Authors
Michihiro Kamijima, Hatsuki Hibi, Masahiro Gotoh, Ken-ichi Taki, Isao Saito, Hailan Wang, Seiichiro Itohara, Tetsuya Yamada, Gaku Ichihara, Eiji Shibata, Tamie Nakajima, Yasuhiro Takeuchi.

Title:
A survey of semen indices in insecticide sprayers.

Journal:
Journal of Occupational Health, 2004; 46: 109-118.

Summary:
Results from both epidemiological and animal studies have suggested that pesticides dichlorodiphenyl trichloroethane (DDT), dieldrin, toxaphene, lindane, endosulfan, brominated pesticides, and chloredecone are reproductive toxins and as such, these chemicals have been strictly regulated or are no longer in use in developed countries. The reproductive toxicity of other pesticides that are still in use (benomyl, carbaryl, carbon disulfide, dinoseb, ethylene oxide, fenchlorphos, molinate, triphenyltin etc.) remains a concern; however the epidemiologic evidence of associated adverse reproductive effects has been inconsistent.

The present study investigated semen indices in male indoor pesticide sprayers who were primarily exposed to organophosphorous (fenitrothion, dichlorovos, chloropyrifos, diazinon, and propetamphos) and pyrethroid insecticides (permethrin, phenothrin). Spraying in narrow spaces resulted in extensive insecticide exposure to the workers in this group. The study subjects were recruited from the sprayers who worked for 9 member companies of a local trade association in central Japan. At an annual medical check-up in March 2000, 18 sprayers (33.3%) volunteered to participate in the study. Eighteen age-matched students or medical doctors were recruited to represent the control group. Two reproductive check-ups for this study were conducted in the summer (June/July 2000) and in the winter (January/February 2001).

A questionnaire was administered to both cases and controls before each check-up to obtain information on the job history and occupational exposures, reproduction, illness, long-term prescriptions, febrile illness within the past 3 months and subjective symptoms. A physical examination and samples of semen, blood and urine were obtained at each check-up. Testicular volume was measured by an orchidmeter at the first examination. Semen indices (volume, pH, sperm counts, sperm motility and morphology) were measured according to World Health Organization guidelines. Radioimmunoassay was used to measure the serum levels of testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH). Systemic diseases were ruled out using routine blood (biochemistry, counts) and urine examinations. Exposure to organophosphorus (OP) insecticides was assessed from erythrocyte true cholinesterase activity (E-ChE).

In this study, sprayers were found to be exposed to pesticides for a significantly longer duration in the summer than in the winter. E-ChE activity of the sprayers was significantly lower than controls in the summer but not in the winter which is coincident with the increased frequency of pesticide use in summer. No significant seasonal differences in the symptoms (headache, vertigo, lassitude, eye irritation, felt ill during and/or after spraying etc.) related to pesticide use in sprayers was observed. The testicular volume, blood and urine examinations did not show significant differences between sprayers and controls. However serum testosterone levels were found to be higher in sprayers during the winter. A higher percentage of slow progressive and non-motile sperm in addition to a lower percentage of rapid progressive sperm was observed in sprayers during the summer. However, a dose-response relationship could not be established between pesticide exposure and semen indices or serum sex hormones, possibly due to small sample size. The linear regression analysis revealed no significant relationship between duration of pesticide spraying work/ exposure frequency and semen indices/ E-ChE/ sex hormone levels.

In summary, during the summer, when there was high exposure to insecticides, the sperm motility and morphology results were indicative of lower semen quality in indoor pesticide sprayers. Moreover, these findings are in agreement with the results in previous studies, adding strength to this study. However, one should be cautious in interpreting or attributing these results to pesticide spraying work. Factors other than pesticide exposure such as high scrotal temperature due to protective pants in sprayers during the summer, socio-economic factors or sexual behavior might be alternative explanations for the low semen quality observed during the summer. Small sample size, low participation level, crude exposure quantification and some unexplainable findings such as higher testosterone levels observed in sprayers during winter (the off-season), are also limitations for this study. Overall, this study indicates a lower semen quality in pesticide sprayers, thereby suggesting the reproductive toxicity of above mentioned pesticides. However, further studies under strictly-controlled sampling design and dose-response relationships are needed to confirm these findings.