The aim was to develop quantitative estimates of farmers’ pesticide exposure to atrazine and to provide an overview of background levels of selected non-persistent pesticides among corn farmers in a longitudinal molecular epidemiologic study.
The study population consisted of 30 Agricultural Health Study farmers from Iowa and 10 nonfarming controls. Farmers completed daily and weekly diaries from March to November in 2002 and 2003 on pesticide use and other exposure determinants. Urine samples were collected at 10 timepoints relative to atrazine application and other farming activities. Pesticide exposure was assessed using urinary metabolites and diaries.
The analytical limit of detection (LOD) ranged between 0.1–0.2 μg/l for all pesticide analytes except for isazaphos (1.5 μg/l) and diazinon (0.7 μg/l). Farmers had higher geometric mean urinary atrazine mercapturate (AZM) values than controls during planting (1.1 vs.
Urinary AZM levels in farmers were largely driven by recent application of atrazine. Therefore, the amount of atrazine applied is likely to provide valid surrogates of atrazine exposure in epidemiologic studies. Elevated background levels of non-persistent pesticides, especially 2,4-D, indicate importance in epidemiologic studies of capturing pesticide exposures that might not be directly related to the actual application.
exposure assessment; pesticide exposure; urine; farmers; prospective studies
We investigated the relationship between agricultural pesticides and colorectal cancer incidence in the Agricultural Health Study. A total of 56,813 pesticide applicators with no prior history of colorectal cancer were included in this analysis. Detailed pesticide exposure and other information were obtained from self-administered questionnaires completed at the time of enrollment (1993-1997). Cancer incidence was determined through population-based cancer registries from enrollment through December 31, 2002. A total of 305 incident colorectal cancers (212 colon, 93 rectum) were diagnosed during the study period, 1993-2002. Although most of the 50 pesticides studied were not associated with colorectal cancer risk, chlorpyrifos use showed significant exposure response trend (p for trend = 0.008) for rectal cancer, rising to a 2.7-fold (95% confidence interval: 1.2-6.4) increased risk in the highest exposure category. Aldicarb was associated with a significantly increased risk of colon cancer (p for trend = 0.001), based on a small number of exposed cases, with the highest exposure category resulting in a 4.1-fold increased risk (95% confidence interval: 1.3-12.8). In contrast dichlorophenoxyacetic acid showed a significant inverse association with colon cancer but the association was not monotonic. Our findings should be interpreted cautiously since the literature suggesting that pesticides are related to colorectal cancer is limited. Nonetheless the possibility of an association between exposure to certain pesticides and incidence of colorectal cancer among pesticide applicators deserves further evaluation.
agriculture; colorectal cancer; farmers; insecticides; occupational exposure; pesticides
Farming and pesticide use have previously been linked to non-Hodgkin lymphoma (NHL), chronic lymphocytic leukemia (CLL) and multiple myeloma (MM). We evaluated agricultural use of specific insecticides, fungicides, and fumigants and risk of NHL and NHL-subtypes (including CLL and MM) in a U.S.-based prospective cohort of farmers and commercial pesticide applicators. A total of 523 cases occurred among 54,306 pesticide applicators from enrollment (1993–97) through December 31, 2011 in Iowa, and December 31, 2010 in North Carolina. Information on pesticide use, other agricultural exposures and other factors was obtained from questionnaires at enrollment and at follow-up approximately five years later (1999–2005). Information from questionnaires, monitoring, and the literature were used to create lifetime-days and intensity-weighted lifetime days of pesticide use, taking into account exposure-modifying factors. Poisson and polytomous models were used to calculate relative risks (RR) and 95% confidence intervals (CI) to evaluate associations between 26 pesticides and NHL and five NHL-subtypes, while adjusting for potential confounding factors. For total NHL, statistically significant positive exposure-response trends were seen with lindane and DDT. Terbufos was associated with total NHL in ever/never comparisons only. In subtype analyses, terbufos and DDT were associated with small cell lymphoma/chronic lymphocytic leukemia/marginal cell lymphoma, lindane and diazinon with follicular lymphoma, and permethrin with MM. However, tests of homogeneity did not show significant differences in exposure-response among NHL-subtypes for any pesticide. Because 26 pesticides were evaluated for their association with NHL and its subtypes, some chance finding could have occurred. Our results showed pesticides from different chemical and functional classes were associated with an excess risk of NHL and NHL subtypes, but not all members of any single class of pesticides were associated with an elevated risk of NHL or NHL subtypes. These findings are among the first to suggest links between DDT, lindane, permethrin, diazinon and terbufos with NHL subtypes.
