Dioxin can damage the
male reproductive system. After the city of
Seveso in
Italy had an explosion that released
dioxin, there was a reduction in the number of males born.
Research done by Paolo Mocarelli has shown that boys who were younger than 19 at the time of the accident went on to have many fewer sons than normal - the usual rate is 51 sons per 100 babies, but in their case, it was only 38 sons per 100. Males older than around 19 were not affected, possibly because they had developed already.
from http://data.intelihealth.com/pcn/menshealth/00283744.htm