and organophosphate pesticides exposure: A meta-analysis

Several epidemiological studies show the association between organophosphate pesticides (OPs) and the risk of non-Hodgkin lymphoma (NHL), yet various research results remain controversial. To explore the hazard of OPs exposure to human health, three kinds of OPs (Terbufos, Malathion, and Diazinon) that are non-halogenated aliphatic compounds were included in the meta-analysis. We searched PubMed and Web of Science Databases for articles published from 1985 to February 2017. The databases were also searched for eligible studies through a manual references search. The random-effect model was utilized to compute the odds ratios (ORs) and 95% confident intervals (CIs). A total of ten observational studies (five cohort, four case-control, and one nested case-control) were included in our meta-analysis, with a pooled OR of 1.22 (95% CI 1.04 to 1.43) of Malathion, Terbufos and Diazinion. The general heterogeneity for OR was moderate (P_h = 0.032, I² = 41.2%). The OR estimates in the subset analyses were utilized to compare the association between the three kinds of OPs and NHL; Terbufos (OR = 1.07, 95% CI 0.85 to 1.36) and Malathion (OR = 1.17, 95% CI 0.82 to 1.67) had a statistically non-significant relationship, whereas Diazinon (OR = 1.39, 95% CI 1.11 to 1.73) was significantly associated with an increased NHL risk. Because immune dysfunction was thought to increase NHL risk, the toxicity levels in the immune system of the three types of OPs were compared. Malathion attacked immune cells via a direct effect and Diazinon disrupted the neuro-immune system, which involves the cholinergic system of lymphocytes via indirect immune damage, whereas an immunotoxic effect involving Terbufos was not reported. Overall, the present meta-analysis indicated a statistically significant association between Diazinon exposure and NHL risk.

High pesticide exposure events and DNA methylation among pesticide applicators in the agricultural health study

Pesticide exposure has been associated with acute and chronic adverse health effects. DNA methylation (DNAm) may mediate these effects. We evaluated the association between experiencing unusually high pesticide exposure events (HPEEs) and DNAm among pesticide applicators in the Agricultural Health Study (AHS), a prospective study of applicators from Iowa and North Carolina. DNA was extracted from whole blood from male AHS pesticide applicators (n = 695). Questionnaire data were used to ascertain the occurrence of HPEEs over the participant's lifetime. Pyrosequencing was used to quantify DNAm in CDH1, GSTp1, and MGMT promoters, and in the repetitive element, LINE-1. Linear and robust regression analyses evaluated adjusted associations between HPEE and DNAm. Ever having an HPEE (n = 142; 24%) was associated with elevated DNAm in the GSTp1 promoter at CpG7 (chr11:67,351,134; P < 0.01) and for the mean across the CpGs measured in the GSTp1 promoter (P < 0.01). In stratified analyses, elevated GSTP1 promoter DNAm associated with HPEE was more pronounced among applicators >59 years and those with plasma folate levels ≤16.56 ng/mL (p-interaction <0.01); HPEE was associated with reduced MGMT promoter DNAm at CpG2 (chr10:131,265,803; P = 0.03), CpG3 (chr10:131,265,810; P = 0.05), and the mean across CpGs measured in the MGMT promoter (P = 0.03) among applicators >59 years and reduced LINE-1 DNAm (P = 0.05) among applicators with ≤16.56 ng/mL plasma folate. Non-specific HPEEs may contribute to increased DNAm in GSTp1, and in some groups, reduced DNAm in MGMT and LINE-1. The impacts of these alterations on disease development are unclear, but elevated GSTp1 promoter DNAm and subsequent gene inactivation has been consistently associated with prostate cancer. Environ. Mol. Mutagen. 58:19-29, 2017. © 2016 Wiley Periodicals, Inc.

Insecticide exposure and farm history in relation to risk of lymphomas and leukemias in the Women's Health Initiative observational study cohort

PURPOSE

Relationships of farm history and insecticide exposure at home or work with lymphohematopoietic (LH) neoplasm risk were investigated in a large prospective cohort of US women.

METHODS

In questionnaires, women self-reported history living or working on a farm, personally mixing or applying insecticides, insecticide application in the home or workplace by a commercial service, and treating pets with insecticides. Relationships with non-Hodgkin lymphoma (NHL), chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, plasma cell neoplasms, and myeloid leukemia were investigated using Cox proportional hazard models. Age and farming history were explored as effect modifiers.

RESULTS

The analysis included 76,493 women and 822 NHL cases. Women who ever lived or worked on a farm had 1.12 times the risk of NHL (95% confidence interval [CI] = 0.95-1.32) compared to those who did not. Women who reported that a commercial service ever applied insecticides in their immediate surroundings had 65% higher risk of CLL/SLL (95% CI = 1.15-2.38). Women aged less than 65 years who ever applied insecticides had 87% higher risk of DLBCL (95% CI = 1.13-3.09).

CONCLUSIONS

Insecticide exposures may contribute to risk of CLL/SLL and DLBCL. Future studies should examine relationships of LH subtypes with specific types of household insecticides.

Investing in prospective cohorts for etiologic study of occupational exposures

Prospective cohorts have played a major role in understanding the contribution of diet, physical activity, medical conditions, and genes to the development of many diseases, but have not been widely used for occupational exposures. Studies in agriculture are an exception. We draw upon our experience using this design to study agricultural workers to identify conditions that might foster use of prospective cohorts to study other occupational settings. Prospective cohort studies are perceived by many as the strongest epidemiologic design. It allows updating of information on exposure and other factors, collection of biologic samples before disease diagnosis for biomarker studies, assessment of effect modification by genes, lifestyle, and other occupational exposures, and evaluation of a wide range of health outcomes. Increased use of prospective cohorts would be beneficial in identifying hazardous exposures in the workplace. Occupational epidemiologists should seek opportunities to initiate prospective cohorts to investigate high priority, occupational exposures.

Non-Hodgkin lymphoma and occupational exposure to agricultural pesticide chemical groups and active ingredients: a systematic review and meta-analysis

This paper describes results from a systematic review and a series of meta-analyses of nearly three decades worth of epidemiologic research on the relationship between non-Hodgkin lymphoma (NHL) and occupational exposure to agricultural pesticide active ingredients and chemical groups. Estimates of associations of NHL with 21 pesticide chemical groups and 80 active ingredients were extracted from 44 papers, all of which reported results from analyses of studies conducted in high-income countries. Random effects meta-analyses showed that phenoxy herbicides, carbamate insecticides, organophosphorus insecticides and the active ingredient lindane, an organochlorine insecticide, were positively associated with NHL. In a handful of papers, associations between pesticides and NHL subtypes were reported; B cell lymphoma was positively associated with phenoxy herbicides and the organophosphorus herbicide glyphosate. Diffuse large B-cell lymphoma was positively associated with phenoxy herbicide exposure. Despite compelling evidence that NHL is associated with certain chemicals, this review indicates the need for investigations of a larger variety of pesticides in more geographic areas, especially in low- and middle-income countries, which, despite producing a large portion of the world's agriculture, were missing in the literature that were reviewed.

