Runoff from a sealcoated parking lot in Fredericksburg, Texas stains the gutter black as it flows to a nearby creek. Coal-tar-based sealcoat is commonly applied in Central Texas. Photo courtesy of the U.S. Geological Survey.
Runoff from a seal-coated parking lot in Fredericksburg, Texas stains the gutter black as it flows to a nearby creek. Coal-tar-based sealcoat is commonly applied in Central Texas. Photo courtesy of the U.S. Geological Survey.

Or will they forfeit the future?

San Antonio, the nation’s seventh largest city at 1.5 million people, may become the nation’s largest city to ban coal tar pavement sealers. Earlier this year the City laid out a schedule to bring this before the San Antonio Council by summer.

Councilman Ron Nirenberg (D8) mentioned the proposed ban in a recent speech and spoke about it January to the San Antonio Express-News. He told the paper that, “I had this issue waiting on my desk the first day in office. Advocates for … water security had been calling for this for quite some time.”

Councilman Nirenberg first drafted a council consideration request in November 2014 with signatures from council members Mike Gallagher (D10), Rey Saldaña (D4), Shirley Gonzales (D5) and Ray Lopez (D6). That list includes five out of the 10 current San Antonio City Council members.

The City’s Citizen’s Environmental Advisory Committee (CEAC) unanimously recommended a ban in a June 2014 letter to the council, citing research by federal and state governments and Baylor University. Coal Tar Free America first met with the CEAC in 2012. One of their former members, Stephen Kale has been a persistent voice on this issue to the community over the years.

YouTube video

A Good Decision?

Banning coal tar pavement sealers hits on all of the core issues which frame good government decisions. It is:

  1. Fiscally responsible:  The cost difference between the products is small if any. Enforcement costs are small and are far outweighed by the cleaner air and water and the likelihood of reduced illness including cancers and the tremendous financial burden that comes with it (see Cancer’s sinister side effect: financial toxicity).
  2. Fair: Suppliers have had over 10 years of notice of the problems with coal tar sealers. That is plenty of time to cycle through supplies and retool for a new generation of more eco-friendly products.
  3. Factual: The data is clear and well-documented by the EPA, USGS, SAWS, City of Austin and numerous states and universities and demonstrates that coal tar pavement sealers have undesirable effects on air, water, soil, frogs, fish, pregnant women, and children. There is no debate of these facts in the unbiased scientific community. We could know more, but we know enough. More local information is included below if you’d want to read more details.

Is it bold? Yes.
Will it improve the City of San Antonio? Yes.
Is it the right thing to do? Yes.
Does it make the world a better place? Yes.
Will it make our children proud of the decision? Yes.

Public Comments Due April 29, 2016

The City of San Antonio is receiving public comments until the end of the month. Comments can be emailed to

sa timeline

History of Coal Tar Sealers in San Antonio

While it is interesting from a scientific perspective to look at how communities with different use, weather, geology and hydrology are affected by coal tar sealers, the fact remains that exposure to coal tar sealers happens most intensely on or near a sealed asphalt surface. In other words, it is akin to exposure to cigarette smoke. While it may be fascinating to consider the city-wide ramifications of cigarette smoke, the greatest affect is personal, and local to our children. The same is true with coal tar sealers.

San Antonio’s Water Supply

A separate agency, San Antonio Water System (SAWS), oversees the water supply of the greater San Antonio area. In 2006 they looked at coal tar pavement sealers. As shown in one of their summary slides here, they found 77% of randomly selected parking lots had coal tar sealers on them.

saws coal tar lots

During this time they also did some stream monitoring and found that for individual and total PAH sampling effects levels were exceeded at 40% of their sampling locations. PAHs or polycyclic aromatic hydrocarbons are the most commonly tested chemical in coal tar pavement sealers, but they can come from any combustion of hydrocarbons. While this is not extensive testing, it found that stream sediments are currently being affected by high PAHs. Some may argue that you can’t prove that this comes from coal tar sealers, but not only is it likely, it is certainly the most cost-effective and reasonable way to control urban PAHs.

