The impact of long-term PM2.5 exposure on specific causes of death: exposure-response curves and effect modification among 53 million U.S. Medicare beneficiaries

Abstract

Background The shape of the exposure-response curve for long-term ambient fine particulate (PM2.5) exposure and cause-specific mortality is poorly understood, especially for rural populations and underrepresented minorities. Methods We used hybrid machine learning and Cox proportional hazard models to assess the association of long-term PM2.5 exposures on specific causes of death for 53 million U.S. Medicare beneficiaries (aged ≥65) from 2000 to 2008. Models included strata for age, sex, race, and ZIP code and controlled for neighborhood socio-economic status (SES) in our main analyses, with approximately 4 billion person-months of follow-up, and additionally for warm season average of 1-h daily maximum ozone exposures in a sensitivity analysis. The impact of non-traffic PM2.5 on mortality was examined using two stage models of PM2.5 and nitrogen dioxide (NO2). Results A 10 μg /m3 increase in 12-month average PM2.5 prior to death was associated with a 5% increase in all-cause mortality, as well as an 8.8, 5.6, and 2.5% increase in all cardiovascular disease (CVD)-, all respiratory-, and all cancer deaths, respectively, in age, gender, race, ZIP code, and SES-adjusted models. PM2.5 exposures, however, were not associated with lung cancer mortality. Results were not sensitive to control for ozone exposures. PM2.5-mortality associations for CVD- and respiratory-related causes were positive and significant for beneficiaries irrespective of their sex, race, age, SES and urbanicity, with no evidence of a lower threshold for response or of lower Risk Ratios (RRs) at low PM2.5 levels. Associations between PM2.5 and CVD and respiratory mortality were linear and were higher for younger, Black and urban beneficiaries, but were largely similar by SES. Risks associated with non-traffic PM2.5 were lower than that for all PM2.5 and were null for respiratory and lung cancer-related deaths. Conclusions PM2.5 was associated with mortality from CVD, respiratory, and all cancer, but not lung cancer. PM2.5-associated risks of CVD and respiratory mortality were similar across PM2.5 levels, with no evidence of a threshold. Blacks, urban, and younger beneficiaries were most vulnerable to the long-term impacts of PM2.5 on mortality.

Outdoor air pollution and cancer: An overview of the current evidence and public health recommendations

“…There were also some significant adverse associations with O 3 and NO 2 68,69 . Although an analysis extended to 53 million Medicare beneficiaries reported no association of PM 2.5 and lung cancer mortality, there may have been confounding by cigarette smoking status in rural populations that were included 70 …”

“…68,69 Although an analysis extended to 53 million Medicare beneficiaries reported no association of PM 2.5 and lung cancer mortality, there may have been confounding by cigarette smoking status in rural populations that were included. 70 Worldwide, ambient PM 2.5 air pollution was estimated to have contributed to 265,267 lung cancer deaths (95% uncertainty interval [UI], 182,903-350,835 lung cancer deaths) in 2017, or 14.1% (95% UI, 9.8%-18.7%) of all lung cancer deaths. 1 The global proportion of lung cancer deaths attributable to ambient PM 2.5 was second only to tobacco smoking (14.1% vs 63.2%).…”

Air Quality Enhancement Districts: democratizing data to improve respiratory health

“…Link between air quality and COVID-19 PM 2.5 refers to particulate matter with aerodynamic diameter equal or less than 2.5 micrometers, consisting of a complex mixture of both solid and liquid droplets suspended in the air. Tiny particles of these sizes are more likely to penetrate deep inside lungs and have the potential to cause significant adverse health effects, including difficulty breathing, heart-attacks, aggravated asthma, decreased lung function, and premature death (Wu et al 2020;Wang et al 2020). In 2015 alone, exposure to PM 2.5 is believed responsible for approximately 8.9 million premature deaths worldwide, with 213,000 premature deaths in the USA and Canada alone (Burnett et al 2018).…”

“…Air quality and regulations in the USA Air quality in the USA continues to improve across the country, with significantly fewer areas designated as out of compliance with current ambient air quality standards. While there is much debate about how well these standards reflect the current state of science to protect public health (Heikkinen 2018;Wang et al 2020;Parker 2016), there has been a steady improvement in air quality for most pollutants across the country, including PM 2.5 (U.S. EPA 2019).…”

“…In March and April 2020, during the COVID-19 pandemic, the U.S. EPA rolled back vehicle emissions standards that directly impact PM 2.5 , and announced plans to leave the current National Ambient Air Quality Standard for PM 2.5 at the 2012 threshold after scientists recommended tightening it to be more reflective of the current state of knowledge regarding PM 2.5 impact on human health (Reilly 2020;Heikkinen 2018). Studies show increased risk of premature death from fine particle pollution at levels much lower than the current PM 2.5 standards, and conclude that there is no threshold level without health risks (Wang et al 2020).…”