Shanghai - A global study confirms that exposure to fine particulate matter (PM10 or PM2.5) increases mortality in the short term. According to the publication in the New England Journal of Medicine (2019;), no threshold value can be identified, so that fine dust concentrations below the applicable limit values are probably also harmful to health. The risk here even rises disproportionately.
The particulate matter, which is mainly produced when burning fossil fuels, penetrates the larger airways with size of less than 10 µm (PM10) and size of less than 2.5 µm (PM2.5) also enters the alveoli. Numerous previous time series analyzes have shown that an increase in PM10 and PM2.5 is associated with increased daily mortality. However, the studies were mostly limited to individual cities, regions or countries.
The "Multi-City MultiCountry ( MCC) Collaborative Research Network “has now for the first time summarized the data from 652 urban regions in 24 countries and compared the two-day exposure data with mortality. Most of the data was collected in China, where particulate matter pollution is significantly higher today than in western countries. Haidong Kan's team in Shanghai also used numerous data from North America and Europe (but not from Germany).
First of all, the results confirm the known facts: An increase in the 2-day average value of the PM10 concentrations of 10 µg / m3 were associated with an increase in all-cause mortality on the same day of 0.44% (95% confidence interval 0.39 to 0.50%). Daytime cardiovascular mortality increased by 0.36% (0.30 to 0.43%) and daytime mortality from respiratory diseases by 0.47% (0.35 to 0.58%).
Every increase of PM2.5 of 10 µg / m3 was associated with an increase in all-cause mortality of 0.68% (0.59 to 0.77%). Cardiovascular mortality increased by 0.55% (0.45 to 0.66%) and daytime mortality from respiratory diseases increased by 0.74% (0.53 to 0.95%).
No limit value recognizable for the harmfulness of fine dust
The dose-effect curves are interesting. On the one hand, there was an increase in mortality below the current limit values of the World Health Organization of 50 µg / m3 for PM10 and 25 µg / m3 for PM2.5. In the study, no limit value for the harmfulness of fine dust could be identified.
On the other hand, the dose-effect curves were non-linear. The increase in the risk of death below the limit values was greater with every 10 µg / m3 increase than with higher exposure. This means that countries with comparatively low particulate matter values such as the USA and parts of Europe can achieve more for the health of the population with further reduction than China, for example, where the highest particulate matter pollution was found.
The non-linearity partly explains why the risk of death in PM2.5 increases with each increase by 10 µg / m3 in China only rose by 41%, in Australia by 142%. Other reasons could be the high air temperatures, according to Kan. This may explain why Sweden had smaller impact than Greece. Since the harmfulness of fine dust is explained by the toxins bound to the particles (such as heavy metals), other differences in air quality could also be important, not to mention possible genetic differences in sensitivity.
The flatter one The dose-response curve at higher exposures could also be related to the population structure. In less developed countries like China, because of the higher birth rate in cities, there are more younger people than in Japan, for example, where the dose-effect curve is significantly steeper. However, these are only speculations. The study can only show the association, but not clarify the causes.
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