Based on the models, for every million people who live near unsealed asphalt for 70 years, or roughly their whole lives, there would be three extra cases of cancer because of exposure to PAHs. Bare asphalt emits some PAHs, but at far lower levels than are found in sealcoat.
That risk is 38 times greater, however, for people living near asphalt sealed with coal tar, the study found. For every million people who spend 70 years living next to sealed pavement, researchers said they would expect about 110 cases of cancer because of the exposure to PAHs.
Most of that risk appears to accrue in childhood. The study found that 50 percent of the cancer risk from PAHs in sealcoated asphalt is acquired within the first six years of life. About 80 percent of a person's risk adds up before age 18.
That's partly because children have different habits than adults. They spend more time near the ground, and they like to put things in their mouths, like their hands or toys. Kids are also smaller, so their exposures to chemicals are more concentrated relative to their body weights.
"Really, what this analysis says is that there's potential harm here. There is risk," said Kenneth Portier, a biostatistician with the American Cancer Society not involved in the research. "What does it mean for me? Maybe I should try to avoid that risk. And especially avoid the risk in my children."
Fortunately, there is an alternative to coal tar-based sealants. A different kind of sealant, made with emulsified asphalt, has much lower levels of PAHs. It's the main kind of sealant used in Western states, but it can also be found in other parts of the country with a bit of searching.
Although the study found an association between coal-tar sealcoat and a higher exposure to a cancer-causing compound, it did not prove that the exposure might cause can
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