Atrazine and cancer: a review of the epidemiologic evidence

The aim of this study was to evaluate the conflicting reports from the Environmental Protection Agency and the Scientific Advisory Panel (Panel) on the carcinogenicity of atrazine in order to determine whether the results from epidemiologic studies support a causal relationship between atrazine and any specific cancer. We reviewed the Environmental Protection Agency and Panel reports in the context of all the epidemiologic studies on the specific cancers of interest. A weight-of-evidence approach leads to the conclusion that there is no causal association between atrazine and cancer and that occasional positive results can be attributed to bias or chance. Atrazine appears to be a good candidate for a category of herbicides with a probable absence of cancer risk. Atrazine should be treated for regulatory and public health purposes as an agent unlikely to pose a cancer risk to humans.

Non-hodgkin's lymphoma and work in agriculture: Results of a two case-control studies in Saskatchewan, Canada

OBJECTIVES

The objective was to examine the association between non-Hodgkin's lymphoma (NHL) and farming-related activities, gender, pesticides exposure, and exposure to chemicals other than pesticides in Saskatchewan.

MATERIALS AND METHODS

Male and female study participants were taken from two separate case-control studies conducted in Saskatchewan province, Canada. A case was defined as any man or woman aged 19 years and older with a first diagnosis of NHL registered by the Saskatchewan Cancer Agency during the study period. Conditional logistic regression was used to fit the statistical models.

RESULTS

Farming exposure and exposure to pesticides-contaminated cloths were related to an increased risk of NHL. Exposure to pesticides was strongly associated with an increased risk of NHL, especially for men.

CONCLUSION

For men, the incidence of NHL was associated with exposure to pesticides after adjusting for other independent predictors.

Pesticides and human chronic diseases: evidences, mechanisms, and perspectives

Along with the wide use of pesticides in the world, the concerns over their health impacts are rapidly growing. There is a huge body of evidence on the relation between exposure to pesticides and elevated rate of chronic diseases such as different types of cancers, diabetes, neurodegenerative disorders like Parkinson, Alzheimer, and amyotrophic lateral sclerosis (ALS), birth defects, and reproductive disorders. There is also circumstantial evidence on the association of exposure to pesticides with some other chronic diseases like respiratory problems, particularly asthma and chronic obstructive pulmonary disease (COPD), cardiovascular disease such as atherosclerosis and coronary artery disease, chronic nephropathies, autoimmune diseases like systemic lupus erythematous and rheumatoid arthritis, chronic fatigue syndrome, and aging. The common feature of chronic disorders is a disturbance in cellular homeostasis, which can be induced via pesticides' primary action like perturbation of ion channels, enzymes, receptors, etc., or can as well be mediated via pathways other than the main mechanism. In this review, we present the highlighted evidence on the association of pesticide's exposure with the incidence of chronic diseases and introduce genetic damages, epigenetic modifications, endocrine disruption, mitochondrial dysfunction, oxidative stress, endoplasmic reticulum stress and unfolded protein response (UPR), impairment of ubiquitin proteasome system, and defective autophagy as the effective mechanisms of action.

Classification of non-Hodgkin lymphoma in Central and South America: a review of 1028 cases

The distribution of non-Hodgkin lymphoma (NHL) subtypes differs around the world but a systematic study of Latin America has not been done. Therefore, we evaluated the relative frequencies of NHL subtypes in Central and South America (CSA). Five expert hematopathologists classified consecutive cases of NHL from 5 CSA countries using the WHO classification and compared them to 400 cases from North America (NA). Among the 1028 CSA cases, the proportions of B- and T-cell NHL and the sex distribution were similar to NA. However, the median age of B-cell NHL in CSA (59 years) was significantly lower than in NA (66 years; P < .0001). The distribution of high-grade (52.9%) and low-grade (47.1%) mature B-cell NHL in CSA was also significantly different from NA (37.5% and 62.5%; P < .0001). Diffuse large B-cell lymphoma was more common in CSA (40%) than in NA (29.2%; P < .0001), whereas the frequency of follicular lymphoma was similar in Argentina (34.1%) and NA (33.8%), and higher than the rest of CSA (17%; P < .001). Extranodal NK/T-cell NHL was also more common in CSA (P < .0001). Our study provides new objective evidence that the distribution of NHL subtypes varies significantly by geographic region and should prompt epidemiologic studies to explain these differences.

Genome-wide study of DNA methylation alterations in response to diazinon exposure in vitro

Pesticide exposure has repeatedly been associated with cancers. However, molecular mechanisms are largely undetermined. In this study, we examined whether exposure to diazinon, a common organophosphate that has been associated with cancers, could induce DNA methylation alterations. We conducted genome-wide DNA methylation analyses on DNA samples obtained from human hematopoietic K562 cell exposed to diazinon and ethanol using the Illumina Infinium HumanMethylation27 BeadChip. Bayesian-adjusted t-tests were used to identify differentially methylated gene promoter CpG sites. We identified 1069 CpG sites in 984 genes with significant methylation changes in diazinon-treated cells. Gene ontology analysis demonstrated that some genes are tumor suppressor genes, such as TP53INP1 (3.0-fold, q-value <0.001) and PTEN (2.6-fold, q-value <0.001), some genes are in cancer-related pathways, such as HDAC3 (2.2-fold, q-value=0.002), and some remain functionally unknown. Our results provided direct experimental evidence that diazinon may modify gene promoter DNA methylation levels, which may play a pathological role in cancer development.

Atrazine and cancer incidence among pesticide applicators in the agricultural health study (1994-2007)

BACKGROUND

Atrazine is a triazine herbicide used widely in the United States. Although it is an animal carcinogen, the mechanism in rodents does not appear to operate in humans. Few epidemiologic studies have provided evidence for an association.

METHODS

The Agricultural Health Study (AHS) is a prospective cohort that includes 57,310 licensed pesticide applicators. In this report, we extend a previous AHS analysis of cancer risk associated with self-reported atrazine use with six additional years of follow-up and more than twice as many cancer cases. Using Poisson regression, we calculated relative risk estimates and 95% confidence intervals for lifetime use of atrazine and intensity-weighted lifetime days, which accounts for factors that impact exposure.

RESULTS

Overall, 36,357 (68%) of applicators reported using atrazine, among whom there were 3,146 cancer cases. There was no increase among atrazine users in overall cancer risk or at most cancer sites in the higher exposure categories compared with the lowest. Based on 29 exposed cases of thyroid cancer, there was a statistically significant risk in the second and fourth quartiles of intensity-weighted lifetime days. There was a similar pattern for lifetime days, but neither the risk estimates nor the trend were statistically significant and for neither metric was the trend monotonic.

CONCLUSIONS

Overall, there was no consistent evidence of an association between atrazine use and any cancer site. There was a suggestion of increased risk of thyroid cancer, but these results are based on relatively small numbers and minimal supporting evidence.

