WHO Air Quality Guidelines

The World Health Organization (WHO) has developed global air quality guidelines based on decades of scientific research into the health impacts of air pollution. The latest update to these guidelines was published in 2021 and reflects accumulated scientific evidence on the adverse effects of air pollutants, even at low concentrations.

WHO guidelines serve as a reference for governments worldwide when developing national air quality standards and public health policies. They provide health-based concentration levels intended to reduce risk; they are recommendations rather than legally binding standards.

Health Impacts of Air Pollution

Air pollution is one of the leading causes of premature mortality worldwide. According to WHO estimates, the combined effects of ambient and household air pollution are associated with approximately 7 million premature deaths each year. The guidelines cover six key pollutants: PM2.5, PM10, nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and carbon monoxide (CO). Fine particles can penetrate deep into the lungs, and some of their components can enter the bloodstream; gaseous pollutants primarily affect the respiratory system.

Short-Term Effects

• Respiratory tract irritation: coughing, scratchy throat, difficulty breathing
• Exacerbation of chronic diseases: increased frequency of asthma attacks, worsening COPD symptoms
• Cardiovascular problems: elevated blood pressure, heart rhythm disturbances
• Eye irritation: redness, itching, tearing

Long-Term Effects

• Respiratory diseases: chronic bronchitis, emphysema, asthma, increased risk of respiratory infections
• Cardiovascular diseases: ischemic heart disease, myocardial infarction, stroke, atherosclerosis
• Lung cancer: PM2.5 particles and certain chemical substances in polluted air have carcinogenic properties
• Neurological effects: studies associate long-term exposure with a higher risk of cognitive impairment
• Adverse pregnancy effects: premature birth, low birth weight, intrauterine growth restriction
• Premature mortality: long-term exposure is associated with a higher risk of early death

High-Risk Groups

• Children: their lungs and immune systems are still developing, making them particularly vulnerable
• Elderly people: age-related changes and chronic diseases amplify the negative impact of pollutants
• Pregnant women: air pollution can affect maternal health and fetal development
• People with chronic diseases: asthma, COPD, cardiovascular diseases, diabetes
• Low socioeconomic populations: limited access to healthcare and higher exposure to pollutants

Scientific Basis of WHO Guidelines

WHO Air Quality Guidelines are based on systematic reviews of scientific studies conducted worldwide. These studies examine the relationship between pollutant concentrations in the air and various health indicators, including mortality, morbidity, hospitalizations, and medical consultations.

The 2021 WHO guidelines became more stringent than the 2005 edition because new scientific evidence showed that adverse effects occur at lower concentrations than previously understood. AQG levels are health-based benchmarks for reducing risk, not a boundary below which the complete absence of health effects is guaranteed.

Key principles in developing guidelines:

• Epidemiological studies: analysis of morbidity and mortality data in different populations with varying pollution levels
• Toxicological research: studying mechanisms of pollutant effects on the human body at cellular and molecular levels
• Dose-response relationships: establishing connections between pollutant concentration and severity of adverse effects
• Vulnerable groups: special attention to pollution impacts on children, elderly, pregnant women, and people with chronic diseases
• International expert review: independent verification and confirmation of findings by leading scientists and public health specialists

WHO Guidelines for Major Air Pollutants

WHO establishes Air Quality Guideline levels (AQG) — recommended pollutant concentrations intended to reduce health risks. Interim Targets (IT) are also defined for countries that cannot yet achieve the main guidelines — these are phased steps toward improving air quality.

Important: The 24-hour values and the 8-hour ozone value correspond to the 99th percentile, meaning 3–4 exceedance days per year. Annual averages are calculated as the mean over the year.

Key WHO Recommendations

• Particular attention to PM2.5: fine particles can penetrate deep into the lungs, and some of their components can enter the bloodstream
• Gradual pollution reduction: even partial reduction in pollutant concentrations brings significant health benefits
• Comprehensive approach: control of all major pollutants is necessary — PM, NO₂, SO₂, O₃, and CO
• Air quality monitoring: establishing and maintaining systems for real-time pollutant concentration monitoring is essential
• Public information: citizens must have access to current air quality information and health protection recommendations
• Policy measures: governments must develop and implement strategies to reduce pollutant emissions, including regulation of transport, industry, and energy sectors

Situation in Armenia

Armenia's currently applicable rules do not set separate limits for PM2.5 and PM10. They set only a 24-hour limit for total suspended particles of 150 μg/m³. The Government has adopted new rules with separate PM2.5 and PM10 values; they are due to apply from 1 November 2027 unless the date is postponed again.

The following 24-hour maximum permissible concentrations currently apply to other pollutants:

• NO₂ — 40 μg/m³
• SO₂ — 50 μg/m³
• O₃ — 30 μg/m³
• Total suspended particles — 150 μg/m³

These figures cannot be compared directly with WHO recommendations when the averaging periods or indicators differ. However, the transition to a new system is already provided for by Decision No. 1142-N. Read more about the transition timeline and the new values in our overview of Decision No. 1142-N.

AirQuality.am will continue to follow the effective date and practical implementation of the new rules.

See also

• What Is AQI — the Air Quality Index and How to Read the US AQI Scale
• What Are PM2.5 and PM10 and How Do They Affect Health?
• Air Pollutants: Sources and Health Effects
• How to Safeguard Yourself from Air Pollution?
• How Can We Reduce Air Pollution in the City?

Sources of information

• WHO Global Air Quality Guidelines 2021: Particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide
• World Health Organization: Ambient (outdoor) air pollution
• WHO Europe: Air pollution

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