Improving Health Risk Assessment as a Basis for Public Health Decisions in the 21st Century.

One-fifth of the way through the 21st century, a commonality of factors with those of the last 50 years may offer the opportunity to address unfinished business and current challenges. The recommendations include: (1) Resisting the tendency to oversimplify scientific assessments by reliance on single disciplines in lieu of clear weight-of-evidence expressions, and on single quantitative point estimates of health protective values for policy decisions; (2) Improving the separation of science and judgment in risk assessment through the use of clear expressions of the range of judgments that bracket protective quantitative levels for public health protection; (3) Use of comparative risk to achieve the greatest gains in health and the environment; and (4) Where applicable, reversal of the risk assessment and risk management steps to facilitate timely and substantive improvements in public health and the environment. Lessons learned and improvements in the risk assessment process are applied to the unprecedented challenges of the 21st century such as, pandemics and climate change. The beneficial application of the risk assessment and risk management paradigm to ensure timely research with consistency and transparency of assessments is presented. Institutions with mandated stability and leadership roles at the national and international levels are essential to ensure timely interdisciplinary scientific assessment at the interface with public policy as a basis for organized policy decisions, to meet time sensitive goals, and to inform the public.

Consideration of the Aerosol Transmission for COVID-19 and Public Health.

This article analyzes the available evidence to address airborne, aerosol transmission of the SARS-CoV-2. We review and present three lines of evidence: case reports of transmission for asymptomatic individuals in association with studies that show that normal breathing and talking produce predominantly small droplets of the size that are subject to aerosol transport; limited empirical data that have recorded aerosolized SARS-CoV-2 particles that remain suspended in the air for hours and are subject to transport over distances including outside of rooms and intrabuilding, and the broader literature that further supports the importance of aerosol transmission of infectious diseases. The weight of the available evidence warrants immediate attention to address the significance of aerosols and implications for public health protection.

A review and critique of U.S. EPA's risk assessments for asbestos.

U.S. Environmental Protection Agency (EPA) recently conducted a risk assessment for exposure to Libby amphibole asbestos that is precedent-setting for two reasons. First, the Agency has not previously conducted a risk assessment for a specific type of asbestos fiber. Second, the risk assessment includes not only an inhalation unit risk (IUR) for the cancer endpoints, but also a reference concentration (RfC) for nonmalignant disease. In this paper, we review the procedures used by the Agency for both cancer and nonmalignant disease and discuss the strengths and limitations of these procedures. The estimate of the RfC uses the benchmark dose method applied to pleural plaques in a small subcohort of vermiculite workers in Marysville, Ohio. We show that these data are too sparse to inform the exposure-response relationship in the low-exposure region critical for estimation of an RfC, and that different models with very different exposure-response shapes fit the data equally well. Furthermore, pleural plaques do not represent a disease condition and do not appear to meet the EPA's definition of an adverse condition. The estimation of the IUR for cancer is based on a subcohort of Libby miners, discarding the vast majority of lung cancers and mesotheliomas in the entire cohort and ignoring important time-related factors in exposure and risk, including effect modification by age. We propose that an IUR based on an endpoint that combines lung cancer, mesothelioma, and nonmalignant respiratory disease (NMRD) in this cohort would protect against both malignant and nonmalignant disease. However, the IUR should be based on the entire cohort of Libby miners, and the analysis should properly account for temporal factors. We illustrate our discussion with our own independent analyses of the data used by the Agency.