Air Quality in Canada

An introduction to fine particulate matter

What is fine particulate matter?

Fine particulate matter is a general term used for an airborne mixture of solid particles and liquid droplets. These particles are <= 2.5 microns in diameter and, although the composition is region-specific, are largely made up of sulphate, nitrate, carbon particles and soil.

Along with ground-level ozone, fine particulate matter is one of the two major components of smog.

From a human perspective, excess fine particulates pose hazards for people with asthma, cardiovascular or lung disease, as well as children and the elderly. These health effects have been associated with both short term (daily) and long term (>year) exposure.

Environmentally, fine particulate matter can influence rates of erosion and contribute to damage to vegetation as well as reduced visibility.

When should we start to worry about fine particulate matter?

Canada's 2015 Ambient Air Quality Standards published 4 different management levels for fine particulate matter:

1. Red (10.5 µg/m3)

2. Orange (6.4-10.4 µg/m3)

3. Yellow (4.0-6.3 µg/m3)

4. Green (0-3.9 µg/m3)

These threshold levels suggest that, while 0-3.9 µg/m3 is ideal, concentrations below 10.5 µg/m3 will meet the annual standard.

Sources: http://www.airqualityontario.com/science/pollutants/particulates.php;

https://www.ec.gc.ca/indicateurs-indicators/default.asp?lang=en&n=029BB000-

Fine particulate matter in Canada

The (Canadian) National Pollution Surveillance Program has an open-source dataset that tracks fine particulate matter across Canada. In this small project, I'll explore how these levels have changed from 2000-2014, using 5 main regions: British Columbia, Prairies and Northern Ontario, Southern Ontario, Southern Quebec and the Atlantic provinces.

Are there any differences in particulate matter concentrations among the regions?

The figure below includes all data from 2000-2014. The squares represent a region's mean and error bars represent 95% confidence intervals.

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Key take home message:

While concentrations seem to change over the course of the timeline within regions, the national average has largely remained stagnant in these 14 years.

Are these changes statistically signifcant?

There was a significant change in concentration over the years in Southern Ontario (t=-2.960, p=0.004) and a near significance in the Prairies and Northern Ontario (t=1.548, p=0.066). It is interesting to note that these interactions are in opposition to each other - Southern Ontario saw a decrease in fine particulate matter over time, while fine particulate matter in the Prairies and Northern Ontario increased.

The significant interaction between concentration and temporal change in Southern Ontario is displayed below, with the shaded section representing 95% confidence around the cubic polynomial line of best fit.

Key take home message:

British Columbia, the Prairies and Northern Ontario, and Atlantic Canada all have similar fine particulate matter concentrations, while Southern Ontario has statistically higher concentrations than those regions, and Southern Quebec has higher still concentrations.

Is there any evidence of temporal variation within regions from 2000-2014?

Click through the slideshow to see how concentrations change over time in each region, with an overlaid national average in the last two figures.

While there were substantial decreases in concentrations from 2000-2012 (driving the significance in our model), 2013 and 2014 saw major increases back to ~2000-2006 levels.

Summary:

We have explored the concentration of fine particulate matter in Canada's airspace, spanning 5 different regions.
There were substantial differences in average concentrations between regions, as Southern Quebec and Southern Ontario had significantly higher concentrations than British Columbia, the Prairies and Northern Ontario, and Atlantic Canada.
Southern Ontario saw a significant decrease in overall fine particulate matter concentrations, and the Prairies and Northern Ontario saw a near-significant increase in concentrations, but, overall, the national average remained unchanged.
Importantly, all regions fell below the 2015 annual standard.

R Code

You can get the full R code for this project on my github page, here.