# Air pollution in Iran

Air pollution in Iran is a significant health and environmental and health hazard. Iran ranks as the third most polluted country in the world. Iran ranks as the sixth most emitting country in the world.
Air pollution in Iran is heavily concentrated in urban areas and reportedly kills 40,000 Iranians a year. High levels of air pollution are a major contributor to diseases including cardiovascular, neurological, lung related diseases as well as birth defects. Health costs associated with premature deaths and treatment of the ill has led to Iran losing 3.2% of its GDP annually.
High levels of pollutants such as carbon monoxide and particulate have been linked due to heavy motor traffic in urban areas. In Tehran, vehicular traffic is responsible for the highest share of pollution. According to Radio Free Europe, government efforts have failed to address the issue and in January 2025, the Iranian government announced it will move its capital away from Tehran among other factors because of pollution.

## Occurrence

Air pollution in Iran represents a significant environmental and public health challenge, particularly in urban centers such as Tehran. It has been reported that 40,000 Iranians a year die of air pollution. The air quality in Tehran frequently exceeds hazardous thresholds, with concentrations of pollutants such as carbon monoxide (CO) and particulate matter (PM) often surpassing international standards. Traffic-related emissions, particularly from nonstandard motor engines, are the primary contributors to this issue. Motor vehicles are responsible for over 90% of CO emissions in Tehran, and approximately 80% of air pollution nationwide. A small proportion of vehicles, including carburetor engines and motorcycles, generate a disproportionately high share of pollutants, with some motorcycles producing emissions up to 60 times greater than standard cars. Measurements of key air pollutants, including PM10, SO2, NO2, and O3, consistently exceed the limits set by the World Health Organization (WHO) and the Environmental Protection Agency (EPA). Mahdi said this contributes to thousands of premature deaths annually in Iran.
Air pollution has been linked to health issues, including in Iran. In Tehran, pollutants such as sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3) were associated with an additional 1,458, 1,050, and 819 deaths, respectively, in 2011. Official estimates from 2013 reported approximately 4,460 annual deaths in Tehran attributable to air pollution. These figures underline the severe impact of poor air quality on public health. Economic assessments further highlight the gravity of the issue; a World Bank report from 2005 estimated that urban air pollution results in an annual economic loss of $640 million, representing 0.57% of Iran’s gross domestic product. More recent analyses have ranked Iran as the third most polluted country globally, with air pollution costing the nation approximately $16 billion per year.
Efforts to mitigate urban air pollution, including tree-planting projects and regulatory programs. These efforts have had limited success. Action against air pollution has been hindered by insufficient regulatory enforcement, outdated vehicle technologies, and nonstandard or illegal energy production methods.

## Health effects

Air pollution is a major global health risk, contributing to a wide range of diseases and premature deaths. Fine particulate matter (PM2.5) is particularly harmful, as it can penetrate deep into the lungs and enter the bloodstream, leading to respiratory and cardiovascular diseases, cancers, and neurological disorders like Alzheimer's disease and dementia. Vulnerable populations, including children, the elderly, and those with pre-existing health conditions, are disproportionately affected.
Particulate matter (PM), a major component of air pollution, consists of a mixture of particles suspended in the air, typically ranging in size from 2.5 to 10 μm (PM2.5 to PM10). These particles are strongly associated with pulmonary and cardiac diseases, including heart attacks, aggravated asthma, and reduced lung function. Smaller particles, such as PM2.5, can penetrate deeper into the respiratory system, increasing the risk of more severe health issues. Long-term exposure to particulate pollution has been linked to a reduction in life expectancy due to increased rates of cardiovascular diseases, lung cancer, and respiratory conditions like chronic obstructive pulmonary disease (COPD). The detrimental effects on health are evident from various studies, highlighting the significant health risks of prolonged exposure to particle pollutants.
Ground-level ozone (GLO), formed through reactions between nitrogen oxides and volatile organic compounds, poses significant risks to human health. It can cause respiratory issues, particularly asthma, by damaging lung tissue and impairing cellular function. Prolonged exposure may lead to chronic respiratory diseases, increased risk of DNA damage, and other health complications.

### Birth defects

Research from Stanford University has linked exposure to traffic-related air pollutants during early pregnancy to an increased risk of serious birth defects, particularly neural tube defects such as spina bifida and anencephaly. Women with the highest exposure to carbon monoxide had nearly double the risk, while those with the highest nitrogen oxide exposure faced nearly triple the risk of anencephaly.
A study by NIH revealed a direct link between pregnant women’s exposure to PM10 and SO2 with low birth weight, and exposure to NO, PM2.5, NO2, and CO with preterm labor. These findings underscore the urgent need for policies aimed at reducing air pollution to mitigate risks of preterm labor and low birth weight in newborns.

