Regulatory and Policy Implications of the Air Pollution to Health Research Paradigm: A U.S. EPA Perspective

BRYAN J HUBBELL

U.S. EPA, Office of Air Quality Planning and Standards

     Abstract Number: 458
     Last modified: January 7, 2010

Abstract
Scientific research linking air pollution sources through exposure to health informs EPA decisions both by establishing the evidentiary basis for air quality standards, and by informing the risk assessments that can help establish the health benefits of revising existing standards. Decisions on levels and forms of standards are policy decisions, which are built on the core of scientific information provided in the Integrated Science Assessment and the risk and exposure assessments conducted based on that Science Assessment.

EPA’s recent reviews of the standards includes an enhanced emphasis on a framework for causal inference based on the synthesis of information from toxicological, clinical, and epidemiological studies. As such, it is increasingly valuable for the research community to think ahead to how the results of a specific research study can be integrated into an overall assessment of the broad scientific questions that are most relevant for policy decisions. This may include an understanding of the role that individual pollutants play within the overall mixture of pollutants that determine air quality and health outcomes in an urban area. It also requires an improved understanding of the roles of sources, exposure routes, ambient mixtures, biological mechanisms, and factors that influence sensitivity to exposures, e.g. genetic markers, preexisting health conditions, etc.

There are significant remaining policy relevant questions for researchers in the air pollution field. These include:
• Where to stop? – with apparently non-threshold pollutants, it is critical to understand impacts at lower concentrations.
• Are we regulating the right things? – more studies on PM composition and ambient mixtures of gases and particles related to different emissions profiles are needed
• Are we protecting at-risk populations? There is an expanding interest in factors that determine susceptibility and vulnerability, e.g. genetic markers.
• Is the suite of standards protective? Given the variety of mixtures to which populations are exposed, are single pollutant standards adequately protective in a multipollutant environment – which mixtures are more toxic, e.g. near roadway, ports, industrial centers, etc.
• Are we adequately capturing exposure? How well do central site monitor based health studies capture important exposures to different pollutants?
• How confident are we? Given current causality paradigm, what are the missing elements that would increase the confidence that pollutants are causally associated with health risks, and that those associations exist at levels below the current standards?

As the research community continues to move forward in addressing air pollution research questions, some specific areas that may help to address the above questions include:
• Additional clinical research into the effects of exposures to low levels of criteria pollutants, including low levels within an overall mixture of pollutants
• Animal studies examining toxicity of different mixtures of pollutants, and focusing on interactions between pollutants within the mixture
• Toxicology and clinical studies examining genetic markers that can identify susceptible subpopulations
• Studies of exposures to mixtures representing different exposure profiles, e.g. central site monitors, near-roadway, ports, high industry – with a focus on the proportion of daily or annual exposure to each mixture.