"Don't Use Coal Tar on Asphalt Pavement," Respected Asphalt Institute Recommends

The respected Asphalt Institute, which provides research and technical assistance to pavement managers and designer engineers primarily in the US, recommends against using coal tar sealants over asphalt.

This isn't the first technical paving source to recommend against the use of coal tar sealants for non-environmental reasons. A European study showed that coal tar sealants are prone to shrinkage cracking and accelerated pavement degradation.

Interesting since the coal tar sealant industry often says "without coal tar sealants, pavements will degrade and fall apart." Now the engineers and scientists who design these pavements say that asphalt pavements will do just fine without the application of coal tar sealant.

Here's what the website says:

How should driveways and parking lots be sealed?


A light application of a slow-setting asphalt emulsion diluted with water should be applied. In most cases, a dilution of one part emulsion to one part water is used. SS-1, SS-1h, CSS-1, or CSS-1h asphalt emulsions are typically used. Commercial sealers are also available. Those containing coal-tar compounds are not recommended. The diluted material is sprayed or squeegeed onto the surface in a thin, uniform coating. The total quantity of diluted sealant normally applied is 0.1 to 0.15 gallons per square yard. Exact quantities should be based on the surface texture, dryness, and degree of cracking or raveling.

Hear from Experts at Nov. 18th Seminar/Free Webinar on PAHs and Coal Tar Sealants

If you've had any questions about the topic of this website, mark this day on your calendar.  This seminar represents a first assemblage of leading experts on this topic from around the country.  Hear from one of the USGS researchers who first published about coal tar sealant pollution; a toxicologist who has been studying coal tar sealants and human exposure and a regulator from Minnesota where there are more bans than anywhere else in the country!  And it is free for the webinar, but you have to register!

Cleanup Costs "Huge Problem;" Drives Another Minnesota Town Toward a Coal Tar Sealant Ban

With more municipal coal tar sealant bans than any other state in the US, another Minnesota community is moving toward passage of a ban.  The real cost of disposing dredged sediment from retention ponds has led the City of Inver Grove Heights to begin the process to pass a ban. 

According to an article in the Minneapolis Star Tribune, Inver Grove Heights found that 25% of their tested stormwater ponds (3 out of 12) showed the presence of polycyclic aromatic hydrocarbons (PAH's).  The sediment from two of the ponds would have to go to a landfill at a cost of $180,000 to $200,000.  The problem is that Inver Grove Heights has 578 stormwater ponds.

"Every city is in the same situation -- it's a huge problem," said White Bear Lake public works director Mark Burch.  White Bear Lake was the first Minnesota community to pass a coal tar sealant ban.

It is reasonable to expect these high levels are caused by coal tar sealant pollution.  "Data we have collected over the last year indicate that there is a good percentage of these pollutants tied to coal-tar sealants," said Don Berger of the Minnesota Pollution Control Agency.  It is estimated that there are over 20,000 stormwater ponds in the Twin Cities area under MS4 permitting, but there are many more private ponds at private facilities and under homeowner association control.

So it seems that industry's solution to the problem of coal tar sealant pollution, stormwater ponds, doesn't really work.  It just delays and moves the cost burden to someone else.  Time to try something else: complete elimination of this product.

New EPA Runoff Study Says Coal Tar Sealant Bans Maybe Most Cost-Effective Way to Control Pollution

The Environmental Protection Agency has completed their runoff report as was promised to Congressman Lloyd Doggett 2 years ago.  The official title is Assessment of Water Quality of Runoff from Sealed Asphalt Surfaces, but perhaps a more appropriate title would be: "An Assessment of PAH Pollution Potential from Pavement Sealants During the Curing Process."  That's because the study used only one coat of sealant (usually 2 are recommended), didn't allow car traffic on the lot, and collected only one runoff sample between 30 and 160 days after application.

Important findings were:

• Runoff from a coal tar sealed surface is about 100 times more potent in PAHs than asphalt based sealant.
• Choosing to ban coal tar sealants may be the most cost-effective way for communities to deal with the pollution impacts of this product. 

Lessons learned, I hope, are:

• Pavement sealants don't always cover as much as the label states; buy a little extra!
• Don't use a toxicity test that is negatively affected by the kind of water used.  And if the first one doesn't work, try another one.  For example, try the Ames Test.
• Don't do your experiment downwind of what appears to be a crumbling coal tar sealed roof.
• If traffic is the major cause of wear and sealant loss during the sealant's life, recognize the limitations of the research.

Austin School District Nears Landmark Decision on Coal Tar Sealants

Over two years ago Austin's school district (AISD) committed to investigate the use of coal tar pavement sealants "as soon as possible."  Now a story in a local newspaper, the Oak Hill Gazette. indicates the district is closer to having an action plan.  The action plan would be the nation's first for coal tar pavement sealants, but hopefully in keeping with the USEPA's Safe School Initiative where schools are encouraged to do everything practicable to minimize hazardous exposures to children.  It is estimated that somewhere near 10,000 schools in the US have coal tar sealant on their pavement.

The City of Austin banned coal tar sealants in 2005, but the remnants of the toxic sealant linger both on  parking lots, playgrounds and the soils near them.  An interim report showed by a toxicologist found the 5 complete exposure pathways for students and teachers at schools.  Coal Tar Free America discussed these findings in a post earlier this year (link).

The final report should be completed in 30 to 45 days.

EPA Shows Toxicity of Coal Tar Sealants in Controlled Study

The much-anticipated EPA analysis of coal tar sealant runoff at Edison, New Jersey is now available.  Actually the preliminary results were presented last year at a conference sponsored by the American Society of Civil Engineers (ASCE).  It is available at this link.  A more thorough publication is expected in the future.

The researchers set up test plots of an asphalt parking lot coated in coal tar sealants, asphalt based sealants, and unsealed asphalt surfaces.  Interestingly the areas were closed to vehicular traffic.  For those of us who pay attention to parking lots and sealants, without traffic or snow plows, pavement sealant can last a very long time. These are the primary mechanisms for sealant loss.  The study, while valuable for comparative purposes, misses an opportunity to measure real world PAH loading from parking lots.

While there is some potential for PAH contamination from cars and tires, these sources would be consistent for all types of surfaces.  Nonetheless, EPA showed that runoff from a coal tar sealed surface is about 100 times more potent in PAHs than asphalt based sealant.

What is surprising is that there is not a whole lot of change between the PAH loading after 24 hours and 30 days.  For coal tar sealants it only reduces by about one-third, which probably is insufficient to claim that the problem with sealants is only soon after the application.

Cleveland Rocks! Park District Avoids Coal Tar Use

Cleveland has long been a symbol of America struggling to emerge out of our industrial past.  Some of the most polluted streams from coal tar waste have been found here downstream of coking facilities.

Now the Cleveland Metro Parks is continuing the vision of a new cleaner, more sustainable future by specifying non-coal tar products for their upcoming pavement maintenance program.  One of the sites that will be using less-toxic materials is the Rocky River Nature Center, which is home to numerous outdoor programs to experience nature.  Here's a well-stated quote from their program guide:

“In the end our society will be
defined by not only what we create
but by what we refuse to destroy.” John Sawhill