A new study suggests that the number of health problems linked to air pollution could be significantly higher than previously estimated. Researchers found that hospital admissions for conditions ranging from heart failure to urinary tract infections increase as air becomes dirtier, even at levels within current guidelines.
The study, published in the BMJ, analysed more than 95 million insurance claims from US hospital inpatients aged 65 or older between 2000 and 2012. The team focused on fine particulate matter (PM2.5), produced by vehicles and power stations, using air quality data to estimate exposure based on patients' home zip codes.
By comparing air pollution levels around the time of hospital visits with other periods, the researchers accounted for factors like age and socioeconomic status. Results confirmed known links between short-term PM2.5 exposure and conditions such as heart failure, pneumonia, and heart attack. However, they also found associations with septicaemia, Parkinson's disease, and urinary tract infections.
Even a small average rise in PM2.5 of 1 microgram per cubic metre over two days was linked to an increase of 68 older people per billion being hospitalised with heart failure the next day. For urinary tract infections, the same rise was associated with 39 additional hospitalisations per billion. The team estimated that such increases occurred on more than 122 days per year in each zip code.
Short-term rises in PM2.5 were also linked to an average annual increase of 634 deaths and about $100m in inpatient and post-acute care costs. The trends persisted even when air quality was within World Health Organization (WHO) limits.
Lead author Yaguang Wei said the findings suggest PM2.5 has a systemic effect on multiple physiological processes, including inflammation and infection. While the study cannot prove causation, the authors say it strengthens calls for a review of air pollution guidelines. Dr Ioannis Bakolis of King's College London, who was not involved, agreed that guidelines need revision, noting that even populations within WHO limits may be substantially affected.