Graphic courtesy of SAWS
Graphic courtesy of SAWS

USGS Research

The United States Geological Survey has completed studies among USGS colleagues and with outside agencies. While some of the results of their work at applicable wherever coal tar sealers are used (see below), they have also studied some of the streams around San Antonio and found:

  • The PAHs were detected most frequently in samples from the Leon Creek and San Antonio River watersheds. 
  • Total PAH concentrations exceeded the Threshold Effects Concentration (TEC)* in 14 percent of the samples and none of the concentrations exceeded the PEC**.
  • Total PAH concentrations in streambed-sediment samples correlate positively with population density; residential, commercial, transportation, and mining land-use categories; and industrial wastewater outfall, wastewater liftstation, and petroleum storage tank potential source of contamination categories.
  •  Mean total PAH concentrations generally are lower in Bexar County samples compared to concentrations in samples collected during previous studies in the Austin and Fort Worth areas, but considering the large ranges and standard deviations associated with the concentrations measured in all three areas, total PAH concentrations are similar.
  • The contribution from each PAH source was estimated by using a chemical mass balance model, which indicated that parking lot coal-tar sealcoat dust is the largest PAH source to the average Bexar County sediment, accounting for 70.2 to 78.9 percent of the PAHs in the mixture. 
kale usgs
Image courtesy of Stephen Kale.

Here’s a summary of their general findings (from their website):

  • Human health
    • Residences adjacent to parking lots with coal-tar-based sealcoat have concentrations of PAHs in house dust 25 times higher than residences adjacent to unsealed pavement or asphalt-sealed pavement.
    • Doses of carcinogenic PAHs through non-dietary ingestion of house dust in residences with coal-tar sealant on the parking lot are 14 times greater than in residences with unsealed pavement, and are more than twice the dose from dietary ingestion, reversing a long-held assumption that dietary PAH exposure exceeds non-dietary exposure.
    • Living adjacent to coal-tar-sealed pavement (a parking lot or driveway, for example) is estimated to increase excess lifetime cancer risk 38 times, and much of the increased risk occurs during early childhood.
  • Environmental health
    • Runoff from freshly applied coal-tar sealcoat is acutely toxic to two test organisms (fathead minnows (Pimephales promelas) and a water flea (Ceriodaphnia dubia)).
    • Toxic effects to test organisms continue for samples collected as long as 111 (3+ months) days following application if organisms also are exposed to ultra-violet light mimicking sunlight.
    • Runoff from coal-tar-sealed pavement, diluted 1:100, causes DNA damage when cells also are exposed to ultra-violet radiation that mimics sunlight.
    • Runoff from coal-tar-sealed pavement, diluted 1:10, impairs the ability of cells to repair DNA damage.
  • Air
    • Emissions of PAHs to air 2 hours after application of coal-tar sealant are 30,000 times greater than from unsealed pavement.
    • Emissions of PAHs to air from parking lots with older (3-8 years) coal-tar sealant are 60 times greater than from unsealed pavement.
    • Total annual PAH emissions from newly applied sealcoat are estimated to be larger than those from vehicles in the U.S.
  • Streams and Lakes
    • PAH concentrations in Lady Bird Lake sediment decline following a ban on coal-tar-based pavement sealants in Austin, Texas.
    • Coal-tar pitch from sealcoat reaches streams and lakes in runoff and soils and unsealed pavement near sealed parking lots.
    • Coal-tar-based sealcoat was determined to be the largest source of PAH contamination to urban lakes sampled by the USGS.
    • Use of coal-tar-based sealcoat is the primary cause of upward trends in PAHs in urban lake sediment.
  • Stormwater runoff
    • Concentrations of polycyclic aromatic hydrocarbons (PAHs) in runoff from pavement with coal-tar-based sealcoat remain elevated for months to years following sealcoat application.
    • Particles in runoff from coal-tar-sealed pavement contained PAHs at concentrations that are 65 times higher than particles in runoff from unsealed asphalt pavement.
    • Runoff from freshly applied coal-tar sealcoat contained elevated concentrations of acridine and carbazole in addition to PAHs.
  • What’s on coal-tar-sealed pavement?
    • Scrapings of dried coal-tar sealant contain 9,400-93,300 mg/kg PAHs.
    • Dust from pavement with coal-tar-based sealcoat has PAH concentrations hundreds to thousands of times higher than dust from pavement with no sealcoat or with asphalt-based sealcoat.
A turtle swims in the San Antonio River. Image courtesy of Stephen Kale.
A turtle swims in the San Antonio River. Image courtesy of Stephen Kale.

* – Threshold effect concentration (TEC) – Concentration of a chemical in sediment below which adverse biological effects are unlikely to occur.

** – Probable effect concentration (PEC) –Concentration of a chemical in sediment above which adverse biological effects are likely to occur.

This story has been republished with permission from

Top image: Runoff from a seal-coated parking lot in Fredericksburg, Texas stains the gutter black as it flows to a nearby creek. Coal-tar-based sealcoat is commonly applied in Central Texas. Photo courtesy of the U.S. Geological Survey.

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Tom Ennis is an engineer with more than 30 years of experience. His efforts and opinions to reduce sealcoat pollution through his blog,Coal Tar Free America, are his own, and not the view his current employer,...