Potential pesticide threat to male fertility

Scientists have found a link between a common pesticide and male infertility. The chemical, chlorpyrifos, which is permitted under EU (European Union) regulations, is widely used in Britain in agriculture and was also, until recently, found in common insecticides for use in private gardens. It can also be found in common household insect killers such as ant poisons. Chlorpyrifos is subject to much stricter control in the US after concerns were raised about its effect on brain function. The new research has found that exposure to the pesticide may suppress levels of testosterone, consequently reducing fertility.

The project, involving collaborative research from the University of Michigan, Harvard University and the US Centers for Disease Control and Prevention in Atlanta took urine samples from 268 males attending a Massachusetts fertility clinic between 2000 and 2003. The samples were analysed for levels of TCPY, a breakdown product of chlorpyrifos. Levels of TCPY varied but higher levels were found to correspond to lower levels of testosterone. Men with the most TCPY in their system typically had 10 per cent less testosterone than men with the least. It is thought that this could reduce men's ability to have children, although the study does not provide a direct link between the pesticide and reduced fertility, as some men with low testosterone or sperm counts are still able to father a child.

Dr Jeremy Meeker, one of the authors of the paper published in January's edition of the journal Epidemiology, called for more research. 'Because it is so common and so many males are exposed to this pesticide, it could be having some negative effects. A decline in testosterone throughout a population could potentially lead to adverse reproductive outcomes'. Garry Hamlin, spokesman for Dow AgroSciences, which makes chlorpyrifos, said experts would be analysing the study but stated that, 'we have done extensive research on animals at doses hundreds of times greater than in this paper and it had no effect on fertility'.