Asphalt Sealant May Increase Cancer Risks

A common asphalt sealant has been linked to increased cancer risks, especially in children, according to a just-released study.

Specifically, asphalt sealed with coal tar, a by-product of steel manufacturing, may be dangerous, said HealthDay News. Coal tar is a common sealant ingredient and is most typically seen in the Eastern United States and is used to update worn out parking lots and driveways. Sealcoat is a black, shiny substance that is either sprayed or painted on asphalt to improve the pavement’s appearance and protect the asphalt beneath. Some 85 million gallons of coal-tar-based sealant are applied to pavements annually in the Eastern U.S. and Canada, said Environmental Science and Technology.

“People like it because it makes the asphalt look like new. The striping shows up really clearly if you have a parking lot,” study author Barbara Mahler, a research hydrologist with the U.S. Geological Survey in Austin, Texas, told HealthDay News. Mahler noted that these shiny black sealcoats are, in essence, concentrated cancer-causing chemicals called polycyclic aromatic hydrocarbons (PAHs). “When tires drive across it, it’s the grinding action of the tires that breaks up the little particles and grinds it up to a dust, essentially,” Mahler said. That dust can be brought into homes from shoes and hands and is washed into area soil and waterways following rains, said Mahler. Prior studies revealed increased PAH levels in vacuumed dust in homes near sealcoat-covered asphalt, the study indicated.

As we’ve previously written, PAH compounds are typically seen in plastics, rubber, and lubricating oil, and are known to cause cancer and birth defects in animals. According to the U.S. Centers for Disease Control and Prevention’s (CDC) Agency for Toxic Substances & Disease Registry (ATSDR), animal testing reveals that PAHs can affect conception and can have this affect on future generations. Animal research also revealed that the offspring of parents exposed to the toxin had increased birth defect rates and decreased body weight. PAHs can have harmful effects on the skin, body fluids, and the ability to fight disease after short- and long-term exposure.

The Department of Health and Human Services (DHHS) “determined that some PAHs may reasonably be expected to be carcinogens” and some who have breathed or touched PAH mixtures have developed cancer; in lab animals, breathing, ingesting, or touching the compounds led to lung, stomach, and skin cancer, said ATSDR.

For this study, which appears in the journal Environmental Science and Technology, the team compared PAH levels in house dust swept from 23 ground-level homes; half were on parking lots coated with coal-tar sealants and half were not, said HealthDay News. These levels were combined with PAH measurements in “soils sampled near parking lots with and without coal tar-based sealants in New Hampshire and Chicago” and numbers were inserted into U.S, Environmental Protection Agency (EPA) models to access a so-called “excess cancer risk.” That risk becomes 38 times greater for those living near asphalt sealed with coal tar, with about 110 additional cases of cancer because of the PAH exposure.

Of most concern was the affect on children. According to the research, some 50 percent of the PAH cancer risk from sealcoated asphalt is accrued in the first six years of life; 80 percent of one’s risk accrues prior to age 18, said HealthDay News.

“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 who was 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,” he added, said HealthDay News.

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