Examining the Shape of the Association between Low Levels of Fine Particulate Matter and Mortality across Three Cycles of the Canadian Census Health and Environment Cohort

Oct 23, 2019Environmental health perspectives

How low levels of fine air pollution relate to death rates in Canada over three census periods

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Abstract

The mean 3-year annual average estimate of PM2.5 exposure ranged from 6.7 to 10 μg/m³ across three Canadian cohorts.

A hazard ratio of 1.053 per 10 μg/m³ change in PM2.5 was estimated after combining data from three cohorts.
This hazard ratio indicates an increased risk of nonaccidental mortality associated with higher PM2.5 exposure.
The association observed was supralinear, meaning that the risk may increase more sharply at higher concentrations.
For the 1991 cohort, the confidence intervals for the hazard ratio exceeded 1 for all concentrations studied.
In the 1996 cohort, significant risk was noted at concentrations above 5 μg/m³, while the 2001 cohort showed risk at concentrations above 2 μg/m³.

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BACKGROUND: Ambient fine particulate air pollution with aerodynamic diameter() is an important contributor to the global burden of disease. Information on the shape of the concentration-response relationship at low concentrations is critical for estimating this burden, setting air quality standards, and in benefits assessments. ≤ 2.5 μ m PM2.5

OBJECTIVES: We examined the concentration-response relationship betweenand nonaccidental mortality in three Canadian Census Health and Environment Cohorts (CanCHECs) based on the 1991, 1996, and 2001 census cycles linked to mobility and mortality data. PM2.5

METHODS: Census respondents were linked with death records through 2016, resulting in 8.5 million adults, 150 million years of follow-up, and 1.5 million deaths. Using annual mailing address, we assigned time-varying contextual variables and 3-y moving-average ambientat aspatial resolution from 1988 to 2015. We ran Cox proportional hazards models foradjusted for eight subject-level indicators of socioeconomic status, seven contextual covariates, ozone, nitrogen dioxide, and combined oxidative potential. We used three statistical methods to examine the shape of the concentration-response relationship betweenand nonaccidental mortality. PM2.5 1 1 × km PM2.5PM2.5

RESULTS: The mean 3-y annual average estimate ofexposure ranged from 6.7 toover the three cohorts. We estimated a hazard ratio (HR) of 1.053 [95% confidence interval (CI): 1.041, 1.065] perchange inafter pooling the three cohort-specific hazard ratios, with some variation between cohorts (1.041 for the 1991 and 1996 cohorts and 1.084 for the 2001 cohort). We observed a supralinear association in all three cohorts. The lower bound of the 95% CIs exceeded unity for all concentrations in the 1991 cohort, for concentrations abovein the 1996 cohort, and abovein the 2001 cohort. PM2.5 8 μ g m / 3 10 -μ g m / 3PM2.5 2 μ g m / 3 5 μ g m / 3

DISCUSSION: In a very large population-based cohort with up to 25 y of follow-up,was associated with nonaccidental mortality at concentrations as low as. https://doi.org/10.1289/EHP5204. PM2.5 5 μ g m / 3

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Examining the Shape of the Association between Low Levels of Fine Particulate Matter and Mortality across Three Cycles of the Canadian Census Health and Environment Cohort

Abstract

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