Global research shows persistent health risks despite declining levels of pollutants

Even as concentrations of air pollutants decrease, the health risks from these pollutants may remain persistently high. This is the conclusion of 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 have changed between 1995 and 2016. The central finding: although concentrations of air pollutants such as particulate matter (PM₁₀P.M_2.5) and nitrogen dioxide (NO₂) have decreased, the associated health risks have hardly changed. The study is published in The Lancet Planetary Health.

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

“The enormous amount of data available through the network has allowed us to analyze the health effects of air pollution on a global scale over a longer period of time and monitor trends,” says Maximilian Schwarz, a scientist at the Institute of Epidemiology in Helmholtz Munich and the lead author of the study.

Many factors could be the cause

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

Schwarz attributes this finding to several factors: “These include the aging of populations in many regions, the fact that older people tend to have more health problems than younger people, and that the sources and composition of air pollutants may have changed.”

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

The research focuses on pollutants for which legal limits apply, such as particulate matter in particulate matter₁₀ and P.M_2.5 size classes, as well as NO₂. “Due to the available data, we could not investigate the impact of other potentially relevant pollutants,” says Schwarz.

These include, for example, ultrafine particulate matter, which is suspected to have a greater impact on human health than larger particles. “Our research underlines the global need for more extensive and comprehensive monitoring. In addition, existing data must be made available for scientific use,” Schwarz continues. This is necessary to be able to investigate new research questions more accurately.

Relevance of health policy

The director of the Institute of Epidemiology, Prof. Dr. Annette Peters, emphasizes that national and international efforts to improve air quality must be better aligned with the stricter recommendations of the World Health Organization (WHO).

“The 2021 updated WHO air quality guidelines 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 of air pollution,” says Peters.