Hospital admission go up for a host of life-threatening illnesses – including sepsis, kidney failure and urinary tract infections – never before linked to pollution on days when air quality is poor, a new study reveals.
Even low exposure raises the risk of the potentially fatal illnesses, according to the research.
It adds to evidence there is no safe amount of tiny particles called PM2.5s that are pumped into the atmosphere by traffic and industry.
The Harvard University researchers found that even short spikes in the harmful particles led to an increase of 5,692 hospitalizations and some $100 million in annual health care costs.
Harvard University researchers have identified a link between spikes in air pollution and hospitalizations for illnesses like sepsis never-before linked to poor air quality
They can be inhaled deep into the lungs where they irritate the lining and enter the bloodstream.
The World Health Organization’s air quality guidelines need revising, say the US team.
An analysis identified several new causes of hospital admissions linked to small increases in particulate matter – such as sepsis and kidney failure. Others included urinary tract and skin infections.
This was on top of established ones like heart and lung conditions, diabetes, Parkinson’s disease and diabetes.
‘The study shows the health dangers and economic impacts of air pollution are significantly larger than previously understood,’ said lead author Yaguang Wei, a doctoral candidate at Harvard TH Chan School of Public Health.
It was based on more than 95 million Medicare hospital insurance claims for adults aged 65 or older in the US from 2000 to 2012.
‘We wanted to shed further light on the risks of exposure to short-term air pollution by searching for links between such pollution and all diseases that are plausible causes of hospitalizations,’ said senior author Dr Joel Schwartz, who heads Wei’s lab.
These were classified into 214 groups and compared with 13 years’ worth of hospital admissions records.
The researchers used data on PM2.5s from the US Environmental Protection Agency (EPA) and matched it with the zip, or postal, codes of participants.
Notably, all of the associations remained consistent even on days when daily PM2.5 levels were below the WHO air quality guideline.
Each 1 μg/m3 (one-millionth of a gram per cubic meter of air) rise in short-term exposure was linked with 5,692 more hospitalizations a year, 32,314 days in the hospital and 634 deaths.
What’s more this included with 2,050 extra admissions and 12,216 days in hospital for diseases not previously connected with PM2.5s – such as sepsis, kidney failure, urinary tract and skin infections.
This remained even when the analysis was restricted to days when the concentration was below the recommended level – suggesting it needs updating.
The newly diseases represent around a third of the effect – suggesting current figures for PM2.5 associated illness ‘might be considerable underestimates.’
‘This study discovered several new causes of hospital admissions associated with short term exposure to PM2.5 and confirmed several already known associations, even at daily PM2.5 concentrations below the current WHO guideline,’ the researchers wrote.
They described the findings published in The BMJ as ‘robust’ owing to the large sample size over a long period of time.
Economically, each 1 μg/m3 in PM2.5s corresponded to $100 million (£78m) in annual in-patient and post-acute care costs, and $6.5 billion (£5bn) in the value of lives lost.
‘These results raise awareness of the continued importance of assessing the impact of air pollution exposure,’ said the study’s principal investigator, Dr Francesca Dominici, a biostatistician.
‘The strong evidence of a link between exposure to PM2.5 and many diseases, even at levels below the WHO guideline and, nationally, the National Ambient Air Quality Standards in the US, suggests both sets of guidelines should be reviewed and updated.’
Dr Matthew Loxham, an air pollution toxicologist at the University of Southampton, who was not involved in the study, said knowledge of the health effects of particulate matter ‘is still lacking in many areas.’
He said: ‘The harder we look, the more we find. Clearly, there is much still to learn, but we should not mistake knowledge gaps for paucity of evidence. The sooner we act, the sooner the world’s population will reap the benefits.’
Dr Loxham and colleagues, writing in an editorial for the journal, call for more research to uncover new disease associations and explore potential causative mechanisms.
World Health Organisation guidelines state the average annual level for PM2.5s should be 10 micrograms per cubic metrer.
Around 91 percent of the world’s population live in places where air quality levels exceed WHO limits.