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 establish target concentration levels for major pollutants at which health risks are minimized.

Health Impacts of Air Pollution

Air pollution is one of the leading causes of premature mortality worldwide. According to WHO estimates, approximately 7 million people die prematurely each year due to exposure to polluted air. The main pollutants — fine particulate matter (PM2.5 and PM10), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and ozone (O₃) — penetrate deep into the respiratory tract and bloodstream, causing serious diseases.

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
• Cognitive impairment: reduced memory and concentration, increased risk of Alzheimer's disease and dementia
• Adverse pregnancy effects: premature birth, low birth weight, intrauterine growth restriction
• Reduced life expectancy: long-term exposure to polluted air reduces life expectancy by several years

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 a systematic review of thousands 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 compared to previous versions (2005) because new scientific evidence showed that adverse effects of pollutants occur even at lower concentrations than previously thought. This means that there is no safe level of air pollution — any exceedance of recommended values carries health risks.

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 Guidelines (AQG) — recommended pollutant concentration levels at which health risks are minimal. Interim Targets (IT) are also defined for countries that cannot yet achieve the main guidelines — these are phased steps toward improving air quality.

Important: 24-hour average values in the table correspond to the 99th percentile, meaning that exceedances of these levels are permitted for no more than 3-4 days per year. Annual averages are calculated as the mean over the year.

Key WHO Recommendations

• Priority on PM2.5 fine particles: they pose the greatest health threat as they penetrate deep into the lungs and 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

Unfortunately, Armenia has not yet adopted standards for PM2.5 and PM10 — the most dangerous air pollutants. This means that there is no legislative control over the concentration of these particles in atmospheric air, despite the fact that they pose the greatest threat to public health.

For other pollutants, Armenia has the following standards (24-hour average MPC - Maximum Permissible Concentration):

• NO₂ — 40 μg/m³ (corresponds to WHO interim target IT-1, 4 times higher than WHO guideline of 10 μg/m³)
• SO₂ — 50 μg/m³ (close to WHO guideline of 40 μg/m³)
• O₃ — 30 μg/m³ (significantly stricter than WHO recommendations)
• Dust (total) — 150 μg/m³ (this indicator does not correspond to WHO standards as it does not distinguish between PM2.5 and PM10)

The Armenia Blackouts project aims to fill this gap by providing real-time data on PM2.5 and PM10 concentrations based on readings from sensors installed by Yerevan Municipality and independent activists. We calculate the Air Quality Index (US AQI) and provide health protection recommendations.

Adopting national standards that comply with WHO guidelines is critically important for protecting the health of Armenia's residents and creating an effective air quality monitoring system.

See also

• Air Quality Index (AQI) — Calculation Methodology and Hazard Levels
• PM2.5 and PM10 Particles and Their Impact on Health
• Major Air Pollutants and Their Impact
• How to Safeguard Yourself from Air Pollution?
• How to Prevent 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

Questions and comments