Global study finds health risks persist despite falling pollutant levels

Even when concentrations of air pollutants decrease, health risks from these pollutants can remain high, concludes an international study led by researchers from Helmholtz Munich.

A global research network examined data from 380 cities to assess how the effects of air pollution on mortality changed between 1995 and 2016. The main finding: although concentrations of air pollutants such as fine particulate matter (PM₁₀PM_2.5) and nitrogen dioxide (NO₂) have decreased, the associated health risks have hardly changed. The study is published in Planetary health in The Lancet.

For their study, the researchers used data from the Multi-Country Multi-City (MCC) Collaborative Research Network, an international collaboration between various research teams. Their goal is to better understand the relationships between environmental stressors (which can be harmful to living organisms), climate and health.

“The huge amount of data available via the network allowed us to analyse the health impacts of air pollution on a global scale over an extended period of time and to monitor trends,” says Maximilian Schwarz, a scientist at the Helmholtz Institute of Epidemiology in Munich and lead author of the study.

There are many factors that can cause this.

According to the study, the risk of mortality did not change significantly over the period considered, despite lower pollutant concentrations.

Schwarz attributes this result to a variety of factors: “These include the aging of the population in many regions, the fact that older people tend to be healthier than younger people, and that the sources and composition of air pollutants may have changed.”

In addition, the study reveals differences in impacts depending on the geographic region and when analyzing the simultaneous influence of various pollutants on mortality.

The study focuses on pollutants regulated by legal limits, such as fine particles in PM₁₀ and PM_2.5 size classes, as well as NO₂“Due to the available data, we were not able to study the impact of other potentially relevant pollutants,” says Schwarz.

These include ultrafine particles, which are suspected of having a greater impact on human health than larger particles. “Our study highlights the need for more comprehensive and extensive monitoring on a global scale. In addition, existing data must be made available for scientific use,” Schwarz continues. This is necessary to investigate new research questions more precisely.

Relevance of health policy

The Director of the Institute of Epidemiology, Professor Annette Peters, stresses that national and international efforts to improve air quality must be more aligned with the stricter recommendations of the World Health Organization (WHO).

“The WHO air quality guidelines updated in 2021 are further validated by the current study. The planned revision of air quality limits at European level is an essential step to better manage the health risks posed by air pollution,” says Peters.