## Environmental effects

Air pollution, according to Mahdi has ecological consequences, affecting groundwater, soil, and the atmosphere. It threatens biodiversity, with studies showing that environmental pollutants contribute to the extinction of various plant and animal species. Toxic airborne substances can also disrupt animal reproduction. Additionally, air pollution leads to acid rain, temperature inversion, and contributes to global climate change through the emission of greenhouse gases. According to Radio Free Europe Iran is the sixth most emitting country in the world.

## Air pollution in Tehran

From 2016 to 2021, Tehran, the Iranian capital, experienced fluctuating air quality, with over 20% of days having an Air Quality Index (AQI) exceeding 100, indicating unhealthy air for sensitive groups. The worst pollution occurred in 2020, with 33.43% of the year marked by an AQI above 100. This was a notable shift from previous years, as studies from 2012–2017 showed that about 32% of days had unhealthy air quality. The city's air quality, however, improved somewhat in the years following the introduction of Iran’s clean air law in 2017, which played a significant role in reducing pollution levels.
In 2020, the monthly distribution of AQI in Tehran revealed substantial variations. March was the only month with relatively clean air, with 13% of the days meeting the air quality standards. From March to October, air quality was generally moderate, with May, April, and October showing the highest proportion of acceptable air quality days. However, December, November, and January saw AQI levels exceeding 100 for over 50% of the days, with December having the most unhealthy air. This pattern of pollution in winter months aligns with trends observed in other regions, where cold temperatures and reduced airflow hinder the dispersal of pollutants.
The seasonal air quality variations in Tehran are caused among other things by temperature inversions and meteorological conditions that limit air movement. During the colder months, heating increases fossil fuel consumption, further exacerbating pollution levels. Interestingly, Tehran's air quality showed improvement in the spring and summer, which typically experience less pollution. Dust storms in late spring and early summer are able significantly elevate particulate matter (PM) levels, posing increased health risks.
Seasonal
Seasonal variations in air pollutant concentrations in 2017-2023 showed that spring experiences the lowest concentrations of pollutants such as PM2.5, NO2, SO2, and CO, while autumn and winter show the highest levels. This trend reflects an inverse relationship with temperature, where colder months have more pollution due to factors like increased vehicle usage, heating, and weaker atmospheric convection. The shallow boundary layer during winter further limits the dispersion of pollutants, causing them to accumulate near the surface.
Conversely, ozone (O3) levels exhibit a direct correlation with temperature, reaching their peak in summer and dropping in winter. According to the study, ozone formation is facilitated climatic conditions, particularly in urban areas.
Emission sources
The emission inventory released on Atmospheric air on Tehran showed that vehicular sources are responsible for a significant portion of the city's total pollution, contributing approximately 84%, compared to 16% from stationary sources. Among stationary sources, power plants are the largest emitter, releasing 40,650 tons of pollutants annually, while railways contribute the least. Mobile sources, particularly passenger cars and motorcycles, dominate emissions, with passenger cars contributing 264,417 tons/year, followed by motorcycles at 149,952 tons/year. The total annual emissions in Tehran amount to about 701,039 tons, with the most significant pollutants being CO, VOCs, and NOx. This reflects a substantial increase in emissions from vehicular sources, with the share growing from 70% to 84% in recent years due to factors like improved fuel quality, more registered cars, and technological advancements in vehicles.
Vehicular sources are the largest contributors to air pollution, with passenger cars being the leading emitter of CO and VOCs, and heavy trucks producing the highest levels of NOx and PM2.5.

## Economic costs

Air pollution's effects on health have led to economic costs. Long-term exposure to air pollutants such as PM2.5 has been linked to chronic diseases like COPD, ischemic heart disease, lung cancer, and diabetes, and according to the study have imposed significant economic burdens on the healthcare system. The treatment costs for these diseases, along with the loss in labor cause economic loss. Specifically, the annual cost of deaths caused by PM2.5 exposure in Iran was estimated to be around 110,713 million US dollars, nearly 3.7% of the country's GDP in 2018.
In terms of treatment costs, cardiovascular diseases were found to incur the highest expenses, followed by diabetes and lung cancer. For example, the cost of treating cardiovascular diseases was 494,543,115 Iranian rials in 2021, with an annual cost of 1881 USD per patient. Other diseases like COPD, stroke, and diabetes also presented significant treatment costs.

## Government action

The Clean Air Act of 2017, introduced under President Hassan Rohani, aimed to mitigate Iran's environmental crises by reducing sulfur levels in mazut, upgrading transportation infrastructure, and mandating cleaner-burning Euro 4 fuels. However, implementation has faced setbacks, especially during winters when natural gas shortages prompted increased mazut burning, resulting in severe urban air pollution and public outcry. Reports revealed that much of the mazut produced exceeded sulfur limits, while cleaner fuel production lagged. Despite promises from officials to address the issue.
In January 2025, the Iranian government announced it will move its capital to Makran because of the high levels of pollution among other problems in Tehran.