
EPA Flags Unreasonable Risk from D4 in Industrial and Environmental Use
EPA draft risk evaluation finds octamethylcyclotetrasiloxane (D4) poses significant risks to workers and aquatic life, signalling regulatory change for industry.


The Environmental Protection Agency (EPA) has proposed a new rule aimed at regulating the use of 1-Bromopropane (1-BP), also known as n-propyl bromide. This proposed regulation comes under the Toxic Substances Control Act (TSCA) and is driven by findings from the EPA's risk evaluations, which identified significant health risks associated with 1-BP. The substance is widely used in various industrial and consumer applications, including vapor degreasing and adhesive manufacturing.
1-Bromopropane is a colourless, volatile liquid with a mildly sweet odour, commonly used as a solvent in cleaning and degreasing operations. It is also used in the production of adhesives, sealants, and insulation materials. According to the EPA, 1-BP exposure can occur through inhalation and dermal contact, posing serious health risks.
The EPA's August 2020 Risk Evaluation and the subsequent December 2022 Revised Risk Determination highlighted several adverse health effects associated with 1-BP. These include neurotoxicity, developmental toxicity, and cancer, particularly from chronic inhalation exposure. The agency determined that these risks are unreasonable, necessitating regulatory intervention to protect human health.
Workers in industries using 1-BP, such as manufacturing and automotive repair, are particularly vulnerable. The proposed rule aims to mitigate these risks by implementing strict workplace controls, including the introduction of a 1-BP Workplace Chemical Protection Program (WCPP). This programme would enforce an exposure concentration limit and require the use of personal protective equipment (PPE).
To address the identified risks, the EPA proposes several key measures:
The EPA is seeking public comments on the proposed rule, which must be received within 45 days of its publication in the Federal Register. The agency will review these comments and may adjust the final rule accordingly. The proposed regulations are part of a broader effort to align with the Biden administration's Cancer Moonshot initiative, aiming to reduce exposure to carcinogens and protect public health.
The EPA has emphasised that while some uses of 1-BP will continue under strict regulation, the overall goal is to eliminate unreasonable risks associated with the chemical. The agency's Economic Analysis projects the cost of these regulations at $14.8 million annually, but the anticipated health benefits, including reductions in cancer risks, are expected to outweigh these costs significantly.
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