February 24, 2023

expert reaction to US study looking at the association of long-term exposure to particulate air pollution with cardiovascular events

A study published in JAMA Network Open looks at long-term exposure to particulate air pollution in California and cardiovascular events.

Dr Peter Ka Hung Chan, Oxford British Heart Foundation Centre of Research Excellence Intermediate Transition Research Fellow in the Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), Oxford Population Health, University of Oxford, said:

“This study has significant improvements over the previous ones on ambient PM2.5 and CVD risk, as it utilised individual-level data (especially for confounder) instead of ecological data used in previous studies.  There were missing data on the confounders, but it should not be a huge problem after the authors’ imputation work; although the use of medical insurance ownership as individual-level socioeconomic status indicator may be too crude and it could leave room of residual confounding (people at lower SES tend to have higher exposure to air pollution and CVD risk, but that correlation doesn’t make the two causally related).

“Like virtually all existing studies on this topic, the air pollution exposure was approximated with an assumption that people are exposed to the level of PM2.5 near their home address 24/7, all year round.  This is a longstanding limitation of air pollution epidemiology, and what the authors have done is a state-of-the-art approach, but we should take actual personal exposure into account in future studies, as actual personal measurements are becoming increasingly feasible and reliable.

“This is not to say PM2.5 at low levels IS NOT harmful, but to say we do not have good enough evidence to quantitatively judge how much harm it is causing at a low level or whether the regulatory standard is sufficient or not, based on this one single study alone.”

‘Association of Long-term Exposure to Particulate Air Pollution With Cardiovascular Events in California’ by Stacey E. Alexeeff et al. was published in JAMA Network Open at 16:00 UK time on Friday 24 February 2023.

DOI: 10.1001/jamanetworkopen.2023.0561

Declared interests

No reply to our request for DOIs was received.