Boys exposed to certain pollutants during adolescence are far less likely to have sons in adulthood, according to a study published in today’s edition of the British scientific journal the Lancet. The study looked at thousands of people in the Taiwanese city of Yucheng who used cooking oil containing high concentrations of PCBs. It found that young men exposed to PCBs before the age of 20 were 35 percent less likely to have sons than those who did not come into contact with the toxic compounds. The results mirrored those of an earlier study of men in Italy who were exposed to extremely high levels of dioxin and were also far more likely to father daughters than sons. The study supports long-held fears that environmental toxins can have dramatic effects on the human reproductive system.