New York: Women exposed to high levels of certain kinds of pollutants are less likely to give birth to male children. That's the startling finding of a new study that reviewed data on pregnant women in San Francisco who were exposed to high levels of polychlorinated biphenyls (PCBs), a group of banned environmental pollutants, in the 1950s and 1960s. And it's not an isolated finding either, reports ScienceDaily. Similar exposure is thought to have occurred in Wales, after a quarry on the edge of Groesfaen village near Cardiff was used as a toxic dumping ground from 1965 to 1972.