Figure 1. Annual ambient PM2.5 air quality standards worldwide. Note: Data for China are for the commercial PM2.5 standard. Source: Nazarenko Y, Pal D, Ariya PA. Air quality standards for the concentration of particulate matter 2.5, global descriptive analysis. Bull World Health Organ. 2021 Feb 1;99(2):125-137D. doi: 10.2471/BLT.19.245704.
The existing annual PM2.5 standards ranged from 8 to 75 µg/m3 in different countries worldwide. Fewer jurisdictions had PM2.5 24-hour standards than annual standards. Notably, only the Russian Federation has a 24-hour standard in the European Region, and it also has a 20-minute PM2.5 standard in addition to 24-hour and annual standards. Most other countries of the former Soviet Union do not have any PM2.5 standards. Ukraine, which has an association agreement with the EU, adopted the EU’s PM2.5 standard to take effect in 2018. The EU supported the creation of the air quality monitoring infrastructure and implementation of the standard in Ukraine since 2015, but the monitoring network was not in effect or completed as of 2020. In the USA, there are primary and secondary standards. The primary standard allows for an adequate safety margin to protect public health, considering the uncertainties of available technical and scientific information. The secondary standard has no attainment deadline and is based on known or anticipated adverse effects on public welfare, including eco-systems, buildings, and monuments.
The EU’s annual PM2.5 ambient air quality standard was relatively lax among the prosperous jurisdictions, notably higher than in Australia, Canada, Japan, Singapore, South Africa, and the USA. In the EU countries, there are also additional PM2.5 objectives set at the national level and based on the average exposure indicator, which is a 3-year running annual mean PM2.5 concentration averaged over selected monitoring stations in urban areas. In the Eastern Mediterranean Region, only Egypt, Pakistan and Saudi Arabia had PM2.5 air quality standards, even though the region is known for high levels of PM2.5 air pollution due to desert dust, fuel-burning emissions, and oil refining. South Africa is the only country in the African Region with a PM2.5 standard. The current annual standard of 20 µg/m3 and the 24-hour standard of 40 µg/m3 will be lowered to 15 µg/m3 and 25 µg/m3, respectively, on 1 January 2030. China uses different PM2.5 standards for the first-class (residential) and the second-class (commercial) zones, which differ substantially: 15 µg/m3 annual and 35 µg/m3 24-hour for the first-class zones and 35 µg/m3 annual and 75 µg/m3 24-hour for the second-class zones. Of the world’s total area of jurisdictions, just under half (47%) had any PM2.5 annual ambient air quality standard. More than one-third of the global population is subject to the least stringent annual standards, exceeding 25 µg/m3 (up to 40 µg/m3 in India).
Areas of low population density generally have the strictest (≤ 15 µg/m3) or medium (20–25 µg/m3) annual PM2.5 standards, whereas areas of high population density are mostly covered by the least stringent annual PM2.5 standards (> 25 µg/m3). However, in areas with the highest population density (> 1000 inhabitants per km2) with a PM2.5 ambient air quality standard, most populations and land were covered by the strictest standards (≤ 15 µg/m3). High population density is therefore no excuse for failing to apply stringent standards. Australia and Canada have among the strictest annual PM2.5 ambient air quality standards (8 and 8.8 µg/m3, respectively) and a low population density but contain several densely populated cities. Singapore had one of the highest population densities yet one of the lowest annual PM2.5 ambient air quality standards (12 µg/m3). China and India had some of the least stringent annual PM2.5 standards in the world (35 and 40 µg/m3, respectively) combined with high but differing population densities (146 and 416 inhabitants per km2). Several densely populated jurisdictions could maintain relatively strict annual PM2.5 ambient air quality standards: Dominican Republic, El Salvador, Japan, Singapore, China (Taiwan only) and Trinidad and Tobago.
How effective are the air quality standards?
The annual PM2.5 ambient air quality standards are often exceeded in the jurisdictions with the highest PM2.5 ambient air pollution. Singapore stood out for its relatively strict annual PM2.5 standard, despite PM2.5 air pollution that considerably exceeded the standard. Where the EU standard was applied, the PM2.5 air pollution was highly variable, ranging from 21 µg/m3 in Bulgaria to 6 µg/m3 in Iceland.
Some countries that have annual levels exceeding 30 µg/m3 but lack any air quality standards include Armenia, Mongolia, Nepal, North Macedonia, Tajikistan and Turkey, and many countries in the African and Eastern Mediterranean regions.
Air quality standards have different levels of legal effect; they may be enforced, target or voluntary standards. The goal to achieve the target standards is generally political, and accountability can lie between responsible government branches. Target standards have no universal enforcement mechanism and no definition of enforcement in the case of non-compliance. Enforced standards carry the possibility that at least one responsible party will bear potential financial, administrative, or other costs resulting from non-compliance. Unless standards are explicitly defined as voluntary, various types of costs for non-compliance are possible. Canada is a notable exception, where PM2.5 ambient air quality standards were defined as voluntary. However, Canada also has a robust and extensive network of air quality monitoring stations that rarely register local exceedances. Outside of this rare context, it should not be justifiable to have voluntary air quality standards. The duty of governments to protect their citizens’ health is not only limited to health care provision but also to ensure that everyone has the prerequisites for good health, such as drinking clean water or breathing clean air.
Figure 2. 24-hour ambient PM2.5 air quality standards worldwide. Note: Data for China are for the commercial PM2.5 standard. Source: Nazarenko Y, Pal D, Ariya PA. Air quality standards for the concentration of particulate matter 2.5, global descriptive analysis. Bull World Health Organ. 2021 Feb 1;99(2):125-137D. doi: 10.2471/BLT.19.245704.
Last updated 2022-08-25
