A recent study on daily ambient fine particulate matter (PM2.5) has revealed that WHO safe levels are only met for a mere 0.001% of the world's population.
The Monash University conducted a pioneering study on the levels of daily ambient fine particulate matter (PM2.5) around the world. The study revealed that just 0.18% of the global land area and a mere 0.001% of the world's population are exposed to levels of PM2.5 that are below the safety limits recommended by the World Health Organization (WHO).
It is noteworthy that while Europe and North America have seen a decline in PM2.5 levels over the past two decades, Southern Asia, Australia, New Zealand, Latin America, and the Caribbean have experienced a surge in levels. Shockingly, over 70% of days worldwide show PM2.5 levels exceeding the safety limits.
Due to the scarcity of pollution monitoring stations worldwide, the lack of data on local, national, regional, and global PM2.5 exposure has been a challenge. However, Professor Yuming Guo from the Monash University School of Public Health and Preventive Medicine led this study and published the findings in Lancet Planetary Health. This study has provided a map illustrating how PM2.5 levels have altered globally over the past decades.
A research team led by Professor Guo used various methods to estimate the levels of PM2.5 concentrations across the globe. They combined traditional air quality monitoring observations, satellite-based meteorological and air pollution detectors, statistical and machine learning methods to generate daily PM2.5 concentrations at a high spatial resolution of approximately 10km ×10km for global grid cells from 2000-2019. The focus of their study was to assess areas above 15 μg/m³ which is the safe limit set by WHO, although this limit is still subject to debate.
The results of the study showed that annual PM2.5 concentration and high PM2.5 exposed days decreased in Europe and northern America, while exposures increased in southern Asia, Australia and New Zealand, and Latin America and the Caribbean. However, despite a slight decrease in high PM2.5 exposed days globally, over 70% of days still had PM2.5 concentrations higher than the WHO safe limit of 15 μg/m³. In southern and eastern Asia, more than 90% of days had daily PM2.5 concentrations higher than the safe limit.
The study also found that Australia and New Zealand had a marked increase in the number of days with high PM2.5 concentrations in 2019. Globally, the annual average PM2.5 concentration from 2000 to 2019 was 32.8 µg/m3, with the highest PM2.5 concentrations in Eastern Asia and Southern Asia, followed by northern Africa. The lowest annual PM2.5 concentrations were found in Australia and New Zealand, other regions in Oceania, and southern America.
The study also observed different seasonal patterns of unsafe PM2.5 concentrations, such as in Northeast China and North India during their winter months (December, January, and February), and in eastern areas of northern America during its summer months (June, July, and August). The study also recorded relatively high PM2.5 air pollution in South America during August and September, and from June to September in sub-Saharan Africa.
The researchers highlighted the importance of their study, stating that it provides a deep understanding of the current state of outdoor air pollution and its impacts on human health. With this information, policymakers, public health officials, and researchers can better assess the short-term and long-term health effects of air pollution and develop air pollution mitigation strategies.
Reference:
Wenhua Yu, Tingting Ye, Yiwen Zhang, Rongbin Xu, Yadong Lei, Zhuying Chen, Zhengyu Yang, Yuxi Zhang, Jiangning Song, Xu Yue, Shanshan Li, Yuming Guo. Global estimates of daily ambient fine particulate matter concentrations and unequal spatiotemporal distribution of population exposure: a machine learning modelling study. The Lancet Planetary Health, 2023; 7 (3): e209 DOI: 10.1016/S2542-5196(23)00008-6