Should atrazine and related chlorotriazines be considered carcinogenic for human health risk assessment?

Chloro-s-triazines have been a mainstay of preemergent pesticides for a number of decades and have generally been regarded as having low human toxicity. Atrazine, the major pesticide in this class, has been extensively studied. In a number of experimental studies, exposure to high doses of atrazine resulted in increased weight loss not attributable to decreased food intake. Chronic studies of atrazine and simazine and their common metabolites show an elevated incidence of mammary tumors only in female Sprague Dawley (SD) rats. On the basis of the clear tumor increase in female SD rats, atrazine was proposed to be classified as a likely human carcinogen by US Environmental Protection Agency (EPA) in 1999. With Fischer rats, all strains of mice, and dogs, there was no evidence of increased incidence of atrazine-associated tumors of any type. Evidence related to the pivotal role of hormonal control of the estrus cycle in SD rats appears to indicate that the mechanism for mammary tumor induction is specific to this strain of rats and thus is not relevant to humans. In humans the menstrual cycle is controlled by estrogen released by the ovary rather than depending on the LH surge, as estrus is in SD rats. However, the relevance of the tumors to humans continues to be debated based on endocrine effects of triazines. No strong evidence exists for atrazine mutagenicity, while there is evidence of clastogenicity at elevated concentrations. Atrazine does not appear to interact strongly with estrogen receptors α or β but may interact with putative estrogen receptor GPR30 (G-protein-coupled receptor). A large number of epidemiologic studies conducted on manufacturing workers, pesticide applicators, and farming families do not indicate that triazines are carcinogenic in these populations. A rat-specific hormonal mechanism for mammary tumors has now been accepted by US EPA, International Agency for Research on Cancer, and the European Union. Chlorotriazines do influence endocrine responses, but their potential impact on humans appears to be primarily on reproduction and development and is not related to carcinogenesis.

The non-Hodgkin lymphomas: a review of the epidemiologic literature

The non-Hodgkin lymphomas (NHL) are a heterogeneous group of B-cell and T-cell neoplasms that arise primarily in the lymph nodes. NHL incidence rates in the US doubled between about 1970 and 1990, and stabilized during the 1990s. NHL accounts for approximately 3.4% of cancer deaths in the US. Although some of the observed patterns in NHL have been related to HIV/AIDS, these conditions cannot fully explain the magnitude of the changes; neither do changes in classification systems nor improved diagnostic capabilities. Studies of occupational and environmental exposures (e.g., pesticides, solvents) have produced no consistent pattern of significant positive associations. Inverse associations with ultraviolet radiation exposure and alcohol and fish intake, and positive associations with meat and saturated fat intake have been reported in several studies; additional studies are needed to confirm or refute these associations. Family history of NHL or other hematolympho-proliferative cancers and personal history of several autoimmune disorders are associated with increased risk of NHL, but are not likely to account for a large proportion of cases. HIV and other infectious agents, such as human herpesvirus 8 and Epstein-Barr, appear to be associated with differing types of NHL, such as some B-cell lymphomas. Future epidemiologic studies should evaluate associations by NHL type, enhance exposure information collected, and elucidate factors that may identify susceptible (or resistant) subpopulations because of genetic, immunologic or other characteristics. The extent to which the etiology of NHL types may differ is important to resolve in ongoing and future studies.

Polychlorinated Biphenyl Levels in Peripheral Blood and Non-Hodgkin's Lymphoma: A Report from Three Cohorts

The incidence of non-Hodgkin's lymphoma (NHL) unrelated to HIV infection has steadily increased over the past several decades and remains substantially unexplained. Limited evidence suggests that increased concentrations of polychlorinated biphenyls (PCB) measured in blood or fat tissue are associated with increased risk of NHL. Although PCB congeners vary in their biological activity, the relation between individual congeners and NHL risk has not been examined previously using prospectively collected biospecimens. We examined congener-specific associations in three prospective cohorts. Prediagnostic serum or plasma concentrations of selected PCB congeners were measured among NHL cases and controls from these cohorts: Janus (190 cases and 190 controls) in Norway and CLUE I (74 cases and 147 controls) and the Nurses' Health Study (30 cases and 78 controls) in the United States. All blood samples were collected in the 1970s or 1980s. We used logistic regression to calculate odds ratios (OR) and 95% confidence intervals (95% CI) for the relations between risk of NHL and lipid-corrected plasma or serum concentrations. Several congeners (i.e., 118, 138, and 153) that were present at higher levels and were moderately to highly correlated with each other showed exposure-response trends with risk of NHL in all three cohorts. These associations were observed primarily among subjects diagnosed closer to the date of blood collection in the two cohorts with sufficient cases to permit stratification by time. Among cases diagnosed within the median years of follow-up (16 years in Janus and 12 years in CLUE I), ORs and 95% CIs for increasing fourths of concentration of congener 118 relative to the lowest fourth were as follows: 2.4 (0.9-6.5), 4.9 (1.6-15.3), and 5.3 (1.5-18.8; P(trend) < 0.005) in Janus and 8.1 (1.0-68.9), 6.6 (0.7-59.0), and 13.0 (1.6-106.8; P(trend) < 0.05) in CLUE I. Similar patterns were seen for congeners 138 and 153 and for total PCBs. Limited evidence of exposure-response trends was also observed for several other congeners. The primary 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane metabolite, p,p'-DDE, was not significantly associated with NHL in most analyses but slightly to moderately confounded the PCB associations. The results from these three cohorts suggest that concentrations of certain PCBs in blood are associated with increased risk of NHL.

Fonofos exposure and cancer incidence in the agricultural health study

BACKGROUND

The Agricultural Health Study (AHS) is a prospective cohort study of licensed pesticide applicators from Iowa and North Carolina enrolled 1993-1997 and followed for incident cancer through 2002. A previous investigation in this cohort linked exposure to the organophosphate fonofos with incident prostate cancer in subjects with family history of prostate cancer.

OBJECTIVES

This finding along with findings of associations between organophosphate pesticides and cancer more broadly led to this study of fonofos and risk of any cancers among 45,372 pesticide applicators enrolled in the AHS.

METHODS

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.

RESULTS

Relative to the unexposed, leukemia risk was elevated in the highest category of lifetime (RR = 2.24; 95% CI, 0.94-5.34, Ptrend = 0.07) and intensity-weighted exposure-days (RR = 2.67; 95% CI, 1.06-6.70, Ptrend = 0.04), a measure that takes into account factors that modify pesticide exposure. Although prostate cancer risk was unrelated to fonofos use overall, among applicators with a family history of prostate cancer, we observed a significant dose-response trend for lifetime exposure-days (Ptrend = 0.02, RR highest tertile vs. unexposed = 1.77, 95% CI, 1.03-3.05; RRinteraction = 1.28, 95% CI, 1.07-1.54). Intensity-weighted results were similar. No associations were observed with other examined cancer sites.

CONCLUSIONS

Further study is warranted to confirm findings with respect to leukemia and determine whether genetic susceptibility modifies prostate cancer risk from pesticide exposure.

