Pesticide exposure and self-reported incident depression among wives in the Agricultural Health Study

BACKGROUND

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.

OBJECTIVES

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.

METHODS

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, 1054 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.

RESULTS

After weighting for age at enrollment, state of residence, education level, diabetes diagnosis, and drop out, 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.

CONCLUSIONS

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.

Dopaminergic neurotoxicity of S-ethyl N,N-dipropylthiocarbamate (EPTC), molinate, and S-methyl-N,N-diethylthiocarbamate (MeDETC) in Caenorhabditis elegans

Epidemiological studies corroborate a correlation between pesticide use and Parkinson's disease (PD). Thiocarbamate and dithiocarbamate pesticides are widely used and produce neurotoxicity in the peripheral nervous system. Recent evidence from rodent studies suggests that these compounds also cause dopaminergic (DAergic) dysfunction and altered protein processing, two hallmarks of PD. However, DAergic neurotoxicity has yet to be documented. We assessed DAergic dysfunction in Caenorhabditis elegans (C. elegans) to investigate the ability of thiocarbamate pesticides to induce DAergic neurodegeneration. Acute treatment with either S-ethyl N,N-dipropylthiocarbamate (EPTC), molinate, or a common reactive intermediate of dithiocarbamate and thiocarbamate metabolism, S-methyl-N,N-diethylthiocarbamate (MeDETC), to gradual loss of DAergic cell morphology and structure over the course of 6 days in worms expressing green fluorescent protein (GFP) under a DAergic cell specific promoter. HPLC analysis revealed decreased DA content in the worms immediately following exposure to MeDETC, EPTC, and molinate. In addition, worms treated with the three test compounds showed a drastic loss of DAergic-dependent behavior over a time course similar to changes in DAergic cell morphology. Alterations in the DAergic system were specific, as loss of cell structure and neurotransmitter content was not observed in cholinergic, glutamatergic, or GABAergic systems. Overall, our data suggest that thiocarbamate pesticides promote neurodegeneration and DAergic cell dysfunction in C. elegans, and may be an environmental risk factor for PD.

S-ethyl-N,N-dipropylthiocarbamate exposure and cancer incidence among male pesticide applicators in the agricultural health study: a prospective cohort

BACKGROUND

The Agricultural Health Study (AHS) is a prospective cohort study of licensed pesticide applicators from Iowa and North Carolina enrolled between 1993 and 1997. EPTC (S-ethyl-N,N-dipropylthiocarbamate) is a thiocarbamate herbicide used in every region of the United States. The U.S. Environmental Protection Agency reports that EPTC is most likely not a human carcinogen; however, the previous epidemiologic data on EPTC exposure and cancer risk were limited.

OBJECTIVES

The purpose of this study was to examine cancer incidence and EPTC use in 48,378 male pesticide applicators enrolled in the AHS.

METHODS

We estimated the rate ratio (RR) and 95% confidence intervals (CIs) for all cancers and selected cancer sites using Poisson regression. We assessed EPTC exposure using two quantitative metrics: lifetime exposure days and intensity-weighted lifetime exposure days, a measure that accounts for application factors that modify personal exposure likelihood.

RESULTS

Among the 9,878 applicators exposed to EPTC, 470 incident cancer cases were diagnosed during the follow-up period ending December 2004 compared with the 1,824 cases among individuals reporting no use. Although EPTC was associated with colon cancer in the highest tertile of both lifetime exposure days and intensity-weighted lifetime days (RR = 2.09; 95% CI, 1.26-3.47 and RR = 2.05; 95% CI, 1.34-3.14, respectively) and the trend test was < 0.01 for both, the pattern of RR was not monotonic with increasing use. There was a suggestion of an association with leukemia. No other associations were observed.

CONCLUSION

In this analysis, EPTC use appeared to be associated with colon cancer and leukemia. However, given the relatively small number of cases in the highest exposure tertile, results should be interpreted with caution, and further investigations are needed.

Efficacy and Compatibility for Fenamiphos and EPTC Applied in Irrigation Water for Nematode and Weed Control in Snapbean Production

A nematicide (fenamiphos) and a herbicide (EPTC) were injected into a sprinkler irrigation system separately and as tank mixtures and applied in 25.4 kl water/ha for nematode and weed control on snapbean. There were no differences (P = 0.05) between methods of injection of fenamiphos + EPTC on efficacy or crop response. The root-gall indices of cultivars Eagle and GV 50 were lower in fenamiphos-treated plots than those treated with EPTC alone and untreated plots. The yield and crop value were greater (P = 0.05) for cultivars Eagle and Nemasnap than GV 50. Fenamiphos 4.48 kg a.i./ha + EPTC 3.36 kg a.i./ha controlled root-knot nematodes, Meloidogyne incognita, ring nematodes, Criconemella ornata, and weeds, and resulted in greater plant growth, yield, and crop value than those from untreated plots. No benefits (P = 0.05) resulted from treatment with fenamiphos at 6.72 kg a.i./ha + EPTC treatment compared with fenamiphos at 4.48 kg a.i. + EPTC.

Effects of DCPA, EPTC, and Chlorpropham on Pathogenicity of Meloidogyne hapla to Alfalfa

Treatments wilh the herbicides chlorpropham (isopropyl m-chlorocarbinilate), DCPA (dimethyl tetrachloroterephthalate), and El'TC (S-ethyl dipropylthiocarbamate), alone or in combination with Meloidogyne hapla Chilwood, significantly reduced the growth of both nemalode-resistant 'Nev Syn XX' atttt susceptible 'Ranger" alfalfa (Medicago saliva L.) seedlings. M. hapla infection of both alfalfas was reduced by all herbicides because of fewer available infective courts in the treated plants. EPTC, however, reduced resistance to M. hapla, as indicated by increased galling of 'Nev Syn XX' plants.