a new study conducted on 212 children in Michigan, us , has revealed that exposure to polychlorinated biphenyls ( pcb ), a common pollutant, while in their mothers' womb has led to a modest lowering of their intelligence quotient ( iq ) level.

Most of these 11-year-old children in the latest study were born to mothers who consumed pcb contaminated fish in the '80s. Previous research had shown that exposure to pcb s had caused neurological problems in infants and pre-school children. But it was believed that the effects would wane with time. Though the cognitive deficiencies of the children studied are not all that serious, researchers are worried as pcb s are widespread in the environment. Further, the pcb exposure in these children were not all that much higher than that found in the average us citizen. The tests were conducted by Joseph L Jacobson, a Wayne State University professor and his wife Sandra W Jacobson, a developmental psychologist. The couple had first documented the neurological problems of these children six years ago.

In the current experiment, these children were given achievement tests and the results showed that the most highly exposed of the lot were three times more likely than their less-exposed counterparts to have intelligence scores in the lower part of the normal iq range. In other words, these children were twice as likely to be at least two years behind in reading comprehension compared to others in the group.