Just imagine a hidden health risk lurking in your driveway or a nearby parking lot that could be harming you, your children, and the nearby environment. A growing number of scientists, community leaders and environmentalists think there is, and many are taking action to do something about it. The problem, they say, rests in the coal tar-based sealcoat that is often applied to asphalt driveways and parking lots to protect the pavement from oils, tire wear and other factors that lessen the life of the surface.
Coal tar sealcoat typically contains 20 to 35 percent coal tar pitch, which is considered by the National Toxicology Program to be a known human carcinogen. Coal tar, a byproduct of the steel manufacturing industry, is made up of about 50 percent polycyclic aromatic hydrocarbons (PAHs) by weight. Many of those PAHs, which includes hundreds of chemical compounds, are believed to cause cancer and promote cancer by altering human DNA. Exposure to PAHs have also been linked to cardiovascular disease and poor fetal development.
Studies by the United States Geological Service (USGS), some academic institutions, and some state and local agencies have identified coal tar sealcoat as a major source of PAH contamination in urban and suburban areas, with a potential concern for human health and aquatic life.
While coal tar-based sealcoat does a good job of protecting pavement, researchers say that it wears into small particles as it ages. Those particles contain high levels of PAHs, which can be tracked into homes and incorporated into house dust. For people who live next to seal-coated pavements, ingestion of PAH-contaminated house dust and soil can result in an elevated risk of cancer, particularly for young children. Exposure to PAHs, especially early in childhood, has been linked by health professionals to an increased risk of lung, skin, bladder and respiratory cancers.
The USGS also says that runoff from coal tar sealcoated pavement is toxic to certain aquatic life, particularly fathead minnows and water fleas, which are commonly used to assess toxicity. Exposure to even diluted runoff from coal tar sealcoated pavement can cause DNA damage and impair DNA repair for aquatic life.
Last month, representatives from the Michigan Department of Environmental Quality (DEQ) met with researchers from the USGS to discuss research on coal tar sealants and PAHs as they relate to stormwater pollution. The Michigan Department of Transportation has agreed to phase out the use of coal tar-based sealcoat.
The use of coal tar sealcoat has been restricted in several communities in Michigan, and has been banned for use or sale completely in Ann Arbor, Van Buren Township and Spring Lake Township. The state of Minnesota and Washington D.C. have also banned the application of coal tar sealants, and proposals to ban the use of the product across Michigan have already been proposed in the state legislature.
Much of the research on PAHs and coal tar-based sealcoat began in 2003 when staff with the city of Austin, Texas found elevated PAH concentrations in some sediment samples collected from small tributaries and drainage in largely residential areas. Such concentrations, researchers with the USGS said, were typically found near manufactured gas plant Superfund sites. The city staff in Austin hypothesized the source came from particles eroded from parking lots that were coated with coal tar-based sealcoat. Subsequent studies by the USGS determined the source to be coal tar-based sealcoat that flake and cling to sediments when washed away by stormwater.
The research resulted in Austin passing a ban on the use and application of coal tar sealants – the first such ordinance in the country.
Judy Crane, a research scientist with the Minnesota Pollution Control Agency, said a study of stormwater ponds and lakes in the state showed about 67 percent of PAHs in those sediments come from coal tar sealants.
"The Minnesota Pollution Control Agency requires municipalities to measure PAH compounds and metals in sediments before they dredge them. They were finding some (sediments) with really high levels, and because of that, they had to dispose of that sediment in a lime-lined landfill. Some were getting estimates of about $250,000 to dispose of it," she said. "At that point, we weren't sure what the source was, but I was familiar with some of the USGS work, and suspected coal tar sealants. And the study confirmed that."
As a result, the use of coal tar based sealants in Minnesota has been banned across the state. However, not everyone agrees with the research.
Anne LeHuray, executive director of the Pavement Coatings Technology Council, which represents dozens of sealcoat manufacturers across the country, said she believes research by the USGS and others that are blaming sealcoat as a source of PAHs is based on faulty science that is skewed to find the results those agencies sought.
