Synthetic chemicals known as PCBs (polychlorinated biphenyls) can damage sperm, but they have no dramatic effects on male fertility, an international team of scientists reports. The study, published in the journal Human Reproduction, looked at the effect of polychlorinated biphenyls on the sperm of men living in four different countries. The researchers also looked at a chemical produced by the breakdown of the insecticide DDT (dichlorodiphenyltrichloroethane), and found no evidence that it damaged sperm.
PCBs are a mixture of over 200 different organic chemicals developed in the 1960s, which were widely used in many products, including electrical devices, paints and plastics. However, their use has been phased out over the past thirty years, after it became clear that like DDT, PCB pollution can persist for decades. The impact of such 'persistent organochlorine pollutants' (POPS) on human fertility is unknown, and previous findings on their impact on sperm are limited and contradictory.
In the latest study, scientists based at the Italian National Agency for New Technologies, Energy and the Environment (ENEA) studied over 700 men living in Greenland, Sweden, Poland and the Ukraine. They assessed the levels of DNA damage in sperm samples from the men, and also measured their blood levels of PCBs. In most of the men, the level of sperm damage was directly related to the levels of PCB - the higher the PCB level, the more damaged the sperm. But surprisingly, the scientists found no such link in men from the Inuit population. The results suggest that something about the genetic make-up or lifestyle of the Inuits could be neutralizing the effects of the PCB damage. 'As usual we wanted a simple answer and instead we found a lot of new questions', said lead author Marcello Spano.
Reassuringly, the sperm damage did not appear to affect the fertility of any of the men, measured using a questionnaire on their reproductive history. In most of the participants, the level of sperm damage was around ten per cent. The probability of fathering a child starts to decrease when levels rise to 20 per cent, with levels of 30-40 per cent causing infertility. However, Spano said that PCBs might 'negatively impact reproductive capabilities' for men who, for other reasons, already have a higher level of damaged sperm.
UK expert Allan Pacey told the BBC News website that the study confirms that 'the relationship between pollutants and sperm damage is a complex one', adding 'thankfully this report suggests that the damage done to sperm by PCBs is not sufficient to cause fertility problems'. Spano said that rather than looking at the effects of PCBs on sperm, future research should concentrate on their effects on the developing fetus, since this could be 'far more relevant as far as health and reproductive consequences are concerned'.