Sealcoating Safety: Separating Fact from Fiction for Pavement Contractors

In the pavement maintenance industry, few topics generate as much debate as sealcoating. Property owners, contractors, and municipal specifiers are often caught between conflicting claims about the safety, environmental impact, and effectiveness of pavement sealants. The Pavement Coatings Technology Council (PCTC) has worked to clarify these issues through independent research and industry expertise. This article separates established fact from persistent fiction, providing pavement professionals with the evidence they need to make informed decisions. For a closer look at the research challenging environmental claims, see Refined Tar Based Sealers Under Scrutiny Pctc Studies.

Understanding Sealcoating Types and Their Safety Profiles

Not all pavement sealers are created equal. The two primary categories are refined tar-based sealers and asphalt emulsion sealers. Each has distinct chemical properties, performance characteristics, and safety considerations that contractors must understand before specifying or applying a product.

Refined Tar-Based Sealers: Composition and Handling

Refined tar-based sealers contain coal tar pitch that has been processed to remove lighter fractions and concentrate the durable, UV-resistant compounds that protect asphalt pavements. These sealers offer superior resistance to petroleum spills, deicing salts, and ultraviolet degradation compared to asphalt emulsion alternatives. Their longevity makes them a cost-effective choice for commercial parking lots, driveways, and municipal streets.

However, these products do require careful handling. Appropriate personal protective equipment should include:

• Long-sleeved shirts and full-length pants to minimize skin exposure
• Work gloves rated for chemical contact
• A hat and face shield when applying overhead or in windy conditions
• Protective creams that block UV rays and create a barrier between skin and sealer

When refined tar sealers contact skin in the presence of sunlight, a temporary irritation resembling sunburn can occur. However, when proper handling procedures are followed and basic personal hygiene is maintained, this should not be a concern. The industry has decades of application experience demonstrating that responsible use eliminates meaningful risk.

Asphalt Emulsion Sealers: An Alternative Approach

Asphalt emulsion sealers are water-based products that use emulsified asphalt as the binding agent rather than coal tar derivatives. They offer lower odor during application and different performance characteristics. While they may require more frequent reapplication than refined tar products, they remain a popular choice for residential driveways and areas where odor sensitivity is a consideration. Understanding the differences between sealer types is essential when selecting the right product for a specific pavement condition and budget. For more on how mix design affects performance, refer to Understanding Sealcoating Mix Designs for Long Lasting Pavement.

Examining Environmental Impact Claims Around Refined Tar Sealants

One of the most hotly contested issues in the sealcoating industry concerns the environmental impact of refined tar-based sealers. Activist groups frequently cite US Geological Survey (USGS) research claiming that sealants are the primary source of polycyclic aromatic hydrocarbons (PAHs) entering waterways and sediments. A careful examination of the evidence tells a different story.

What the Independent Research Actually Shows

Multiple independent studies have failed to support the USGS claims. Research conducted on New York Harbor and Puget Sound in Seattle found that sealant contributes less than 1 percent of PAHs found in sediment samples at those locations. A separate statistical analysis of the Illinois River, conducted by researchers at the Universities of Illinois and Milwaukee-Wisconsin, suggested that sealcoat contributes no more than a few percent of total PAH loading.

Critics of the USGS position point to methodological issues in the original studies, including data manipulation concerns and circular reasoning in the analytical approach. The independent studies that followed have consistently aligned with industry-funded research, suggesting that refined tar-based sealers are not the significant environmental contaminant they have been portrayed to be.

Putting PAH Levels in Perspective

Polycyclic aromatic hydrocarbons are a class of compounds that occur naturally in the environment from sources including forest fires, vehicle exhaust, tire wear, and even barbecue grilling. Attributing all PAH presence in waterways to sealcoat oversimplifies a complex picture. The table below summarizes the key sources of PAHs and their relative contributions based on the independent studies cited above.

Understanding the broader context of pavement materials and their engineering properties is critical for making informed decisions. For more on pavement design and construction methods, see Asphalt Pavement Engineering Mix Design Construction Methods Rehabilitation.

The Science Behind Sealcoating Odor and Health Concerns

Perhaps the most common source of concern among property owners and the general public is the strong odor associated with refined tar-based sealer application. Many assume that a strong smell indicates toxicity or health risk. The science of odor perception tells a very different story.

