The Independent (London)

May 26, 2000, Friday

Jeremy Laurance, Health Editor

THE FIRST scientific evidence that low-level environmental pollution with dioxin, the toxic byproduct of incinerating waste, has a direct effect on reproduction has been uncovered by Italian researchers.

The scientists studied the population of Seveso in northern Italy, the scene of a devastating explosion at a chemical factory in 1976 which released large quantities of dioxin into the atmosphere. They found that families born to those living even some way from the disaster have a sharply skewed sex ratio, with more girls born than boys.

Professor Paolo Mocarelli and colleagues of the department of laboratory medicine at Desio Hospital, in Milan found that men with the highest dioxin levels were least likely to have boys. But the effect was evident even at very low levels of 20 nanograms per kilogram of bodyweight, only 20 times the estimated average concentration of dioxin in humans in industrialised countries.

For those aged under 19 at the time of the accident, the sex ratio of their children was 62 boys born for every 100 girls, compared with a normal sex ratio of 106 boys to 100 girls, according to the study which was published in The Lancet. Dioxin is a highly toxic by-product of many industrial processes and is released in burning waste and wood.

Michael Meacher, the Environment minister, announcing measures for dealing with waste that will lead to a small increase in incineration over 15 years, said yesterday that the risks of dioxin had been exaggerated and that more was released from burning bonfires than incinerating waste.

Professor Mocarelli, speaking from Milan, said assessing a safe level of dioxin was "complicated". He said: "Relatively low levels of dioxin are having an effect on males. We have shown for the first time that the human male reproductive system is very sensitive to dioxin."

How dioxin affects the male reproductive system is unclear. Scientists have reported a decreased proportion of male births in Denmark, the Netherlands, USA and Canada, in certain occupational groups such as sawmill workers and in those exposed to air-pollution from incinerators.

Professor Mocarelli compared the male and female birth rates to couples from Seveso with levels of dioxin in blood samples taken from them in 1976.

The 239 men and 296 women in the study were aged between 3 and 45 at the time of the explosion.

Only men were affected by the pollutant. The families of women who were exposed to high levels of dioxin and married men from outside the area were unaffected. But the families of exposed men who married women from outside the area had the skewed sex ratio.

The researchers conclude: "The observed effects ... started at concentrations of less than 20 nanograms per kilogram of bodyweight.  This could have important public health implications."