Systematic review of the association between long-term exposure to fine particulate matter and mortality

ABSTRACT

We used a transparent systematic review framework based on best practices for evaluating study quality and integrating evidence to conduct a review of the available epidemiology studies evaluating associations between long-term exposure to ambient concentrations of PM_2.5 and mortality (all-cause and non-accidental) conducted in North America. We found that while there is some consistency across studies for reporting positive associations, these associations are weak and several important methodological issues have led to uncertainties with regard to the evidence from these studies, including potential confounding by measured and unmeasured factors, exposue measurement error, and model misspecification. These uncertainties provide a plausible, alternative explanation to causality for the weakly positive findings across studies. Using a causality framework that incorporates best practices for making causal determinations, we concluded that the evidence for a causal relationship between long-term exposure to ambient PM_2.5 concentrations and mortality from these studies is inadequate.

KEYWORDS:

• Causal framework
• mortality
• particulate matter

Acknowledgments

We thank Ms. Carla Walker for her assistance on this manuscript.

Declaration of interest

All of the authors are employees of Gradient, an independent environmental risk science consulting firm. The work reported in this paper was conducted during the normal course of employment, with financial support by the American Petroleum Institute (API). J.E. Goodman and R.L. Prueitt have previously given presentations or testimony on topics related to air pollution at scientific conferences and meetings with regulatory agencies, with funding provided by API. All other authors declare that they have not been involved in any regulatory activities related to the contents of this paper. This manuscript is the professional work product of the authors, and the opinions and conclusions offered within are not necessarily those of their employers or the financial sponsor of the work.

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Additional information

Funding

This work was supported by the American Petroleum Institute [No Grant].