A City Council committee ordered staff to research the issue, drafted an ordinance to outlaw the widely used products and recommended its passage. Aldermen cited federal, state and academic studies that found that coal tar sealants contain high levels of toxic chemicals, steadily wear off and crumble into dust tracked into houses and washed into waterways.
But the coal tar industry was ready for a fight. After Austin, Texas, in 2005 became the first U.S. city to ban coal tar sealants, industry leaders formed a tax-exempt lobbying group and started funding their own research - all in an effort to convince homeowners and elected officials that coal tar sealants are safe.
Industry representatives have cited their studies in presentations arguing that bans on coal tar sealants would do little to eliminate toxic chemicals in the environment. Promotional materials from contractors and manufacturers say the papers show that government studies are flawed, or "lies," as one brochure describes them.
"My members don't want to sell a product that causes harm," Anne LeHuray, executive director of the Pavement Coatings Technology Council, the industry lobbying group, said in an interview.
The industry's efforts have worked in some cases. Since 2010, cities including Des Plaines and Springfield, Mo., and the states of Illinois, Michigan and Maryland have rejected coal tar-related legislation after LeHuray and local contractors intervened.
"It seemed too confusing," said Patricia Haugeberg, a Des Plaines alderman who moved to table the suburb's proposed 2011 ban.
In a February presentation to contractors, a top industry representative boasted that they are beating government scientists "on their own turf."
Yet a Chicago Tribune review of the two industry-funded studies published in a peer-reviewed scientific journal in recent years found they fall short of proving their authors' contention that coal tar sealants pose few, if any, threats to human health and wildlife. And, the Tribune found, the industry has at times overstated the findings supporting coal tar.
Manufacturers promote coal tar pavement sealants as a way to extend the life of asphalt and brighten it every few years with a fresh black sheen. The products are most commonly used in states east of the Continental Divide; in the West, contractors tend to use asphalt-based sealants that contain significantly lower levels of worrisome chemicals.
Coal tar sealants contain up to 35 percent coal tar pitch, partially refined waste from steelmaking that the National Toxicology Program and the International Agency for Research on Cancer consider a known carcinogen. Among the chemicals of concern in the products are polycyclic aromatic hydrocarbons, or PAHs, which not only pose a cancer risk but can trigger developmental problems and impair fertility, according to the U.S. Environmental Protection Agency.
Peer-reviewed studies by government scientists have found that coal tar sealants are a major source, and sometimes the dominant source, of PAH contamination in urban areas. Other sources of the chemicals include vehicle exhaust and factory emissions.
In response to the growing body of federal research and regulatory pressures, the coal tar industry turned to a pair of consulting firms frequently hired by corporations dealing with environmental, health or safety issues - Exponent Inc. and Environ International. The industry-funded papers, published in a minor journal called Environmental Forensics, contend that coal tar sealants are at best a minor source of pollution.
The Exponent study, for instance, concludes that vehicle exhaust and industrial pollution are far bigger sources of PAHs than coal tar. But the finding is largely based on an older scientific model that does not include coal tar sealants as a potential source, leading the researchers to conclude that PAHs in the environment "can be explained in the absence of any contribution" from pavement sealants.
Kirk O'Reilly, an Exponent senior scientist and the study's chief author, said government researchers have overstated their conclusions and failed to consider "the large body of literature" about the chemicals. The government research, O'Reilly said in email response to questions, "does not prove that sealers are a source."
But at the end of his paper, O'Reilly acknowledges that coal tar sealants "cannot be eliminated as a PAH source."
The Environ International study, meanwhile, tested whether PAHs declined in Austin after the city's 2005 coal tar ban took effect. In a 2010 paper, the researchers reported they found that little had changed 2 1/2 years later, and industry representatives continue to cite the study as evidence that banning their products would not reduce PAHs in homes and waterways.
But coal tar pavement sealants weren't used in some areas where sediment samples were collected, including roadways and parking lots built after the Austin ban took effect, according to the text of the study. Austin also didn't require existing coal tar to be stripped from pavement, meaning many potential sources of pollution remained after the ban.
The researchers state that it could take more than two years to determine whether the Austin coal tar ban worked. One of the most dangerous PAHs, benzo(a)pyrene, is federally listed as a persistent chemical like DDT and PCBs, which were banned during the 1970s but took years to decline in the environment.
