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

Pinault L, Tjepkema M, Crouse DL, et al. · Environmental health : a global access science source · 2016

doi.org/10.1186/s12940-016-0111-6 Read the full paper ↗142 citationscc by

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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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.