Driveway and playground sealers are used every day around the country, and we don’t think too much about what chemicals may be in them, just as long as they do the job for which they are intended.
Coal-tar based sealants are toxic to aquatic life and to humans, not only damaging DNA, but also impairing DNA’s ability to repair. This is according to two studies, one by the U.S. Geological Survey (USGS) that showed that rainwater runoff after a coal-tar-based sealant’s application resulted in 100 percent mortality to minnows and water fleas, part of the base of the food chain. The second study was done by the Ecole Nationale des Travaux Publics de l’Etat (ENTPE).
Pavement sealers containing coal-tars in use today have extremely high levels of polycyclic aromatic hydrocarbons (PAHs). According to the Agency for Toxic Substances and Disease Registry (ATSDR), PAHs are a group of over “100 different chemicals formed during the incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco or charbroiled meat.”
The bottom line is that coal-tars are a known human carcinogen, while several PAHs are probable human carcinogens, and some others are toxic to fish and other aquatic life, according to the USGS. The two studies were done to address concerns over the impact to aquatic life after rainfall occurs hours or even days after a coal-tar sealant is applied.
Sylvie Bony, who led the study at the Ecole Nationale des Travaux Publics de l’Etat (ENTPE), a French research agency in Lyon, France, said “The simultaneous occurrence of DNA damage and impairment of DNA repair has important implications for cell health.” The results of this study were published in the journal Science of the Total Environment, under the title: Exposure to runoff from coal-tar-sealed pavement induces genotoxicity and impairment of DNA repair capacity in the RTL-W1 fish liver cell line.
The USGS has been studying coal-tar sealants as a source of PAHs for 10 years now, and the findings from the two studies are consistent with the known toxicity and genotoxicity of the chemicals. The USGS study was published in the journal Environmental Science and Technology, under the title: Acute Toxicity of Runoff from Sealcoated Pavement to Ceriodaphnia dubia and Pimephales promelas.
The states of Minnesota and Washington have already banned the sale and use of coal-tar-based sealants. Many home and building supply retailers, such as Home Depot, Lowe’s, True Value, and Ace Hardware have already stopped carrying coal-tar-based sealers.
One industry group, The Pavement Coating Technology Council, disagrees with the studies, saying coal-tar-based sealers perform better than asphalt-based sealers. They also say the sealer is not harmful to fish or the environment, despite what the USGS or anyone else says.