"They are basing it all on – not just flawed science – but bad science," she asserted. "I went to Van Buren Township and asked them if it was their goal to ban PAHs, and if they are going to ban other sources – the employees in these communities aren't experts – and they said no.
"Clearly, this is an opportunity to get rid of something to say they did something. There's no scientific, valid reason for these bans to pass. They do no environmental good, and they do economic harm."
LeHuray points to dozens of other sources of PAHs in the environment, and their widespread finding of the compounds across the globe as evidence.
"The thing about PAHs in general – they are the single most studied suite of chemicals in the environment, and they are found absolutely everywhere. They have been found in remote alpine lakes and in the Arctic. They are ubiquitous," she said. "They are found in your food supply – by grilling meat, vegetables and fish, but also in coffee and tea and hot chocolate. They are in anything you heat up. If you roast coffee, you're making PAHs."
There are, indeed, hundreds, if not thousands, of sources of PAHs in the environment and in our homes. In short, PAHs are compounds made from a mix of carbon and hydrogen formed most often by the incomplete burning of animals or plant matter, coal or petroleum and other organic materials. Cigarette smoke is one of the main contributors of PAHs in an indoor environment, but panfrying food and fireplaces also produce PAHs. That black soot that builds up in chimneys is chock-full of carcinogenic PAH compounds. Outside, they are produced by BBQ grills, fires, car exhaust, asphalt pavements, asphalt sealcoat and many other sources. They are even found in mothballs, some special-purpose skin creams, and some anti-dandruff shampoos. They exist in the air by clinging to tiny particulate matter, in aquatic sediments and soil.
Of all the PAHs that exist, the United States Environmental Protection Agency (EPA) has classified seven as probable human carcinogens, and 16 as priority pollutants. The environmental and human effects of PAHs depend on which are present and their concentrations.
While LeHuray doesn't dispute that coal tar-based sealcoat contains PAHs, she said she doesn't believe that sealcoat is a major source of PAH contamination in homes or the environment. Instead, she said, she believes studies by the USGS and others that are blaming sealcoat as a source of contamination are simply looking for a way to justify their jobs.
"There is a phrase called 'emerging contaminants of concern,'" she said. "That typically means we are looking for other contaminants to keep our funding stream going."
The Great Lakes Restoration Initiative, a federally-funded effort focusing mostly on stopping invasive species, improving wetlands and removing outdated dams, also supports research into issues of emerging concern. In March, the USGS released a study about contaminants in Great Lakes tributaries, which included the Clinton and Rouge rivers.
The study found one or more chemical compounds in 92.5 percent of all 709 samples taken, with mixtures of 10 or more compounds in 34 percent of samples. The Clinton River, at Auburn Hills, tested positive for 53 different compounds in a single sample. Among the compounds the USGS tested for were six PAHs. Findings showed 56 percent to 85 percent of samples were PAHs.
Steve Corsi, a research hydrologist with the USGS’ Wisconsin Water Science Center who contributed to the study, said researchers at the time didn't focus on sources of contamination, but what contamination exists.
"There are all sorts of (PAHs) in sealcoat. The question is probably how are PAHs distributed. There are many that are in sealcoat, and many other sources in the environment," he said. "The distribution of concentrations for different PAHs is what changes from source to source."
The study cast a wide net on the collection of contaminants. Those results have now helped to determine future areas of study. For instance, Corsi said he and others are working on a study focusing on pesticides in Great Lakes tributaries. Next year, studies will focus on PAH levels and sources, with pharmaceuticals and personal care products the focus of study the following year.
The most recent study released, Corsi said, looked at only six PAHs.
"From those six, we can't do source apportionment. That just tells us if there could be problems from PAHs," he said. "The next sample we will do 40-plus, and we will have enough to do some sort of source apportionment, or fingerprinting, of PAHs."
The study of Great Lakes tributaries will be independent of USGS researchers in Texas, who determined that coal tar sealants were a main source of PAH contamination in stormwater sediments there.
