Air quality in Europe shows significant improvements over the last two decades, study finds
Despite air quality improvements, 98.10%, 80.15% and 86.34% of the European population lives in areas exceeding the WHO recommended levels for PM2.5, PM10 and NO2, respectively
A study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, and the Barcelona Supercomputing Center - Centro Nacional de Supercomputación (BSC-CNS), has consistently estimated daily ambient concentrations of PM2.5, PM10, NO2 and O3 across a large ensemble of European regions between 2003 and 2019 based on machine learning techniques. The aim was to assess the occurrence of days exceeding the 2021 guidelines of the World Health Organization (WHO) for one or multiple pollutants, referred to as “unclean air days”.
The research team analysed pollution levels in more than 1,400 regions in 35 European countries, representing 543 million people. The results, published in Nature Communications, show that overall suspended particulate matter (PM2.5 and PM10) and nitrogen dioxide (NO2) levels have decreased in most parts of Europe. In particular, PM10 levels decreased the most over the study period, followed by NO2 and PM2.5, with annual decreases of 2.72%, 2.45% and 1.72% respectively. In contrast, O3 levels increased annually by 0.58% in southern Europe, leading to a nearly fourfold rise in unclean air days.
The study also looked at the number of days on which the limits for two or more pollutants were exceeded simultaneously, a confluence known as a “compound unclean air day”. Despite the overall improvements, 86.3% of the European population still experienced at least one compound unclean day per year during the study period, with PM2.5-NO2 and PM2.5-O3 emerging as the most common compound combinations.
The results highlight the significant improvements in air quality in Europe followed by the decline of PM10 and NO2, while PM2.5 and O3 levels continue to exceed WHO guidelines in many regions, resulting in a higher number of people exposed to unclean air levels. "Targeted efforts are needed to address PM2.5 and O3 levels and associated compound unclean days, especially in the context of rapidly increasing threats from climate change in Europe," says Zhao-Yue Chen, ISGlobal researcher and lead author of the study.
"Our consistent estimation of population exposure to compound air pollution events provides a solid basis for future research and policy development to address air quality management and public health concerns across Europe," points out Carlos Pérez García-Pando, ICREA and AXA Research Professor at the BSC-CNS.
Heterogeneous geographical distribution
The research team has developed machine learning models to estimate high-resolution daily concentrations of major air pollutants like PM2.5, PM10, NO2 and O3. This data-driven approach creates a comprehensive daily air quality picture for the European continent, going beyond sparsely distributed monitoring stations. The models gather data from multiple sources, including satellite-based aerosol estimates, existing atmospheric and climate data, and land use information. By analysing these air pollution estimates, the team calculated the annual average number of days in which the WHO daily limit for one or more air pollutants is exceeded.
Despite air quality improvements, 98.10%, 80.15% and 86.34% of the European population lives in areas exceeding the WHO recommended annual levels for PM2.5, PM10 and NO2, respectively. These results closely match the European Environment Agency (EEA)'s estimates for 27 EU countries using data from urban stations only. Additionally, no country met the ozone (O3) annual standard during the peak season from 2003 to 2019. Looking at short-term exposure, over 90.16% and 82.55% of the European population lived in areas with at least 4 days exceeding WHO daily guidelines for PM2.5 and O3 in 2019, while the numbers for NO2 and PM10 were 55.05% and 26.25%.
During the study period, PM2.5 and PM10 levels were highest in northern Italy and eastern Europe, while PM10 levels were highest in southern Europe. High NO2 levels were mainly observed in northern Italy and in some areas of western Europe, such as in the south of the United Kingdom, Belgium and the Netherlands. Similarly, O3 increased by 0.58% in southern Europe, while it decreased or showed a non-significant trend in the rest of the continent. On the other hand, the most significant reductions in PM2.5 and PM10 were observed in central Europe, while for NO2 they were found in mostly urban areas of western Europe.
The complex management of ozone
The average exposure time and population exposed to unclean air concentrations of PM2.5 and O3 is much higher than for the other two pollutants. According to the research team, this highlights the urgency of greater control for these pollutants and the importance of addressing the increasing trend and impact of O3 exposure.
Ground-level or tropospheric O3 is found in the lower layers of the atmosphere and is considered a secondary pollutant because it is not emitted directly into the atmosphere, but is formed from certain precursors - such as volatile organic compounds (VOCs), carbon monoxide (CO) and nitrogen oxides (NOx) - that are produced in combustion processes, mainly in transport and industry. In high concentrations, ozone can damage human health, vegetation and ecosystems.