Imazethapyr, a heterocyclic aromatic amine, is a widely used crop herbicide first registered for use in the United States in 1989. We evaluated cancer incidence among imazethapyr-exposed pesticide applicators enrolled in the Agricultural Health Study. The Agricultural Health Study is a prospective cohort of 57,311 licensed pesticide applicators in the U.S., enrolled from 1993-1997. Among the 49,398 licensed pesticide applicators eligible for analysis, 20,646 applicators reported use of imazethapyr and 2,907 incident cancers developed through 2004. Imazethapyr exposure was classified by intensity-weighted lifetime exposure days calculated as [years of use × days per year × intensity level]. Poisson regression analysis was used to evaluate the relationship between imazethapyr exposure and cancer incidence. We found significant trends in risk with increasing lifetime exposure for bladder cancer (p for trend 0.01) and colon cancer (p for trend 0.02). Rate ratios were increased by 137% for bladder cancer and 78% for colon cancer when the highest exposed were compared with the nonexposed. The excess risk for colon cancer was limited to proximal cancers, (Rate Ratio =2.73, 95% confidence intervals 1.42, 5.25, p for trend 0.001). No association was observed for prostate, lung, rectum, kidney, oral, pancreas, lymphohematopoietic cancers or melanoma. These findings provide new evidence that exposure to aromatic amine pesticides may be an overlooked exposure in the etiology of bladder and colon cancer. The use of imazethapyr and other imidazolinone compounds should continue to be evaluated for potential risk to humans.
pesticides; bladder; colon; occupational exposures
Farmer's lung, or hypersensitivity pneumonitis, is an important contributor to respiratory morbidity among farmers.
Using the 1993–7 enrolment data from the Agricultural Health Study, we conducted a cross‐sectional study of occupational risk factors for farmer's lung among ∼50 000 farmers and farm spouses in Iowa and North Carolina using hierarchical logistic regression controlling for age, state, and smoking status. Participants provided information on agricultural exposures, demographic characteristics, and medical history via self‐administered questionnaires. Approximately 2% of farmers (n = 481) and 0.2% of spouses (n = 51) reported doctor‐diagnosed farmer's lung during their lifetime. We assessed farmers and spouses separately due to different information on occupational exposure history. Only pesticide exposures represented lifetime exposure history, all other farm exposures represented current activities at enrolment.
Among farmers, handling silage (OR = 1.41, 95% CI 1.10 to 1.82), high pesticide exposure events (OR = 1.75, 95% CI 1.39 to 2.21), and ever use of organochlorine (OR = 1.34, 95% CI 1.04 to 1.74) and carbamate pesticides (OR = 1.32, 95% CI 1.03 to 1.68) were associated with farmer's lung in mutually‐adjusted models. The insecticides DDT, lindane, and aldicarb were positively associated with farmer's lung among farmers. Current animal exposures, while not statistically significant, were positively associated with farmer's lung, particularly for poultry houses (OR = 1.55, 95% CI 0.93 to 2.58) and dairy cattle (OR = 1.28, 95% CI 0.86 to 1.89). The occupational data were more limited for spouses; however, we saw similar associations for dairy cattle (OR = 1.50, 95% CI 0.72 to 3.14) and organochlorine pesticides (OR = 1.29, 95% CI 0.64 to 2.59).
While historic farm exposures may contribute to the observed associations with pesticides, these results suggest that organochlorine and carbamate pesticides should be further evaluated as potential risk factors for farmer's lung.
Depression in women is a public health problem. Studies have reported positive associations between pesticides and depression, but few studies were prospective or presented results for women separately.
We evaluated associations between pesticide exposure and incident depression among farmers’ wives in the Agricultural Health Study, a prospective cohort study in Iowa and North Carolina.
We used data on 16,893 wives who did not report physician-diagnosed depression at enrollment (1993-1997) and who completed a follow-up telephone interview (2005-2010). Among these wives, 1,054 reported physician diagnoses of depression at follow-up. We collected information on potential confounders and on ever use of any pesticide, 11 functional and chemical classes of pesticides, and 50 specific pesticides by wives and their husbands via self-administered questionnaires at enrollment. We used inverse probability weighting to adjust for potential confounders and to account for possible selection bias induced by the death or loss of 10,639 wives during follow-up. We used log-binomial regression models to estimate risk ratios and 95% confidence intervals.
