Pollution peaks: alerts save lives … provided the thresholds are low enough

A French study shows that alerts on pollution peaks in Île-de-France reduce mortality. But the researchers insist: exposure to pollutants is dangerous on a daily basis, even well below the alert thresholds.

Air pollution is now recognized as a risk factor in its own right, especially for respiratory and cardiovascular health. In France, around 47,000 premature deaths are attributable to air pollution each year, according to a recent report from Public Health France. Since 2007, alert procedures have been put in place in Île-de-France in order to reduce emissions of PM10 particles when their concentrations exceed critical thresholds. But if these measures have demonstrated their effectiveness in reducing the intensity of pollution peaks, their benefits on public health remain little evaluated. Researchers from Inserm and Sorbonne University, in collaboration with the University of San Diego, analyzed data from the Ile-de-France between 2000 and 2015 in order to draw an initial assessment.

The fine particles PM10 (whose diameter is less than 10 microns) are mainly produced by heating, especially with wood, road traffic as well as agricultural activities or on construction sites. The concentrations of these particles have been measured for about thirty years in Île-de-France by the Airparif association, whose database was used for this work published in the journal Environment International . “It is very complicated to establish a cause and effect link on the basis of retrospective observational data such as those at our disposal”, warns Anna Alari, researcher at the Pierre Louis Institute of Epidemiology and Public Health, co-author of this study. ” But thanks to a so-called “quasi-experimental” analysis method, we are now able to sufficiently free ourselves from confounding factors and thus really assess the effect of certain measures. “

Insufficient alert policy

The researchers noted two important dates over the period studied: 2007 and 2011. The first corresponds to the establishment of a first information threshold of pollution peaks involving interventions, when the concentration of PM10 exceeded the threshold of 80 µg / m3. The second is the year in which this threshold was lowered to 50 µg / m3. The results indicate that no effect on mortality was observed after 2007. It was not until 2011 to see a decrease of 7% to 25% in daily cardiovascular mortality, or nearly 390 deaths avoided according to scientists’ estimates. It has been shown in recent years that particles are involved in the occurrence of myocardial infarction, cerebrovascular accidents (stroke), acute coronary syndromes and promote decompensations in heart failure. Effects largely caused by an increase in inflammatory processes.

These results support our initial hypothesis, namely that an alert threshold that is too high does not allow effective interventions for human health. », Comments Anne Alari. “ But exposure to any level of pollutant concentrations has a definite effect on health; it is not as if there is a threshold below which the health effect is zero! The alert policy makes it possible to urgently manage extreme exposure situations but is not at all sufficient to fight against the harmful effects of air pollution on health.

The burden of daily pollution

Pollution peaks are indeed only the tip of the iceberg and researchers stress the need for structural changes to limit the exposure of populations on a daily basis. ” In 2015, Paris remained among the European capitals most affected by air pollution », Notes Anna Alari. ” Since then, various measures have been taken, such as the delimitation of low-emission zones.

Airparif data show over the last few years an overall trend of improving air quality and in particular a slight but constant drop in PM10 concentrations. Last year, eight episodes of PM10 pollution were observed against 10 in 2019, indicates the 2020 report published by the association on May 20. “ The public is focusing more on pollution peaks, which are more visible, but the chronic pollution breathed in day after day represents a greater health issue. “, However notes Pierre Pernot, communications director of Airparif who specifies that in 2019 nearly three quarters of Ile-de-France residents were exposed to concentrations of PM10 which exceed the annual WHO recommendations set at 20 μg / m3. And adults are not the only victims of this air pollution: recent work has shown an effect of pollutants on the cognitive development of young people.


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