Researchers in 2008 expanded their findings to test parking lots and adjacent ponds or lakes that may be effected by runoff from coal tar sealants. Those tests included nine cities in the United States, including lots in Commerce Township and sediments in South Commerce Lake, in western Oakland County.
Of the nine cities tested, PAH samples taken in Commerce Township showed the highest level of PAHs in the country, followed by samples in Chicago; Washington D.C.; Austin, Texas; New Haven, Connecticut; Minneapolis, Minnesota; Seattle, Washington; Salt Lake City, Utah; and Portland; Oregon. Cites west of the Rocky Mountains and the Continental Divide, where asphalt or petroleum-based sealcoat is primarily used, had drastically lower levels of PAH.
Overall, dust swept from parking lots in six cities east of the Continental Divide had a median PAH concentration of 2200 parts per million, with unsealed parking lot dust registering a median of 27 parts per million. In western states, the parking lot dust of asphalt-based sealcoat was 2.1 parts per million, and .8 parts per million for unsealed parking lots. Dust samples taken in Commerce Township had a cumulative average of 3,400 parts per million from coal tar sealed parking lots, and 47 parts per million on non-sealcoated parking lots.
"The other sources of PAHs, such as fallout of industrial emissions, exhaust particles, tire-wear residue or leaking motor oil, because PAHs from such sources are equally likely to occur on both unsealcoated and sealcoated lots," the researchers said in the report.
The study also stated that lakes sampled east of the Continental Divide had higher levels of PAH concentrations.
"Lakes in the central and eastern cities where pavement was sampled have bottom sediments with higher PAH concentrations than do those in western cities relative to degree of urbanization," the study states. "Bottom-sediment PAH assemblages are similar to those of sealcoated pavement dust regionally, impacting coal tar-based sealcoat as a PAH source to the central and eastern lakes."
PAH in dust poses a greater risk to humans than PAHs that settle in water. That is because PAHs tend to bind to particulates in the air, or in the soil or sediments, rather than is found independent in the air or water table. PAHs in raw water tends to absorb particulate matter and are removed by filtration before reaching the tap, according to the EPA.
Nicholas Schroeck, director of the Transnational Environmental Law Clinic at Wayne State University, said he receives calls from the community about whether coal tar sealants are harmful.
"Certainly, with the coal tar sealant, the answer is 'yes,'" he said. "They contain enough PAHs that it is something that you should be concerned with. There are more PAHs in the sealant than in asphalt or oil."
Schroeck said he expects more communities in Michigan will consider restricting or banning the use of coal tar sealants.
"The potential threat to the rivers, lakes and streams in the Great Lakes state is what I would be concerned about. It runs off the pavement and into waterbodies, and the concentrations in those waterbodies pose a health risk to aquatic life.
"In Oakland County, with so many inland lakes, it's something that people should be aware of and look for an alternative. It's definitely providing a pollution load every time it washes off."
Eric Diesing, with the Clinton River Watershed Council, said while the group itself hasn't conducted any studies regarding coal tar sealants, it is considering what direction to take on the issue next year and in the future, as the issue is expected to expand into the watershed.
Rebeca Esselman, a watershed planner with the Huron River Watershed Council, said the council began looking at the issue about two years ago, after coal tar sealants were banned in Minnesota. The group has since become the most active in the state, reaching out to communities to talk about potential dangers.
"We started reaching out to the communities in the watershed and providing materials on the issue, and asking to get in front of city councils and township boards to present about coal tar sealants and ask them to take action," Esselman said.
In Michigan, the municipalities of Byron Township, Charlevoix, Clark Township, Erie Township, Fruitland Township, Laketon Township, Scio Township, the Village of Shepherd, Powell Township, Whitehall, Whitehall Township and White River Township have restricted government or public use of coal tar sealants. Ann Arbor, Spring Lake Township and Van Buren Township have banned the use or sale of coal tar based sealcoat. Additionally, the University of Michigan, Lake Superior State University and Kalamazoo College have ended the use of coal tar based sealants on their campuses.
