Air Pollution: Facts And Figures

Air pollution is a serious issue that contributes to approximately 4.2 million premature deaths annually worldwide, according to the World Health Organization (WHO). It is the second highest risk factor for non-communicable diseases and has negative health impacts, including respiratory and cardiovascular problems such as asthma and heart disease. The main sources of outdoor air pollution include the energy, transport, waste management, urban planning, and agricultural sectors. Indoor air pollution, caused by sources like heating and cooking, also poses significant health risks. Particulate matter (PM), carbon monoxide (CO), ground-level ozone, and nitrogen dioxide (NO2) are among the key pollutants addressed in the WHO's Global Air Quality Guidelines, which offer guidance on thresholds and targets for reducing health risks associated with air pollution.

Particulate matter (PM)

The WHO Global air quality guidelines (AQG) provide interim targets to promote a gradual shift from high to lower concentrations and their associated health benefits. For example, through the achievement of interim target one (35 µg/m3), around 300,000 deaths would be saved worldwide annually. The guidelines also offer qualitative statements on good practices for the management of certain types of particulate matter (PM), such as black carbon/elemental carbon, ultrafine particles, and particles originating from sand and dust storms.

Some particles are directly emitted into the air (primary particulate matter). They come from sources such as cars, trucks, buses, factories, construction sites, and the burning of wood. Other particles may be formed in the air from the chemical change of gases (secondary particles). They are indirectly formed when gases from burning fuels react with sunlight and water vapour, resulting from fuel combustion in motor vehicles, power plants, and other industrial processes.

Carbon monoxide (CO)

To ensure the safety of individuals, the EPA sets and reviews standards for CO in outdoor air under the Clean Air Act. These standards assist state, tribal, and local agencies in maintaining safe levels of CO. Additionally, the WHO Global Air Quality Guidelines (AQG) provide guidance on thresholds and limits for key air pollutants, including CO, that pose health risks. These guidelines are developed through a transparent, evidence-based decision-making process and offer qualitative statements on the management of certain types of particulate matter, such as black carbon.

Identifying carbon monoxide poisoning involves considering the victim's environment and immediate past living or work situation. Were they exposed to sources of carbon monoxide, such as uncontrolled fires, motor vehicles, or fuel-burning heaters in a poorly ventilated enclosed space? Are others in the same environment displaying similar symptoms? Once identified, it is crucial to move the victim out of the contaminated area into fresh air, as carbon monoxide will eventually be eliminated from the blood through normal ventilation. However, emergency measures should be initiated immediately, as serious health damage may occur before the elimination of CO from the bloodstream.

Ozone (O3)

Ozone exposure has been linked to serious health risks, including immediate and long-term effects. Short-term exposure to high ozone levels can cause immediate health problems, especially for vulnerable individuals. A study of lifeguards in Galveston found that high ozone levels led to greater obstruction of their airways at the end of the day. Additionally, ozone exposure can trigger respiratory issues in people with asthma or chronic obstructive pulmonary disease (COPD), requiring medical treatment and hospitalisation.

Long-term exposure to ozone over periods longer than eight hours, including days, months, or years, has been associated with more serious health consequences. Scientific studies have found links to increased respiratory illnesses, metabolic disorders, nervous system issues, reproductive problems, and increased respiratory and cardiovascular-related mortality. The impact of ozone exposure on an individual's health can vary depending on factors such as ozone levels, breathing rate, and the amount of time spent outdoors.

Climate change plays a significant role in enhancing the conditions for ozone formation. Wildfires contribute to the transport of ozone-forming pollutants, and high temperatures combined with emissions create ideal conditions for ozone to form. Addressing air pollution is crucial for protecting public health, and policymakers must implement measures to reduce emissions and improve air quality, especially in low- and middle-income countries where the impact is most severe.

Nitrogen dioxide (NO2)

Studies have shown that indoor concentrations of nitrogen dioxide are influenced by factors such as the use of gas cookers, the absence of extractor fans, the lack of central heating, and cigarette smoking. In homes with gas stoves, nitrogen dioxide concentrations can range from 25 to 70 μg/m3, while homes without gas stoves typically have lower levels, ranging from 13 to 40 μg/m3.

In a Spanish study conducted between 1996 and 1999, average annual indoor concentrations of nitrogen dioxide ranged from 12.5 to 14.7 μg/m3. Similarly, an Italian population-based study found that the weekly mean indoor concentration in the kitchen during the winter was 62 μg/m3, higher than in the summer at 38 μg/m3.

Traffic control measures have been effective in reducing NO2 levels in some cities. For example, London's Ultra Low Emission Zone initiative resulted in a 36% reduction in NO2 levels in the first six months after its launch in 2019. Despite these efforts, most cities continue to have unhealthy levels of NO2, posing health risks for much of the world's population.

Non-exhaust emissions

The particulate matter (PM) released from non-exhaust emissions is made up of micrometre-sized particles, which can cause serious health issues. Multiple epidemiological studies have linked exposure to this particulate matter with acute respiratory infections, lung cancer, and chronic respiratory and cardiovascular diseases. Additionally, researchers have found correlations between fine particulate matter exposure and fatality rates in previous coronavirus epidemics.

To mitigate non-exhaust emissions, several measures have been proposed. These include comprehensive regulation of tires, reducing vehicle weight, and decreasing vehicle-kilometers traveled. Promoting public transport, walking, and biking relative to private vehicle use can also help reduce non-exhaust emissions. While some technological improvements, such as regenerative braking in electric and hybrid vehicles, can reduce brake wear emissions, other factors, such as increased vehicle weight, can still contribute to non-exhaust emissions from road particles and tire wear.

Addressing non-exhaust emissions is crucial in tackling the broader issue of air pollution, which is a significant risk factor for non-communicable diseases. While most outdoor air pollution sources are beyond individual control, concerted action by policymakers in sectors like energy, transport, waste management, and urban planning is necessary to implement effective solutions.

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