A recent study of the male partners in couples attending a Massachusetts infertility clinic between 2002 and 2003 suggests that frequent exposure to the modern non-persistent pesticides, which (unlike the fat soluble organochlorine pesticides) have left the body within days or, at most, weeks, appeared to correlate with significant declines in testosterone levels.

The study looked at the urinary concentrations of 3,5,6-trichloro-2-pyridinol (TCPY) and 1-naphthol (1N) - metabolites of
chlorpyrifos, carbaryl and naphthalene. The study found that the levels of TCPY were inversely correlated with levels of testosterone and that this was dose dependent - the highest levels of exposure being associated with the greatest declines in testosterone.

Exposure to these pesticides may be through diet (chlorpyrifos and carbaryl are registered for use on many crops) or inhaled as they are also used as urban and domestic insecticides. Although chlorpyrifos is generally non-persistent, when used indoors, away from sunlight, rain and extreme temperatures, it may remain stable for up to four years.

There is also concern that high TCPY/IN levels may not just be associated with lower levels of testosterone but with increased sperm
damage and reduced sperm concentration and motility.

Many developed countries have been experiencing declines in male fertility so these potential impacts of pesticide exposure maybe significant.

Meeker JD, Ryan L, Barr DB, Hauser R Exposure to nonpersistent
insecticides and male reproductive hormones, Epidemiology 2006, 17: 61-68

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First Published October 2006

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