The damage to sperm increased with the level of exposure to the chemicals in European men but did not have the same effect on 193 Inuits men from Greenland in the study.

"We can only speculate, at this stage, that genetic make-up and/or lifestyle factors seem to neutralise or counterbalance the pollutants in this group," Dr Marcello Spano, of the Italian National Agency for New Technologies, Energy and the Environment (ENEA) said in the statement.

PCBs are mixtures of synthetic organic chemicals that have been used in hundreds of industrial and commercial applications.

More than 1.5 billion pounds (680.4 million kilos) of PCBs were made in the United States before production was stopped in 1977, according to the US Environmental Protection Agency.

Spano and his colleagues tested the amount of DNA damage in the sperm of 700 men from Sweden, Poland, Ukraine and Greenland in the European Union project.

They also measured levels of a marker in blood samples for PCBs in the body and questioned the men about their lifestyle, occupation and reproductive history.

The median level of damaged sperm DNA in the men was 10 percent and the large majority of men in that group were fertile. The odds of fathering a child start to diminish when damaged sperm reaches 20 percent, according to the scientists.

"PCB exposure might negatively impact reproductive capabilities especially for men who, for other reasons, already have a higher fraction of defective sperm," Spano said.

The scientists, whose findings are reported online by the journal Human Reproduction, said more research is needed into the effects of PCBs, a class of compounds that includes 200 toxic by-products.

They also stressed the need for more information on the impact of exposure of unborn babies which could be more relevant to health and reproductive consequences.