Safer Sealing to Protect People and the Environment. HRWC is advocating for policy changes and educating residents to protect the watershed from toxic coal tar.

In Michigan, coal tar-based sealcoat is applied widely on driveways, parking lots, and even playgrounds. Sealcoat applicators and their customers say the product enhances the look of weathered asphalt surfaces and prolongs product life. However, coaltar sealcoat can pose significant risks to humans and aquatic life.

HRWC has met with several townships to advocate for ordinances that prohibit sealcoats containing coal tar. There are alternative products that are comparably priced. Many have done so. We are also working to get a statewide ban.

Coal tar sealcoats are incredibly high in polycyclic aromatic hydrocarbons, or PAHs. PAHs are of concern because many of these compounds have been identified as toxic, mutagenic, teratogenic (causing birth defects) and/or probable human carcinogens. Coal tar sealants contain 1000 times more PAHs than asphalt-based sealants (a readily available alternative) and are the number one source of PAHs in lake sediments. In fact, studies show up to 50-75% of all PAHs found in sediments within the Great Lakes region comes from coal tar sealcoat.

PAHs from coal tar sealcoat are released into the environment in several ways. When applied, these compounds volatilize into the air, affecting air quality. As the sealcoat weathers, dust from the pavement makes its way into homes on shoes and clothing. When it rains, loose particles move into soils, stormwater catch basins, lakes, and rivers.

Elevated concentrations of many PAHs were detected in sediment samples taken within the Huron River Watershed.

In rivers and lakes, PAHs are found primarily in the sediments. Organisms that spend part or all of their life cycle in contact with these sediments can experience adverse effects due to exposure to elevated concentrations of PAHs. Affected organisms include mammals, birds, fish, amphibians and plants. Studies have linked PAH exposure in aquatic animals to stunted growth, reduced reproduction, difficulty swimming, liver problems, altered development, immune system impairment and death.

For someone who spends their lifetime living adjacent to coal tar sealcoated pavement, the average excess cancer risk is estimated to be 38 times higher than the urban background exposure. Much of the increased risk occurs during early childhood. Children play on and near these surfaces and are, therefore, more likely to inhale or ingest PAHs associated with coal tar sealcoat.

Homeowners and those who manage grounds for private entities such as churches, daycares or businesses can:
Consider eliminating sealcoating as a maintenance practice for asphalt surfaces

If sealcoating cannot be eliminated, use asphalt-based sealcoat rather than coal tar sealcoat. There are contractors who will apply asphalt-based sealcoat, and this alternative is also available at most hardware stores. (Most major hardware store chains have already removed coal tar sealcoat from their shelves.)

Cities and other municipalities can:
Pass an ordinance banning the use of coal tar sealant within the municipality.

Adopt a resolution committing to the reduction or elimination of the use of coal tar sealant on city property.

Universities and schools can:
Commit to phase out the use of coal tar sealcoat on their properties. The University of Michigan, for example, does not use coal tar sealers and limits asphalt-based sealcoating to special cases.

A growing number of communities are choosing to ban the use of high PAH pavement sealers including coal tar based sealers.  The following communities have adopted ordinances that make it illegal to sell or apply high PAH pavement sealers:

Huron River Watershed Communities
Ann Arbor
Ann Arbor Township
Pittsfield Township
Scio Township
Van Buren Township
West Bloomfield
Wolverine Lake

Other Michigan Communities
Grosse Ile
Spring Lake Township
Traverse City

Learn how to identify a coal tar or other sealant products with high PAH content. You can request a Materials Safety Data Sheet (MSDS) or look at the product label. Avoid products with the following identifiers:

Coal Tar Based Sealants

  1. CAS#65996-92-1
  2. CAS#65996-93-2
  3. CAS#65996-89-6
  4. CAS#8007-45-2
  5. Coal Tar
  6. Coal Tar Pitch
  7. Coal Tar Distillates
  8. RT-12
  9. Refined Tar
  10. Refined Coal Tar Pitch
  11. Coal Tar Pitch Volatiles
  12. Tar
  13. Related terms

Other High PAH Sealants

  1. CAS#64742-90-1
  2. CAS#69013-21-4
  3. Steam-cracked Petroleum Residues
  4. Steam-cracked Asphalt
  5. Pyrolysis Fuel Oil
  6. Pyrolysis Oil
  7. Heavy Aromatic Pyrolysis Oil
  8. Heavy Fuel Oil (HFO)
  9. Heavy Pyrolysis Oil (HPO)
  10. Ethylene Tar
  11. Ethylene Bottoms
  12. Related terms

Near the Huron River Watershed area, these companies offers alternatives to high PAH sealcoats (Be sure to specifically request asphalt based sealers as many of these companies offer multiple products):

If you represent a company that will offer alternatives to coal-tar and service the Washtenaw/Wayne/Oakland/Livingston County area and would like to be listed here, please contact

Find other companies that offer alternatives (nationwide)

For More Information

USGS Fact Sheet on Coal-Tar Sealcoat

Minnesota Pollution Control Agency’s FAQs on coal tar based sealant

Freshwater Future’s Coal-Tar website, including sample ordinance and resolution language.

North Carolina State University, Urban Waterways: PAHs in Urban Waters

U-Wisconsin Fact Sheet, Avoiding High Costs from Stormwater Sediment Contaminated by Coal-Tar Based Asphalt Sealcoats.

Coal-Tar Scientific Studies

  • Note: These pdfs are not provided due to copyright restrictions.

Mahler et al. 2012. Coal-Tar-Based Pavement Sealcoat and PAHs: Implications for the Environment, Human Health, and Stormwater Management. Environmental Science and Technology 46, 3039-3045.

Mahler et al. 2014. Concentrations of polycyclic aromatic hydrocarbons (PAHs) and azaarenes in runoff from coal-tar- and asphalt-sealcoated pavement. Environmental Pollution 188: 81-87. (Link)

Pryer, et al. 2010. Coal-tar based pavement sealant toxicity to freshwater macroinvertebrates. Environmental Pollution 158, pp. 1932-1937 (Link)

Titaley, Ivan A., et al. 2016. “Identification and Toxicological Evaluation of Unsubstituted PAHs and Novel PAH Derivatives in Pavement Sealcoat Products.” Environmental Science & Technology Letters, April. doi:10.1021/acs.estlett.6b00116. (Link)

Van Metre et al. 2010. Contributions of PAHs from Coal Tar Pavement Sealcoat and Other Sources to 40 U.S. Lakes, Science of the Total Environment 409, pp.334-344.(Link)

Witter et al. 2014. Coal-tar-based sealcoated pavement: A major PAH source to urban stream sediments. Environmental Pollution 185: 59-68. (Link)