After weighting for age at enrollment, state of residence, education level, diabetes diagnosis, and not dropping out of the cohort, wives’ incident depression was positively associated with diagnosed pesticide poisoning, but was not associated with ever using any pesticide. Use of individual pesticides or functional or chemical classes of pesticides was generally not associated with wives’ depression. Among wives who never used pesticides, husbands’ ever use of individual pesticides or functional or chemical classes of pesticides was generally not associated with wives’ incident depression.
Our study adds further evidence that high level pesticide exposure, such as pesticide poisoning, is associated with increased risk of depression and sets a lower bound on the level of exposure related to depression, thereby providing reassurance that the moderate levels of pesticide exposure experienced by farmers’ wives likely do not increase risk.
depression; female; incidence; pesticides; spouses
Although impaired lung function in general has been associated with an increased risk of lung cancer, past studies typically have not attempted to investigate separately the obstructive and restrictive components of respiratory impairment. To deal with this question further, data from a large (n = 176 997) cohort of male Swedish construction workers, for whom spirometry measurements before follow‐up were available, were analysed.
Cancer incidence for 1971–2001 was obtained through linkage with the national cancer registry. Using a modification of the Global Initiative for Chronic Obstructive Lung Disease criteria for chronic obstructive pulmonary disease (COPD), subjects were classified into five categories of lung function: normal, mild COPD, moderate COPD, severe COPD and restrictive lung disease (RLD). Rate ratios (RR) and 95% confidence intervals (CI) for lung cancer across lung function categories were calculated using Poisson regression, adjusted for age and smoking. Other end points (histological types of lung cancer, non‐lung tobacco‐related cancers, other cancers, total mortality) were also investigated.
834 incident cases of lung cancer were identified. Increased rates of lung cancer were observed for both COPD (mild: RR 1.5, 95% CI 1.2 to 1.9; moderate/severe: RR 2.2, 95% CI 1.8 to 2.7) and RLD (RR 2.0, 95% CI 1.6 to 2.5) relative to normal lung function. These associations did not meaningfully change on applying follow‐up lag times of 5, 10 and 15 years after spirometry. When analysed by histological type, associations with both COPD and RLD were stronger for squamous cell carcinoma and small cell carcinoma, and weaker for adenocarcinoma. Both COPD and RLD were associated with increased rates of total mortality.
Obstructive and restrictive impairments in lung function are associated with increased lung cancer risk.
Vitamin D and its metabolites are believed to impede carcinogenesis by stimulating cell differentiation, inhibiting cell proliferation, and inducing apoptosis. Certain pesticides have been shown to deregulate vitamin D’s anti-carcinogenic properties. We hypothesize that certain pesticides may be linked to prostate cancer via an interaction with vitamin D genetic variants.
We evaluated interactions between 41 pesticides and 152 single nucleotide polymorphisms (SNPs) in nine vitamin D pathway genes among 776 prostate cancer cases and 1,444 male controls in a nested case-control study of Caucasian pesticide applicators within the Agricultural Health Study. We assessed interaction P-values using likelihood ratio tests from unconditional logistic regression and a False Discovery Rate (FDR) to account for multiple comparisons.
Five significant interactions (P<0.01) displayed a monotonic increase in prostate cancer risk with individual pesticide use in one genotype and no association in the other. These interactions involved parathion and terbufos use and three vitamin D genes (VDR, RXRB and GC). The exposure-response pattern among participants with increasing parathion use with the homozygous CC genotype for GC rs7041 compared to unexposed participants was noteworthy (low versus no exposure: odds ratio (OR)=2.58, 95% confidence interval (CI)=1.07–6.25; high versus no exposure: OR=3.09, 95%CI=1.10–8.68; P-interaction=3.8×10−3).
In this study, genetic variations in vitamin D pathway genes, particularly GC rs7041, a SNP previously linked to lower circulating vitamin D levels modified pesticide associations with prostate cancer risk.
Because our study is the first to examine this relationship, additional studies are needed to rule out chance findings.
pesticide; vitamin D; prostate cancer; VDR; RXR
Background: Pesticide exposure may be positively associated with depression. Few previous studies have considered the episodic nature of depression or examined individual pesticides.
Objective: We evaluated associations between pesticide exposure and depression among male private pesticide applicators in the Agricultural Health Study.
