Research by an EU-supported international team of scientistshas shown that polychlorinated biphenyls (PCBs) -- synthetic organicchemicals found widely in the environment and absorbed in the diet -- may damage sperm.
But, lead author Dr Marcello Spanò, of theItalian National Agency for New Technologies, Energy and theEnvironment (ENEA), stressed that the study had found no dramaticeffects on human fertility and had not revealed any serious publichealth threat. However, the findings were a warning and furtherresearch was needed.
The study, reported on line (Thursday 13October) in Europe's leading reproductive medicine journal HumanReproduction, also looked at dichlorodiphenyldichlorethylene (DDE) –a breakdown product of DDT – but found that it did not appear todamage sperm DNA.
The impact of persistent organochlorinepollutants (POPs), of which PCBs and DDT are two, on human fertilityis still unknown and there are limited and contradictory findings sofar as to whether PCBs and DDT/DDE damage human sperm. This study,which is part of a wide-ranging project known as INUENDO, set outalso to see whether these two POPs damage sperm by altering itschromatin integrity. (Chromatin is the DNA and associated proteins thatmake up a chromosome).
The research, which is the first tocollate data about reproductive effects of POPs from a generalpopulation, involved over 700 men – 193 Inuits from Greenland, 178Swedish fishermen, 141 men from Warsaw in Poland and 195 men fromKharkiv in Ukraine.
The scientists used Sperm Chromatin StructureAssay (SCSA) to test the integrity of sperm samples from themajority of the volunteers and assess the level of DNA damage – the DNAfragmentation index (DFI). They measured blood serum for levels ofhexachlorobiphenyl (CB-153), which is a marker for total nondioxin-like PCBs in the body. The men also answered questionnaires ontheir lifestyle, occupations and reproductive history.
Theresults produced an intriguing and puzzling finding: among the Europeanmen overall, the DFI rose in concert with rising levels of PCBs in theblood, with sperm DNA fragmentation reaching a 60% higher average levelin the group exposed to the highest levels of POPs. But, no suchsignificant association was found among the Inuit men.
"Theresults from the Inuit cohort are surprising and reassuring. As usual,we wanted a simple answer and instead we found a lot of new questions,"said Dr Spanò, who is Group Leader, Reproductive Toxicology, Section ofToxicology and Biomedical Sciences at ENEA in Rome. "We can onlyspeculate, at this stage, that genetic make-up and/or lifestyle factorsseem to neutralise or counterbalance the pollutants in this group."
Itcould be, he said, that the profile of the pollutants played a role.PCBs are a class of compounds that include around 200 toxic by-products(congeners). "We measured only two important POPs as it would be aHerculean task to consider them all, so we are seeing only the tip ofthe iceberg."
Dr Spanò said it was important to keep the resultsin perspective. The median level of damaged sperm DNA was 10% and thelarge majority of men in the study were fertile. The probability offathering a child starts to decrease when the proportion of damagedsperm reaches about 20% and becomes negligible from 30-40% onwards."PCB exposure might negatively impact reproductive capabilitiesespecially for men who, for other reasons, already have a higherfraction of defective sperm," he said.
Research priorities nowinclude time-to-pregnancy studies (already underway) and regionaldifferences. "But what we badly need are data on exposure of unbornbabies, as the endocrine disruption hypothesis suggests that foetal andperi-natal exposure could be more relevant as far as health andreproductive consequences are concerned," he said.
He added thatthere were few epidemiological studies of the reproductive effects ofPOPs and population studies were imperative for better risk assessment.This research paper was the first of many that would report the overallfindings of the project. INUENDO was a major undertaking only madepossible by the skill and enthusiasm of the international researchteams and the thousands of people who had contributed information andbiological samples, said Dr Spanò. "We are indebted to them."
 PCBs – synthetic organic chemicals that have been used in hundreds of industrial and commercial applications.
Exposure to PCB and p,p'- DDE in European and Inuit populations: impacton human sperm chromatin integrity. Human Reproduction.doi:10.1093/humrep/dei297.
 DDT – a pesticide once widely usedfor insect control, banned in most western countries in the 1970s, butstill used in some sub-tropical countries.
 POPs – Under the 2001Stockholm Convention on POPs, signed by nearly all countries under theauspices of UNEP (the global treaty to protect human health andenvironment from POPs), there is a binding commitment to reduce andultimately, where feasible, eliminate a range of chemicals, includingPCBs, with PCBs being totally eliminated by 2025. The convention alsorestricts production and use of DDT, which is now acceptable only fordisease vector control where no effective alternatives exist.
INUENDO (INUit-ENDOcrine): Acronym for "Biopersistent organochlorinesin diet and human fertility. Epidemiological studies in time topregnancy and semen quality in Inuit and European populations". INUENDOis an EU cost shared research project undertaken between 1 January 2002and 30 June 2005. Co-ordinated by Prof. Jens Peter Bonde, ÅrhusUniversity Hospital, Denmark and undertaken by nine European researchteams. Website: www.inuendo.dk
 Sperm Chromatin Structure Assay(SCSA): A technique for assessing sperm quality invented by Prof. DonEvenson, University of South Dakota, USA.
The above story is based on materials provided by European Society for Human Reproduction and Embryology. Note: Materials may be edited for content and length.
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