PAHs Increasing in Urban U.S. Lakes

Speaker: Dr. Barbara J. Mahler

PAHs Increasing in Urban U.S. Lakes

Thursday, April 14, 2011
10:30 a.m. – 12:00 noon
H-137 U.S. Capitol Building

On April 14, 2011, the Environmental and Energy Study Institute (EESI), Water Environment Federation (WEF), and Office of Rep. Lloyd Doggett (D-TX) held a briefing featuring new studies by the U.S. Geological Survey (USGS) which found coal tar-based pavement sealants as a major source of polycyclic aromatic hydrocarbons (PAHs) in urban lakes across the country. PAHs are a significant environmental topic because several are probable human carcinogens, they are toxic to fish and other aquatic life, and their concentrations have been increasing in urban lakes in recent decades. The speaker for this briefing was:

Handout: Coal-Tar-Based Pavement Sealcoat, Polycyclic Aromatic Hydrocarbons (PAHs), and Environmental Health

Audio recording of briefing and Q&A (mp3)

Highlights from Speaker Presentation

  • Sediment cores can be studied, much like rings on trees, to go back in time and assess sources of water contamination. While sediment cores have shown a decrease in contaminants like DDT and lead since the 1970s, PAH concentrations have increased in urban lakes.
  • PAHs (polycyclic aromatic hydrocarbons) are organic contaminants created from burning motor oil, coal, or cigarettes, manufacturing tires, and others. PAHs are composed of six atom benzene rings with many different configurations and varieties. Those with fewer rings are usually more toxic, soluble, and volatile, while PAHs with more rings are carcinogenic and more easily attach to sediments.
  • Seven different PAHs are qualified as probable human carcinogens by the Environmental Protection Agency (EPA) and have been linked to harmful effects on sperm in men, and on umbilical cords in pregnant women, with connections to slower cognitive development in young children.
  • The City of Austin received funding from the EPA to study sediment profiles near residential and light commercial areas for PAH concentrations greater than 1,500 mg/kg, numbers normally associated with coking of coal or tire manufacturing. U.S. Geological Survey (USGS) found that the only product with PAH concentrations higher than 1,500 mg/kg amongst motor oil, diesel engine emissions, asphalt, etc. was coal tar-based sealcoat.
  • Coal tar-based sealcoat is a liquid product sprayed on black tops to beautify and protect asphalt, and is most commonly used on parking lots, driveways, and playgrounds – not often for public roads. Coal tar is derived from coal tar pitch – residue created from the coking of coal – a known human carcinogen.
  • Asphalt-based sealants have PAH concentrations of 50 mg/kg, while coal tar-based sealants have PAH concentrations of 100,000 mg/kg.
  • Over time, abrasion wears down the sealcoat and turns it into a fine powder that is mobilized by adhesion, tracking by shoes, wind, volatilization, and storm run-off.
  • Lesions, liver abnormalities, tumors, decreased juvenile growth, and increased mortality found in fish populations have been connected with PAHs in the water. While these types of PAHs are insoluble and do not affect our drinking water, they affect humans through inhalation, ingestion, and dermal exposure.
  • USGS analyzed house dust in several apartments in Austin. PAH concentrations in dust in apartments next to parking lots with coal tar sealants were 25 times higher than in dust in apartments next to parking lots with asphalt-based or no sealants.
  • The District of Columbia; City of Austin; Dane County, Wisconsin; and several municipalities in Minnesota have banned the sale and use of coal tar-based products.
  • On April 13, 2011, the Washington State Senate passed what is likely to become the first statewide ban on the use and sale of coal tar sealants.

Related Media Coverage

This briefing was held in cooperation with the USGS Office of Water Quality and its National Water-Quality Assessment (NAWQA) Program.

For more information, contact us at communications [at] or (202) 662-1884.

Please click here to subscribe to our e-mail list for event notices or newsletters.