Robert DeMott, an Environ toxicologist and the study's chief author, has told contractors and elected officials that Austin's move to eliminate coal tar sealants failed to make a difference, largely because there are so many other sources of PAHs. But in an interview he acknowledged that his study didn't reach such a definitive conclusion.
"The question boils down to how much of a change is a meaningful change," DeMott said. "If you remove one part out of thousands of contributors, will you ever be able to see a difference? That is a question that remains unanswered."
Asked if industry funding affected their conclusions, the Exponent and Environ researchers said their opinions are their own.
Barbara Mahler, one of the government scientists who first identified coal tar sealants as a major source of PAH contamination, said industry representatives haven't accurately represented her research findings in their presentations.
"They make very misleading statements, and if you don't know any better, it can all sound convincing," Mahler said in an interview. "The conclusions of their studies are they can't reach any conclusions. But you wouldn't know that from what they say to the public."
During the past decade, Mahler and Peter Van Metre of the U.S. Geological Survey roiled the coal tar industry with a series of peer-reviewed studies that found high levels of PAH contamination in areas where coal tar sealants are used. Dramatically lower levels were found in Western cities.
In Lake in the Hills, Ill., about 50 miles northwest of Chicago, they found levels of benzo(a)pyrene in dust from coal tar-covered driveways that were up to 5,300 times higher than the level that triggers an EPA Superfund cleanup at polluted industrial sites.
The USGS scientists also found that parking lots with 3- to 8-year-old sealant released 60 times more PAHs into the air than parking lots without sealant. Other researchers from the EPA and the University of New Hampshire have found significantly higher PAH levels in runoff from parking lots sealed with coal tar than in runoff from asphalt-sealed lots.
"This is a common-sense issue," said Judy Crane, a scientist for the Minnesota Pollution Control Agency who determined that coal tar sealants are the leading source of PAH contamination in Minneapolis-St. Paul stormwater ponds. "You can see the stuff flaking off and being tracked inside or washed into waterways."
New research from Baylor University adds to that troubling picture. The study, published in January in the peer-reviewed scientific journal Environmental Science and Technology, found that exposure to coal tar-contaminated dust during the first six years of life significantly increases the risk of developing cancer.
"It's very difficult to attribute environmental cancers to any one source, and PAHs are everywhere," said Spencer Williams, a Baylor research toxicologist and the study's chief author. "But these coal tar sealers are a big dollop of PAHs that you wouldn't get anywhere else."
A month after the study came out, the industry lobbying group hosted an hourlong Web presentation that promised to teach contractors "how you can be successful in defense and what to say to customers, media, and even state and local officials who have questions about the lifeblood of your business." One of the sponsors was Koppers Inc., a Pittsburgh-based company that processes coal tar at a plant in west suburban Stickney, Ill.
Mike Juba, a Koppers health and safety official, urged contractors to stress the industry-funded science in conversations with customers. He also advised them to talk about their contributions to local economies.
"To eliminate a useful product and put the businesses and jobs of real people at risk ... hurts more people than it helps," Juba said during the presentation. Koppers and Juba did not return calls seeking comment.
There are signs that the industry's initial successes in places like Des Plaines might be fading. The state of Washington, counties in New York and Maryland, and more than two dozen Minnesota cites have banned coal tar sealants. More than 40 contractors in the Minneapolis-St. Paul area and 25 others in Wisconsin have signed pledges to not sell the products.
"Once people are educated about this, they realize it just makes sense to stop adding hazardous materials to the environment when there are other options that don't pose the same hazards," said Al Innes, a Minnesota state official who oversees an EPA-funded program that seeks to reduce the use of coal tar sealants.
Officials in Springfield, Mo., rejected a coal tar ban in 2010 after industry officials and the scientists they funded gave presentations saying the proposal was misguided. One of the opposition's key arguments was that there was no proof that PAH contamination was a problem in local streams.
But in November, a researcher from Missouri State University reported to local officials that he had found high levels of PAHs in nearly half of the two dozen samples he collected from Springfield-area waterways. The highest concentrations were found near parking lots covered in coal tar sealants.
"The industry pulled out all the stops because they didn't want us to set a precedent for other cities," said Cindy Rushefsky, a Springfield, Ill., councilwoman. "We've got our own data and the data is strong. Austin is not unique, and neither are we. They should see the writing on the wall."
She plans to reintroduce the proposal later this year.