Air Quality Assessment Tools: A Guide for Public Health Practitioners Prabjit Barn, Peter Jackson, Natalie Suzuki, Tom Kosatsky, Derek Jennejohn, Sarah Henderson, Warren McCormick, Gail Millar, Earle Plain, Karla Poplawski, Eleanor Setton Summary • Several tools exist to assess local air quality, including the impact of specific sources, emissions, and meteorological conditions. • Information generated from the use of air quality assessment tools can inform decisions on permitting of emissions, industrial siting, and land use; all can impact local air quality, which in turn can influence air pollution related health effects of a population. • The five tools discussed in this guide (highlighted with case examples) address different components of air quality: o Emissions inventories are databases of air pollution sources and their emissions, which allow for the monitoring of pollution releases to the air; emissions inventories can feed into other tools, such as dispersion models. o Dispersion modeling uses data on emissions, meteorology, and topography to provide estimates of ambient pollutant concentrations at specific receptor sites. o Source apportionment helps to identify important sources in an area by using information on ambient pollutant levels. o Mobile monitoring, in contrast to traditional fixed site monitoring, allows for a better understanding of pollutant concentrations and their sources, both temporally and, very importantly, spatially; Data collected by mobile monitoring projects can feed into models, such as land-use regression. o Land use regression uses a combination of local information to provide the best estimates of ambient pollution in a specific area. • Health impact assessment is an example of direct application of information generated by air quality assessment tools, to understand the air quality related health impacts of a population. Introduction Air quality impacts both the environment and health. Air quality management aims to limit negative impacts through a variety of activities, including legislation, policies, and plans to manage emissions and monitor ambient air quality. Air quality assessments inform air quality management activities by providing an understanding of how pollutant sources, emission characteristics, topography, and meteorological conditions contribute to local air quality. Specific December 2011 National Collaborating Centre for Environmental Health air quality assessment tools can help answer a variety of questions which are integral to air quality management activities, including: • How can frequently poor air quality be improved? • Which source(s) or source sectors contribute to poor air quality? • How can air quality impacts be minimized? • Which regions are most affected? • Should existing sources be targeted for emissions reductions? • What location, for new sources, could minimize air quality impacts? • Will emissions from a proposed new source result in a substantial degradation in air quality? Although air quality assessment tools are valuable when informing decisions that impact local air quality, their use may be overlooked by public health practitioners. The information conveyed by these tools is often highly technical and typically accessible only to trained air quality management personnel. As a result, useful information may not be available to support decisions on emissions permitting, industrial siting, and land use, as well as the development of public health messages. The objective of this guide is to increase the understanding and accessibility of these tools to better support public health responses and policy decisions on local air quality. The specific assessment tools discussed in this guide are: (1) emissions inventories, (2) dispersion modelling, (3) source apportionment, (4) mobile monitoring, and (5) land use regression. Health Impact Assessment is discussed as a direct application of information provided by air quality assessment tools. A brief overview of key sources and pollutants in British Columbia (BC) and their health impacts is provided to give context to the tools. A description of the BC air quality monitoring network, current practices in BC, regarding land use, emissions permitting, and health messaging, follows. The remainder of the guide provides a description of each tool, as well as advantages and limitations of their use. Finally, local examples are provided for each tool, to highlight their use in air quality management in the province. Key Pollutants and Sources Pollutants Air pollutants are gases or particles in the atmosphere which have been linked to harmful human health or environmental effects. Pollutants can be categorized according to their formation (primary or secondary), their sources, and their chemical composition and characteristics. Pollutants can be primary or secondary. Primary pollutants are released directly into the atmosphere while secondary pollutants are formed through reactions between pollutants already present in the atmosphere, also known as precursors. Fine particulate matter (particles smaller than 2.5 µm in aerodynamic diameter) is an example of both a primary and secondary pollutant. These particles can be formed directly through combustion processes, including activities involving wood burning or vehicle engines, and can also be formed through reactions between pollutants, such as nitrogen oxides (NOx), volatile organic compounds (VOCs), and sulfur oxides (SOx). Ground level ozone is a secondary pollutant that is formed through reactions between NOx and VOCs in the presence of sunlight. Environment Canada classifies major pollutants into four main groups; 1) criteria air contaminants, 2) persistent organic pollutants, 3) heavy metals, and 4) Toxics.1 Criteria air December 2011 National Collaborating Centre for Environmental Health 2 contaminants are typically the focus of air quality management activities, including pollutant monitoring and objective setting. Criteria air contaminants include: fine particulate matter (PM2.5), coarse particulate matter (PM10), sulphur dioxides (SOx), nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO), ammonia (NH3), and ozone. See Table 1 for a summary of these pollutants. The ambient levels of many of these pollutants are monitored in the province (see section on BC’s monitoring network). Table 1 Summary of Key Pollution Criteria Air Contaminants and their sources Pollutant Description Major sources Particulate • Mixture of solid and liquid • Motor vehicle engines, industrial matter (PM) particles with different chemical processes, wood burning; breakdown of and physical properties in air materials including earth’s crust; reactions between pollutants such as NOx, VOCs • PM10 particles are 10 microns (µm) in aerodynamic diameter and NH3 and smaller • PM2.5 particles are 2.5 µm in aerodynamic diameter and smaller; PM2.5 particles can penetrate further down in the respiratory system compared to larger particles Ozone • A reactive oxygen species • Reactions between NOx and VOCs in presence of sunlight Nitrogen • A group of reactive gases that • Motor vehicles, wood burning, industrial oxides (NOx) include nitric oxide (NO) and processes (power generation, use of industrial boilers and diesel generators, nitrogen dioxide (NO2) petroleum refining) • NO2 is odorous, brown and highly corrosive Sulphur • A colourless gas that has a • Marine vessels, smelting, petroleum dioxide (SO2) pungent odour that smells like a refining, diesel engines struck match. Carbon • A colourless, odourless gas • Motor vehicles, waste incineration space monoxide produced from incomplete heating combustion of fuel. Volatile • A group of carbon-containing • Transportation, industry (oil and gas, organic gases and vapors (e.g., petroleum refining, pulp and paper mills), compounds benzene, toluene, xylene) consumer products (solvents, paints, cleaning products), residential wood combustion • React with NOx to form ozone Ammonia • A colourless gas with a pungent • Agricultural activities odor December 2011 National Collaborating Centre for Environmental Health 3 Sources Sources of air pollution can be categorized as fixed or mobile. Fixed sources are stationary sources that emit pollutants from specific geographical areas, whereas the mobile category encompasses non-stationary sources, such as motor vehicles and non-road equipment. In BC, several key sources contribute to regional and local air quality. Sources of pollutants can be quite varied in terms of their types and locations, but the majority of pollutant sources in the province are typically linked to fossil fuel or biomass combustion. Within urban areas, the mobile category, specifically the transportation sector, is generally the largest source of pollutants, such as NOx, SO2, CO and PM. Throughout most of the province, the major sources of SO2 are fixed 2 emitters, such as the oil and gas sector, pulp and paper production, and metal smelting, while 3 within the Lower Fraser Valley, the marine sector is the largest source of SO2 emissions. In dry environments, dust formed through the breakdown of crustal material can be an important source of PM10 and to a lesser extent PM2.5. In the Interior, in addition to dust, sources such as prescribed and open burning, wood industries, and residential wood heating are major generators of PM2.5. Although residential wood burning has traditionally been an important source in rural communities, local research shows that even in some urban areas, including Vancouver and