Children exposed to relatively high levels of PCBs in the womb may have an increased risk of developing autism, a new study suggests. PCBs, or polychlorinated biphenyls, are man-made chemicals once used in a wide range of products, from electrical appliances to fluorescent lighting. Use of these chemicals was banned in the 1970s because of concerns about their health effects. But since they do not easily break down, PCBs still linger in the environment - and in people. In the new study, researchers found that when pregnant women had relatively high levels of certain PCBs in their blood, their children were about 80 percent more likely to be diagnosed with autism versus other kids. Those children also had a roughly twofold higher risk of intellectual disabilities unrelated to autism. "Autism is a complex condition with many different causes, and those causes vary among individuals," said Kristen Lyall, lead researcher on the study. Experts believe that for children to develop autism, they have to have a genetic susceptibility and be exposed to certain environmental factors during critical periods of early brain development. Researchers are still trying to figure out what those environmental factors are. But some suspects include prenatal exposure to poor nutrition, certain infections, heavy air pollution and pesticides, according to the non-profit Autism Speaks. The new findings suggest that PCBs could be another one of the "puzzle pieces," said Lyall.