An association between air pollution and mortality in six U.S. cities

Area of Science:

• Environmental Health
• Epidemiology
• Public Health

Background:

• Previous studies linked particulate air pollution to mortality but lacked controls for smoking and other health risks.
• Cross-sectional studies in U.S. metropolitan areas showed associations between air pollution and annual mortality rates.
• Concerns existed regarding the methodology of prior research, particularly the omission of key confounding factors.

Purpose of the Study:

• To investigate the association between air pollution and mortality while controlling for individual risk factors.
• To quantify the impact of air pollution on mortality rates in a prospective cohort.
• To identify specific components of air pollution contributing to excess mortality.

Main Methods:

• A prospective cohort study involving 8111 adults across six U.S. cities.
• 14-to-16-year mortality follow-up data utilized for analysis.
• Cox proportional-hazards regression modeling applied to survival data, adjusting for individual risk factors like smoking.

Main Results:

• Cigarette smoking showed the strongest association with mortality rates.
• Statistically significant associations between air pollution and mortality were observed after adjusting for smoking and other risk factors.
• The most polluted cities had a 26% higher mortality rate ratio compared to the least polluted (CI: 1.08-1.47).
• Air pollution was associated with increased deaths from lung cancer and cardiopulmonary disease, but not other causes.
• Fine particulates, including sulfates, demonstrated the strongest association with mortality.

Conclusions:

• Fine-particulate air pollution, or associated complex mixtures, likely contributes to excess mortality in U.S. cities.
• While unmeasured risk factors cannot be entirely ruled out, the findings suggest a causal link.
• Public health strategies addressing air quality, especially fine particulate matter, are warranted.