Methods: We analyzed data for 10 pesticide classes and 50 specific pesticides used by 21,208 applicators enrolled in 1993–1997 who completed a follow-up telephone interview in 2005–2010. We divided applicators who reported a physician diagnosis of depression (n = 1,702; 8%) into those who reported a previous diagnosis of depression at enrollment but not follow-up (n = 474; 28%), at both enrollment and follow-up (n = 540; 32%), and at follow-up but not enrollment (n = 688; 40%) and used polytomous logistic regression to estimate odds ratios (ORs) and 95% CIs. We used inverse probability weighting to adjust for potential confounders and to account for the exclusion of 3,315 applicators with missing covariate data and 24,619 who did not complete the follow-up interview.
Results: After weighting for potential confounders, missing covariate data, and dropout, ever-use of two pesticide classes, fumigants and organochlorine insecticides, and seven individual pesticides—the fumigants aluminum phosphide and ethylene dibromide; the phenoxy herbicide (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T); the organochlorine insecticide dieldrin; and the organophosphate insecticides diazinon, malathion, and parathion—were all positively associated with depression in each case group, with ORs between 1.1 and 1.9.
Conclusions: Our study supports a positive association between pesticide exposure and depression, including associations with several specific pesticides.
Citation: Beard JD, Umbach DM, Hoppin JA, Richards M, Alavanja MCR, Blair A, Sandler DP, Kamel F. 2014. Pesticide exposure and depression among male private pesticide applicators in the Agricultural Health Study. Environ Health Perspect 122:984–991; http://dx.doi.org/10.1289/ehp.1307450
Pendimethalin, a widely used herbicide, has been classified as a group C possible human carcinogen by the U.S. Environmental Protection Agency. We evaluated the incidence of cancer in relation to reported pendimethelin use among pesticide applicators in the Agricultural Health Study, a prospective cohort of licensed pesticide applicators in Iowa and North Carolina.
Information on pesticide use came from two questionnaires (enrollment and take-home). The present analysis includes 9089 pendimethalin-exposed and 15,285 nonpendimethalin-exposed pesticide applicators with complete information on pendimethalin use and covariates from a take-home questionnaire. We conducted Poisson regression analyses to evaluate the association of pendimethalin exposure with cancer incidence (mean follow-up = 7.5 years) using two exposure metrics: tertiles of lifetime days of exposure and tertiles of intensity-weighted lifetime days of exposure.
Overall cancer incidence did not increase with increasing lifetime pendimethalin use, and there was no clear evidence of an association between pendimethalin use and risks for specific cancers. The risk for rectal cancer rose with increasing lifetime pendimethalin exposure when using nonexposed as the reference (rate ratio = 4.3; 95% confidence interval = 1.5–12.7 for the highest exposed subjects; P for trend = 0.007), but the association was attenuated when using the low exposed as the referent group (P for trend = 0.08). Similar patterns for rectal cancer were observed when using intensity-weighted exposure-days. The number of rectal cancer cases among the pendimethalin-exposed was small (n = 19). There was some evidence for an elevated risk for lung cancer, but the excess occurred only in the highest exposure category for lifetime pendimethalin exposure. The trends for lung cancer risk were inconsistent for different exposure metrics.
We did not find a clear association of lifetime pendimethalin exposure either with overall cancer incidence or with specific cancer sites.
To examine the association between pesticide use during pregnancy and gestational diabetes mellitus (GDM) among wives of licensed pesticide applicators.
RESEARCH DESIGN AND METHODS
Using data from the Agricultural Health Study (AHS), we estimated the association between self-reported pesticide-related activities during the first trimester of the most recent pregnancy and GDM among 11,273 women whose pregnancy occurred within 25 years of enrollment.
A total of 506 (4.5%) women reported having had GDM. Women who reported agricultural pesticide exposure (mixing or applying pesticides to crops or repairing pesticide application equipment) during pregnancy were more likely to report GDM (odds ratio [OR] 2.2 [95% CI 1.5–3.3]). We saw no association between residential pesticide exposure (applying pesticides in the home and garden during pregnancy) and GDM (1.0 [0.8–1.3]). Among women who reported agricultural exposure during pregnancy, risk of GDM was associated with ever-use of four herbicides (2,4,5-T; 2,4,5-TP; atrazine; or butylate) and three insecticides (diazinon, phorate, or carbofuran).
These findings suggest that activities involving exposure to agricultural pesticides during the first trimester of pregnancy may increase the risk of GDM.
