Associations between fine particulate matter and mortality in the 2001 Canadian Census Health and Environment Cohort

Area of Science:

• Environmental Health
• Epidemiology
• Public Health

Background:

• Large cohort studies have investigated the link between fine particulate matter (PM2.5) air pollution and mortality.
• However, a consensus on the concentration-response relationship shape is lacking.

Purpose of the Study:

• To examine the shape of the association between PM2.5 exposure and cause-specific mortality.
• To develop and apply novel methods for estimating PM2.5 exposure and analyzing concentration-response functions.

Main Methods:

• A new Canadian cohort of 2.4 million individuals was established using 2001 census data.
• Annual PM2.5 estimates (1998-2011) were derived from remote sensing and ground measurements.
• Cox survival models and Shape Constrained Health Impact Functions were used to analyze mortality risks.

Main Results:

• Increased hazard ratios (HR) for non-accidental mortality (1.18 per 10μg/m³), cardiovascular (1.25), cardio-metabolic (1.27), ischemic heart disease (1.36), and COPD (1.24) were observed.
• Concentration-response curves were supra-linear for non-accidental, cardio-metabolic, ischemic heart disease, respiratory, and COPD mortality, indicating higher relative risks at lower concentrations.
• Sub-linear curves were suggested for pneumonia and lung cancer mortality.

Conclusions:

• The association between ambient PM2.5 concentrations and mortality is non-linear for multiple causes of death.
• The findings underscore the importance of considering the shape of the concentration-response function in air pollution health impact assessments.