What the Canadian Refined Coal Tar Sealer Study Reveals About Pavement Safety

In June 2016, Canada’s Departments of Environment and Health released a draft screening risk assessment of coal tar and coal tar distillates for public review and comment. This assessment, which the Pavement Coatings Technology Council (PCTC) evaluated and submitted comments on, examined refined tar-based sealers (RTS) through multiple exposure pathways. For contractors who apply these products regularly, the findings provide important context about occupational and public safety. The study examined three distinct routes of potential exposure and calculated risk using internationally recognized metrics. Refined Tar Sealer Vs Asphalt Based Sealer a comparison helps professionals understand the practical differences between these two pavement protection options.

How the Canadian Assessment Evaluated Refined Coal Tar Sealer Risks

The Canadian screening risk assessment focused primarily on industrial uses of crude and refined coal tar substances. Because these materials are used in industrial processes, most potential exposures are occupational in nature. The draft assessment considered both worker and public exposure scenarios, applying rigorous scientific methodology to determine whether refined coal tar-based sealants pose genuine health concerns under normal use conditions.

Three Exposure Pathways Under Review

The Canadian agencies evaluated three distinct routes through which someone might be exposed to RTS compounds. Each pathway was assessed independently using available scientific data and established toxicological methods.

1. Inhalation during application: The assessment considered risks from breathing in airborne particles or vapors while refined tar-based sealers are being applied to pavement surfaces.
2. Dermal contact during application: This pathway evaluated what happens when RTS comes into contact with skin during mixing, spreading, or cleanup operations.
3. Indirect exposure through house dust: This pathway looked at whether polycyclic aromatic hydrocarbons (PAHs) from RTS-coated pavements could be tracked into homes and accumulate in household dust.

For a broader understanding of the regulatory landscape surrounding these products, contractors may also want to review the Refined Tar Sealer Vs Asphalt Based Sealer What pavement contractors need to know about current industry standards and best practices.

Key Findings on Occupational Exposure

The Canadian assessment reached clear conclusions on the two occupational exposure pathways:

…the few available studies indicate that short-term health effects are limited, localized and generally reversible.

This conclusion on inhalation risk is significant because it comes from Canadian government scientists, not from industry representatives. For contractors who apply RTS products regularly, this finding supports the position that when proper safety protocols are followed, short-term inhalation exposure does not produce lasting health consequences.

On the dermal exposure pathway, the assessment was equally clear:

Given the infrequent nature of the exposure and the limited duration for which it is expected to occur, the conclusion is that incidental dermal exposure to [RTS] does not constitute a human health concern.

This finding is noteworthy because incidental skin contact is the most common form of exposure for pavement maintenance workers. The assessment determined that the combination of infrequent exposure events and short contact duration keeps risks well within acceptable boundaries.

Understanding the Margin of Exposure Methodology

For the third exposure pathway involving PAHs in house dust, the Canadian agencies used a methodology known as Margin of Exposure (MOE). This approach is formally endorsed by the World Health Organization (WHO) and the European Food Safety Authority (EFSA) for evaluating chemical risks. An MOE value represents the ratio between the lowest dose that causes an adverse effect in laboratory studies and the estimated human exposure level.

Both WHO and EFSA use an MOE of 10,000 as the threshold below which risks may warrant regulatory concern. Values above 10,000 indicate that the margin between harmful doses and actual human exposure is large enough to be considered safe. This standardized threshold provides a consistent benchmark for comparing risks across different substances.

Comparing MOE Values Across Everyday Substances

The U.S. National Library of Medicine maintains a reference table of MOE values for substances that people encounter regularly. These values help put calculated risks into practical perspective. Higher MOE values indicate a larger safety margin and therefore lower potential risk.

As the table illustrates, many common foods and beverages have MOE values far below 10,000, meaning they are consumed regularly despite having narrower safety margins than what regulatory agencies consider concerning.