Nationally, more than 45 cities have banned or restricted the use of coal tar based sealants, including Austin, Texas and San Antonio, Texas; as well as the states of Minnesota and Washington. Several counties, including Montgomery and Prince George counties, in Maryland; Suffolk County, in New York; and Dane County, in Wisconsin, have banned the use of coal tar sealants. The San Diego Unified School District; the University of Illinois, Springfield; Lake Forest College, in Illinois, and others have also banned or restricted its use.
Federal legislation to limit the use of coal tar sealant was last introduced in 2013 by Rep. Lloyd Doggett (D-Texas). The Austin congressman's bill (HR 1625) would have created the Coal Tar Sealants Reduction Act of 2013, which would have amended the Toxic Substances Control Act to phase out the sale, transport and production of coal tar sealants. That bill died in the House Committee on Energy and Commerce.
In addition, some national home improvement chains have discontinued the sale of coal tar sealants, including Ace Hardware, Lowe's and The Home Depot.
"We haven't sold products with coal tar sealants for several years, about 10 years, I believe," said Stephen Holmes, director of corporate communications for The Home Depot.
Proposals to ban the use of coal tar sealants in Michigan were first introduced in 2009 by former state Rep. Rebekah Warren (D-Ann Arbor). That legislation, and three subsequent bills based on it, have all died in committees, where the proposals failed to gain a hearing.
The most current legislation was proposed on December 17, 2015, by Rep. Kristy Pagan (D-Canton), as HB 5174. That bill was referred to the House Committee on Natural Resources, where it has yet to be taken up.
Pagan, who also represents Van Buren Township, said the bill came up just after the city passed its ban on coal tar sealants.
"Coal tar driveway sealcoats present a real health and safety risk for Michigan residents, and are damaging to our air and waterways," she said. "I am proud to represent Van Buren Township, which just passed Michigan's first municipal ban on coal tar sealant, and am excited to lead the charge for a statewide ban on the sale and application of this toxic and all-too common product."
Rep. Andrea Lafontaine (R), who represents parts of Macomb and St. Clair counties, chairs the House Committee on Natural Resources. A spokesman from her office said she has been in communication with Pagan; however, the bill has not yet been scheduled to be picked up this fall.
State Sen. Rebekah Warren, of Ann Arbor, said she and Pagan have been working on an updated version of the bill that she expects to be introduced into the Senate in September or October. She said the issue first came up when a constituent brought it to her attention.
"There are a lot of concerns in terms of the potential carcinogenic properties," she said about coal tar sealants. "We introduced a ban in 2008 at the end of the session, just to get it on record. We have a new version that Kristy Pagan and I have been working on for a while. Both of our individual communities have taken action on it."
In 2015, a team of researchers with the Huron River Watershed Council set out to look for effects of coal tar sealants in the environment. The group identified detention ponds in Ann Arbor that capture high amounts of runoff from parking lots and driveways. Sampling from three detention ponds found highly toxic levels of PAH, which the researchers believe is coming from coal tar sealants. The research spurred the city's subsequent ban on certain sealcoat with high levels of PAHs.
Ann Arbor's ban on coal tar sealants also includes any pavement sealant that has a PAH content of higher than .1 percent, which essentially restricts the use of sealants to petroleum-based sealing products. The city's ordinance prohibits any person from selling or applying coal tar or other PAH content sealant within the city; nor may a person allow such sealants to be applied on their property.
Under the ordinance, all commercial applicators must register with the city prior to applying pavement sealant in the city. Applicators that register must pay a registration fee and provide the sealant product name, type of use and PAH content. Those who violate the ordinance are subject to a civil infraction, punishable by a fine of not more than $10,000.
While the city's ban went into effect on July 3, Matt Naud, environmental coordinator for the city, said enforcement and a registration process will begin after the first of the year.
"Registration won't start until January 1," he said. "The tough part was to get word out. People have jobs booked, and we didn't want to slow any of that work."
