2023-09-28 07:29:16
by Cristina Marrone
Nitrogen dioxide (which comes from any combustion, even at home) and carbon monoxide are among the most dangerous pollutants. The limitation: the studies don’t take indoor pollution into account
It has been known for some time that air pollution causes heart attacks, strokes, respiratory diseases and lung cancers and consequently premature deaths. Only in Italy the premature deaths caused by pollution were 52,300 in 2020, with approximately 3,000 hospital admissions. Now a new meta-analysis published in Neurology has highlighted a disturbing new fact: the risk of stroke increases in the five days following exposure to air pollution.
“Previous research has established a connection between long-term exposure to air pollution and an increased risk of stroke,” said study author Ahmad Toubasi of the University of Amman in Jordan. «However – underlines the scientist – the correlation between short-term exposure to pollution and stroke has never been very clear. For our study, instead of looking at weeks or months of exposure, we looked at just the next five days and found a link between short-term exposure to pollution and an increased risk of stroke.”
The most dangerous pollutants
The meta-analysis reviewed 110 different studies that recorded over 18 million cases of stroke. The researchers examined pollutants such as nitrogen dioxide (which is released from any combustion, even domestic ones), ozone, carbon monoxide, sulfur dioxide and different sizes of particulate matter, including PM1, which are polluting particles with a diameter of less than 1 mm. micron. Naturally, PM 2.5, which includes inhalable particles from motor vehicle exhausts, industrial combustion and forest fires, and PM 10, composed of dust from roads and construction sites, were also studied.
And give
The data that has emerged is once again quite alarming. It was observed that people exposed to higher concentrations of various types of air pollution had a higher risk of suffering a stroke. Higher concentrations of nitrogen dioxide were linked to a 28% increased risk of stroke while high ozone levels increased the risk of stroke by 5%. With carbon monoxide an increase in stroke risk of 26% was observed while with sulfur dioxide the risk increased by 15%. As regards the risk of stroke in relation to the size of the particulate matter, a high concentration of PM1 was correlated with an increase in stroke risk of 5% while the results with PM 2.5 and PM 10 are similar with an increased risk of 15%. the first and 14% the second.
Higher levels of air pollution have also been linked to a higher risk of death from stroke. Elevated concentrations of nitrogen dioxide have been linked to a 33% increase in the risk of death from stroke, of sulfur dioxide to a 60% increase, of PM2.5 and a 9% increase, and of PM10, to a by 2%. However, it should be underlined that today in Europe there are no longer fuels containing sulfur dioxide, the danger of which has been known for some time. «There is a strong and significant association between air pollution and the occurrence of stroke, as well as death from stroke within five days from exposure,” Toubasi said. “This highlights the importance of global efforts to create policies that reduce air pollution. This could reduce the number of strokes and their consequences.”
Indoor exposure is prevalent and never calculated
The authors highlight a limitation of the meta-analysis: almost all studies were conducted in high-income countries, while limited data are available for low- and middle-income countries. But this is not the only limit. As underlined by Giorgio Buonanno, full professor of Environmental Technical Physics at the University of Cassino and at the Queensland University of Technology in Brisbane (Australia), generally in studies to calculate exposure to PM 2.5 levels the values of an outdoor public control unit in relation to the population residing in the area, and from here the incidence of a specific pathology is observed (which could be lung cancer, dementia, cardiovascular diseases).
The control unit could be representative of air quality in an urban outdoor context, but the problem is that indoor exposure, which represents 85% of the total, is neglected. The quality of outdoor air in cities, therefore, is not representative of the individual’s exposure to pollutants. The contaminants studied come from construction sites, roads, car and truck exhaust fumes, factories and fires. «But in reality every combustion source releases polluting particles of various sizes including fireplaces, pellet stoves, gas cookers but also, albeit to a lesser extent, induction hobs. For this reason, indoor exposure to pollutants is prevalent since we spend a lot of time in closed and poorly ventilated environments” underlines Buonanno. Paradoxically, a person who lives in the mountains breathes very clean air that is almost free of pollutants when he is away from home. But once inside, with the wood or pellet stove turned on, indoor exposure to pollutants skyrockets and lasts longer. The risk of stroke for this person will probably be greater than someone who lives in a metropolis.
September 28, 2023 (modified September 28, 2023 | 07:29)
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