Dalvie, M; Myers, J; Riebow, J.; Dyer, S; Millar, B; Masoka, X; Omar, S.; Robin, T. G.; Thompson, M. L
Epidemiology: September 2003

Metabolites of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), used in many developing countries including South Africa for the control of malaria vectors, have been shown to be endocrine disruptors in vitro and in vivo. The study hypothesis was that male vector control workers highly exposed to DDT in the past should demonstrate clinically significant exposure-related anti-androgenic and/or estrogenic effects reflected in abnormalities in hormone levels, semen, sexual function and fertility. A cross-sectional study of 60 workers from 3 camps situated near the Malaria Control Center (MCC) in Tzaneen was performed. Tests included a questionnaire, a physical examination, semen analysis (produced via coitus interruptus or masturbation) and blood sampling before and after a gonadotropin releasing hormone (GnRH) challenge (100 [mu]g). Semen count, density and motility using the World Health Organisation's criteria, and morphology using the Tygerberg criteria, were determined. Serum DDT metabolites and basal and post GnRH challenge hormone levels were measured. Forty-eight (81.0%) out of 60 participants produced a semen sample, and 31 (51.8%) completed all tests in full. The mean age of partcipants was 45.3 +/- 9.1 years; mean years of education was 6.9 +/- 2.7 years. The mean number of years worked at the MCC was 15.8 +/- 7.8 years & mean serum DDT, 94.3 +/- 57.1 [mu]g/g of lipid. Mean baseline E2 (mean = 62.4 +/- 29.9 pg/ml) levels exceeded the normal reference range. The mean sperm count was 93.8 +/- 130.3 million, density 74.6 +/- 85.1 million/ml, normal morphology 2.5 +/- 1.8 percent, using strict Tygerberg criteria Associations between DDT exposure measures (years worked at MCC and DDT metabolites) and reproductive outcomes were weak and inconsistent. The most important finding was a positive relationship of baseline E2 and testosterone with DDT metabolites, especially with p'p' DDT and DDD. The strongest association was a linear regression relationship between baseline estradiol and p'p' DDT (= 1.14 +/- 0.33 pg/ml/mg/g lipid, p = 0.001, R2 = 0.31, n = 46; adjusted for age and SHBG). An overall anti-androgenic mechanism best explains the results, but with a number of inconsistencies. Associations might be due to chance as multiple comparisons were made (n = 175). The results therefore suggest that DDT exposure experienced by male malaria vector control workers does not result in clinically or subclinically meaningful adverse reproductive effects.

(C) 2003 Lippincott Williams & Wilkins, Inc.