Air pollution increases the risk of occurrence and severity of illnesses that are sometimes disabling and fatal.

Exposure to air pollution increases the risks of contracting or worsening a large number of pathologies that reduce quality of life. Some are particularly debilitating and cause premature death.

 

All the bodies concerned

Exposure to air pollution first harms the functioning of the respiratory system. On average, an adult breathes around 12 liters of air every day. Via the mechanism of respiration, we are therefore exposed to pollutants present suspended in the air. Exposure to gases and polluting particles thus increases the risk of occurrence and worsening of lung cancer, chronic obstructive pulmonary disease (COPD), asthma and laryngitis.

But this exposure to air pollution has a more global impact on all organs, systems or functions. The finest particles, in particular, can pass the pulmonary barrier and enter the blood circulation, then irrigating the various organs. Air pollution thus increases, for example, the risks of contracting or worsening myocardial infarction (also called heart attack), stroke, Parkinson's disease, or type 1 or 2 diabetes. .

Main impacts of air pollution on health

The risk of occurrence and severity of pathologies linked to air pollution varies depending on the air pollutants: the air pollutants identified as being harmful to human health in a country like France are particles (including fine and ultrafine particles), nitrogen dioxide, low-level ozone, sulfur dioxide and carbon monoxide.

The International Agency for Research on Cancer (IARC), a specialized agency of the WHO, classified outdoor air pollution and more specifically particles as carcinogenic in 2013.


 

Certain particularly sensitive populations

Epidemiological studies show that age, state of health - and therefore indirectly precariousness - and genetic predispositions influence sensitivity to air pollution. Certain population groups, such as children, the elderly and individuals suffering from chronic respiratory or cardiovascular pathologies are particularly concerned by the effects of air pollution. 

For example, older people are more susceptible due to a reduction in their antioxidant capacities and the adaptation capacity of their defense system. As exposure to certain pollutants leads to a reduction in peripheral oxygenation, an increase in blood viscosity and changes in heart rate, people suffering from coronary or heart failure are more sensitive to air pollution. In aging societies, sensitivity to air pollution is therefore likely to increase.

 

The example of the great smog of London

Awareness of the effects of air pollution on health owes much to a tragic episode that occurred in London between December 5 and 9, 1952.

For five days, a thick cloud of smoke coming from factories and individual coal-fired heaters stagnated over the London area. Concentrations of particles and sulfur dioxide have reached concentrations of up to 1600 and 2800 micrograms per cubic meter respectively (current concentrations are more of the order of a few micrograms to a few tens of micrograms per cubic meter in Paris and in London), leading to an exceptional excess mortality. A recent analysis brings the number of excess deaths observed up to February 12 to 000.

This health disaster has raised awareness among public opinion and public authorities. It led to the creation of specific legislation to combat air pollution: the Clean Air Act (1956) in the United Kingdom, the Air Pollution Control Act (1955), then Clean Air Act (1963, extended in 1970) in the United Kingdom. United States, and the Law of August 2, 1961 in France. 

 

 

Air pollution, harmful in the short and long term

 

Effects of acute exposure to pollution

Acute exposure to air pollutants – exposure to certain concentrations of air pollutants on the order of an hour or a day – has short-term health impacts that can occur in the following days until a few weeks after exposure.

Epidemiological studies thus show that exposure to daily variations in the concentrations of air pollutants (notably particles, low-altitude ozone, nitrogen dioxide and sulfur dioxide) has a short-term impact on health, particularly on hospitalizations and mortality. It is to mitigate the impact of acute exposure to high concentrations of air pollution that emergency measures can be put in place as part of the transition to an air pollution episode.

 

Effects of chronic pollution

Chronic exposure to air pollutants, namely exposure to air pollutants over long periods (several years) has impacts on human health that can occur in the medium or long term.

Exposure to air pollutants does not only have short-term effects, particularly on the most vulnerable part of the population. It also has a significant long-term impact on the life expectancy of the entire population, and the results of epidemiological studies show that these effects are preponderant compared to the short-term effects of pollution.

If the intensity of health risks linked to air pollution is lower than that of other risk factors such as tobacco or alcohol, the size of the exposed population being large, the benefit associated with a Reducing population exposure to pollutants is important in terms of public health.
 

 

Finding your way around the dangerousness thresholds of air pollution

Several thresholds exist to understand the impact of exposure to air pollution on health.

Air pollution thresholds recommended by the World Health Organization (WHO) correspond to the concentrations of air pollution from which an international scientific consensus exists to affirm that from these thresholds, exposure to an air pollutant is harmful to health. These thresholds concern either chronic exposure or acute exposure to air pollution (see detail). The more these thresholds are exceeded, the greater the impact of air pollution on health.

Regulatory limit values correspond to the maximum concentrations of air pollutants that French and European regulations set as not to be exceeded in order to avoid, prevent or reduce harmful effects on human health or the environment. These limit values ​​concern chronic pollution. These thresholds, which date from 2008 and must soon be lowered from 2030, are higher than the thresholds recommended by the WHO (see detail).

