Introduction: special issue of air quality, atmosphere and health for air pollution and health: bridging the gap from sources-to-health outcomes

The U.S. Environmental Protection Agency has established the National Ambient Air Quality Standards for six principal air pollutants (criteria pollutants): carbon monoxide (CO), lead (Pb), nitrogen dioxide, particulate matter in two size ranges [less than 2.5 μm (PM2.5) and less than 10 μm (PM10)], ozone, and sulfur dioxide (http://www.epa. gov/air/criteria.html). While associations have been identified between these pollutants and adverse health effects, considerable uncertainty remains with regards to methods and approaches to understanding which gas or particulate components are most toxic, which sources and source combinations emit these compounds and their precursors, the mechanisms of actions of the pollutants and their causal relationships to adverse health effects, effect of confounding factors that obscure the relationship between toxicity and health, and which populations are susceptible. The pollutant – health relationship is all the more complicated for particulate matter since it is composed of many components and is distributed over a wide range of sizes that differentially deposit in human airways (EPA 2006a [ozone criteria document (CD)], EPA 2006b (Pb CD), EPA 2008a [NOx integrated science assessment (ISA)], EPA 2008b (SOx ISA), EPA 2009 (PM ISA), EPA 2010 (CO ISA)). Air pollution and health research continues to reduce these uncertainties across the source-to-health effects paradigm as described by the National Research Council (NRC 1998, 1999, 2001, 2004), EPA (EPA 2006a, b, 2008a, b, 2009, 2010), and Solomon et al. (2011a and references within). Linking air pollution to adverse health effects and minimizing the risk from air pollution is complicated and requires expertise across a range of scientific disciplines from atmospheric to exposure to health sciences as well as inclusion of air quality managers and policy makers who develop and implement Policies related to reducing air pollution on national, regional, and local scales to protect public health and welfare. Interaction among these groups at different points in time helps to identify gaps in knowledge and suggests future research directions. March 2010 provided one such opportunity through “Air Pollution and Health: Bridging the Gap from Sources to Health Outcomes,” an international specialty conference by the American Association for Aerosol Research (AAAR, http:// aaar.2010specialty.org/; Solomon et al. 2011a). The conference was chaired by Drs. Paul A. Solomon (U.S. EPA) and Maria Costantini (HEI) and was designed to help disseminate and integrate results from scientific studies that cut across the range of air pollution and health-related disciplines of the source-to-health effects continuum. Conference objectives are listed in Table 1. The conference addressed the science of air pollution and health within a multipollutant framework, focusing across five key science areas: sources, atmospheric sciences, exposure, dose, and health effects as identified by the NRC (1998). Eight key policy-relevant science questions that integrated across various parts of these science areas formed the basis of the meeting. A ninth question addressed the policy implications of the findings. The science questions are listed in Table 2. This was AAAR’s third international specialty conference and extends the findings presented at AAAR’s first specialty conference “Particulate Matter: Atmospheric Sciences, Exposure, and the Fourth P. A. Solomon (*) Office of Research and Development, U.S. Environmental Protection Agency, Las Vegas, NV 89119, USA e-mail: solomon.paul@epa.gov Air Qual Atmos Health (2012) 5:3–8 DOI 10.1007/s11869-011-0165-0