The Pavement Coatings Technology Council (PCTC) has been at the forefront of defending refined tar-based sealers (RTS) against regulatory challenges driven by disputed scientific claims. Understanding the science behind polycyclic aromatic hydrocarbons (PAHs), the limitations of detection methods, and the real-world impact of bans on contractors and communities is essential for anyone in the pavement maintenance industry. This article examines the ongoing debate, the peer-reviewed research challenging US Geological Survey (USGS) conclusions, and what pavement professionals need to know about the regulatory landscape. For foundational knowledge, see our article on Asphalt Pavement Engineering Mix Design Construction Methods Rehabilitation which covers pavement design principles.
The Science of PAHs and Refined Tar-Based Sealers
Polycyclic aromatic hydrocarbons are organic compounds that occur naturally in coal, crude oil, and gasoline. They are produced whenever organic materials are burned, including forest fires, vehicle exhaust, and residential wood burning. Understanding the distinction between natural background PAHs and those potentially attributable to pavement sealers is critical to the regulatory debate.
PCTC-Sponsored Research Findings
Research sponsored by the PCTC has made significant strides in challenging the narrative that refined tar-based sealers are a major source of PAH contamination. A landmark before-and-after study published in a peer-reviewed science journal in late 2010 examined PAH levels in Austin, Texas, following that city’s 2006 ban on RTS use. The study found that the amounts and sources of PAHs remained unchanged after the ban, suggesting that RTS was not a significant contributor to PAH levels in the environment.
PAH Fingerprint Analysis
Further analysis of PAH fingerprint data published by the USGS has proven to be even more revealing. Forensic fingerprinting is a well-established scientific method used to identify the sources of hydrocarbons in environmental samples. When applied to the USGS data, fingerprint analysis shows that refined tar-based sealers cannot be identified as a predominant, significant, or even identifiable part of the mix of PAH sources. The first PCTC-sponsored research paper describing this fingerprint analysis has been accepted for publication in a peer-reviewed science journal, with a second paper submitted that includes a detailed critique of the USGS mathematical model.
The USGS Model: Garbage In, Garbage Out
The second PCTC scientific paper examines the mathematical model on which opponents of refined tar-based sealer base their claims. An expert in identifying different sources of PAHs in the environment reviewed the model and concluded that it is fundamentally flawed. The model, designed for air pollutant analysis, was applied to sediment data without validation. As one expert noted, the model would identify refined tar-based sealer as the major source of PAHs in a ham sandwich. This highlights the danger of using untested models to drive public policy.
Regulatory Battles and Their Consequences
Despite the growing body of scientific evidence challenging the USGS conclusions, several jurisdictions have moved to ban refined tar-based sealers. The disconnect between science and policy has had real consequences for contractors, small businesses, and communities.
Washington State: Policy Ignoring Science
In 2011, Washington State legislators considered a statewide ban on refined tar-based sealers. The state’s own Department of Ecology conducted a study showing that RTS was, if present at all, a vanishingly small contributor to Washington State sediments. According to the USGS model, more than half of all PAHs in Seattle’s Lake Ballinger supposedly come from refined tar-based sealer. Yet fingerprint analysis of the same data shows the actual percentage is much closer to zero percent.
Despite the clear absence of a demonstrated problem, the Washington legislature passed and the governor signed a bill banning refined tar-based sealer statewide. During hearings, several legislators bragged about shutting down Washington State’s only working coal mine and discussed attempts to ban coal exports from the Port of Seattle, revealing an animus toward any material associated with coal.
Suffolk County, New York: Bans Without Evidence
Similarly, Suffolk County, New York, passed a ban on refined tar-based sealers. The USGS model claimed more than half of PAHs in Long Island’s Newbridge Pond derived from RTS, but fingerprint analysis again indicated that RTS could have contributed only a small percentage, if any, of the PAHs. Analysis of the extensive data collected by Suffolk County as part of its Clean Water Act compliance showed that no sediments or water bodies in the county contained excess PAH levels. A PCTC member had long been a responsible manufacturer in Suffolk County, and many local contractors voiced opposition to the ban, but the legislature imposed it anyway.