Because pesticides may operate through different mechanisms, the authors studied the risk of prostate cancer associated with specific pesticides in the Agricultural Health Study (1993–2007). With 1,962 incident cases, including 919 aggressive prostate cancers among 54,412 applicators, this is the largest study to date. Rate ratios and 95% confidence intervals were calculated by using Poisson regression to evaluate lifetime use of 48 pesticides and prostate cancer incidence. Three organophosphate insecticides were significantly associated with aggressive prostate cancer: fonofos (rate ratio (RR) for the highest quartile of exposure (Q4) vs. nonexposed = 1.63, 95% confidence interval (CI): 1.22, 2.17; Ptrend < 0.001); malathion (RR for Q4 vs. nonexposed = 1.43, 95% CI: 1.08, 1.88; Ptrend = 0.04); and terbufos (RR for Q4 vs. nonexposed = 1.29, 95% CI: 1.02, 1.64; Ptrend = 0.03). The organochlorine insecticide aldrin was also associated with increased risk of aggressive prostate cancer (RR for Q4 vs. nonexposed = 1.49, 95% CI: 1.03, 2.18; Ptrend = 0.02). This analysis has overcome several limitations of previous studies with the inclusion of a large number of cases with relevant exposure and detailed information on use of specific pesticides at 2 points in time. Furthermore, this is the first time specific pesticides are implicated as risk factors for aggressive prostate cancer.
aggressive prostate cancer; cohort study; farming; organophosphate insecticides; pesticide exposure; prostate cancer
To assess whether pesticide use practices were associated with injury mortality among 51,035 male farmers from North Carolina and Iowa enrolled in the Agricultural Health Study.
We used Cox proportional hazards models adjusted for age and state to estimate fatal injury risk associated with self-reported use of 49 specific pesticides, personal protective equipment, specific types of farm machinery, and other farm factors collected 1–15 years preceding death. Cause-specific mortality was obtained through linkage to mortality registries.
We observed 338 injury fatalities over 727,543 person-years of follow-up (1993–2008). Fatal injuries increased with days per year of pesticide application, with the highest risk among those with 60+ days of pesticide application annually (Hazard Ratio (HR) =1.87; 95% Confidence Interval (CI) = 1.10, 3.18). Chemical-resistant glove use was associated with decreased risk (HR=0.73; 95%CI=0.58, 0.93), but adjusting for glove use did not substantially change estimates for individual pesticides or pesticide use overall. Herbicides were associated with fatal injury, even after adjusting for operating farm equipment, which was independently associated with fatal injury. Ever use of five of 18 herbicides (2,4,5–T, paraquat, alachlor, metribuzin, and butylate) were associated with elevated risk. In addition, 2,4–D and cyanazine were associated with fatal injury in exposure-response analyses. There was no evidence of confounding of these results by other herbicides.
The association between application of pesticides, particularly certain herbicides, and fatal injuries among farmers should be interpreted cautiously but deserves further evaluation, with particular focus on understanding timing of pesticide use and fatal injury.
pesticides; mortality; wounds; injuries
Lung cancer patients with mutations in EGFR tyrosine kinase have improved prognosis when treated with EGFR inhibitors. We hypothesized that EGFR mutations may be related to residential radon or passive tobacco smoke.
This hypothesis was investigated by analyzing EGFR mutations in seventy lung tumors from a population of never and long-term former female smokers from Missouri with detailed exposure assessments. The relationship with passive-smoking was also examined in never-smoking female lung cancer cases from the Mayo clinic.
Overall, the frequency of EGFR mutation was 41% [95% Confidence Interval (CI): 32-49%]. Neither radon nor passive-smoking exposure was consistently associated with EGFR mutations in lung tumors.
The results suggest that EGFR mutations are common in female, never-smoking, lung cancer cases from the U.S, and EGFR mutations are unlikely due to exposure to radon or passive-smoking.
EGFR mutations; never-smokers; lung cancer; radon; passive-smoking; second hand smoke; tobacco smoke
Methyl bromide is a genotoxic soil fumigant with high acute toxicity, but unknown human carcinogenicity. Although many countries have reduced methyl bromide use because of its ozone depleting properties, some uses remain in the United States and other countries, warranting further investigation of human health effects.
We used Poisson regression to calculate rate ratios (RR) and 95% confidence intervals (CI) for associations between methyl bromide use and all cancers combined and 12 specific sites among 53,588 Agricultural Health Study (AHS) pesticide applicators with follow-up from 1993–2007. We also evaluated interactions with a family history for four common cancers (prostate, lung, colon, and lymphohematopoietic). We categorized methyl bromide exposure based on lifetime days applied weighted by an intensity score.
