Blogs > Ecology > Toxic pavement sealants threaten our waterways

Toxic pavement sealants threaten our waterways

image (1)

View more images on our Flickr site

Toxic pavement sealantsOn July 22, the New York Senate passed S.6308A which would prohibit the sale of pavement products containing coal tar and high levels of polycyclic aromatic hydrocarbons. The bill now awaits passage in the New York Assembly. The legislation would provide crucial protection to human health and aquatic ecosystems. In short, polycyclic aromatic hydrocarbons, or PAHs, are a class of very toxic and carcinogenic compounds which can be found in our lakes, streams, and even our homes which are causing harm to human health and aquatic ecosystems.

Where do we find PAHs?

PAHs are found in coal, crude oil, and gasoline. They are created and released into the environment by heating and burning material that contains carbon such as coal. These compounds are toxic, carcinogenic and have been proven hazardous for human health and aquatic life.

A major source of PAH contamination is coal tar pavement sealants. Coal tar is the byproduct left over from the processing and distillation of coal. This byproduct comes in the form of a thick toxic black sludge which is extremely high in PAHs and is the primary product used in coal-tar based pavement sealants. Coal-tar pavement sealant is applied to driveways, parking lots, and even playgrounds to seal asphalt in order to “protect and beautify” the asphalt. Unfortunately, these sealants contain  high concentrations (up to 40%) of toxic PAHs.

Further, the toxic PAHs in pavement sealants do not remain on the pavement after application instead they erode down into dried particles. These toxic particles are transported by rain, wind, car tires, and shoes into surrounding areas including into our homes as house dust and into our waterways attaching to sediments. Commercial contractors that apply sealants recommend reapplication every three years because of this erosion creating a constant source of PAHs in our environment.

pavement sealantUnited States Geological Survey sediment core samples taken from 40 lakes in urban areas across the U.S. identified an increase in PAHs in urban lakes and streams over the last 40 years. Source tracing from these sediment core samples show coal-tar based sealant was the largest source of PAHs contributing about one-half of PAH concentration. Another study of fifteen stormwater ponds in the Minneapolis-St. Paul, Minnesota metropolitan area identified coal-tar based sealants as the source of 67.1% of PAH contamination.

So how toxic are PAHs from coal tar sealants?

USGS extensively outlines the toxicity of coal-tar sealants to human and aquatic health. Human exposure to PAHs has been linked to several cancers including malignancies of the digestive tract, reproductive systems, respiratory tract and urinary system, and more. PAH exposure has also been linked to decreased cognitive development in children who had increased prenatal exposure to PAHs.

The Department of the Interior identified coal-tar sealants as an environmental justice issue. It found coal-tar based sealants as a major source of PAH contamination in urban areas for large parts of the Nation which may be disproportionately affecting minority, low-income, and tribal populations. 

PAHs are also extremely toxic to aquatic ecosystems. PAH exposure to aquatic organisms occurs through dermal exposure, respiration, or consumption of contaminated prey, or sediment. This exposure results in malformations, decreased behavioral activity, decreased reproduction, decreased rate of survival.  

Exposure to runoff from coal-tar sealed pavement resulted in 100 percent mortality of two aquatic organisms: day-old fathead minnows and water fleas up to 42 days after seal coat application. PAH exposure is linked to a wide range of biological dysfunctions in fish including neoplasia, reduced reproductive success and other types of endocrine disruptions, and more.

What can be done?

Coal-tar is classified in the U.S. as a hazardous waste product if disposed of on land pursuant to the U.S. Resource Conservation Recovery Act, but a 1992 exclusion allows coal tar to be recycled. Unfortunately, the process of recycling coal tar into a pavement sealant does not keep this hazardous material from harming human health and the environment.

Bans and local ordinances have been enacted by other states and municipalities including Minnesota; Washington D.C.;Austin, Texas; and Suffolk County here in New York. In New York, there is currently a procurement ban for use of coal-tar sealants being used on stated owned driveways, parking lots, and playgrounds. 

Riverkeeper supports banning the use of coal-tar and high PAH sealants across the state and strongly backs the passage of A.1304A/S.6308A sponsored by Assembymember Linda Rosenthal and Senator Jen Metzger which would prohibit the sale of pavement products containing coal-tar. Please contact your Assemblymember and urge them to pass this vital legislation.

Tell Gov. Hochul to block invasive species at the Erie and Champlain canals
Become a Member