Other Jurisdictions and Ongoing Threats
Some measures promoting or establishing bans in other jurisdictions expired or were avoided in 2011, but the threat persists. The USGS and local activists continue publishing articles using the discredited USGS model as the basis for claims that refined tar-based sealer is a significant source of PAHs.
Key Differences Between Pavement Sealer Types
Understanding the differences between refined tar-based sealers and alternatives such as asphalt emulsion sealers is fundamental to evaluating the regulatory debate. Each type has distinct performance characteristics, environmental profiles, and application requirements. For detailed information on alternatives, read our guide on Asphalt Emulsion Sealers What Contractors Need to Know.
| Property | Refined Tar-Based Sealer | Asphalt Emulsion Sealer | Acrylic Sealer |
|---|---|---|---|
| Primary Binder | Coal tar pitch | Asphalt emulsion | Acrylic polymer |
| Resistance to Fuel and Oil | Excellent | Moderate | Good |
| Typical Service Life | 3-5 years | 1-3 years | 2-4 years |
| Color Retention | Good (jet black) | Fades to brown | Excellent |
| Cost per Square Foot | Moderate | Low | High |
| PAH Content Debate | Central issue | Lower PAH levels | Minimal PAHs |
| Application Temperature | Cold applied | Cold applied | Cold applied |
The table above summarizes the key differences. It is worth noting that the PAH content of refined tar-based sealers has been the subject of extensive scientific scrutiny, and as discussed, the evidence linking these products to environmental PAH contamination is far weaker than regulators assume.
Performance Considerations for Contractors
Contractors choose refined tar-based sealers for several practical reasons:
- Fuel and oil resistance – RTS provides superior protection against gasoline and diesel spills common in parking lots and driveways.
- Longevity – With a typical service life of 3 to 5 years, RTS offers extended protection between reapplications.
- Aesthetic appeal – The deep black color of refined tar-based sealer is preferred by many property owners.
- Cost effectiveness – The longer service life translates to lower lifetime cost for property owners.
- Adhesion to existing pavement – RTS bonds well to aged asphalt surfaces, providing durable protection against oxidation and water intrusion.
For projects requiring surface preparation before sealing, see our article on Tearing Up the Pavement Modern Cold Milling and Pavement Removal Equipment.
What the Industry Can Do: Protecting Access to Refined Tar-Based Sealers
Science supports the conclusion that the only impact of bans on refined tar-based sealers is to harm business, especially small businesses, and the communities that rely on those businesses. However, scientific evidence alone has not been enough to prevent ill-advised regulations.
Staying Informed and Involved
Refined tar-based sealer manufacturers and users at all levels must be aware of developments and become involved in the regulatory process. Here are key steps every pavement professional should take:
- Monitor local regulations – Watch for proposed bans or restrictions in your city, county, or state. These often start at the local level before spreading.
- Engage with the PCTC – The Pavement Coatings Technology Council tracks legislative developments nationwide and provides resources for industry advocacy.
- Talk to elected representatives – Share your experience and the scientific evidence with local and state officials before they vote on restrictions.
- Educate your customers – Property owners may hear about environmental concerns and ask questions. Being able to explain the science builds trust.
- Support peer-reviewed research – Continued funding of scientific studies is essential to counter misleading claims with real data.
Understanding the Broader Context
The campaign against refined tar-based sealers is part of a broader regulatory environment affecting many construction materials. Understanding how materials science, environmental policy, and construction practice intersect is increasingly important for industry professionals. For related information on building material performance, see our article on Residential Glass Technology Low E Coatings Gas Fills.
The Path Forward
While continuing to study refined tar-based sealers in the environment, it is clear that scientific publications, while essential to the debate, must be supplemented with direct action and challenges to misinformation. The PCTC continues to push back against regulatory overreach by funding rigorous science and engaging directly with policy makers. The pavement maintenance industry must do its part by staying informed, getting involved, and advocating for evidence-based policy.
Your involvement is key. Watch and listen for developments that might impact refined tar-based sealer in your communities. Let the PCTC know about proposed restrictions, talk with your elected representatives, and share the science with anyone who will listen. A product that has served the pavement maintenance industry for decades deserves to be judged on facts, not fear.