Octamethylcyclotetra- siloxane (D4); TSCA Review

In 2017, a WEEL for D4 was published. The development and maintenance of WEELs now falls under the AIHA Guideline Foundation and its OEL Committee. AIHA has been engaged in the development and maintenance of high-quality occupational exposure limits (OELs) for worker health protection for over 45 years and can serve as a partner to EPA to share critical knowledge, experience and expertise regarding the setting of health protective OELs. The AIHA OEL Committee was formed to establish and publish health-based OELs and has the overall mission of protecting workers and communities from occupational and environmental hazards through the application of scientific knowledge. The AIHA OEL Committee is an independent organization that is composed of health science experts that are experienced in setting OELs, using a rigorous science-based approach. Committee members cover a span of public health sciences including occupational hygiene, toxicology, epidemiology, medicine, and risk assessment science. The committee uses the same rigorous scientific approaches used by other health-based exposure limit groups. The committee's methodologies, technical approaches, and administrative procedures are available for review, and the latest occupational risk assessment methods are applied to ensure the use of the best available science in committee deliberations. The committee also provides an opportunity for engagement with interested stakeholders and is committed to transparency and open access to the science behind its work products. Thus, AIHA is well positioned to engage with and assist EPA regarding best practices in OEL applying existing OELs for risk assessment and risk management for D4 and other high priority chemicals. The recommended WEEL value for D4 is 10 ppm as an 8-hour time-weighted average (TWA). The WEEL documentation is attached to this submission and referenced below. We note that the WEEL and EPA's draft risk evaluation appear to use the same high-quality study to establish a point of departure (POD), that is WIL Research 2001. However, the inhalation exposure concentration that EPA derived as a threshold for determining unreasonable risk of injury to human health is far different from the WEEL. AIHA believes the risk evaluation would benefit from a description of why that difference exists. Moreover, AIHA believes that EPA should apply the policies it proposed in the amendments to the regulations regarding Procedures for Chemical Substance Risk Evaluations, specifically those risk-related factors included in the risk evaluation to determine whether unreasonable risk is presented 40 CFR 702.39(f)(3): (i)The severity of the hazard (e.g., the nature of the hazard and irreversibility of the hazard); (ii)Exposure-related considerations (e.g., likely duration, intensity, and frequency of exposure); (iii)The population exposed (including any potentially exposed or susceptible subpopulations (PESS)); and (iv)The confidence in the information used to inform the hazard and exposure values, including an evaluation of the strengths, limitations, and uncertainties associated with the information used to inform the risk estimate and the risk characterization.