Regulatory information and alert thresholds correspond to the concentrations of air pollution observed over a day or an hour from which French and European regulations require the implementation of emergency measures to limit the short-term impacts of air pollution on health. In common parlance, we speak of an episode of air pollution. They correspond to acute exposure to air pollution. (see detail).

 

The health impact of air pollution, a science in motion

Several recent studies open new avenues of understanding on the impact of air pollution on health, an area in which scientific research regularly advances knowledge.

Although we have known for a long time that the impact of air pollution on health is not strictly proportional to the concentrations of pollutants in the air (linear exposure-response relationship), these studies seem to show that this impact would be greater per unit of exposure at lower concentrations (supralinear exposure-response relationship). If confirmed, this would imply that current epidemiological studies would underestimate the impact of air pollution on mortality in areas of low exposure.

Other epidemiological studies tend to show that there is no threshold below which no health effects are observed, particularly concerning fine particles. In this regard, the WHO emphasizes that the recommended thresholds are levels above which serious health effects occur with high certainty: this means that below these levels, health effects can nevertheless be observed and should be investigated to be better understood.
 

 

A significant health impact in Île-de-France

Epidemiological studies show that the levels of pollutants currently observed in Île-de-France are still harmful to health.

 

In Île-de-France

The reference study in Île-de-France, carried out by the Île-de-France Regional Health Observatory on the basis of Airparif data, estimates that air pollution is responsible for 7 premature deaths each year in the region, representing a loss of life expectancy of almost 900 months, and 10% of total mortality in Île-de-France. These impacts would be avoided by reducing the concentrations of fine particles, nitrogen dioxide and low-altitude ozone below the thresholds recommended by the WHO.

However, this impact on health is decreasing, due to the reduction in emissions and concentrations of air pollutants over the last 20 years. For example, the impact of fine particles on health in Île-de-France fell by 40% between 2010 and 2019 (see detail).

Impacts of air pollution in Île-de-France

These estimates relate to premature deaths which is the most serious consequence of exposure to air pollution, but pollution also causes non-fatal but disabling pathologies.

Pyramid of the effects of air pollution

Pyramid of the effects of air pollution

(source: Montreal Public Health Department - 2003)

 

In the world, in Europe and in France

Worldwide, the WHO estimates that air pollution – indoors and outdoors – is responsible for 6,7 million premature deaths each year, 89% of which occur in low- and middle-income countries (see detail). For the WHO, air pollution is one of the greatest environmental risks to health and, along with climate change and the collapse of biodiversity, is one of the three major planetary crises.

The European Environment Agency (EEA) estimates that air pollution is the greatest environmental risk to health in Europe. It estimates that air pollution was responsible, in 2023, for 253 premature deaths in Europe (see detail).

In France, Public Health France (SPF) estimates that air pollution is responsible for 40 premature deaths each year, representing a loss of life expectancy of nearly 000 months, and 8% of total mortality in the population. French population (see detail).

 

 

How do we know that air pollution is harmful to health?

Epidemiological studies carried out since the 1990s show that exposure to air pollution leads to an increased risk of certain pathologies and excess mortality, which is a consensus in the scientific literature.

These studies are based on the statistical analysis of the relationships observed between indicators of exposure to air pollutants (ambient concentrations of particles or polluting gases) and the occurrence of health events in the population (death, hospitalizations for a pathology data, asthma attacks seen in medical consultation, etc.). 
For the study of short-term effects, they are based on the comparison of hourly or daily variations of air quality indicators (concentration of pollutants in ambient air) and the short-term occurrence of health events.

To study long-term effects, cohort studies are based on the comparison of annual or multi-annual variations of air quality indicators (concentrations of pollutants in ambient air measured or modeled) and the occurrence at medium or long term health events. The latter take into account numerous individual factors (age, sex, smoking, education level, body mass index, etc.) to specifically identify and characterize the health impact of air pollution. They require relatively long follow-up and the participation of a large number of subjects.

In addition, toxicological studies provide insight and biological rationality to the statistical relationships highlighted in epidemiological studies, highlighting mechanisms of action specific to pollutants commonly encountered in the atmosphere: mechanisms of irritation, inflammation , oxidation, reduction in the ability of blood to carry oxygen, etc.

The concordance and consistency of these studies support the causal nature of health risks from air pollutants.
 


Air pollution and COVID-19

Beyond the impact of confinement on the reduction in pollutant emissions, from a health point of view, links between COVID-19 and air pollution have been highlighted during the pandemic from different angles :

  • the health impact of air pollution is an aggravating factor in the epidemic;
  • confinement at home calls for vigilance regarding the quality of the air inside one's home;
  • Air pollution is a factor in the spread of the SARS-Cov-2 virus.

To better understand these issues, read the analysis of health specialists from the Association for Pollution Prevention.

The impacts of containment measures on air pollution in Île-de-France, particularly on pollutants from traffic and permitted tertiary and industrial activities, have been documented by Airparif and its counterparts in the different French regions as well as by L'INERIS on a national level.

 

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