8-Hydroxydeoxyguanosine levels in human leukocyte and urine according to exposure to organophosphorus pesticides and paraoxonase 1 genotype

OBJECTIVE

In order to investigate a role of paraoxonase 1 (PON1) polymorphism in organophosphorus (OP)-induced 8-hydroxydeoxyguanosine (8-OHdG) levels, urinary metabolites of OP, PON1 genotypes, and 8-OHdG levels in leukocyte and urine were measured in OP indoor insecticide sprayers and controls in summer and winter.

METHODS

The study population contained 18 male sprayers and age-matched 18 male controls. Sprayers were primarily exposed to OP insecticides (mainly fenitrothion, dichlorvos, chlorpyrifos, and diazinon), and partially to pyrethroids (mainly permethrin) and carbamates (mainly propoxur). Urinary metabolites of OP were measured by gas chromatography-mass spectrometry. 8-OHdG levels in leukocyte and urine were measured by ELISA kit. PON1 genotype was identified using allele-specific fluorogenic TaqMan probes.

RESULTS

The mean concentrations of urinary dimethyl phosphate (DMP) and total dialkyl phosphates (DAP) in summer and those of 8-OHdG in summer and winter were significantly higher in OP sprayers than controls. This resulted in a significant positive correlation between 8-OHdG levels and urinary DMP or DAP, suggesting a correlation between OP metabolites and production of oxidative stress. Of PON1 genotypes, incidences of Q/Q, Q/R, and R/R types were 17, 39, and 44% in OP sprayers and controls, respectively. Although PON1 polymorphism did not contribute to the leukocyte and urinary 8-OHdG levels, the urinary OP metabolite concentrations in summer showed a significant decrease as the number Q allele decreased.

CONCLUSION

These results indicate that an increase in OP metabolites is associated with a high level of oxidative stress in OP sprayers, although the contribution of the PON1 polymorphism to the metabolism of OP is still unclear.

Agricultural pesticide use and risk of t(14;18)-defined subtypes of non-Hodgkin lymphoma

Pesticides have been specifically associated with the t(14;18)(q32;q21) chromosomal translocation. To investigate whether the association between pesticides and risk of non-Hodgkin lymphoma (NHL) differs for molecular subtypes of NHL defined by t(14; 18) status, we obtained 175 tumor blocks from case subjects in a population-based case-control study conducted in Nebraska between 1983 and 1986. The t(14;18) was determined by interphase fluorescence in situ hybridization in 172 of 175 tumor blocks. We compared exposures to insecticides, herbicides, fungicides, and fumigants in 65 t(14;18)-positive and 107 t(14;18)-negative case subjects with those among 1432 control subjects. Multivariate polytomous logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Compared with farmers who never used pesticides, the risk of t(14;18)-positive NHL was significantly elevated among farmers who used animal insecticides (OR = 2.6; 95% CI, 1.0-6.9), crop insecticides (OR = 3.0; 95% CI, 1.1-8.2), herbicides (OR = 2.9; 95% CI, 1.1-7.9), and fumigants (OR = 5.0; 95% CI, 1.7-14.5). None of these pesticides were associated with t(14;18)-negative NHL. The risk of t(14;18)-positive NHL associated with insecticides and herbicides increased with longer duration of use. We conclude that insecticides, herbicides, and fumigants were associated with risk of t(14;18)-positive NHL but not t(14;18)-negative NHL. These results suggest that defining subsets of NHL according to t(14;18) status is a useful approach for etiologic research.

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.

Residential Insecticide Use and Risk of Non-Hodgkin's Lymphoma

Previous studies have linked non-Hodgkin's lymphoma (NHL) with occupational exposure to insecticides, but residential use is largely unexplored. In this population-based case-control study, we examined NHL risk and use of insecticides in the home and garden. We identified NHL cases, uninfected with HIV, diagnosed between 1998 and 2000 among women and men ages 20 to 74 years in Iowa and the metropolitan areas of Los Angeles, Detroit, and Seattle. Controls were selected using random digit dialing or Medicare files. Computer-assisted personal interviews (1,321 cases and 1,057 controls) elicited data on insecticide use at each home occupied since 1970. Insecticide levels were measured in dust taken from used vacuum cleaner bags (682 cases and 513 controls). We previously reported a positive association with dichlorodiphenyldichloroethylene levels in carpet dust residues. Here, we focus on insecticides that were commonly used after 1970, the time period covered by our questionnaire. People whose homes were treated for termites had elevated NHL risk (odds ratio, 1.3; 95% confidence interval, 1.0-1.6). Risk was modestly, although not significantly, elevated in all but one study center and in all sexes and races. The elevation in risk was restricted to people whose homes were treated before the 1988 chlordane ban. There was a significant trend of increasing risk with increasing levels of alpha-chlordane residues in dust (P(trend) = 0.04) and a marginally significant trend for gamma-chlordane (P(trend) = 0.06). We found no evidence of associations for insects overall, for specific types of insects other than termites, or for elevated residues of other insecticides. We concluded that chlordane treatment of homes for termites may increase residents' NHL risk.

Triazine Herbicides and Epithelial Ovarian Cancer Risk in Central California

OBJECTIVE

We sought to determine whether women with ovarian cancer have increased occupational exposure to triazine herbicides.

METHODS

A population-based case-control study of incident cases (n=256) and random digit-dialed control subjects (n=1122) was conducted. Participants were administered telephone interviews to obtain agricultural work history. These histories were used with the statewide pesticide usage database to calculate cumulative exposure estimates. The data were analyzed by stratified analysis and unconditional logistic regression techniques.

RESULTS

The analysis of ever versus never occupational exposure to triazines demonstrated that cases were slightly but not significantly more likely to be exposed than control subjects (adjusted odds=1.34; 95% confidence interval=0.77-2.33). There was no evidence of a dose-response relationship between triazines and ovarian cancer (P=0.22).

CONCLUSIONS

Considered with previous studies and animal laboratory data, the current evidence is not persuasive as to the presence or absence of an association between ovarian cancer and triazine exposure.

Organochlorines in Carpet Dust and Non-Hodgkin Lymphoma

BACKGROUND

The incidence of non-Hodgkin lymphoma (NHL) has risen over the past several decades. Reasons for this increase are largely unexplained.

METHODS

In this population-based case-control study, we examined NHL risk and exposure to organochlorine compounds using concentrations in carpet dust as an exposure indicator. We identified NHL cases, uninfected with HIV, diagnosed between 1998 and 2000 among women and men ages 20-74 years in Iowa, Los Angeles County, and the Detroit and Seattle metropolitan areas. Controls were selected using random-digit-dialing or Medicare files. Organochlorine concentrations were measured in vacuum bag dust from 603 white cases and 443 white controls who had owned most of their carpets for at least 5 years.

