NASSCO Report – EPA & the Toxic Substances Control Act

This article examines the Environmental Protection Agency’s (EPA) risk evaluation of styrene under the Toxic Substances Control Act (TSCA) as it relates to the cured-in-place pipe (CIPP) industry.

Styrene is a widely used industrial chemical with governmental concerns related to potential health risks. Under the 2016 amendments to TSCA, the EPA conducted a comprehensive risk evaluation to determine whether styrene presents an unreasonable risk to the health and safety of workers or the environment.

Styrene is a volatile organic compound used in the production of polystyrene plastics and resins, among other items. With annual production in the millions of tons, it ranks among one of the most widely used industrial chemicals in the United States.

In 2016 Congress significantly revised TSCA with the Chemical Safety for the 21st Century Act. This Act strengthened the EPA’s authority to evaluate and regulate existing chemicals. It is under this framework that styrene was selected as one of the first 20 high-priority chemicals for risk evaluation.

The TSCA risk evaluation framework mandates a four-part process for a chemical risk evaluation. The components are Hazard Identification, Exposure Assessment, Risk Characterization and Risk Determination.

The EPA interpretation of these components breaks down as follows:

• Hazard Identification: Outlines how EPA determines whether styrene can cause harm and under what conditions.
• Exposure Assessment: Assesses the frequency, duration and levels of styrene exposure across different populations.
• Risk Characterization: Integrates hazard data and exposure data to create the final report data to estimate potential health risks.
• Risk Determination: EPA concludes whether styrene presents an “unreasonable risk” to human health or the environment under specific circumstances and conditions of use.

In EPA’s Draft Risk Evaluation on Styrene released in December 2023, the EPA completed an in-depth evaluation of styrene’s hazards, exposures and potential health effects. The key findings from this risk evaluation break down as follows:

In the hazard category the EPA identified a concern of neurological effects, liver toxicity and evidence of lymphohematopoietic carcinogenicity with the primary route of entry being inhalation.

In their exposure assessment EPA considered multiple exposure pathways for styrene. The primary focus was on occupational settings (specifically in styrene production and processing of styrene-based products). In addition, consumer and environmental exposures were analyzed but found to have relatively lower concern.

In the Risk Determination section EPA has concluded that styrene poses an unreasonable risk to workers in certain industrial conditions primarily due to chronic inhalation. However, for consumers and the general population, the current conditions of use did not present unreasonable risk.

The public and industry response followed a 60-day public comment period. The industry stakeholders have proposed scientific research and studies that indicate EPA’s risk models overestimate actual workplace exposures while completely underestimating the effectiveness of companies existing safety and health programs. Such programs include hazard communication training, use and training of personal protective equipment, industry monitoring of workers exposures, and hazard communication.

In addition, recent peer reviewed scientific studies published in the journals Environmental and Molecular Mutagenesis, Journal of Occupational and Environmental Medicine, and the Journal of Toxicology and Environmental Health have all indicated that there is no consistent or compelling evidence that occupational styrene exposure is associated with elevated cancer mortality or risk, including lung and lymphohematopoietic cancers.

What is the next step for EPA and where do we currently stand on the EPA timeline? Keeping in mind that on Dec. 18, 2024, EPA listed styrene as a “high priority” candidate, this initiated the prioritization process that allows a 90-day comment period which ended March 2025. Next EPA will open “Screening review and proposed priority designation” with a 90-day comment period expected in 3rd quarter 2025. The final phase will be the EPA “Final priority designation.” At this time (approximately December 2025) EPA will decide whether styrene is a high priority substance, a low priority substance, or withdraw prioritization.
If during this process EPA finalizes its finding of unreasonable risk, the TSCA regulations require it to propose specific risk management measures within two years of the report. These requirements could possibly include restrictions on styrene or exposure limits of styrene on workers.

In conclusion, EPA’s evaluation of styrene under the amended TSCA framework demonstrates an aggressive approach to the chemical risk assessment process. These findings may reinforce the need to prioritize worker health and safety when using styrene. While we have seen the outcome of this EPA process with some chemicals such as Formaldehyde and Methylene Chloride, the issue surrounding styrene will likely serve as a precedent in plotting the future of chemical regulation on industry.

Dennis Pivin, CSP, is NASSCO Director of Health, Safety and Environmental.