Pregnant women exposed to air pollution put their children at an increased risk of three different types of cancer, according to new research presented at the AACR Annual Meeting 2013.

In their study, researchers identified that prolonged exposure to traffic-related air pollution can increase a child's risk of acute lymphoblastic leukemia and two other rare childhood cancers.

Julia Heck, Ph.D., M.P.H., assistant researcher in the Department of Epidemiology at the University of California, Los Angeles School of Public Health, said:

"The main reason for undertaking this study was that we know much more about the causes of adult cancers than we do of the causes of childhood cancers. We studied pregnancy exposures because the fetus is likely to be more vulnerable to environmental factors during that time, and we also know that certain childhood cancers originate in utero."

They used data from the California Cancer Registry to analyze a sample of children born between 1998 and 2007 who were diagnosed with cancer before the age of five. A total of 3,590 children were randomly selected.

The researchers used the California Line Source Dispersion Modeling Version 4 (CALINE4) to estimate local traffic exposure among the mothers when they were in their third trimester of pregnancy and also during their child's first year of life.

They based the estimates on local emissions from gasoline vehicles and diesel trucks within a 1,500 meter radius of the mothers.

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Pre-natal exposure to air pollution raises a child's risk of developing some cancers

As exposure to traffic-related pollution increased by each interquartile range, the researchers identified a 4 percent increased risk of acute lymphoblastic leukemia (of 4 percent), a 14 percent increased risk of retinoblastoma, as well as a 17 percent increased risk of germ cell tumors.

The researchers were not able to accurately determine the most important period in terms of exposure as the estimates were highly correlated across all trimesters as well as the first year of life.

Heck concluded:

"This is the first study that's ever been reported on air pollution as it relates to rarer pediatric cancers, so it needs to be replicated in other states or in other countries. It would be interesting to determine if there are specific pollutants like benzene or polycyclic aromatic hydrocarbons that are driving these associations."

Other research that identified health complications associated with pre-birth air pollution exposure was carried out by researchers in New York who found that children exposed to urban air pollution before birth were more likely to have a lower IQ than less exposed children.

Written by Joseph Nordqvist