Research by an European Union-supported international team of scientists has shown that polychlorinated biphenyls (PCBs) - synthetic organic chemicals found widely in the environment and absorbed in the diet - may damage sperm.

But, lead author Dr Marcello Span?f the Italian National Agency for New Technologies, Energy and the Environment (ENEA), stressed that the study had found no dramatic effects on human fertility and had not revealed any serious public health threat. However, the findings were a warning and further research was needed.

The study, reported on line (Thursday 13 October) in Europe's leading reproductive medicine journal Human Reproduction, also looked at dichlorodiphenyldichlorethylene (DDE) - a breakdown product of DDT - but found that it did not appear to damage sperm DNA. The impact of persistent organochlorine pollutants (POPs), of which PCBs and DDT are two, on human fertility is still unknown and there are limited and contradictory findings so far as to whether PCBs and DDT/DDE damage human sperm. This study, which is part of a wide-ranging project known as INUENDO, set out also to see whether these two POPs damage sperm by altering its chromatin integrity. (Chromatin is the DNA and associated proteins that make up a chromosome).

The research, which is the first to collate data about reproductive effects of POPs from a general population, involved over 700 men - 193 Inuits from Greenland, 178 Swedish fishermen, 141 men from Warsaw in Poland and 195 men from Kharkiv in Ukraine.