This story is a supplement to the feature "Is China's Pollution Poisoning Its Children?" which was printed in the August 2008 issue of Scientific American.
Tongliang children born in 2002, when the local coal-burning power plant was still open, scored worse on tests of motor and social skills than did their counterparts born in 2005, one year after the plant stopped operating. Researchers classified children as developmentally delayed if they scored below 85 on a standard assessment known as the Gesell test. The children born in 2002 had higher concentrations in their white blood cells of PAH-DNA adducts—DNA alterations caused by exposures to harmful chemicals, called polycyclic aromatic hydrocarbons (PAHs) in polluted air. Among children born in 2002, adduct frequency closely correlated with developmental delay.