RESULTS

NHL risk was elevated if any of the polychlorinated biphenyl (PCB) congeners (PCBs 105, 138, 153, 170, or 180) was detected (odds ratio = 1.5; 95% confidence interval = 1.2-2.0). Risk was elevated in the top tertile of PCB 180 (1.7; 1.1-2.6) and in the top 2 tertiles of total PCBs (middle tertile, 1.6 [1.1-2.4]; top tertile 1.5 [1.0-2.2]). There was a positive trend in risk with increasing PCB 180 levels (P trend = 0.03). NHL risk was elevated if dichlorodiphenyldichloroethylene (DDE) was detected (1.3; 1.0-1.7), but only among men. A positive, but not monotonic, dose-response relationship was observed for DDE (P trend = 0.02).

CONCLUSIONS

Our findings suggest an increased risk of NHL associated with exposure to PCBs, with evidence of greater effects for PCB 180. There is also some evidence of an association with DDE.

Herbicides and nitrates in groundwater of Maryland and childhood cancers: a geographic information systems approach

This hypothesis-generating study explores spatial patterns of childhood cancers in Maryland and investigates their potential associations with herbicides and nitrates in groundwater. The Maryland Cancer Registry (MCR) provided data for bone and brain cancers, leukemia, and lymphoma, for ages 0-17, during the years 1992-1998. Cancer clusters and relative risks generated in the study indicate higher relative risk areas and potential clusters in several counties. Contingency table analysis indicates a potential association with several herbicides and nitrates. Cancer rates for the four types have a crude odds ratio (OR) = 1.10 (0.78-1.56) in relationship to atrazine, and an OR = 1.54 (1.14-2.07) for metolachlor. Potential association to mixtures of three compounds give an OR = 7.56 (4.16-13.73). A potential association is indicated between leukemia and nitrates, OR = 1.81 (1.35-2.42), and bone cancer with metolachlor, OR = 2.26 (0.97-5.24). These results give insight to generate a hypothesis of the potential association between exposure to these herbicides and nitrates and specific types of childhood cancer.

Cancer Incidence Among Pesticide Applicators Exposed to Atrazine in the Agricultural Health Study

BACKGROUND

Atrazine is the most heavily applied agricultural pesticide for crop production in the United States. Both animal and human studies have suggested that atrazine is possibly carcinogenic, but results have been mixed. We evaluated cancer incidence in atrazine-exposed pesticide applicators among 53,943 participants in the Agricultural Health Study, a prospective cohort study of licensed pesticide applicators in Iowa and North Carolina.

METHODS

We obtained detailed pesticide exposure information using a self-administered questionnaire completed at the time of enrollment (1993-1997). Cancer incidence was followed through December 31, 2001. We used adjusted Poisson regression to calculate rate ratios (RRs) and 95% confidence intervals (CIs) of multiple types of cancer among atrazine exposed applicators. P(trend) values were calculated using atrazine exposure as a continuous variable, and all statistical tests were two-sided. Two exposure metrics were used: quartiles of lifetime days of exposure and quartiles of intensity-weighted lifetime days of exposure.

RESULTS

36,513 (68%) applicators reported ever using atrazine; exposure was not associated with overall cancer incidence. Comparisons of cancer incidence in applicators with the highest atrazine exposure and those with the lowest exposure, assessed by lifetime days (RR(LD)) and intensity-weighted lifetime days (RR(IWLD)) of exposure yielded the following results: prostate cancer, RR(LD) = 0.88, 95% CI = 0.63 to 1.23, P(trend) =.26, and RR(IWLD) = 0.89, 95% CI = 0.63 to 1.25, P(trend) =.35; lung cancer, RR(LD) = 1.91, 95% CI = 0.93 to 3.94, P(trend) =.08, and RR(IWLD) = 1.37, 95% CI = 0.65 to 2.86, P(trend) =.19; bladder cancer, RR(LD) = 3.06, 95% CI = 0.86 to 10.81, P(trend) =.18, and RR(IWLD) = 0.85, 95% CI = 0.24 to 2.94, P(trend) =.71; non-Hodgkin lymphoma, RR(LD) = 1.61, 95% CI = 0.62 to 4.16, P(trend) =.35, and RR(IWLD) = 1.75, 95% CI = 0.73 to 4.20, P(trend) =.14; and multiple myeloma, RR(LD) = 1.60, 95% CI = 0.37 to 7.01, P(trend) =.41, and RR(IWLD) = 2.17, 95% CI = 0.45 to 10.32, P(trend) =.21.

CONCLUSIONS

Our analyses did not find any clear associations between atrazine exposure and any cancer analyzed. However, further studies are warranted for tumor types in which there was a suggestion of trend (lung, bladder, non-Hodgkin lymphoma, and multiple myeloma).

Pesticide product use and risk of non-Hodgkin lymphoma in women

A population-based, incidence case-control study was conducted among women in upstate New York to determine whether pesticide exposure is associated with an increase in risk of non-Hodgkin lymphoma (NHL) among women. The study involved 376 cases of NHL identified through the State Cancer Registry and 463 controls selected from the Medicare beneficiary files and state driver's license records. Information about history of farm work, history of other jobs associated with pesticide exposure, use of common household pesticide products, and potential confounding variables was obtained by telephone interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using an unconditional logistic regression model. The risk of NHL was doubled (OR = 2.12; 95% CI, 1.21-3.71) among women who worked for at least 10 years at a farm where pesticides were reportedly used. When both farming and other types of jobs associated with pesticide exposure were combined, there was a progressive increase in risk of NHL with increasing duration of such work (p = 0.005). Overall cumulative frequency of use of household pesticide products was positively associated with risk of NHL (p = 0.004), which was most pronounced when they were applied by subjects themselves. When exposure was analyzed by type of products used, a significant association was observed for mothballs. The associations with both occupational and household pesticides were particularly elevated if exposure started in 1950-1969 and for high-grade NHL. Although the results of this case-control study suggest that exposure to pesticide products may be associated with an increased risk of NHL among women, methodologic limitations related to selection and recall bias suggest caution in inferring causation.

Risk of Non-Hodgkin's Lymphoma and Family History of Lymphatic, Hematologic, and Other Cancers

Background: An elevated risk of developing non-Hodgkin's lymphoma (NHL) has been associated with a family history of NHL and several other malignancies, but the magnitude of risks and mechanisms are uncertain. Methods: We used self-reported family history data from a recent multicenter U.S.-based case-control studies of NHL to evaluate familial aggregation of NHL with various hematolymphoproliferative and other cancers. Estimates of familial aggregation were obtained as hazard ratios (HR) that compare incidence of different cancers in first-degree relatives of NHL cases with that in the first-degree relatives of NHL controls. Limitations of the study included low participation rates (76% for cases and 52% for controls) and potential differential accuracy of recall. Results: Risk of NHL was elevated in relatives of NHL cases [HR, 2.9; 95% confidence interval (95% CI), 0.95–8.53]; the aggregation seems to be stronger for siblings (HR, 7.6; 95% CI, 0.98–58.8) and for male relatives (HR, 6.2; 95% CI, 0.77–50.0). Risk of Hodgkin's lymphoma seems to be also elevated among relatives of early-onset (&lt;50 years) NHL cases (HR, 3.2; 95% CI, 0.88–11.6). Evaluation of family history of other cancers provided modest evidence for an increased risk of melanoma of the skin (HR, 2.9; 95% CI, 1.08–7.75), pancreatic cancer (HR, 2.1; 95% CI, 0.96–4.43), stomach cancer (HR, 1.8; 95% CI, 0.91–3.63), and prostate cancer (HR, 1.3; 95% CI, 0.87–1.99). Conclusions: These results are consistent with previous findings of familial aggregation of NHL, Hodgkin's lymphoma, and a few other cancers. The pattern of male-specific and sibling-specific familial aggregation of NHL we observed, if confirmed, may shed new light on the possible mechanisms that underlie familial aggregation of the disease.

