The meaning of twins? - link with air pollution

Pediatrics for Parents, April, 1989

The Meaning of Twins? More twins may mean more air pollution! A Scottish study found that increased polychlorinated hydrocarbons and polychlorinated biphenyls in the air results in more twins in both humans and cattle. Under these conditions, the human twin rate went from a normal of 3 to 13 per thousand births to 11 to 16 per thousand births.

The increase in cattle was more dramatic -- from a normal 0 to 2 percent to 16 to 20 percent. The researchers were hesitant to draw a definite cause and effect relationship and urged further studies. Another study rejected the idea of increased twins, but did find other problems. These included "an apparent excess of eye defects among babies, a rise in the incidence of leukemia, and a statistically significant excess of death from bronchitis."