Information

Introduction

In November 2022, the BelAQI air quality index was adapted to the new and stricter guideline values of the World Health Organization (WHO). The BelAQI index is used to classify short-term air quality (hours/days). An index scale from 1 to 10 is used, where 1 indicates excellent air quality and 10 indicates horrible air quality. More information about the new BelAQI index can be found here.

Need to adapt the annual scales

In addition to its short-term impact, air pollution also has a chronic or long-term impact on health. Annual average concentrations are used as indicators for long-term impact. The long-term health impact is more significant than the short-term impact. The guideline values intended to protect us against the long-term impact of air pollution were also tightened by the WHO in 2021. The new WHO guideline values are the result of meta-analysis: based on the most recent epidemiological studies, it appeared that there is still a significant health impact even at concentrations below the (former) 2005 guideline values.

The European Union (through EU Directive 2008/50) also applies legally enforceable annual limit values. The current EU annual limit values are less stringent than the WHO health guideline values.

The table below lists the EU limit values and the former and new WHO guideline values for particulate matter (PM_2.5 and PM₁₀) and nitrogen dioxide (NO₂):

(*) indicative limit value from 2020 onwards

Table 1: current European annual limit values and the former (2005) and new (2021) WHO annual guideline values

Because the concentration scales used by IRCEL and the three regions to visualise long-term impact were no longer in line with the new WHO guideline values, they were adapted. Three reference points were used in this process:

-          Annual average concentrations higher than the WHO annual guideline value fall into class 5 or higher

-          Annual average concentrations higher than the legally enforceable EU limit value fall into the highest class

-          Annual average concentrations lower than half the WHO annual guideline value fall into class 2 or lower

The other concentration classes were defined pragmatically.

This results in the following 10 concentration classes:    

Table 2: concentration classes for annual average concentrations of PM₁₀, PM_2.5 and NO₂

For ozone (O₃) and Black Carbon (BC), there are no EU annual limit values or WHO health guideline values. The annual average concentration classes for ozone were not adapted. For BC, the annual average class boundaries were derived through the correlation that exists between BC and NO₂ annual average concentrations.

Air quality is not getting worse

Compared with the concentration classes used previously, the maps will appear “redder”. However, this does not mean that air quality itself is deteriorating. On the contrary, we observe that air quality has been improving for several decades. It does mean that health risks already occur at lower concentrations than previously estimated.

In order to further reduce the negative effects of air pollution on health, the three regions have developed air quality plans with ambitious objectives.

BelAIR app

The BelAIR smartphone application maps the current air quality for every location in Belgium. The app also displays long-term concentrations (annual averages) for each location over the past five years. The new annual average concentration scales are used to classify long-term air quality.