Air pollution is a complex and ever-changing mixture of various chemical, biological and physical elements that can be toxic to humans. Every day, an adult inhales 10,000 to 20,000 liters of air with an average of 99% oxygen and nitrogen, but which can also contain various pollutants that can cause health effects.

There are different sources of air pollution (natural, related to human activities …). More and more studies highlight health effects that can be differentiated according to the source of emission considered.

Air pollution results both from:

• Pollutant emissions from various sectors of activity (industry, transport, agriculture, heating, etc.);
• phenomena of natural origin (Saharan sand winds, soil erosion, volcanic eruptions …);
• Chemical reactions occurring in the atmosphere between the so-called “primary” pollutants (particles, nitrogen oxides, sulfur oxides, etc.) which are directly emitted by the pollution sources and which are at the origin of the formation of so-called “secondary” pollutants (ozone, particles, etc.);
• phenomena of import and export of air pollution that can occur on a large scale.

Pollutants most harmful to health

The chemical pollutants that cause the greatest public health concerns are:

• The particles of outdoor air, classified as carcinogenic to humans since 2013 by the International Agency for Research on Cancer (IARC). The toxicity of these particles comes from both their composition and their size. The finer the particles, the more they are able to penetrate deeply into the pulmonary tree (see diagram below) and to go through the bloodstream to other organs. Various chronic diseases (cancers, cardiovascular and respiratory pathologies) develop after several years of exposure to particles, even at low levels of concentration. Other effects are more and more highlighted: possible effects on reproduction, risk of premature birth, impaired neurodevelopment of the child, dementia in the elderly … At present, particles are pollutants air for which health effects are the most documented.
• Ozone
• Nitrogen dioxide (NO2), a highly irritating substance of the respiratory tract and the main respiratory effects described in humans are shortness of breath, bronchial obstruction, asthma attacks, or bronchitis.
• Volatile organic compounds (benzene, formaldehyde, 1,3-butadiene …)
• Polycyclic aromatic hydrocarbons (PAHs such as benzo [a] pyrene)
• Metals (such as arsenic, chromium and cadmium).
• Biological agents, such as pollen and mold, can also be responsible for health effects. In addition, there are several types of interactions between air pollutants and pollens, since certain chemical air pollutants can promote the allergic reaction by lowering the threshold of bronchial reactivity and / or by accentuating the irritation of the nasal mucosa or ocular and can also act on the pollen grains, for example via deformation or rupture of the wall of the pollen grain, which would then allow them to penetrate deeper into the respiratory system than whole pollen grains.

Effects of air pollution on health

Effects of air pollution on health are observed as follows:

• an exposure of a few hours to a few days (acute, so-called short-term exposure) to this pollution: ocular or respiratory irritation, asthma attacks, exacerbation of cardiovascular and respiratory disorders that may lead to hospitalization, and the most serious cases at death;
• a multi-year exposure (chronic, so-called long-term exposure) to air pollution; in this case, the health effects can be defined as the contribution of this exposure to the development or aggravation of chronic diseases such as: cancers, cardiovascular and respiratory pathologies (asthma, chronic obstructive pulmonary disease, heart failure) , neurological disorders, etc.

Health and economic impacts of air pollution

According to the WHO, air pollution is the main environmental risk for health in the world. For example, exposure to indoor and outdoor air pollution leads to premature death each year (“premature death” because exposure to air pollution shortens life) by about 6.5 million people.

In the WHO Europe area (53 countries), it is estimated that about 600 000 deaths per year are related to air pollution (482 000 are due to outdoor air pollution and 117 200 to indoor air pollution). According to a study published in 2015 by WHO and the Organization for Economic Co-operation and Development (OECD), the economic cost of these 600 000 premature deaths as well as diseases caused by indoor and outdoor air pollution in the WHO’s Europe area in 2010 reached 1.6 trillion (or 1.6 trillion) US dollars.

Does improving air quality really translate into improved health?

Several epidemiological studies have analyzed the health impact of a decrease in pollution levels. These so-called intervention studies confirmed that the health benefits were very real when the air quality improves.

For example, the Irish government’s ban on the sale of bituminous coal in Dublin in 1990 resulted in a net decrease in particulate matter concentrations, coupled with a 6% decline in total mortality in the following 6 years intervention.

The decline in fine particulate matter (PM2.5) concentrations in the United States between the early 1980s and the early 2000s was accompanied by an improvement in life expectancy, with a gain of over 7 months of life expectancy following the lowering of atmospheric concentrations of PM2.5 particles by 10 μg / m3, which represented a total of 15% of the improvement in life expectancy during this period.

Focus on biomass combustion (residential heating)

In a report published in 2015, WHO states that residential wood or coal heating is a significant source of air pollution both outside and inside buildings (except in the case of efficient heating appliances for the reduction of polluting emissions).

In France, PM2.5 emissions from wood heating were more than halved between 1990 and 2013. Nevertheless, the residential-service sector accounted for 51% of national PM2.5 emissions in 2016.

In addition to particles (especially fine and ultrafine particles, so easily transportable particles over long distances of up to several hundred kilometers), and particulate compounds such as carbon black and organic carbon, the combustion of biomass leads to the emission of various gases with toxic potential for human health in outdoor air and which are in particular carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds ( benzene, formaldehyde, acrolein …), polycyclic aromatic hydrocarbons (aldehydes, phenols …), metallic elements (mercury, arsenic, lead …), dioxins and furans.

According to WHO, particles from wood combustion are associated with an exacerbation of respiratory diseases, particularly asthma and chronic obstructive pulmonary disease (COPD), bronchitis and otitis media.

According to the literature, there is no reason to consider biomass burning particles to be less harmful to health than other urban sources of pollution, but there are few studies on the effects of biomass burning. cardiovascular effects of these particles. On the other hand, there is evidence linking wood burning to certain respiratory symptoms.

Therefore it is crucial to have efficient waste management systems in place so that all waste goes to the proper places, and does not get burnt or thrown in rivers or the sea.