Naud said the city mailed notices to all sealcoat applicators within a 30-mile radius of the city, as well as reaching out to the three main Michigan manufacturers of sealcoat. He said applicators who aren't aware of the ban aren't likely to be fined immediately. "If I talk to a contractor once and they do it again, then we will have a problem," he said.
Naud said the issue came to light when the city was notified of contamination on city property. Specifically, he said there was a detention pond on Plymouth Road that was adjacent to a parking lot that had been treated with coal tar-based sealcoat. Sediments in the detention pond had high levels of PAH.
"Now, you have contamination that is leaving a private property and entering a detention pond that might have to be dealt with as hazardous material," Naud said.
The city in previous years had to deal with a massive clean up at a former MichCon gas treatment site on the Huron River. About $4 million at the time was spent on cleanup, which was primarily funded by DTE Energy.
"This wasn't on our radar," Naud said of the contamination believed to be associated with coal tar sealants. "When it came up and we saw the USGS data, we wanted to get ahead of it."
Naud said there haven't been any legal challenges to the city's ordinance. If there were, he said, he believes the city has a right and responsibility to control contaminants that enter the stormwater system, which it must do under federal clean water laws.
"We own the stormwater system and are required to manage it in a way that protects health and the environment," he said. "We banned phosphorus fertilizer in 2006, and we got a lot of pushback then. But the market changed, and there are other products out there, even if its not as effective. That's secondary to the environmental burden that is placed on us."
Christie Alwin, an environmental quality specialist with the Michigan DEQ, said the department is coordinating with the USGS to look at coal tar sealants.
"From our perspective, there is a potential for there to be runoff on parking lots that have been resurfaced and sealed, and that could make its way to a stormwater pond or detention basin," she said. "Over time, we want to understand the quality of those sediments and the requirements of those. Looking at it from a stormwater program perspective, 'How do we make sure those sediments are properly disposed, and what do we know about the impacts of PAHs?'"
Additionally, the federal EPA, as part of a recent court settlement with several environmental groups, has agreed to consider comments restricting the use of coal tar sealants in certain industrial stormwater permits issued by the agency.
Oakland County Water Resources Commissioner Jim Nash said he is not aware of any testing of stormwater basins for PAH in Oakland County, but said he would be in favor of such testing and investigating the issue further.
"In Oakland County, we depend on our lakes for our economy," he said. "Anything we can do to make our lakes more pure would be a great thing in our mind. I think, maybe, we should do some testing. I think it's a very good idea."
The use of coal tar sealants at the county and local level isn't always known.
Whether local school districts are using coal tar sealants on parking lots or playgrounds isn't entirely clear. Officials at Birmingham Public Schools said the district uses a "polymer-based sealant." However, experts in the sealant industry said sealant bases are either made from coal tar or asphalt emulsion, which is a petroleum-based product. However, some asphalt-based products do have a polymer additive, which is used to increase durability. Officials in the Rochester Community Schools district said the district doesn't use sealants. Likewise, the use of asphalt sealants in the Bloomfield Hills Schools district is very limited.
"Typically, we only use sealants to black out old traffic markings to make changes," said Brian Goby, director of physical plant services for the Bloomfield Hills district. "This is rare, usually a very small area, and that hasn't been done in quite a few years."
Local municipalities also have similar practices regarding parking lot maintenance. For instance, the city of Birmingham doesn't treat parking lots, with the exception of patching pot holes or full replacement. "We patch them, but we don't refresh or seal them," said Lauren Wood, director of public services for Birmingham. "Parking lots, as a general rule, we just keep them safe and patch them."
Bloomfield Township Director of Public Works Tom Trice said the township doesn't sealcoat parking lots because he doesn't believe there is any added benefit to do so.
"We would never do that. There's no real reason to do it," he said. "It creates a maintenance headache because once you do it, you have to continue doing it. The sealcoat people will claim it extends the life of the asphalt by keeping the oil out, but the asphalt industry hasn't found that to be true."
In terms of alternative sealcoats, the industry standard in Michigan is coal tar based sealcoat, which manufacturers and applicators say is the most durable product available. Petroleum-based, or asphalt-based sealcoat, applicators say, doesn't have the same durability or shine that coal tar sealcoat offers, even though both are about the same price.
