breakpoints PM2.5 AQIs

Green in India means red in Norway

Marianne Amble

Air quality standards around the world varies widely – but may be more aligned going forward

Huge variations in AQI thresholds

Below is a comparison of the different breakpoints (max values) of the PM2.5 values in various air quality indices (AQIs). The differences in classification are astonishing. A level of PM2.5 of 28 μg/m3 translates to “Good” in India and “Excellent” in China while it would be deemed “Poor” in Europe and “High” in Norway.

The variations are biggest in the lower levels of pollution. At levels above 150 μg/m3, all the AQIs listed here agree that the air is really unhealthy.

breakpoints PM2.5 AQIs
Breakpoints for PM2.5 values for various air quality indexes. Please note that colours used in the illustration have been adjusted for easier comparison and may differ from official standards. Sources: See table 1 further down.

Who follows the WHO?

We find a similar difference in the guidelines or standards for annual PM2.5 levels. The WHO guideline of 10 μg/m3 is yet to be implemented in major regions and countries, see illustration below.

Annual PM2.5 standards
Annual air quality standards for PM2.5. Sources:

EU is revising its Ambient Air Quality Directives

EU is currently revising its air quality standards and its EU rules. Scientific evidence points to more damaging effects of notably fine particulate matter (PM2.5) at lower levels than the current EU standards. The ongoing initiative aims to align the EU standards with new evidence and also to align the European rules with the WHO guidelines.

The revision also seeks to address improvements in legislative framework, and to support local authorities in air quality monitoring and modelling. Air pollution remains the major environmental health risk in Europe. Premature deaths due to air pollution could be reduced by 55% in 2030 if existing measures were implemented by all Member States.

Expect tighter standards going forward

The air quality standards are under revision not only in EU. WHO themselves are revising their guidelines, expected ready in early 2021. The Indian authorities are to update the national Indian standards and are expected to make them more stringent, according to The Times of India. Norway is also considering to lower current standard to comply with the WHO guidelines.

This listing is not comprehensive – work is ongoing in several countries to tighten the standards. Particulate matter stands out as the pollutant with the most damaging effect on people’s health and will very likely be the focus for revisions to come.

Local differences in pollution levels and policies may explain the variation we see in air quality standards today. However, as air quality monitoring becomes more widespread and the evidence of the harm caused by particulate matter increase, we can expect the levels to be gradually harmonised.

A bit more detail on the AQIs

An air quality index (AQI) is used to communicate the levels of air pollution to the public. The AQIs are defined by government agencies. The indices are often grouped into bands of pollution level, with corresponding naming, colour code and public health advice.

An AQI is typically based on a set of pollutants, such as PM2.5, PM10, NO2, SO2 and ground level ozone (O3). The different AQIs may included different pollutants, and they are calculated by different formulas, often weighting the most prominent pollutant most. The result is typically a number between 0-500, divided into band levels from good to very unhealthy. The interested reader may find more information here.

The table below summarizes the different PM2.5 bands of concentration (in μg/m3) for a selected set of Air Quality Indices.

Band values pm2.5 AQIs
Table 1. PM2.5 values for various Air Quality Indexes. Please note that colours used in the illustration have been adjusted for easier comparison and may differ from official standards. Sources:
US AQI Breakpoints | Air Quality System | US EPA

Want to monitor your local air quality?

Airmine is developing an air quality monitor. Reasonably priced (subscription-based) and with PM-sensors. We are currently in the pilot testing stage and will continue to roll out monitors this spring. We will keep you updated on the progress!