"Ozone management presents a complex challenge due to its secondary formation pathway. Conventional air pollution control strategies, which focus on reducing primary pollutant emissions, may not be sufficient to effectively mitigate O3 exceedances and associated compound unclean days," says Joan Ballester Claramunt, ISGlobal researcher and senior author of the study. However, addressing climate change, which influences ozone formation through increased sunlight and rising temperatures, is crucial for long-term ozone management and protection of public health," he adds.
The challenge of compound episodes
Despite improvements in air pollution, the research team reported that over 86% of Europeans experienced at least one day with compound air pollution events each year between 2012 and 2019, where multiple pollutants exceeded WHO limits simultaneously. Among those compound days, the contribution of PM2.5-O3 compound days increased from 4.43% in 2004 to 35.23% in 2019, becoming the second most common type in Europe, indicating a worrying trend. They mainly occur in lower latitudes during warm seasons and are likely linked to climate change and the complex interplay between PM2.5 and O3.
Warmer temperatures and stronger sunlight in summer boost O3 formation through chemical reactions. Subsequently, higher levels of O3 will accelerate the oxidation of organic compounds in the air. This oxidation process leads to the condensation of certain oxidized compounds, forming new PM2.5 particles. Additionally, climate change increases the likelihood of wildfires, which further elevate both O3 and PM2.5 levels. “This complex interplay creates a harmful loop, highlighting the urgent need to address climate change and air pollution simultaneously,” explains Ballester Claramunt.
Reference
Main study: Chen, Z.Y., Petetin, H., Turrubiates, R.F.M., Achebak, H., García-Pando, C.P. and Ballester, J., 2024. Population exposure to multiple air pollutants and its compound episodes in Europe, Nature Communications. Doi: 10.1038/s41467-024-46103-3
Related study: Chen, Z.Y., Turrubiates, R.F.M., Petetin, H., Lacima, A., García-Pando, C.P. and Ballester, J., 2024. Estimation of pan-European, daily total, fine-mode and coarse-mode Aerosol Optical Depth at 0.1° resolution to facilitate air quality assessments. Science of The Total Environment, p.170593. Doi: 10.1016/j.scitotenv.2024.170593
JOURNAL
Nature Communications
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Population exposure to multiple air pollutants and its compound episodes in Europe
ARTICLE PUBLICATION DATE
13-Mar-2024
Curbing coal-burning emissions translates
to health gains for children
COLUMBIA UNIVERSITY'S MAILMAN SCHOOL OF PUBLIC HEALTH
Residential heating by coal has for decades been the major contributor to the high levels of air pollution in Krakow, Poland. New research finds a nearly 40 percent decline in the annual average concentration of respirable particulate matter (PM2.5) in Kraków, Poland, between 2010 and 2019 following the implementation of policies targeting emissions from the burning of coal and other solid fuels. Researchers show the improvement in air quality translated to substantial benefits for children’s outcomes, including fewer cases of asthma and better birth outcomes.
The findings by researchers at Columbia University Mailman School of Public Health and Jagiellonian University Medical College in Krakow appear in the journal Environmental Research Letters.
The researchers modeled health gains that would have occurred in 2010 if PM2.5 had been at the lower level achieved in 2019 through policy changes The benefits included 505 fewer new cases of asthma in the 1-14 age group (a 35.7% decline), 81 fewer preterm births (16.8% decrease), and 52 fewer cases of low birth weight (12.3% decrease).
They also modeled gains based on a second hypothetical, which assumed that city had adhered to the WHO’s 2005 guidelines on PM2.5. They found this scenario of a 74% reduction in PM2.5 would have avoided 780 new asthma cases in the 1-14 age group (54.5% decrease), 138 preterm births (28.3% decrease), and 90 cases of low birth weight (21.2% decrease).
In 2021, Krakow was ranked 28th out of 858 European studies in air pollution related-mortality in the ISGlobal-Ranking of Cities survey. These high levels of pollution have been attributed largely to the use of coal-burning ovens in residential spaces, and to a lesser extent transportation and power plant emissions. Government interventions, including a co-financing program to replace coal-burning stoves in the 1990s, markedly improved the city’s air quality, positively impacting children’s health outcomes. However, according to researchers, levels of human-derived air pollution, such as emissions from motor vehicles, is still a concern.
