Washington Coal Tar Sealer Ban: What Pavement Contractors Must Know About Statewide Restrictions

Washington state made history in 2011 when Governor Chris Gregoire signed the nation’s first statewide ban on refined coal tar-based pavement sealers into law. This landmark legislation fundamentally altered how contractors approach sealcoating projects. For building professionals and paving contractors, understanding the Canadian refined coal tar sealer study findings that contributed to this regulatory shift provides essential context for why these restrictions emerged and how they continue to shape best practices in pavement protection today.

The Scope and Context of Washington’s Coal Tar Sealer Ban

When Washington became the first state to prohibit refined coal tar-based sealers on asphalt pavement, it marked a significant escalation from earlier local ordinances. Prior to the statewide action, coal tar sealers had been banned only in a handful of municipalities, with Austin, Texas, passing the initial local ban in 2006. The Washington law demonstrated that what had been a patchwork of city-level restrictions could expand to statewide regulatory control. Industry observers noted at the time that refined tar sealer coal tar ban discussions were gaining momentum in multiple state legislatures, making Washington’s move a potential bellwether for nationwide regulatory trends.

What the Ban Specifically Prohibits

The Washington law applies to refined coal tar-based pavement sealers used on asphalt surfaces including driveways, parking lots, and roadways. The ban covers products containing coal tar pitch, a byproduct of the coking process used in steel manufacturing. These sealers have been widely used for decades because of their durability and resistance to petroleum spills. The ban covers both application and sale within the state, meaning crews cannot bring coal tar sealers from neighboring states for Washington projects.

The Regulatory Path to Statewide Action

State Representative David Frockt sponsored the bill, arguing that the transition to alternative sealers would not significantly impact businesses. According to reports from The Seattle Times, Frockt stated that “Nobody felt their business was going to be impacted if they had to go to the other sealants.” Environmental advocacy groups had been raising concerns about polycyclic aromatic hydrocarbons (PAHs) in coal tar sealer runoff for years, and a growing body of scientific research was drawing connections between these compounds and potential environmental and health risks. Washington’s action represented a culmination of these converging pressures.

Communities That Paved the Way

Before Washington’s statewide action, several communities had already taken steps to restrict coal tar sealers:

• Austin, Texas passed the nation’s first municipal ban in 2006, setting a precedent for other cities
• Several municipalities in the Great Lakes region adopted restrictions based on concerns about PAH contamination in waterways
• Washington’s local governments in environmentally sensitive areas had begun exploring restrictions prior to the state-level action
• Scientific studies linking coal tar sealer runoff to sediment contamination in urban lakes and streams provided the evidentiary foundation for these early bans

Coal Tar Sealers Versus Asphalt-Based Alternatives

Understanding the distinction between coal tar-based sealers and asphalt-based emulsion alternatives is crucial for contractors navigating the post-ban landscape. While both products serve the same fundamental purpose of protecting asphalt pavement, their chemical compositions and performance characteristics differ substantially. A thorough comparison of refined tar sealer versus asphalt-based sealer options helps contractors make informed decisions that balance performance requirements with regulatory compliance.

Chemical Composition and Performance Factors

The higher PAH content in coal tar sealers became the central point of contention during the Washington legislative process. Industry defenders argued that PAHs exist naturally and come from sources including vehicle exhaust, tire wear, and wood burning. However, Washington lawmakers decided that the added contribution from coal tar sealers was significant enough to warrant restriction.

Performance Trade-Offs in the Field

From a contractor’s perspective, the choice between these product categories involves evaluating several performance trade-offs:

1. Durability under traffic: Coal tar sealers traditionally offered superior resistance to gasoline and diesel spills, making them popular for commercial parking lots and gas stations. Asphalt emulsions have improved significantly but may require more frequent reapplication in high-spill areas.
2. Application characteristics: Both product types can be applied using similar equipment including spray systems and squeegee applications. Asphalt emulsions require more careful attention to curing conditions, particularly temperature and humidity.
3. Appearance and aesthetics: Coal tar sealers produce a deeper, richer black finish that many property owners prefer. Modern asphalt emulsion formulations have narrowed this visual gap considerably.
4. Environmental compliance: Asphalt-based sealers carry significantly lower regulatory risk. Contractors working in states considering similar bans can avoid business disruption by transitioning proactively.

The Science Debate Behind the Regulatory Action

The Washington coal tar sealer ban was not without controversy. The refined tar sealer versus asphalt-based sealer debate that played out during the legislative process revealed deep divisions between environmental researchers and industry scientists over the interpretation of available data. Understanding both sides of this argument is essential for contractors who need to explain their material choices to clients and regulatory bodies.

