Sexing Up Sealants

It's hard to make pollution stories sexy, and harder still when the pollutant on trial is something like coal-tar sealant, since nobody knows what it is.

Sexy or not, however, coal-tar sealant is all over Austin – city staff estimate that some 600,000 gallons of the sticky black goo are applied each year to protect and beautify Austin's parking lots. Coal-tar sealant is also toxic, which is why Council Member Lee Leffingwell made a big deal last Friday out of announcing a proposal to ban parking lot sealant from Austin pavement at Barton Springs, where random men in speedos livened up the press conference, as well as the otherwise impenetrable issue.

In a peer-reviewed study released in June, city staff and the U.S. Geological Survey found that water downstream from sealed parking lots frequently showed "hot spots" of PAH contamination – polycyclic aromatic hydrocarbon, a class of chemicals that for years have been increasing in urban waterways, although no one has been able to figure out why. In their study, the city and USGS claim they've cracked the code, and argue that sealants could be responsible for a vast majority of PAH contamination nationwide.

Here's how it works: Coal-tar sealant isn't so bad as long as it stays stuck to the parking lot. Unfortunately, it does not, (which is why manufacturers recommend frequent reapplication). It flakes off over time and washes off into lakes and streams, where it sits in the creek bed making aquatic critters ill in the gills. In the water, the PAHs pose no known health threat to humans. If it flakes off in the rain, however, critics warn it could also flake off under other circumstances, which is one more reason not to go traipsing around hot parking lots in bare feet, and one more reason to give the stuff the boot. Hence the ban, which would prohibit the use of coal-tar sealants within Austin and its extraterritorial jurisdiction and the sale of the sealant within Austin.

"The environmental risk of anyone continuing to use coal-tar sealants in Austin is unacceptable," said Leffingwell. If the rest of council gets on board, the ban will take the city a step farther than the rather oxymoronic "voluntary ban" City Council called for in 2004. Leffingwell hopes to put the ban before council for official approval on Nov. 17. That will take Austin into territory no other city has trod, a fact Leffingwell proudly trumpeted. "We're on the leading edge on this one," he said.

Industry isn't so sure that a ban is the answer. Bob Demont, a toxicologist with the consulting firm ENVIRON International, which has been working with the sealant industry group to independently study the issue, said he expects the link between coal-tar sealants and PAH contamination to be a matter of continuing debate. "I think it's too early to determine what management approaches might be effective for [PAH contamination] in Austin," Demont said.

Leffingwell said he doubted the ban would have a major economic impact on local purveyors of parking lot products – other kinds of sealants would continue to be legal. He also admitted that there are downsides to leaving lots unsealed. "It does have a pleasing aesthetic impact," he said of sealants. So maybe coal tar is a little sexy after all.