Why Sealcoat Smells: The Naphthalene Factor

The distinctive odor of refined tar sealer comes primarily from naphthalene, a compound that the human nose can detect at extraordinarily low concentrations. The odor threshold for naphthalene is approximately three parts per billion (ppb). Compare that to common household substances:

• Naphthalene in sealcoat: odor detectable at 3 ppb
• Nail polish remover (acetone): odor detectable at 7,000 ppb
• Bleach (chlorine): odor detectable at 10 ppb
• Gasoline: odor detectable at 500 ppb

The American Conference of Governmental Industrial Hygienists (ACGIH) establishes exposure guidelines for occupational settings. For naphthalene, the threshold limit value considered safe for workers over an eight-hour workday is 10,000 ppb, or ten parts per million. This creates a safety margin of more than three orders of magnitude between what a person can smell and what would constitute a health concern.

Air Sampling Evidence and Inhalation Risk

Multiple air sampling studies conducted during actual sealcoating operations have demonstrated that refined tar-based sealers pose insignificant inhalation risk to applicators, manufacturers, or the general public. These studies measure actual airborne concentrations during spraying and squeegeeing operations and compare them against established safety thresholds. In every case, measured concentrations fall well below levels of concern, even for workers spending full shifts in the application area.

Historical Evidence of Safe Use

The safety record of coal tar derivatives extends far beyond pavement sealcoating. Coal tar has been listed by the US Food and Drug Administration (FDA) as a “generally recognized as safe and effective” active ingredient for over-the-counter medicines. Millions of people worldwide use coal tar soaps, shampoos, and creams to treat skin conditions such as eczema, psoriasis, and dandruff, with concentrations up to five percent coal tar.

Research on long-term health effects has been conducted over nearly a century. Studies examining patient populations who intentionally exposed themselves to high doses of coal tar over extended periods for medical treatment have reached a consistent conclusion: there is no evidence linking coal tar exposure to increased cancer risk. Similarly, insurance carriers report a general lack of claims related to sealcoat exposure over the entire history of the industry.

Generations of family-owned businesses have operated in the sealcoat manufacturing and application industry with zero reports of adverse chronic health effects that can be attributed to sealcoat exposure. This real-world evidence, spanning decades and thousands of workers, provides powerful support for the safety of these products when used as directed.

Best Practices for Responsible Sealcoating Application

Understanding the facts about sealcoating safety and environmental impact empowers contractors to apply these products responsibly and communicate effectively with their customers. The following best practices represent the industry standard for safe, effective sealcoating.

Site Preparation and Public Communication

1. Post notice of sealcoating activity at least 24 hours before application begins, allowing building occupants and vehicle owners to plan accordingly.
2. Block access to treated areas and post clearly visible signs warning of wet sealant.
3. Ensure adequate ventilation in enclosed or partially enclosed areas such as parking garages.
4. Schedule application when weather conditions are favorable: temperatures above 50 degrees Fahrenheit, no rain forecast, and low wind speeds to minimize overspray.
5. Keep children and pets away from active work areas until the sealant has fully cured, typically 24 to 48 hours depending on product and conditions.

Applicator Safety Protocols

Contractors should establish written safety protocols that include the following elements:

• Mandatory use of appropriate PPE including long sleeves, pants, gloves, and eye protection
• Availability of protective creams at all job sites
• Training on proper handling and spill response procedures
• Routine equipment inspection to prevent leaks and drips
• First aid supplies accessible at every worksite

When customers express concerns about sealcoating odors, contractors can explain that the strong smell is a function of the human nose extreme sensitivity to naphthalene, not an indicator of danger. Providing factual information helps build trust and reinforces the professionalism of the contractor.

Environmental Stewardship on the Job Site

Responsible contractors take additional steps to minimize any potential environmental impact:

• Use drip pans and catch basins to contain any spills or drips from application equipment
• Clean equipment over containment areas, not directly on pavement or soil
• Dispose of leftover sealant and rinse water according to local regulations
• Avoid application within 100 feet of storm drain inlets unless they are sealed during work
• Use the minimum application rate recommended by the manufacturer to achieve proper coverage

The relationship between building materials and overall construction quality extends beyond the pavement surface itself. For an example of how material selection impacts building performance in other contexts, see Residential Glass Technology Low E Coatings Gas Fills. Just as low-emissivity coatings and gas fills enhance window energy efficiency, proper sealcoating formulation and application extend pavement life and performance.

Sealcoating remains one of the most cost-effective pavement preservation strategies available. When contractors base their practices on sound science rather than sensational claims, they protect both their customers pavement investments and their own reputation for professionalism. The evidence is clear: refined tar-based sealers, when handled responsibly, are safe for applicators, protect the environment, and deliver superior pavement protection that extends the life of asphalt surfaces for years.