“Fetuses, infants, and children are uniquely vulnerable to air pollution,” explains study senior author Frederica Perera, PhD, DrPH, professor of environmental health sciences and director of translational research at the Columbia Center for Children’s Environmental Health at Columbia Mailman, “Our results show very large benefits can be achieved for children’s health by curbing fossil fuel emissions.”
“This is one of the first studies describing the impact of pollution on the Polish pediatric population,” noted study first author Agnieszka Pac, MSc., PhD, chair of Epidemiology and Preventive Medicine at Jagiellonian University Medical College, Krakow, Poland. “New policies must take into account children’s health, especially given that children often engage in vigorous outdoor activities, making them vulnerable to higher doses of pollutants.”
In earlier studies, the researchers reported a significant improvement in air quality based on personal air monitoring in our Kraków cohort study of pregnant women and their children based on personal air monitoring. They also identified links between air pollution exposure and birth outcomes, growth trajectories, lung function, developmental delays, behavioral problems, and cancer risk.
Additional authors of the new study include Renata Majewska, Natalia Nidecka, and Elzbieta Sochacka-Tatara from Jagiellonian University Medical College. This study was supported by a grant from an anonymous foundation.
JOURNAL
Environmental Research Letters
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Health benefits to the pediatric population from reduction of ambient particulate matter in Krakow, Poland
ARTICLE PUBLICATION DATE
13-Mar-2024
Multiple air pollutants linked to asthma symptoms in children
SPOKANE, Wash. – Exposure to several combinations of toxic atmospheric pollutants may be triggering asthma symptoms among children, a recent analysis suggests.
The study, published in the journal Science of the Total Environment, showed that 25 different combinations of air pollutants were associated with asthma symptoms among 269 elementary school children diagnosed with asthma in Spokane, Washington. In line with previous research, the Washington State University-led study revealed a socioeconomic disparity—with one group of children from a lower-income neighborhood exposed to more toxic combinations, a total of 13 of the 25 identified in this research.
“It’s not just one pollutant that can be linked to asthma outcomes. This study examined the variety and combinations of air toxics that may be associated with asthma symptoms,” said lead author Solmaz Amiri, a WSU researcher in the Elson S. Floyd College of Medicine.
While other studies have focused on a limited number of pollutants, Amiri and her colleagues used the data-crunching power of machine learning techniques to analyze the potential exposure effects of 109 air pollutants and their combinations on asthma outcomes.
The researchers drew on data collected and modeled by the Environmental Protection Agency on air toxics present in individual neighborhoods surrounding 10 Spokane elementary schools. They also accessed anonymized data from the elementary schools for reports of students diagnosed with asthma who experienced symptoms such as coughing, wheezing, difficulty breathing and the need to use an inhaler.
The study looked at asthma symptoms occurring in 2019 and 2020 in the six months before the pandemic lockdowns started in March 2020. The researchers then associated these data with air pollutant exposures that occurred within those six months and with two longer-term exposure periods of three years and five years prior to the asthma symptoms.
The researchers found that three specific pollutants were significantly associated with asthma symptoms across all three exposure periods.
The toxicants involved may have unfamiliar names – 1,1,1 trichloroethane, 2-nitropropane and 2, 4, 6 trichlorophenol – but they derive from commonly used materials. The first is a widely used solvent in industry but was formerly used in household cleaners and glues. The second is an additive to paints and other finishes, and the third is an anti-septic and anti-mildew agent that was banned in the 1980s but may still be found in some pesticides and preservatives made before then.
“Some of these air toxics were discontinued in the U.S., but they can still be found in materials that may be in storage or people have in their backyard or garage. Other air toxics still exist at least in the environment,” said Amiri.
This study did not intend to pinpoint the source of any one air pollutant or the exact reason why one group of children from a lower-income neighborhood was highly exposed to air pollutants. However, proximity of known air pollution sources may play a role, Amiri said, such as living close to a highway with a lot of traffic or facilities that use solvents, such as paint producers or factories.
The finding of a likely socioeconomic disparity in air toxic exposures is consistent with previous research showing that children from lower-income areas, often indicated by schools with a higher percentage of students who qualify for free or reduced meals, are exposed to a wide variety of air pollutants in the neighborhoods where they live.
While the current study is limited to the mid-sized city of Spokane, Amiri noted that the findings align with another study in New York City which found similar air pollutants significantly associated with asthma outcomes.
“Both in Spokane and New York City, regardless of the setting – how large or small the cities are – these air toxics appear to be influencing asthma among children,” she said.
This study received support from the National Institutes of Health and the Ramboll Foundation.
JOURNAL
Science of The Total Environment
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