Europe will require radical measures to meet the new WHO Air Quality Guidelines

07 February 2022

A new study led by scientists from the BSC shows that European countries need to drastically reduce the levels of the main air pollutants to protect citizens’ health.

Unprecedented emission reductions are needed throughout Europe to comply with the new 2021 World Health Organization (WHO) Air Quality Guidelines, according to a new article led by scientists from the Barcelona Supercomputing Center (BSC) published in Environmental Research Letters. The study quantifies the increase in the percentage of measurement stations that exceed each new air quality guideline across all the countries reporting air quality information to the European Environmental Agency (EEA).

Air pollution is the single largest environmental health risk in Europe and a major cause of premature death and disease. Now, thanks to the advances in the research into the human health impacts from air pollution, we know that adverse effects begin at much lower concentrations than previously understood. The latest scientific evidence is reflected in the new 2021 WHO Air Quality Guidelines, which represent a major revision over the previous ones set in 2005.

The WHO’s new guidelines recommend air quality levels for six pollutants, where evidence has advanced the most on health effects from exposure: nitrogen dioxide (NO₂), particulate matter (PM2.5 and PM10), ozone (O₃), sulfur dioxide (SO₂), and carbon monoxide (CO). Almost all the 2021 recommended concentrations are significantly more stringent. For the most harmful pollutants, such as NO₂ and PM2.5, the new annual average limits are 75% lower (from 40 to 10 µg/m3) and 50% lower (from 10 to 5 µg/m3), respectively.

Non-compliance, defined as the percentage of total stations that exceed the limits for each pollutant, was already substantial with 2005 WHO’s recommendations across Europe. With the new 2021 guidelines, the BSC study shows dramatic increases in non-compliance, especially for NO2, PM10 and PM2,5 (from 8%, 50% and 77% to 88%, 85% and 98%). Across non-compliant stations, the median distance to compliance also jumps significantly (from 16%, 26% and 41% to 120%, 41% and 160%). For O₃, a new average 6 monthly peak limit is exceeded at 97% of stations.

“The new guidelines set limits at which above there is high confidence in the adverse effects on human health. The fact that the majority of European citizens are currently breathing such damaging levels of air pollutants is highly concerning,” said BSC researcher Dene Bowdalo.

Lessons learned from COVID-19 lockdowns

The researchers analyzed monitoring data during business as usual conditions between 2017 and 2019, before the onset of the COVID-19 pandemic. However, the article also evaluates the impact that emission reductions during COVID-19 lockdowns had on non-compliance to extract some lessons to give scale to the challenge in meeting the new WHO Air Quality Guidelines.

Decreases in non-compliance were only significant on the most stringent 3-month COVID-19 period (15 March-15 June 2020), especially for NO2, which is mainly produced by diesel engines. However, despite an average reduction of 32% in road transport activity during 2020, more than 50% of stations which measure NO2 across Europe still remain non-compliant. This implies that radical measures, such as zero-emissions zones, or the ban on the sale of fossil fuel vehicles, would be needed to sufficiently reduce concentrations in line with the current WHO recommendations.

“Despite the dramatic changes to transport and industry through the COVID-19 lockdowns, for many pollutants we were still nowhere near meeting the guidelines. This evidences that only radical actions to alter the current structures of our urban areas will be able to sufficiently reduce the levels of air pollutants,” said Bowdalo.

Compliance with the new WHO guidelines is estimated to prevent 66% of premature deaths attributed to PM2.5 exposure in Europe, and these numbers will naturally apply greater pressure on the EU to revise its own standards. EU standards have consistently lagged decades behind the WHO guidelines, but despite this, countries still are frequently exceeding limits. For even more ambitious standards to be effective, they should be accompanied by strong supporting measures so that the transition does not leave anyone behind.

This is particularly important for countries with lower income, which are typically exposed to higher pollution levels but depend on polluting energy sources or those disproportionately affected by natural emission sources. Some air pollutants are also short-term climate forcers (e.g. black carbon) and a number of win-win mitigation policies can improve both air quality and mitigate climate change at a potentially lower cost of intervention.

The legislative proposal for the revision of the EU's standards is scheduled at the tail-end of 2022, and the factors outlined in this work need to be carefully considered by the EU before any new standards are set.