Low PM2.5 still tracks Canadian mortality
In 299,500 Canadians, a 10 μg/m³ rise in PM2.5 was linked to HR 1.26 for non-accidental death even at mean 6.3 μg/m³.
Source
Risk estimates of mortality attributed to low concentrations of ambient fine particulate matter in the Canadian community health survey cohort
Study at a glance
- Design
- Cohort — CCHS cohort Cox models of mortality vs low ambient PM2.5
- N
- N=299500 · 299,500 Canadian Community Health Survey respondents after exclusions
- Population
- Canadian adults in the CCHS linked to ambient PM2.5
- Outcome
- Non-accidental and cause-specific mortality per 10 μg/m³ PM2.5
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Low PM2.5 still tracks Canadian mortality
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Final sample was 299,500 respondents.
The final analytical sample was 299,500 respondents (note slight inconsistencies due to rounding).
How was exposure timed relative to death?
For each year in the cohort, respondents were assigned a PM 2.5 value corresponding to the mean of the three previous years to the follow-up year; therefore, exposure always preceded response.
What they did
Cox models in the CCHS cohort assigned 3-year satellite/land-use PM2.5 and followed deaths up to 12 years, adjusting for socioeconomic, ecological, and behavioural covariates.
What they found
Fully adjusted non-accidental HR was 1.26 per 10 μg/m³; respiratory mortality was strongest (HR 1.52). Risk remained elevated below the then-WHO 10 μg/m³ guideline.
The limits
What it doesn't show
Wide confidence intervals on the low-concentration spline; residual confounding from unmeasured smoking intensity or indoor sources cannot be ruled out, and mobility was only partly captured.
Key terms
- PM2.5
- Fine particulate matter with aerodynamic diameter ≤2.5 μm.
- Hazard ratio (HR)
- Relative mortality hazard associated with a 10 μg/m³ PM2.5 increment.
- CCHS cohort
- Canadian Community Health Survey respondents linked to vital statistics.
- Three-year moving average
- PM2.5 assigned as the mean of the three years before each follow-up year.
- Concentration–response
- Shape of mortality risk across the observed PM2.5 range.
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Mean cohort PM2.5 was about:
Common questions
How large was the cohort?
299,500 respondents after exclusions.
What was mean PM2.5?
6.3 ± 2.5 μg/m³ from the 3-year moving average.
Non-accidental HR per 10 μg/m³?
1.26 (95% CI 1.19–1.34) fully adjusted.
Which cause had the largest HR?
Respiratory disease mortality, HR 1.52.
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