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Air Pollution

Hamilton, ON

Air pollution is a ubiquitous exposure that has been shown to have a variety of negative health impacts, such as propagating the development of chronic diseases in the cardiorespiratory and neurological systems. We are interested in air pollution exposure from repeated respiratory contact by individuals over a prolonged period of time (i.e., years).

ONPHEC Goals

  • Quantify the burden of chronic diseases from long-term exposure to ambient air pollution

  • Investigate the effectiveness of air pollution interventions

 

Exposures to major air pollutants include:

Fine particulate matter

Particles with aerodynamic diameter ≤2.5 µm are referred to as fine particulate matter (PM2.5). PM2.5 is typically made up of components such as sulphate, nitrate, and black carbon, and has been associated with various health effects, including increased cardiovascular mortality and neurodegenerative diseases. We currently have data on annual mean PM2.5 concentrations at 1km × 1km resolution for the years 1998-2012 across Ontario. Estimated concentrations were derived from satellite observations, in combination with outputs from a global atmospheric chemistry transport model, and calibrated using information on land cover, elevation, and aerosol composition1.

ONPHEC studies that have assessed the effects of PM2.5 on chronic disease include:

  • Exposure to ambient air pollution and the incidence of dementia: a population-based cohort study

  • Ambient fine particulate matter and mortality among survivors of myocardial infarction: population-based cohort study

  • Spatial association between ambient fine particulate matter and incident hypertension

  • Risk of incident diabetes in relation to long-term exposure to fine particulate matter in Ontario, Canada

 

Nitrogen dioxide

Nitrogen dioxide (NO2) is typically produced from burning fuel, and is present in higher concentrations in areas with increased vehicle emissions or industrial activity (e.g., close to major roadways). NO2 exposure can lead to a number of health issues, such as increased asthma symptoms, chronic respiratory diseases, and neurodegenerative diseases.

Our Ontario-wide NO2 data was derived from a 2006 national land-use regression model developed using estimated concentrations from fixed-site monitors from the National Air Pollution Surveillance Network. The model includes a number of predictors (e.g., industrial land use, road length) in conjunction with spatially-varying multipliers to capture the spatial gradient of NO2 concentrations2.

ONPHEC studies that have assessed the effects of NO2 on chronic disease include:

  • Exposure to ambient ultrafine particles and nitrogen dioxide and incident hypertension and diabetes

  • Exposure to ambient air pollution and the incidence of dementia: a population-based cohort study

 

Ozone

Ground-level ozone (O3) is created from chemical reactions between nitrogen oxides and volatile organic compounds, and is the main component of smog. Exposure to elevated levels of O3 is known to result in cardiorespiratory issues such as exacerbation of chronic obstructive pulmonary disease.

We have O3 data from a 2002-2009 warm-season average exposure surface at 21km × 21km resolution across Ontario, derived using optimal interpolation technique. This technique combines the true observations of O3 with air quality prediction models that account for the meteorological and chemical patterns of O33.

ONPHEC studies that have assessed the effects of O3 on chronic disease include:

  • Exposure to ambient air pollution and the incidence of dementia: a population-based cohort study

 

Ultrafine particulate matter

Particles with aerodynamic diameter ≤0.1 µm are referred to as ultrafine particulate matter (UFP). Experimental and animal evidence has shown that short-term exposure to UFP may lead to oxidative stress and affect vascular function.

Our UFP data is currently restricted to the City of Toronto, Ontario. Estimated concentrations were derived from land-use regression models based on measurements collected in 2014 from a mobile monitoring campaign conducted over three weeks. The model includes a number of predictors, such as distance to highways, on-street trees, and length of bus routes4.

ONPHEC studies that have assessed the effects of UFP on chronic disease include:

  • Exposure to ambient ultrafine particles and nitrogen dioxide and incident hypertension and diabetes

  • Long-term exposure to ambient ultrafine particles and incidence of lung cancer, chronic obstructive pulmonary disease, and adult-onset asthma in Toronto, Canada

 

Oxidant capacity

Oxidant capacity (Ox) is novel measure of air pollution exposure, which provides an assessment of regional differences in the ability of PM2.5 to cause oxidative stress – a mechanism thought to play an important role in air pollution-related health effects.

We estimate Ox as a weighted average of the redox potentials of NO2 and O3. Namely, Ox ≈ ⅓ NO2 + ⅔ O3, to account for O3 being a stronger oxidizing agent than NO25.

We are interested in evaluating if regional differences in Ox may contribute to regional differences in PM2.5-associated health effects. Several studies are currently underway using ONPHEC to assess the impact of Ox, and its interaction with PM2.5, on the new onset of major chronic diseases.

 

1 van Donkelaar A, Martin RV, Brauer M, Boys BL. Use of satellite observations for long-term exposure assessment of global concentrations of fine particulate matter. Environ Health Perspect 2015; 123:135–143.

2 Hystad P, Setton E, Cervantes A et al. Creating national air pollution models for population exposure assessment in Canada. Environ Health Perspect 2011; 119:1123–1129.

3 Robichaud A, Ménard R. Multi-year objective analyses of warm season ground-level ozone and PM2.5 over North America using real-time observations and Canadian operational air quality models. Atmos Chem Phys 2014; 14:1769-1800.

4 Weichenthal S, Van Ryswyk K, Goldstein A et al. Characterizing the spatial distribution of ambient ultrafine particles in Toronto, Canada: A land use regression model. Environ Pollut 2016; 208(Pt A):241–8.

5 Weichenthal S, Lavigne E, Evans G et al. Ambient PM2.5 and risk of emergency room visits for myocardial infarction: impact of regional PM2.5 oxidative potential: a case-crossover study. Environ Health 2016; 15:46.