What are the health issues associated with outdoor air pollution?
What is air pollution?
Air pollution refers to contamination of the atmosphere by a mixture of gaseous compounds and airborne particulate matter that degrade air quality. It has adverse effects on human health and the environment.
Today, nine out of 10 people worldwide breathe polluted air according to the World Health Organization (WHO). Air pollution therefore affects everyone to differing degrees depending on the location and emission source.
What are the different sources of pollution?
There are many sources of pollution.
- Natural sources: plant pollen, volcanic activity, sand haze, sea spray, etc.
- Sources related to human activities: transport, heating, industry, agriculture, pesticide use, buildings, construction work and materials, and so on.
Are some places more polluted than others?
No areas are completely free from pollution – not even mountains or rural regions – as pollutants can be carried by the wind for hundreds or even thousands of kilometres. That being said, pollution levels are highest near emission sources, such as major roads or industrial sites.
What are the main air pollutants?
Air pollution is caused by a wide variety of pollutants, which can be chemical, biological or physical.
Chemical pollution encompasses gaseous compounds, such as volatile organic compounds (VOCs) and inorganic compounds (nitrogen and sulphur oxides, ammonia). These can also occur as particles, for example in the form of metals or black carbon. Airborne particulate matter (PM) is a complex mixture of substances whose composition and concentration vary depending on the pollution source and the distance from it.
With regard to biological agents in the air, special attention is paid to plant pollen and mould, due to their allergenicity.
Moreover, some air pollutants are subject to regulatory monitoring:
- sulphur dioxide (SO2),
- nitrogen oxides (NOx), including nitrogen dioxide (NO2),
- ozone (O3),
- airborne particulate matter (PM2.5 and PM10),
- carbon monoxide (CO),
- benzene (C6H6),
- polycyclic aromatic hydrocarbons (PAHs), including benzo[a]pyrene (B[a]P),
- metallic elements contained in particles, such as lead, nickel, arsenic, cadmium and mercury.
Coarse particles, fine particles, ultrafine particles – what do all these terms mean?
Airborne PM can be directly emitted into the atmosphere (primary particles) or form in the atmosphere through chemical reactions between different particles (secondary particles). This distinction illustrates the full complexity of air pollution phenomena.
PM is defined by its size and the way it is measured. The smaller it is, the more deeply it can penetrate the respiratory tract.
A distinction is made between:
- PM10: particles with a median aerodynamic diameter of 10 micrometres (µm) or less. They are smaller in diameter than a human hair or a grain of sand. This size is similar, for example, to that of pollen grains or mould spores. PM10 mainly settle in the upper airways, for example in the nose and throat, but they can sometimes reach the bronchi.
- Often considered part of PM10, ‘coarse’ particles actually refer to those with a diameter between 2.5 µm and 10 µm (PM2.5–10). They therefore form a subcategory of PM10.
- PM2.5 or fine particles: particles with a median aerodynamic diameter below 2.5 micrometres (µm). They are comparable in size to certain bacteria. These particles deeply penetrate the respiratory tract, potentially reaching the pulmonary alveoli and sometimes even entering the bloodstream.
- Ultrafine particles (UFPs), also called nanoparticles, are particles with a diameter most often below 0.1 µm (100 nanometres). Their small size allows them to directly penetrate the pulmonary alveoli. They can cross blood vessel walls and affect other organs.
The measurement of ambient air particles has changed over time with the development of new technologies and growing knowledge about their health effects. Today, PM10 and PM2.5 are monitored in France, while UFPs have also been measured over the past few years.
What are the health effects of air pollution?
This is how many people die every year from air pollution in France according to Santé publique France.
The effects of air pollution have been known for many years. The most well-documented effects primarily involve the respiratory system, which is the first to be affected, as well as the cardiovascular system. These effects depend on the frequency and duration of exposure.
Short-term exposure to air pollution can cause irritation of the eyes, nose or throat, exacerbate chronic conditions such as asthma or allergies, and in some cases lead to serious acute complications, such as myocardial infarction, which can be fatal.
Long-term exposure is responsible for the development of cardiovascular disease, chronic respiratory disease and lung cancer. The International Agency for Research on Cancer (IARC) has classified air pollution, as well as the fine particles that make it up, as known human carcinogens.
Moreover, recent studies have shown that air pollution can affect other organs:
- The brain and nervous system (cognitive disorders and neurodegenerative disease),
- Fertility and foetal development (premature birth, low birth weight),
- The hormonal system (metabolic syndrome),
- Etc.
Health effects have been observed even at the lowest concentrations, with no evidence of a threshold, especially for PM.
What are the WHO guidelines?
In 1987, WHO established – and has since updated – guidelines to protect public health from the effects of air pollution. For each pollutant considered, WHO compiles knowledge on its short- and long-term health effects. Revising these values helps to take account of new studies on this topic published in the scientific literature. The most recent report, published in 2021, focused on PM (PM10, PM2.5), nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3) and carbon monoxide (CO). For example, in this report, WHO recommends an annual average concentration of PM10 not exceeding 15 µg/m3.
These guidelines served as a basis for the European regulations on ambient air quality assessment and management. These regulations set a framework for monitoring air quality in European Union Member States. They establish regulatory values (as annual averages, and for periods of peak pollution) to protect human health and plants.
Are some people more vulnerable to air pollution?
Infants, children, pregnant women, the elderly, people with chronic respiratory or cardiovascular disease and those who are overweight or diabetic are more vulnerable to air pollution.
In addition to individual vulnerability, some groups of people are more exposed to pollution on account of their environment or activities:
- People living near a major road or industrial site,
- Workers present or working on the road network (including drivers),
- Populations living in urban areas.
What can be done to reduce air pollution?
In recent years, several studies have estimated the health impact of air pollution, including its economic cost, to help guide public policies and support the implementation of actions.
Collectively:
Taking action to sustainably reduce air pollution would significantly improve the health and quality of life of the population.
Since the 1970s, air pollution has been one of the main environmental issues addressed by European policy. This policy aims to develop and implement measures to improve ambient air quality. This is achieved, for example, by reducing emissions across different areas of activity, improving the quality of energy (heating and engine fuels, etc.), and assessing and managing ambient air quality.
The aim of the new European directive on ambient air quality is to lower the regulatory values so that they ultimately align with the WHO guidelines.
Despite an overall improvement in air quality over the past few decades, efforts still need to be made to reduce air pollution, particularly by analysing local differences in pollution sources and levels.
Individually:
Every citizen has a role to play when it comes to improving air quality. If everyone takes action, the combined effect can be significant:
- Get around by public transport, on foot, by bike, or by carpooling;
- Use efficient, low-emission heating equipment and only heat when necessary;
- Comply with the rules prohibiting the burning of green waste.
Does climate change have effects on air pollution?
Climate change and air pollution are interconnected. In fact, some pollutants are also greenhouse gases and environmental conditions can promote the formation of certain types of pollutants. For example:
- Ozone is forming more frequently under conditions of strong sunlight;
- Fire risk is increasing and covering a wider area, leading to higher concentrations of fine particles;
- The Saharan sand haze season is becoming longer, with sand haze becoming more frequent and more intense, resulting in higher particulate concentrations;
- Pollen emissions are increasing due to higher atmospheric CO2 levels, and plants are expanding their geographic range, bringing new pollen varieties to regions where they were previously absent.z