Arguments based on what works best, Ann Arbor's Naud said, aren't considering health and environmental factors.
"DDT worked really well," he said "Lead paint worked really well, but they had some environmental issues that we didn't know about for a long time."
Because of the wide availability of coal tar-based products in the middle and eastern regions of the United States, and because of its superior durability and look, the industry standard for sealcoat has been coal tar sealcoat, said Nick Whitehurst, president of True North Asphalt, in Rochester Hills.
However, due to the increasing number of bans and restrictions on coal tar-based sealcoat, the manufacturers have started producing an alternative, which is a petroleum-derivative sealcoat that Whitehurst said holds up better than traditional asphalt, or petroleum-based, sealcoat.
Sold under the name Black Diamond, manufacturers and suppliers of the product, such as Surface Coating Co., in Auburn Hills, say the product holds up well, and has a significantly lower PAH content, with suppliers saying the sealcoat is about two percent PAHs. Asphalt-based sealcoat, by comparison, has about .005 percent PAH.
The Black Diamond sealcoat is now approved for application in several locations where coal tar sealants are prohibited for use, such as Austin and San Antonio, Texas. However, the new alternative isn't permitted for use in Ann Arbor or Van Buren Township, which limit PAH content to .1 percent and one percent, respectively.
Whitehurst said his company started offering the Black Diamond product a year ago, with about 90 percent of his business consisting of coal tar sealant and 10 percent the new alternative. He said business quickly turned to about 50/50 use. Now, he said about 90 percent of his customers have Black Diamond sealant applied, with about 10 percent requesting coal tar based sealant.
"People have said they like the look of the Black Diamond," he said. "Coal tar has a bit of a blue hue, and darkens up over a week or so. Black Diamond is jet black the day you put it down. It also doesn't have the same smell as coal tar. It has very little odor."
In terms of asphalt emulsion for petroleum-based sealcoat, he said the price is expensive for what he believes is a subpar product.
Whitehurst said the company will still apply asphalt-based sealcoat, but will only do it on larger speculative projects. Likewise, he said some customers specifically request coal tar-based products even though others are available.
"We are doing the federal reserve bank in Detroit in a couple of weeks. They specifically asked us to use coal tar," he said.
Whitehurst said the decision to switch to the petroleum-based alternative for most projects was based on the quality of the product, the look and lack of odor. Further, he said, the product doesn't have a benzene additive that coal tar sealants have, which causes a irritating rash, similar to a sunburn.
"We started applying it last year," he said. "After we saw how it lasted through the winter, we were confident we could sell it and get similar results to coal tar."
Steve Erdodi, owner of Tuff Coat Sealcoating, in Waterford, said his company has switched to an asphalt emulsion, or petroleum-based sealcoat, rather than using the new alternative or traditional coal tar sealants.
In order to add to the durability of the petroleum-based sealcoat, he said the product he uses has polymer additives, which increase the durability. The switch, he said, required a new storage facility at his business, which resulted in an investment of about $30,000.
"It's not easily available locally, so we ordered a new storage tank and have a delivery that is made for us," Erdodi said. "It's a real commitment."
Erdodi said the product is different than Black Diamond, in that it has a lower PAH level, and believes it would be available to use in communities like Ann Arbor or Van Buren. He said his main reason for switching products was out of concern for health and the environment.
"It gets on your shoes and in the waterways, and once it's on your shoes, it gets into your own world," he said about coal tar sealants. "The danger isn't just the day its applied. There are airborne concerns. The best we can do is to stop using this product."
As a side benefit to quitting the use of coal tar sealants, Erdodi said it has been easier to recruit employees.
"I was amazed with how many potential employees were knowledgable about it," he said. "They know on their own. They are picking up on this. Coal tar burns your skin. You get 'pitch burn,' and I don't know anyone who the pitch didn't burn. The guys don't have that element anymore. And the odor is reduced, as well."