Thursday, 7 July, 2022
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Study finds air-pollution's impact on health may be worse than thought

The number of health problems linked to air pollution could be far higher than previously thought. The Guardian reports that this is according to research suggesting hospital admissions for conditions ranging from heart failure to urinary tract infections increase as air becomes dirtier. Air pollution has already been associated with a number of conditions, from strokes to brain cancer, miscarriage and mental health problems. However, the research suggests the impact could be far wider, despite looking at only one component of air pollution, chiming with a global review published earlier this year that indicated almost every cell in the body may be affected by dirty air.

“The drive behind (the new research) was to do the most comprehensive study ever conducted at looking at all possible causes of hospitalisation that could be [linked] to exposure to fine particulate matter,” Professor Francesca Dominici, of Harvard University and co-author of the study, according to the report.

Dominici and colleagues report how they analysed more than 95m insurance claims made between 2000 and 2012 by hospital inpatients in the US aged 65 or older enrolled in the Medicare programme. The results back up previous studies showing a link between short-term exposure to dirty air and conditions such as heart failure, pneumonia and heart attack.

Indeed, the analysis suggests even a small average rise in PM2.5 of 1 micrograms per cubic metre over a two-day period is linked to an increase of 68 older people per billion being taken to hospital with heart failure the next day.

The team’s analysis further reveals air pollution is linked to more than just hospital visits: the data shows short-term increases in PM2.5 were linked to an average annual increase of 634 deaths, and about $100m in costs for inpatients and post-acute care. Even when the team looked at days when the air quality was within the limits set by the World Health Organisation (WHO), they found the trends remained.

While the study cannot prove that air pollution causes the diseases, the team say it adds weight to calls for air pollution guidelines to be reviewed.

Dr Ioannis Bakolis, of King’s College London, who was not involved in the study, agreed. He is quoted in the report as saying: “These guidelines need to be revised, as even the 9% of the population that lives within the WHO limits may be substantially by affected by air pollution concentrations and its associated costs, according to the findings of the study.”

Objective: To assess risks and costs of hospital admission associated with short term exposure to fine particulate matter with diameter less than 2.5 µm (PM2.5) for 214 mutually exclusive disease groups.
Design: Time stratified, case crossover analyses with conditional logistic regressions adjusted for non-linear confounding effects of meteorological variables.
Setting: Medicare inpatient hospital claims in the United States, 2000-12 (n=95 277 169).
Participants: All Medicare fee-for-service beneficiaries aged 65 or older admitted to hospital.

Main outcome measures: Risk of hospital admission, number of admissions, days in hospital, inpatient and post-acute care costs, and value of statistical life (that is, the economic value used to measure the cost of avoiding a death) due to the lives lost at discharge for 214 disease groups.
Results: Positive associations between short term exposure to PM2.5 and risk of hospital admission were found for several prevalent but rarely studied diseases, such as septicemia, fluid and electrolyte disorders, and acute and unspecified renal failure. Positive associations were also found between risk of hospital admission and cardiovascular and respiratory diseases, Parkinson’s disease, diabetes, phlebitis, thrombophlebitis, and thromboembolism, confirming previously published results. These associations remained consistent when restricted to days with a daily PM2.5 concentration below the WHO air quality guideline for the 24 hour average exposure to PM2.5. For the rarely studied diseases, each 1 µg/m3 increase in short term PM2.5 was associated with an annual increase of 2050 hospital admissions (95% confidence interval 1914 to 2187 admissions), 12 216 days in hospital (11 358 to 13 075), US$31m (£24m, €28m; $29m to $34m) in inpatient and post-acute care costs, and $2.5bn ($2.0bn to $2.9bn) in value of statistical life. For diseases with a previously known association, each 1 µg/m3 increase in short term exposure to PM2.5 was associated with an annual increase of 3642 hospital admissions (3434 to 3851), 20 098 days in hospital (18 950 to 21 247), $69m ($65m to $73m) in inpatient and post-acute care costs, and $4.1bn ($3.5bn to $4.7bn) in value of statistical life.
Conclusions: New causes and previously identified causes of hospital admission associated with short term exposure to PM2.5 were found. These associations remained even at a daily PM2.5 concentration below the WHO 24 hour guideline. Substantial economic costs were linked to a small increase in short term PM2.5.

Yaguang Wei, Yan Wang, Qian Di, Christine Choirat, Yun Wang, Petros Koutrakis, Antonella Zanobetti, Francesca Dominici, Joel D Schwartz

[link url=""]The Guardian report[/link]

[link url=""]BMJ abstract[/link]

[link url=""]BMJ editorial[/link]

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