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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.

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How large was the CCHS analytical cohort?

299,500 respondents after excluding unlinked, out-of-age-range, recent-immigrant, and unmapped cases.

What mean PM2.5 did the cohort experience?

6.3 ± 2.5 μg/m³ from a 3-year moving average.

What was the fully adjusted non-accidental mortality HR per 10 μg/m³ PM2.5?

1.26 (95% CI 1.19–1.34).

Which cause of death showed the strongest PM2.5 association?

Respiratory disease mortality, HR 1.52 (1.26–1.84) per 10 μg/m³.

How was exposure timed relative to death?

Each year used the mean PM2.5 of the three preceding years so exposure always preceded response.

Did risk appear only above the WHO 10 μg/m³ guideline?

No—increased mortality was observed even at concentrations below 10 μg/m³.

What spatial resolution was the PM2.5 surface?

About 1 km² (0.01° × 0.01°) after geographically weighted regression.

What was mean follow-up?

7.6 ± 2.7 years, with up to 12 years after cohort entry.

How did circulatory-disease HRs compare with the literature?

HR 1.19 was generally consistent with Harvard Six Cities and other international estimates.

Which HRs were not significantly above one in fully adjusted models?

Cerebrovascular disease and lung cancer.

How was PM2.5 related to income?

Mean exposure rose as income fell and was highest in the poorest quintile.

What behavioural covariates entered the fully adjusted Cox models?

Smoking, alcohol consumption, BMI, and fruit/vegetable consumption, plus socioeconomic and ecological covariates.