Adipose tissue levels of organochlorine pesticides and polychlorinated biphenyls and risk of non-Hodgkin's lymphoma

In this nested case-control study we examined the relationship between non-Hodgkin's lymphoma (NHL) and organochlorine pesticide exposure. We used a data set originally collected between 1969 and 1983 in the U.S. Environmental Protection Agency National Human Adipose Tissue Survey. Adipose samples were randomly collected from cadavers and surgical patients, and levels of organochlorine pesticide residues were determined. From the original study population, 175 NHL cases were identified and matched to 481 controls; 173 controls were selected from accident victims, and 308 from cases with a diagnosis of myocardial infarction. Cases and controls were mainly from cadavers (> 96%) and were matched on sex, age, region of residence within the United States, and race/ethnicity. Conditional logistic regression showed the organochlorine pesticide residue heptachlor epoxide to be significantly associated with NHL [compared with the lowest quartile: third quartile odds ratio (OR) = 1.82, 95% confidence interval (CI), 1.01-3.28; fourth quartile OR = 3.41, 95% CI, 1.89-6.16]. The highest quartile level of dieldrin was also associated with elevated NHL risk (OR = 2.70; 95% CI, 1.58-4.61), as were higher levels of oxychlordane, p,p'-DDE [p,p'-1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], and ss-benzene hexachloride (ORs = 1.79, 1.99, and 2.47, respectively). The p-values for trends for these associations were significant. In models containing pairs of pesticides, only heptachlor epoxide and dieldrin remained significantly associated with risk of NHL. Limitations of this study include collection of samples after diagnosis and a lack of information on variables affecting organochlorine levels such as diet, occupation, and body mass index. Given the persistence of pesticides in the environment, these findings are still relevant today.

Agricultural Pesticide Use, Familial Cancer, and Risk of Non-Hodgkin Lymphoma

To investigate whether the association between agricultural pesticide use and the risk of non-Hodgkin's lymphoma (NHL) is modified by a family history of hematopoietic cancer, including leukemia, myeloma, and lymphoma, we analyzed pooled data on white men from three population-based, case-control studies of NHL conducted in Iowa/Minnesota, Kansas, and Nebraska. Information on the agricultural use of insecticides, fungicides, and herbicides; a family history of cancer; and other risk factors was obtained by interviewing 973 cases and 2,853 controls or, if deceased, their next-of-kin (37% of cases, 43% of controls). The NHL risk was estimated by odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for age, state of residence, type of respondent, and use of hair dye. Compared to men with no family history of cancer, the ORs (95% CIs) of NHL was 1.5 (1.3–1.8) for men with a family history of nonhematopoietic cancer, and 2.7 (1.9–3.7) for those with a history of hematopoietic cancer among first-degree relatives. This positive association was noted for each group of NHL defined according to the Working Formulation, and was most pronounced for small lymphocytic NHL. Among direct respondents, farmers who used pesticides and had a positive family history of cancer or hematopoietic cancer were not at elevated risk of NHL, compared to nonfarmers who had no family cancer history. However, among proxy respondents, ORs were elevated for farmers who had a positive family history of hematopoietic cancer and used animal insecticides (OR = 4.6; 1.9–11.2), crop insecticides (OR = 4.7; 1.6–13.4), or herbicides (OR = 4.9; 1.7–14.2), although the interaction of family history of cancer and agricultural pesticide use was not statistically significant. In summary, the joint effects of the family cancer history and pesticide use were limited to proxy respondents with wide CIs and, thus, provide little evidence that a family history of cancer modifies the association of agricultural exposures with NHL.

Mortality among triazine herbicide manufacturing workers

Atrazine produces mammary gland cancer in one strain of rats and has been classified as an endocrine modulator. Epidemiologic studies have reported associations between agricultural use of atrazine and several forms of cancer. This study evaluated mortality patterns among workers at a plant that made atrazine and other triazine herbicides. The study covered the time period 1970-1997 and included 2213 people employed for at least 6 mo in operations related to the manufacture or formulation of atrazine and other triazine herbicides at a plant in Louisiana (LA). Vital status was determined for all but six subjects. Standardized mortality ratios (SMRs) with 95% confidence intervals (CIs) compared employees' mortality rates with those of the LA industrial corridor general population. Subjects had a total of 32,473 person-years of observation and a median of 15.8 yr since hire. There were 84 observed/118 expected deaths from all causes combined (SMR = 72, CI = 57-89) and 22/21 total cancer deaths (SMR = 106, CI = 66-160). Subjects had 4/1.1 deaths from non-Hodgkin's lymphoma (SMR = 372, CI = 101-952); this increase was not concentrated in the subgroup with long duration of employment and many years since hire. There were 6/4.8 (SMR = 124, CI = 46-271) digestive cancer and 7/6.3 (SMR = 112, CI = 45-230) lung cancer deaths. Data on other forms of cancer were sparse. This study was limited by its small size, by the relatively young age and short follow-up of its subjects, and by the lack of exposure data. It did not provide evidence that employment in triazine herbicide manufacturing and formulating operations was associated causally with overall or cause-specific mortality.

National Health Interview Survey mortality among US farmers and pesticide applicators

BACKGROUND

The mortality experience of pesticide-exposed workers across the US has not been thoroughly studied.

METHODS

Cox regression mortality analyses adjusted for the complex sample survey design were performed on mortality-linked 1986-1994 National Health Interview Survey (NHIS) data.

RESULTS

Nine thousand four hundred seventy-one farmers and pesticide applicators with 571 deaths were compared to 438,228 other US workers with 11,992 deaths. Age-adjusted risk of accidental death, as well as cancers of the nervous and lymphatic/hematopoietic systems, was significantly elevated in male and female pesticide-exposed workers; breast, prostate, and testicular cancer mortality risks were not elevated.

CONCLUSIONS

Compared to all other workers, farmers and pesticide applicators were at greater risk of accidental mortality. These pesticide-exposed workers were not at an increased risk of cancers possibly associated with exposure to estrogen analogue compounds, but were at an increased risk of hematopoietic and nervous system cancers. NHIS mortality follow-up represents an important occupational health surveillance instrument.