A total of 7,814 applicators (14.6%) used methyl bromide, predominantly before enrollment. Based on 15 exposed cases, stomach cancer risk increased monotonically with increasing methyl bromide use (RR=1.42; 95% CI: 0.51–3.95 and RR=3.13; 95% CI: 1.25–7.80 for low and high use compared with no use; ptrend=0.02). No other sites displayed a significant monotonic pattern. Although we previously observed an association with prostate cancer (follow-up through 1999), the association did not persist with longer follow-up. We observed a non-significant elevated risk of prostate cancer with methyl bromide use among those with a family history of prostate cancer, but the interaction with a family history did not achieve statistical significance.
Our results provide little evidence of methyl bromide associations with cancer risk for most sites examined; however, we observed a significant exposure-dependent increase in stomach cancer risk. Small numbers of exposed cases and declining methyl bromide use might have influenced our findings. Further study is needed in more recently exposed populations to expand on these results.
methyl bromide; fumigant; pesticide; cancer
Uncovering SNP (single nucleotide polymorphisms)-environment interactions can generate new hypotheses about the function of poorly characterized genetic variants and environmental factors, like pesticides. We evaluated SNP-environment interactions between 30 confirmed prostate cancer susceptibility loci and 45 pesticides and prostate cancer risk in 776 cases and 1,444 controls in the Agricultural Health Study. We used unconditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Multiplicative SNP-pesticide interactions were calculated using a likelihood ratio test. After correction for multiple tests using the False Discovery Rate method, two interactions remained noteworthy. Among men carrying two T alleles at rs2710647 in EH domain binding protein 1 (EHBP1) SNP, the risk of prostate cancer in those with high malathion use was 3.43 times those with no use (95% CI: 1.44–8.15) (P-interaction = 0.003). Among men carrying two A alleles at rs7679673 in TET2, the risk of prostate cancer associated with high aldrin use was 3.67 times those with no use (95% CI: 1.43, 9.41) (P-interaction = 0.006). In contrast, associations were null for other genotypes. Although additional studies are needed and the exact mechanisms are unknown, this study suggests known genetic susceptibility loci may modify the risk between pesticide use and prostate cancer.
The Agricultural Health Study (AHS) is a prospective study of licensed pesticide applicators (largely farmers) and their spouses in Iowa and North Carolina. We evaluate the impact of occupational pesticide exposure misclassification on relative risks using data from the cohort and the AHS Pesticide Exposure Study (AHS/PES).
We assessed the impact of exposure misclassification on relative risks using the range of correlation coefficients observed between measured post-application urinary levels of 2,4-dichlorophenoxyacetic acid (2,4-D) and chlorpyrifos metabolite and exposure estimates based on an algorithm from 83 AHS pesticide applications.
The correlations between urinary levels of 2,4-D and chlorpyrifos metabolite and estimated exposure intensity scores from the expert-derived algorithm were about 0.4 for 2,4-D (n=64), 0.8 for liquid chlorpyrifos (n=4), and 0.6 for granular chlorpyrifos (n=12). Correlations of urinary levels with individual exposure determinants (e.g., kilograms of active ingredient used, duration of application, or number of acres treated) were lower and ranged from −0.36 to 0.19. These findings indicate that scores from an a priori expert-derived algorithm developed for the AHS were more closely related to measured urinary levels than the several individual exposure determinants evaluated here. Estimates of potential bias in relative risks observed in the AHS based on the correlations from the AHS/PES and the proportion of the AHS cohort exposed to various pesticides indicate that nondifferential misclassification of exposure using the algorithm would bias some estimates toward the null, but less than the misclassification associated with individual exposure determinants.
Based on these correlations and the proportion of the AHS cohort exposed to various pesticides, the potential bias in relative risks from nondifferential exposure misclassification is reduced when exposure estimates are based on an expert algorithm compared to estimates based on separate individual exposure determinants often used in epidemiologic studies. Although correlations between algorithm scores and urinary levels were quite good (i.e., correlations between 0.4 and 0.8), exposure misclassification would still bias relative risk estimates in the AHS towards the null and diminish study power.
