Last Updated on April 21, 2025
Coal tar sealer is one of the most commonly used materials in road and driveway construction. However, many people often confuse coal tar sealer with asphalt and bitumen. In this section, we’ll explain what coal tar sealer really is and clear up any confusion surrounding its use.
What Is a Coal Tar Emulsion Sealer?
If you’ve ever been near a road construction site during the final stages of paving, you may have noticed a strong, distinctive smell in the air. That odor is most likely from the coal tar emulsion sealer.
A coal tar emulsion sealer is a thick, black liquid applied as a protective coating to asphalt surfaces, especially roads and driveways. It is a byproduct of the coke production process during steel manufacturing, where coal is heated in the absence of air to produce coke and coal tar. The sealer is then made by emulsifying coal tar with water and additives to form a spreadable, durable surface treatment.
Coal tar sealers are widely used in the United States for their durability and ability to protect asphalt surfaces from moisture, UV rays, chemicals, and general wear and tear.
Is Coal Tar Emulsion Sealer Safe?
The safety of coal tar sealers has become a growing concern among health and environmental experts. While these sealers are effective in prolonging the life of asphalt surfaces, they also contain toxic chemicals that pose risks to both human health and the environment.
Coal tar sealers are rich in polycyclic aromatic hydrocarbons (PAHs) — a group of chemicals known to be carcinogenic (cancer-causing). These toxic compounds can become airborne or wash into nearby water bodies during rain, where they contaminate soil, streams, and aquatic life.
If fish or aquatic animals absorb PAHs from contaminated environments, and humans then consume these animals, it may increase the risk of developing cancer and other serious health issues.
Due to these health hazards:
- Many U.S. cities and states have started banning the use of coal tar-based sealers.
- Environmental agencies are pushing for alternative asphalt sealants, such as asphalt-based or acrylic-based emulsions, which are less harmful.
In summary, although coal tar sealers offer excellent protection and longevity for asphalt surfaces, their negative impact on human health, wildlife, and the environment has led to increased regulation and calls for safer alternatives.
How Does Coal Tar Sealer Harm Us?
Coal tar sealer doesn’t remain confined to the surface where it’s applied. Once it dries, it begins to erode, breaking down into fine dust particles. These particles spread into the environment, posing serious risks to both human health and nature.
Humans and animals can be exposed to the toxic components of coal tar sealer through inhalation, ingestion, or skin contact. Children are especially vulnerable due to their close contact with the ground and developing immune systems.
The main harmful component is Polycyclic Aromatic Hydrocarbons (PAHs), a group of chemicals known to cause severe health issues. Long-term exposure to PAHs has been linked to:
- Gastrointestinal cancer
- Bladder cancer
- Skin cancer
- Lung cancer
- Birth defects
Coal tar toxins also have a devastating impact on aquatic life. When rainwater washes over a sealed driveway, it carries PAHs into nearby storm drains and ponds. This contaminated runoff can kill fish and other aquatic organisms, permanently disturbing the local ecosystem.
While some manufacturers may claim their products are safe, numerous studies show that the effects of coal tar-based sealers are long-lasting and hazardous.
Final Thought
Given the serious environmental and health hazards, it’s natural to wonder about safer alternatives to coal tar sealers. One widely recommended substitute is the asphalt emulsion sealer.
Unlike coal tar, asphalt emulsion sealers are made with minerals, polymers, and other eco-friendly components that offer durability without toxic side effects. However, it’s important not to dilute asphalt emulsion with water or other substances, as doing so can compromise its effectiveness and longevity.
FAQs
Is coal tar a good sealer?
Coal tar is highly effective in terms of hardness, deep black finish, fuel resistance, and longevity. These properties make it a preferred choice for many users. However, its environmental and health impacts make it a controversial product.
Is coal tar banned?
Yes, coal tar-based sealers have been banned in numerous cities and states across the United States due to their harmful effects on human health and the environment.
Is tar harmful to humans?
Absolutely. Coal tar contains PAHs, which are known carcinogens. Exposure can lead to several types of cancers, including skin, lung, bladder, and gastrointestinal cancers, along with potential birth defects. It also harms wildlife by contaminating the surrounding ecosystem.