Cancer incidence among triazine herbicide manufacturing workers

This study evaluated cancer incidence and prostate specific antigen (PSA) testing among workers at a plant in Louisiana (LA) that made atrazine and other triazine herbicides. The study covered the time period 1985 through 1997 and included 2045 subjects, of whom 757 worked for the company that owned the plant and 1288 were contract employees. Linkage with a population-based cancer registry and review of death certificates and plant medical records identified cancer cases. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) compared subjects' cancer incidence rates with those of a regional general population. Plant medical records provided data on the proportion receiving PSA tests among male company employees. Subjects had 46 observed and 40 expected cases of all cancers combined (SIR = 114, CI = 83-152) and had 11/6.3 prostate cancers (SIR = 175, CI = 87-312). The prostate cancer excess was greater in actively working company employees (5/1.3, SIR = 394, CI = 128-920) than in contract employees or inactive company employees (6/5.0, SIR = 119, CI = 44-260) and was limited to men under 60 years of age. Of the 11 prostate cancer cases, nine were diagnosed at an early clinical stage. From 1993 to 1999, the proportion of male company employees who had at least one PSA test was 86% for those who reached 40 years of age while actively working and was 98% for those who reached 45 years of age. The observed prostate cancer increase may have been due to the frequent PSA testing of actively working company employees. There is no epidemiologic or other information that clearly supports a causal relation between atrazine and prostate cancer.

Cancer incidence among a cohort of female farm residents in New York State

A retrospective cohort study of cancer incidence among 6,310 female farm residents who were New York Farm Bureau members, or members' spouses or relatives, was conducted from 1980 through 1993. Similar to the previous findings for New York State male farmers, the female farm resident cohort experienced significantly lower cancer rates for all cancers combined, and for lung cancer, compared with rural nonfarm female residents. In addition, significantly low rates for colorectal cancer and ovarian cancer were found among the female cohort members. Nonsignificant excesses were found for thyroid and liver cancers. The findings suggest that female farm residents in this cohort might have experienced some of the same cancer-protective factors as male farmers.

Questionnaire assessment of nonoccupational pesticide exposure in epidemiologic studies of cancer

Pesticides have been examined in epidemiologic studies as environmental risk factors for cancer, in part, due to the identification of carcinogenic properties of some of these chemicals using animal models. Although the majority of these epidemiologic studies have focused on occupational pesticide exposure, nonoccupational pesticide exposure has also been investigated. The objective of this paper is to review the methodological issues of nonoccupational pesticide exposure assessment, including identifying the methods that have been used to assess self-reported nonoccupational pesticide exposure in epidemiologic studies of cancer, and discussing the strengths and limitations of the current methodology as well as possible enhancements that could be incorporated into future investigations. Issues of exposure assessment that will be reviewed include specificity, recall, and characteristics of pesticide exposure. Additionally, sources of nonoccupational pesticide exposure other than residential will be briefly reviewed.

Association between xenobiotic gene polymorphisms and non-Hodgkin's lymphoma risk

The last four decades have seen a significant increase in the incidence of non-Hodgkin's lymphoma (NHL) as a possible result of increasing environmental carcinogen exposure, particularly pesticides and solvents. Based on the increasing evidence for an association between carcinogen exposure-related cancer risk and xenobiotic gene polymorphisms, we have undertaken a case-control study of xenobiotic gene polymorphisms in individuals with a diagnosis of NHL. Polymorphisms of six xenobiotic genes (CYP1A1, GSTT1, GSTM1, PON1, NAT1, NAT2) were characterized in 169 individuals with NHL and 205 normal controls using polymerase chain reaction-based methods. Polymorphic frequencies were compared using Fisher's exact tests, and odds ratios for NHL risk were calculated. Among the NHL group, the incidence of GSTT1 null and PON1 BB genotypes were significantly increased compared with controls, 34% vs 14%, and 24% vs 11% respectively. Adjusted odds ratios calculated from multivariate analyses demonstrated that GSTT1 null conferred a fourfold increase in NHL risk (OR = 4.27; 95% CI, 2.40-7.61, P < 0.001) and PON1 BB a 2.9-fold increase (OR = 2.92; 95% CI, 1.49-5.72, P = 0.002). Furthermore, GSTT1 null combined with PON1 BB or GSTM1 null conferred an additional risk of NHL. This is the first time that a PON1 gene polymorphism has been shown to be associated with cancer risk. We conclude that the two polymorphisms, GSTT1 null and PON1 BB, are common genetic traits that pose low individual risk but may be important determinants of overall population NHL risk, particularly among groups exposed to NHL-related carcinogens.

Organophosphate-based pesticides and genetic damage implicated in bladder cancer

Organophosphate-based pesticides have been associated with pathology and chromosomal damage in humans. There are also epidemiologic links with cancer. The few screening tests for low-level occupational exposure are of doubtful sensitivity; this investigation evaluated four methods. Blood samples were studied from 10 farmers before and after occupational exposure to organophosphate-based pesticides and five unexposed controls. The standard cholinesterase test was insensitive to the exposure (P=0.815). However, a significant increase in Howell-Jolly bodies within erythrocytes was observed (P=0.001). Cytogenetic studies on routine and aphidicolin-induced blood cultures revealed that following organophosphate exposure the total number of gaps and breaks on human chromosomes was significantly increased (P=0.004 and P=0.0006, respectively). We concluded that Howell-Jolly body and fragile site analysis were sensitive indicators of nuclear damage resulting from low-level occupational exposure to organophosphate. Such nuclear damage could be implicated in carcinogenesis. The development of bladder cancer is one such example.

Risk factors for non-Hodgkin's lymphoma according to family history of haematolymphoproliferative malignancies

BACKGROUND

Aetiological profiles of non-Hodgkin's lymphoma (NHL) may differ depending upon whether the disease is inheritance-related or sporadic. Because familial risk (a probable surrogate of inheritance-relatedness) of NHL is influenced by haematolymphoproliferative malignancies (HLPM), we evaluated whether non-familial risk factors differ between NHL with and without a family history of HLPM, using the Selected Cancers Study data.

METHODS

Cases were 1511 men aged 31-59 and diagnosed with NHL during 1984-1988. Controls were men without NHL, frequency-matched to cases by age range and cancer registry (n = 1910). These groups were compared: cases with a family history of HLPM and without, and controls without such a family history.

RESULTS

Polytomous logistic regression analyses showed that the odds ratio (OR) estimates of homosexual behaviour were 18.2 (95% confidence interval (CI) : 4.8-69.4) and 5.6 (95% CI : 3.3-9.5) for NHL with and without a family history of HLPM, respectively. The corresponding estimates were 3.9 (95% CI : 1.7-8.9) and 2.2 (95% CI : 1.5-3.1) for history of enlarged lymph nodes. Variables only related to NHL with a family history were use of heroin (OR = 15.6, 95% CI : 3.4-70.4), exposure to a chlorinated hydrocarbon pesticide (OR = 2.3, 95% CI : 1.0-5.0), occupational exposure to plywood, fibreboard or particleboard (OR = 2.0, 95% CI : 1.2-3.4) and history of liver diseases (other than hepatitis or cirrhosis) (OR = 6.5, 95% CI : 1.2-36.2). The association between homosexual behaviour and NHL among men with a family history was stronger for those aged 31-44, especially for B-cell type of the disease.