What the Canadian MOE Calculation Means for RTS Products

The Canadian government agencies, using U.S. Geological Survey (USGS) estimates of PAH concentrations in residences, calculated an MOE of 15,500 for refined coal tar-based sealant exposure through house dust. This value was derived by calculating MOE values for each age group and then weighting them according to the time length of exposure for each demographic. The resulting lifetime adjusted MOE came to 15,500.

To interpret this number in practical terms, an MOE of 15,500 places the potential health risk from RTS-related PAH exposure approximately halfway between the risk from eating bacon (MOE of 10,000) and the risk from drinking treated tap water (MOE of 20,000). Both bacon and tap water are consumed by millions of people daily without regulatory restrictions.

PCTC Critique of USGS Data Quality

It is worth noting that PCTC has frequently criticized the USGS data that served as the basis for the house dust PAH calculations. The council has questioned the scientific integrity of the data collection process used by USGS in its studies of PAHs in residential environments. Despite using what PCTC considers questionable data, the Canadian assessment still arrived at an MOE value substantially above the 10,000 safety threshold.

For a deeper examination of how data quality and research methodology issues have shaped the pavement coatings debate, contractors should review the analysis of Examining White Hat Bias in Pavement Science How PCTC data quality act challenges are reshaping the research landscape around refined tar-based sealers.

Practical Implications for Pavement Maintenance Contractors

The Canadian assessment provides pavement maintenance professionals with several practical takeaways that can inform both business decisions and customer conversations.

Worker Safety Considerations

The assessment’s findings on occupational exposure provide reassurance that refined tar-based sealer products, when used according to manufacturer guidelines, do not present significant health risks to applicators. The conclusions regarding both inhalation and dermal exposure support the use of standard personal protective equipment rather than extreme precautions.

• Standard work gloves provide adequate protection for incidental dermal contact during normal application procedures
• Basic respiratory protection during application is appropriate, though the assessment found inhalation risks to be limited and reversible
• Good hygiene practices such as washing hands before meals remain recommended but the urgency of these practices is lower than some alarmist narratives suggest

Communicating Risk Assessment Results to Customers

Property owners and facility managers who ask about the safety of refined tar-based sealers can be given straightforward information based on the Canadian assessment. The MOE methodology provides an internationally recognized framework that translates complex toxicological data into understandable comparisons.

When customers raise concerns, contractors can reference these data points:

• The Canadian government calculated an MOE of 15,500 for RTS-related PAH exposure, well above the 10,000 threshold that international health agencies use to indicate safety concern
• This safety margin is larger than the margin for bacon (10,000), coffee (500), or orange juice (400), all of which are consumed without regulatory restriction
• Occupational exposure during application was found to produce only limited, localized, and reversible effects
• Incidental skin contact does not constitute a human health concern according to the Canadian health and environment agencies

Staying Informed on Regulatory Developments

The regulatory landscape for pavement sealers continues to evolve on both sides of the U.S.-Canada border. Contractors who offer sealcoating services should monitor these developments to anticipate changes in product availability, labeling requirements, and application restrictions. The Canadian draft assessment represents one of the most thorough government evaluations of refined tar-based sealer safety conducted to date, and its findings carry weight in future regulatory decisions.

For a broader perspective on the ongoing debate surrounding these products and the scientific evidence that informs it, the discussion of Refined Tar Based Sealers Under Fire the Science behind the pavement coatings debate provides additional context for contractors facing questions from concerned customers.

Conclusion

The Canadian screening risk assessment of coal tar and coal tar distillates provides important scientific support for the continued use of refined tar-based sealers in pavement maintenance. By applying the internationally recognized Margin of Exposure methodology, Canadian government scientists determined that potential risks from RTS products fall well within acceptable safety boundaries. The calculated MOE of 15,500 exceeds the 10,000 threshold used by WHO and EFSA, placing the risk from these products below the level that warrants regulatory concern. Combined with the assessment’s findings that occupational exposure through inhalation and skin contact poses no significant health threat, the Canadian study represents a rigorous, science-based evaluation that pavement contractors can reference with confidence.