Previous research demonstrates increased prostate cancer risk for pesticide applicators and pesticide manufacturing workers. Although underlying mechanisms are unknown, human biomonitoring studies indicate increased genetic damage (e.g. chromosomal aberrations) with pesticide exposure. Given that the nucleotide excision repair (NER) pathway repairs a broad range of DNA damage, we evaluated interactions between pesticide exposure and 324 single-nucleotide polymorphisms (SNPs) tagging 27 NER genes among 776 prostate cancer cases and 1444 male controls in a nested case–control study of white Agricultural Health Study pesticide applicators. We determined interaction P values using likelihood ratio tests from logistic regression models and three-level pesticide variables (none/low/high) based on lifetime days of use weighted to an intensity score. We adjusted for multiple comparisons using the false discovery rate (FDR) method. Of the 17 interactions that met FDR <0.2, 3 displayed a monotonic increase in prostate cancer risk with increasing exposure in one genotype group and no significant association in the other group. Men carrying the variant A allele at ERCC1 rs2298881 exhibited increased prostate cancer risk with high versus no fonofos use [odds ratio (OR) 2.98; 95% confidence interval (CI) 1.65–5.39; Pinteract = 3.6 × 10−4; FDR-adjusted P = 0.11]. Men carrying the homozygous wild-type TT genotype at two correlated CDK7 SNPs, rs11744596 and rs2932778 (r2 = 1.0), exhibited increased risk with high versus no carbofuran use (OR 2.01; 95% CI 1.31–3.10 for rs11744596; Pinteract = 7.2 × 10−4; FDR-adjusted P = 0.09). In contrast, we did not observe associations among men with other genotypes at these loci. While requiring replication, our findings suggest a role for NER genetic variation in pesticide-associated prostate cancer risk.
To explore associations with prostate cancer and farming, it is important to investigate the relationship between pesticide use and single nucleotide polymorphisms (SNPs) in xenobiotic metabolic enzyme (XME) genes.
We evaluated pesticide-SNP interactions between 45 pesticides and 1,913 XME SNPs with respect to prostate cancer among 776 cases and 1,444 controls in the Agricultural Health Study.
We used unconditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Multiplicative SNP-pesticide interactions were calculated using a likelihood ratio test.
A positive monotonic interaction was observed between petroleum oil/petroleum distillate use and rs1883633 in the oxidative stress gene glutamate-cysteine ligase (GCLC) (p-interaction=1.0×10−4); men carrying at least one variant allele (minor allele) experienced an increased prostate cancer risk (OR=3.7, 95% CI: 1.9–7.3). Among men carrying the variant allele for thioredoxin reductase 2 (TXNRD2) rs4485648, microsomal epoxide hyrdolase 1 (EPHX1) rs17309872, or myeloperoxidase (MPO) rs11079344, increased prostate cancer risk was observed with high compared to no petroleum oil/petroleum distillate (OR=1.9, 95% CI: 1.1–3.2, p-interaction=0.01), (OR=2.1, 95% CI: 1.1–4.0, p-interaction=0.01), or terbufos (OR=3.0, 95% CI: 1.5–6.0 p-interaction=2.0×10−3) use, respectively. No interactions were deemed noteworthy at the false discovery rate = 0.20 level; the number of observed interactions in XMEs was comparable to the number expected by chance alone.
We observed several pesticide-SNP interactions in oxidative stress and phase I/phase II enzyme genes and risk of prostate cancer. Additional work is needed to explain the joint contribution of genetic variation in XMEs, pesticide use, and prostate cancer risk.
Prostate cancer; pesticides; xenobiotic metabolizing enzymes; single nucleotide polymorphism; interaction
Pesticide exposures can be reduced by use of personal protective equipment as well as proper mixing and application practices. We examined the effects of risk-accepting personality on personal protective equipment (PPE) use and mixing and application practices among private pesticide applicators and their spouses within the Agricultural Health Study (AHS) in Iowa and North Carolina and commercial applicators in Iowa. The AHS follow-up questionnaire included four questions designed to assess attitudes toward risk. Analysis was limited to those who were currently working on a farm or registered as a commercial applicator and indicated current pesticide use (n=25,166). Respondents who answered three or more questions in the affirmative (private applicators: n=4,160 (21%); commercial applicators: n=199 (14%); spouses: n=829 (23%)) were classified as having a risk-accepting personality. Logistic regression was used to evaluate specific work practices associated with risk-accepting attitudes. Among private applicators, the likelihood of using any PPE when mixing or loading pesticides was lower among risk-acceptors compared to risk-averse individuals (odds ratio (OR) = 0.72; 95% Confidence Interval (CI): 0.65 – 0.79). A similar relationship was observed among commercial applicators (OR = 0.77, 95% CI: 0.34 – 1.77) but not among spouses (OR = 1.09, 95% CI: 0.90 – 1.33). Among private applicators, risk-acceptors were more likely than the risk-averse to apply pesticides within 50 ft of the home (OR=1.21; 95% CI: 1.01 – 1.44), compared to further than ¼ mile. Our findings suggest that the decisions to use personal protective equipment and properly handle/apply pesticides may be driven by risk-accepting personality traits.