CONCLUSIONS

This study suggests differences in the risk factor profiles between NHL with and without a family history of HLPM. The higher risks of NHL for homosexual behaviour and heroin use, surrogates of HIV infection, in men with a family history of HLPM imply that genetic susceptibility may be influential on the occurrence of HIV-related NHL.

Pesticide exposures in children with non-Hodgkin lymphoma

BACKGROUND

The association between pesticide exposure and non-Hodgkin lymphoma (NHL) in adults has been the subject of numerous case-control and cohort studies. However, to the authors' knowledge, data regarding pesticide exposures in children diagnosed with NHL have been lacking.

METHODS

The Children's Cancer Group conducted a study comparing 268 children who developed NHL or leukemia with bulk disease with a group of matched, randomly selected regional population controls. The telephone interviews of both the case and control mothers included selected questions regarding occupational and home exposures to pesticides around the time of the index pregnancy and exposure of the child.

RESULTS

A significant association was found between risk of NHL and increased frequency of reported pesticide use in the home (odds ratio [OR] = 7.3 for use most days; trend P = 0.05), professional exterminations within the home (OR = 3.0; P = 0.002), and postnatal exposure (OR = 2.4; P = 0.001). Elevated risks were found for T-cell and B-cell lymphomas; for lymphoblastic, large cell, and Burkitt morphologies; and in both young (age < 6 years) and older children. There was an increased risk of NHL with occupational exposure to pesticides (OR = 1.7) that was not significant overall, but that was significant for Burkitt lymphoma (OR = 9.6; P < 0.05).

CONCLUSIONS

The results of the current study provide further evidence linking pesticide exposure to the risk of NHL, but the authors were unable to implicate any specific agent.

A population-based case-control study of farming and breast cancer in North Carolina

We examined the role of farming and pesticide exposure among 862 cases and 790 controls in a population-based, case-control study of breast cancer conducted in North Carolina between 1993 and 1996. We obtained exposure information through personal interview. Increasing duration of farming was inversely associated with breast cancer risk; odds ratios (95% confidence intervals) were 1.2 (0.8-1.7), 0.8 (0.5-1.2), 0.7 (0.5-1.1), and 0.6 (0.4-0.9) for 1-10, 11-17, 18-23, and >23 years of farming, respectively, relative to nonfarmers. Inverse associations persisted when farming was restricted to calendar time periods of 2,2-bis(p-chlorophenyl)- 1,1,1-trichloroethane (DDT) use or to farming at ages 9-16. Among women who farmed, odds ratios (ORs) were elevated for those who reported being present in fields during or shortly after pesticide application (OR = 1.8, 95% CI = 1.1-2.8) and for those who reported not using protective clothing while applying pesticides (OR = 2.0; 95% CI = 1.0-4.3), but not among those who reported using protective clothing (OR = 0.8; 95% CI = 0.4-1.8). We conclude that residence or work on farms may be associated with a reduced risk of breast cancer. Nevertheless, our results suggest a possible increased risk of breast cancer among a subgroup of farming women who were most likely to be exposed to pesticides.

Cancer in veterinarians

OBJECTIVES

Veterinarians come into contact with several potentially carcinogenic exposures in the course of their occupation. These exposures include radiation, anaesthetic gases, pesticides (particularly insecticides), and zoonotic organisms. This review aims to summarise what is known about the carcinogenic risks in this profession.

METHODS

The levels of exposure to potential carcinogens in the veterinary profession are examined and evidence is reviewed for carcinogenesis of these substances in humans at doses similar to those experienced by veterinarians. The few published studies of cancer in veterinarians are also summarised.

RESULTS

Veterinarians have considerable potential for exposure to several known and potential carcinogens. Risks may be posed by work in clinics with poorly maintained x ray equipment, by use of insecticides, and from contact with carcinogenic zoonotic organisms. The few studies available suggest that veterinarians have increased mortality from lymphohaematopoietic cancers, melanoma, and possibly colon cancer.

CONCLUSIONS

The exposures examined in this review are not unique to the veterinary profession, and, as a consequence, information gathered on the carcinogenic risks of these exposures has implications for many other occupations such as veterinary nurses, animal handlers, and some farmers, as well as dentists, radiographers, and anaesthetists.

Evidence for the induction of apoptosis by endosulfan in a human T-cell leukemic line

Several organochlorinated pesticides including DDT, PCBs and dieldrin have been reported to cause immune suppression and increase susceptibility to infection in animals. Often this manifestation is accompanied by atrophy of major lymphoid organs. It has been suggested that increased apoptotic cell death leading to altered T-B cell ratios, and loss of regulatory cells in critical numbers leads to perturbations in immune function. The major objective of our study was to define the mechanism by which endosulfan, an organochlorinated pesticide, induces human T-cell death using Jurkat, a human T-cell leukemic cell line, as an in vitro model. We exposed Jurkat cells to varying concentrations of endosulfan for 0-48 h and analyzed biochemical and molecular features characteristic of T-cell apoptosis. Endosulfan lowered cell viability and inhibited cell growth in a dose- and time-dependent manner. DAPI staining was used to enumerate apoptotic cells and we observed that endosulfan at 10-200 microM induced a significant percentage of cells to undergo apoptotic cell death. At 48 h, more than 90% cells were apoptotic with 50 microM of endosulfan. We confirmed these observations using both DNA fragmentation and annexin-V binding assays. It is now widely being accepted that mitochondria undergo major changes early during the apoptotic process. We examined mitochondrial transmembrane potential (deltapsim) in endosulfan treated cells to understand the role of the mitochondria in T-cell apoptosis. Within 30 min of chemical exposure, a significant percentage of cells exhibited a decreased incorporation of DiOC6(3), a cationic lipophilic dye into mitochondria indicating the disruption of deltapsim. This drop in deltapsim was both dose- and time-dependent and correlated well with other parameters of apoptosis. We also examined whether this occurred by the down regulation of bcl-2 protein expression that is likely to increase the susceptibility of Jurkat cells to endosulfan toxicity. Paradoxically, the intracellular expression of bcl-2 protein was elevated in a dose dependent manner suggesting endosulfan-induced apoptosis occurred by a non-bcl-2 pathway. Based on these data, as well as those reported elsewhere, we propose the following sequence of events to account for T-cell apoptosis induced by endosulfan: uncoupling of oxidative phosphorylation --> excess ROS production --> GSH depletion --> oxidative stress --> disruption of deltapsim --> release of cytochrome C and other apoptosis related proteins to cytosol --> apoptosis. This study reports for the first time that endosulfan can induce apoptosis in a human T-cell leukemic cell line which may have direct relevance to loss of T cells and thymocytes in vivo. Furthermore, our data strongly support a role of mitochondrial dysfunction and oxidative stress in endosulfan toxicity.