ROCHESTER, N.Y., Dec. 9 (UPI) -- Fetal exposure to two chemicals -- polychlorinated biphenyls, or PCBs, and DDE, a product of the breakdown of the insecticide DDT -- can dampen infants' immune response to the tuberculosis vaccine, according to a new study of mothers and children.
Both chemicals have been banned in many countries, including the United States, but are considered persistent pollutants, which pose health risks long after being introduced into the environment, can accumulate. The effects of such pollutants can pass between species through the food chain.
PCBs were used in manufacturing and consumer products in the United States until 1979, but most people have detectable PCB concentrations in their blood. DDT was banned in the United States in 1972, though many countries still use it to control the spread of malaria by mosquitoes.
"There are thousands of pollutants similar to PCBs and DDT with unknown health implications," said Dr. Todd Jusko, an assistant professor at the University of Rochester, in a press release.
Researchers analyzed blood samples and immune responses from 516 mother-infant pairs in Eastern Slovakia. Maternal and cord blood were collected at birth, the infants were immunized for tuberculosis within four days of birth, and blood samples were again collected when the babies were six months old.
The chemicals were detected in 99 percent of the blood samples, and infants with the highest levels of PCBs also had the lowest levels of tuberculosis antibodies. Infants with PCB levels in the 75th percentile had 37 percent lower antibodies than infants in the 25th percentile.
A similar association between DDE levels and antibodies was also found, and children exposed to both chemicals had lower antibody levels than if exposed to either chemical alone.
The study is published in Environmental Health Perspectives.