Those carcinogenic and neurotoxic chemicals are released into the air in the form of vapors or fine particulates. Before the plant closed, they were easily breathed in by people, including pregnant women in Tongliang.

Compared to kids born before the plant closed, children born after also performed better on tests measuring their motor and social developmental skills.

“These findings indicate that regulation can rapidly decrease exposure and improve health outcomes among the most sensitive populations,” said Deliang Tang, the study’s lead author and associate professor of environmental health sciences at the Mailman School of Public Health at Columbia University, in a statement.

Researchers, who published their results in the journal PLOS ONE, took samples of cord blood to measure the levels of a protein that helps the survival and proper functioning of nerve cells in these small children’s brains, which undergo rapid changes as they grow. The study was the first to measure how this protein, called brain-derived neurotrophic factor, is affected by exposure to the chemicals in the air.

“The concern is that early brain development may not occur as it should since these are so key in inducing the development and functioning of neurons,” said Frederica Perera, director of the Columbia Center for Children’s Environmental Health and a study author.

Coal-fired power plants account for about 70 percent of electricity produced in China, and there are hundreds of the plants in the country.

If the study results hold true in other parts of China, the worry is that large numbers of Chinese children could be growing up having similar cognitive issues because of pollutant exposure.

What was particularly concerning to the researchers was that the polluting chemicals actually bind to parts of the DNA of the babies in utero.

“They leave a sort of fingerprint of exposure,” Perera said. Once the pollutants are breathed in, she said, they can be readily transferred across the placenta and reach the fetus.

“Improvements in children’s early brain development will benefit them over their entire life course in terms of ability to learn in childhood, ability to succeed and contribute to society and achieve their full potential, so hence the importance of policies that are centered on protecting the developing child,” Perera said.

She and her colleagues are working on studies that look at the same chemicals in kids in New York City, largely from vehicle exhaust emissions of the many cars, trucks and buses in the city