Summary of air quality criteria
Published
The purpose of the air quality criteria is to prevent health effects of air pollution. The criteria are set so low that most people can be exposed to these levels without any adverse effects on health. Healthy people may be exposed to much higher levels without any health effects.
About the publication
A working group from the Norwegian Institute of Public Health and the Norwegian Environment Agency is responsible for the "Outdoor Air Handbook – Air Quality Criteria".
This handbook reviews the scientific basis for determining air quality criteria for several air pollution components. It is intended for people with a natural scientific background, but the brief summaries of each chapter will be more easily accessible to the public. The handbook is under revision and will be updated in 2024.
We have previously conducted summaries of the current knowledge and determination of air quality criteria in 1992, 2013, 2016 and 2020. The work is based on reports from the World Health Organization (WHO) and the US Environmental Protection Agency (EPA), as well as separate systematic and narrative literature searches with emphasis on review articles and meta-analyses.
In 2021, WHO published comprehensive systematic reviews and meta-analyses of population studies on the health effects of various air pollution components, with purpose to revise the recommendations for health. A method for evaluating literature was used, which provided a good basis for judging which studies should be included or rejected when making new recommendations.
We have used these comprehensive reviews to establish new air quality criteria for the daily and annual averaging time of the classic air pollutants (nitrogen dioxide, particulate matter, ozone, sulphur dioxide and carbon monoxide). In addition, we have included Nordic population studies in our assessments. WHO limited the systematic review to mortality and exacerbation of asthma. Thus, no new knowledge has been acquired for the other health outcomes such as other respiratory diseases, cardiovascular diseases, neurological diseases, diabetes and birth outcomes. Health effects triggered by very short-term exposures (minutes, hour) have not been revised in 2024, and the sections on clinical- and animal studies, as well as mechanistic studies, have not been changed.
Determination of air quality criteria
The determination of air quality criteria is based on international research, and most criteria are based on population studies. Experimental studies in humans, animals and cell cultures are included to elucidate mechanisms and causal relationships. Since population studies describe associations and not necessarily causal relationships, experimental studies have been used to support the findings in the population studies.
The task of the working group has been to present the knowledge base necessary to establish air quality criteria. As air pollution levels in Norway are lower than in many other countries, we have focused on studies conducted in areas with such low levels of air pollution. The criteria are set so low that, based on current knowledge, most people can be exposed to these levels without experiencing adverse health effects from air pollution. This means that vulnerable groups such as people with respiratory diseases, cardiovascular diseases, and diabetes, and pregnant women, children and the elderly are protected as much as possible against the health effects of air pollution.
The purpose of air quality criteria
It is important to gather knowledge about the health effects of air pollution at the levels that are relevant for Norway. The air quality criteria will also be a tool for evaluating measures and setting national targets and limit values for various components. When determining the criteria, financial, administrative or technical considerations are not taken into account. However, the determination of the limit values in the Ambient Air Quality Chapter 7 under the Norwegian Pollution Control Act will be influenced by such factors. Furthermore, the “Air Quality Criteria Handbook” contains valuable information about health effects of air pollution that will be useful and interesting for various authorities, institutions, vulnerable groups, and individuals.
Overview of current air quality criteria
There are a number of different air pollution components in outdoor air that can lead to health effects. A total of 23 different components has been assessed for harmful effects. Air quality criteria have been set for 16 of the components. These components can cause health effects both after very short-term and after long-term exposures. That's why we have air quality criteria for many different averaging times from 15 minutes to annual. Many of the air pollution criteria comply with WHO's recommendations, but some have been set stricter after an overall assessment. We also have criteria for other components than WHO.
|
Component |
Averaging time |
Air quality criteria |
|
PM10 |
24-hour |
30 μg/m3 |
|
PM10 |
Annual |
15 μg/m3 |
|
PM2.5 |
24-hour |
15 μg/m3 |
|
PM2.5 |
Annual |
5 μg/m3 |
|
NO2 |
15 min |
300 μg/m3 |
|
NO2 |
1-hour |
100 μg/m3 |
|
NO2 |
24-hour |
25 μg/m3 |
|
NO2 |
Annual |
10 μg/m3 |
|
Ozone |
1-hour |
100 μg/m3 |
|
Ozone |
8-hour |
80 μg/m3 |
|
Ozone |
Peak season* |
60 μg/m3 |
|
SO2 |
15 min |
300 μg/m3 |
|
SO2 |
24-hour |
20 μg/m3 |
|
CO |
15 min |
80 mg/m3 |
|
CO |
1-hour |
25 mg/m3 |
|
CO |
8-hour |
10 mg/m3 |
|
CO |
24-hour |
4 mg/m3 |
|
Benzene |
Annual |
1 μg/m3 |
|
B[a]P |
Annual |
0.1 ng/m3 |
|
Arsenic |
Annual |
2 ng/m3 |
|
Lead |
Annual |
0.1 μg/m3 |
|
Cadmium |
Annual |
2.5 ng/m3 |
|
Chromium (Cr VI) |
Annual |
0.1 ng/m3 |
|
Mercury |
Annual |
0.2 μg/m3 |
|
Manganese |
Annual |
0.15 μg/m3 |
|
Nickel |
Annual |
10 ng/m3 |
|
Vanadium |
24-hour |
0.2 μg/m3 |
*Average of daily maximum 8-hour mean ozone concentration in the six consecutive months with the highest six-month running-average ozone concentration.
Abbreviations in the table: PM =particulate matter. PM10 particles with aerodynamic size below 10 micrometres, PM2.5 is the fine fraction, particles with aerodynamic size below 2.5 micrometres. CO = carbon monoxide, NO2 = nitrogen dioxide, SO2 = sulphur dioxide, B(a)P = benzo(a)pyrene.
