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Low Levels of Air Pollution and Health: Effect Estimates, Methodological Challenges, and Future Directions


Purpose of Review

Fine particle (PM2.5) levels have been decreasing in the USA over the past decades. Our goal was to assess the current literature to characterize the association between PM2.5 and adverse health at low exposure levels.

Recent Findings

We reviewed 26 papers that examined the association between short- and long-term exposure to PM2.5 and cardio-respiratory morbidity and mortality. There is evidence suggesting that these associations are stronger at lower levels. However, there are certain methodological and interpretational limitations specific to studies of low PM2.5 levels, and further methodological development is warranted.


There is strong agreement across studies that air pollution effects on adverse health are still observable at low concentrations, even well below current US standards. These findings suggest that US standards need to be reevaluated, given that further improving air quality has the potential of benefiting public health.

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Fig. 1
Fig. 2


Tot m:

total mortality

CVD m:

cardiovascular mortality

CHF m:

Congestive Heart failure mortality

IHD m:

Ischemic heart disease mortality

Circul m:

Circulatory mortality

Resp m:

Respiratory mortality


COPD mortality

Pneum m:

Pneumonia mortality


Chronic lower respiratory disease mortality

Tot HA:

total hospital admissions


cardiovascular hospital admissions


cardiovascular Emergency Visits

Resp EV:

Respiratory Emergency Visits

Resp HA:

Respiratory hospital admissions

Circul HA:

Circulatory hospital admissions


Papers of particular interest, published recently, have been highlighted as: •• Of major importance

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National Institutes of Health NIH/NIEHS grants P30 ES000002, P30 ES009089, and R01 ES024332; HEI grant 4953-RFA14-3/16-4. Research described in this article was conducted under contract to the Health Effects Institute (HEI), an organization jointly funded by the United States Environmental Protection Agency (EPA) (Assistance Award No.CR-83467701) and certain motor vehicle and engine manufacturers. The contents of this article do not necessarily reflect the views of HEI, or its sponsors, nor do they necessarily reflect the views and policies of the EPA or motor vehicle and engine manufacturers.

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Correspondence to Antonella Zanobetti.

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Papadogeorgou, G., Kioumourtzoglou, MA., Braun, D. et al. Low Levels of Air Pollution and Health: Effect Estimates, Methodological Challenges, and Future Directions. Curr Envir Health Rpt 6, 105–115 (2019).

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  • Air pollution
  • Mortality
  • Hospital admissions
  • Fine particles, PM2.5
  • Low levels
  • Concentration-response