personal protective equipment; risk-accepting behavior; Agricultural Health Study; pesticide
Background. Lipid metabolism processes have been implicated in prostate carcinogenesis. Since several pesticides are lipophilic or are metabolized via lipid-related mechanisms, they may interact with variants of genes in the lipid metabolism pathway. Methods. In a nested case-control study of 776 cases and 1444 controls from the Agricultural Health Study (AHS), a prospective cohort study of pesticide applicators, we examined the interactions between 39 pesticides (none, low, and high exposure) and 220 single nucleotide polymorphisms (SNPs) in 59 genes. The false discovery rate (FDR) was used to account for multiple comparisons. Results. We found 17 interactions that displayed a significant monotonic increase in prostate cancer risk with pesticide exposure in one genotype and no significant association in the other genotype. The most noteworthy association was for ALOXE3 rs3027208 and terbufos, such that men carrying the T allele who were low users had an OR of 1.86 (95% CI = 1.16–2.99) and high users an OR of 2.00 (95% CI = 1.28–3.15) compared to those with no use of terbufos, while men carrying the CC genotype did not exhibit a significant association. Conclusion. Genetic variation in lipid metabolism genes may modify pesticide associations with prostate cancer; however our results require replication.
The Agricultural Health Study (AHS), a large prospective cohort, was designed to elucidate associations between pesticide use and other agricultural exposures and health outcomes. The cohort includes 57,310 pesticide applicators who were enrolled between 1993 and 1997 in Iowa and North Carolina. A follow-up questionnaire administered 5 years later was completed by 36,342 (63%) of the original participants. Missing pesticide use information from participants who did not complete the second questionnaire impedes both long-term pesticide exposure estimation and statistical inference of risk for health outcomes. Logistic regression and stratified sampling were used to impute key variables related to the use of specific pesticides for 20,968 applicators who did not complete the second questionnaire. To assess the imputation procedure, a 20% random sample of participants was withheld for comparison. The observed and imputed prevalence of any pesticide use in the holdout dataset were 85.7% and 85.3%, respectively. The distribution of prevalence and days/year of use for specific pesticides were similar across observed and imputed in the holdout sample. When appropriately implemented, multiple imputation can reduce bias and increase precision and can be more valid than other missing data approaches.
agriculture; cohort studies; missing data; pesticides; precision
Objectives: To identify and quantify determinants of captan exposure among 74 private orchard pesticide applicators in the Agricultural Health Study (AHS). To adjust an algorithm used for estimating pesticide exposure intensity in the AHS based on these determinants and to compare the correlation of the adjusted and unadjusted algorithms with urinary captan metabolite levels.
Methods: External exposure metrics included personal air, hand rinse, and dermal patch samples collected from each applicator on 2 days in 2002–2003. A 24-h urine sample was also collected. Exposure determinants were identified for each external metric using multiple linear regression models via the NLMIXED procedure in SAS. The AHS algorithm was adjusted, consistent with the identified determinants. Mixed-effect models were used to evaluate the correlation between the adjusted and unadjusted algorithm and urinary captan metabolite levels.
Results: Consistent determinants of captan exposure were a measure of application size (kilogram of captan sprayed or application method), wearing chemical-resistant (CR) gloves and/or a coverall/suit, repairing spray equipment, and product formulation. Application by airblast was associated with a 4- to 5-fold increase in exposure as compared to hand spray. Exposure reduction to the hands, right thigh, and left forearm from wearing CR gloves averaged ∼80%, to the right and left thighs and right forearm from wearing a coverall/suit by ∼70%. Applicators using wettable powder formulations had significantly higher air, thigh, and forearm exposures than those using liquid formulations. Application method weights in the AHS algorithm were adjusted to nine for airblast and two for hand spray; protective equipment reduction factors were adjusted to 0.2 (CR gloves), 0.3 (coverall/suit), and 0.1 (both).
Conclusions: Adjustment of application method, CR glove, and coverall weights in the AHS algorithm based on our exposure determinant findings substantially improved the correlation between the AHS algorithm and urinary metabolite levels.
agriculture; captan; dermal exposure—pesticides, determinants of exposure; exposure assessment—mixed models; orchards; pesticide exposure; variance components