London, Feb 19: Men should avoid smoking and drinking as the toxins in them could harm not only their future children but grandchildren also, scientists say. According to a study conducted by the US scientists, smoking, drinking alcohol, cocaine use and exposure to pesticides causes chemical changes to semen.

The effect of such change goes a long way resulting in abnormalities in their baby and those born in future generations. Animal studies showed abnormalities caused by environmental toxins were caused by genetic changes that were passed on through generations, researchers said. ''When you harm the male reproductive system you can see multi-generational harm transmitted through the male gamete. This new research has human implications because it suggests an avenue of harm and a model of trans-generational effects, '' said Dr Cynthia Daniels from Rutgers University.

For the study, female rats were given daily injections of the pesticide vinclozolin during the period when the sex of embryos is determined.

Male offspring had abnormalities including prostate and sperm development problems, and genetic changes that the researchers found were passed on through four generations when the males were mated with healthy females.

Specific genes involved in the production of sperm that were permanently altered by exposure to the pesticide were identified, the Daily Telegraph reported.

''In addition to the spermatogenic and prostate abnormalities, trans-generational effects on numerous disease states were observed including tumour development and kidney disease, '' said one of the researchers Dr Matthew Anway.

UNI