The Industry’s Position on PAH Science

The Pavement Coatings Technology Council (PCTC) actively opposed the Washington ban, arguing that the scientific basis for the legislation was flawed. PCTC Executive Director Anne LeHuray communicated to state officials and investigative journalists that the effort to reduce PAHs in the environment by banning coal tar sealers would be ineffective. The council’s position rested on several key arguments:

• PAHs are naturally occurring compounds that exist in the environment from sources including forest fires, volcanic activity, and petroleum seeps
• Urban PAH contributions from vehicle emissions, asphalt pavement wear, and atmospheric deposition dwarf those from pavement sealers
• Mathematical models used to apportion PAH sources relied on what the PCTC characterized as cherry-picked data that overstated the sealer contribution
• The ban would not achieve meaningful environmental improvements but would impose real costs on contractors and property owners

LeHuray’s critique highlighted a fundamental challenge in environmental regulation: scientific uncertainty means different stakeholders reach opposite conclusions from the same evidence. Washington regulators weighed this uncertainty differently than industry scientists did, deciding the precautionary principle justified action.

Environmental Research Driving the Restrictions

On the other side of the debate, environmental researchers pointed to a growing body of studies linking coal tar sealer runoff to elevated PAH levels in urban waterways, sediments, and fish populations. Key studies that influenced the Washington decision included:

1. US Geological Survey studies that found parking lots sealed with coal tar products had PAH runoff concentrations ten to fifty times higher than lots sealed with asphalt emulsions
2. Sediment core analyses from urban lakes showing that PAH levels in sediments increased dramatically in the decades following widespread adoption of coal tar sealers
3. Biological studies demonstrating that PAHs from sealer runoff accumulate in aquatic organisms and can reach concentrations of concern for human health through food chain transfer
4. Comparative studies showing that asphalt-based sealers contribute negligible amounts of PAHs to runoff compared to coal tar formulations

For contractors, the practical implication of this research is clear: even if the precise magnitude of the environmental impact remains debated, the direction of the evidence consistently points toward coal tar sealers as a significant controllable source of PAH loading in urban environments. This makes them a logical target for regulators seeking to reduce overall PAH burdens.

How Washington’s Ban Reshaped the Pavement Maintenance Industry

The Washington coal tar sealer ban triggered a cascade of changes throughout the pavement maintenance sector, affecting manufacturers, distributors, contractors, and property owners alike. These effects extended well beyond Washington’s borders as other states and municipalities evaluated similar measures.

Supply Chain Adjustments and Product Innovation

The immediate effect of the Washington ban was a restructuring of the sealer supply chain in the Pacific Northwest. Distributors revised their inventory strategies, while manufacturers accelerated development of alternative formulations. Advances that emerged from this innovation push included polymer-modified asphalt emulsions approaching coal tar sealers in durability, acrylic-based formulations with excellent UV stability, and low-VOC options meeting stricter air quality regulations.

Financial Implications for Contractors

The transition from coal tar to asphalt-based sealers carried real financial implications for pavement maintenance contractors. The higher per-gallon cost of alternative products meant either thinner profit margins or higher prices for customers. Contractors who educated their clients about the regulatory reasons for the switch often found property owners willing to accept modest price increases, particularly when framed as an investment in environmental responsibility.

However, the cost impact went beyond materials. Contractors had to invest time in:

• Training crews on the different application characteristics of asphalt emulsion products
• Adjusting application schedules to account for the generally longer curing times of alternative sealers
• Developing new quality assurance procedures to ensure consistent results with less familiar materials
• Educating customers about why their parking lots or driveways would be sealed with a different product than in previous years

The Broader Regulatory Trend

Washington’s ban did not remain an isolated case. Other jurisdictions followed suit, and the regulatory landscape for pavement sealers has continued to evolve. Contractors operating in multiple states must now track a complex patchwork of restrictions that vary by location. Some states have followed Washington’s lead with statewide bans, while others have left the decision to local municipalities, creating an uneven regulatory terrain that challenges multi-state operations.

Looking Ahead: Lessons for Pavement Professionals

The Washington coal tar sealer ban offers enduring lessons for the pavement maintenance industry. As coal tar pavement sealers and the science debate continue to influence regulatory decisions, contractors who stay informed about both the scientific evidence and the policy landscape will be best positioned to adapt. The industry has demonstrated remarkable resilience, developing improved products and best practices that serve both business objectives and environmental goals.

Key takeaways for contractors navigating this regulatory environment include:

1. Monitor legislative activity in your state and local jurisdictions to anticipate potential restrictions before they take effect
2. Develop relationships with multiple suppliers to ensure access to compliant products when regulations change
3. Invest in training and certification programs that demonstrate your commitment to environmentally responsible pavement maintenance practices
4. Build the cost of compliant materials into your pricing models so that regulatory transitions do not erode your margins
5. Document your material choices and the rationale behind them to demonstrate regulatory compliance during inspections or audits
6. Educate clients proactively about why material choices may change over time, positioning yourself as a knowledgeable professional who stays ahead of industry developments

The Washington experience shows that regulatory change is a recurring reality in the pavement maintenance industry. Contractors who treat regulatory awareness as a core business competency will navigate restrictions more effectively. By understanding the science, the alternatives, and the market dynamics that drive decisions, pavement professionals can turn compliance challenges into opportunities for demonstrating expertise and building client trust.