Every day, an adult breathes in 10,000 to 20,000 liters of air, depending on their body type, activities, and other factors… In addition to oxygen (O2) and nitrogen (N2), which together account for an average of 99% of its composition, this air contains pollutants of natural origin (sea spray, dust, pollen, etc.) or resulting from human activities (road traffic, energy production, industry, agriculture, etc.).

The entry of these pollutants into the body can have short- and long-term health consequences.

Short-term risks

Even at low levels, exposure to pollutants can cause, on the same day or in the days that follow, irritation of the eyes, nose, and throat, but can also exacerbate chronic respiratory conditions (asthma, bronchitis, etc.) or increase the risk of a heart attack, and even lead to death.

A study on the short-term impact of particulate matter (PM10) on mortality in 17 French cities between 2007 and 2010 was conducted by Santé publique France. The results show that a 10 µg/m³ increase in PM10 levels on a given day and over the preceding five days is associated with a 0.5% increase in non-accidental mortality. The excess risk is higher among people aged 75 and older (+1.04%), and the effects on mortality are more pronounced in the summer.

These results confirm those of studies conducted since 1997 in France and other countries, most of which have concluded that there is an increase, on the one hand, in mortality and hospitalizations due to cardiovascular causes attributable to fine particulate matter (PM10 and PM2.5), and, on the other hand, an increase in mortality and hospitalizations due to respiratory causes, attributable to ozone (O3) and nitrogen dioxide (NO2) in the summer.

A second study on the short-term impact of nitrogen dioxide (NO₂) on mortality in 18 French urban areas between 2010 and 2014 shows that a 10 µg/m³ increase in NO₂ on the current day and the previous day (0-1-day lag) results in a 0.75% increase in non-accidental mortality (95% CI: [0.4–1.10]). The effects of NO₂ are more pronounced among people aged 75 and older and during the warm season. Thus, a 10 µg/m³ increase in NO₂ is associated with a 3.07% increase in non-accidental mortality the following day among people aged 75 and older. These associations remain stable after adjusting for PM10. These results confirm that exposure to NO2, as a marker of traffic-related pollution, is associated in the short term with mortality, even at concentrations—on an annual average—that comply with European regulations and the WHO guideline value. They also provide exposure-risk relationships that can be used to conduct quantitative assessments of the health impact of air pollution.

Long-term risks

In the longer term, even at low concentration levels, exposure to air pollution over several years can have far more significant health effects than in the short term. Numerous studies demonstrate the role of air pollution in reduced life expectancy and mortality, as well as in the development of cardiovascular diseases, respiratory diseases, and lung cancer. Indeed, through direct cellular toxicity that can lead to genetic alterations, through indirect effects via pro-inflammatory reactions and oxidative stress, and by weakening the body’s defense mechanisms, pollutants can cause:

• cardiovascular effects: a reduction in heart rate variability, an increase in blood pressure and blood coagulability, and the progression of atherosclerosis leading to the development of coronary heart disease (myocardial infarction) and strokes.

• Respiratory system: reduced respiratory capacity, increased bronchial reactivity, and abnormal cell growth that can lead to the development of chronic obstructive pulmonary disease (COPD), asthma, lower respiratory tract infections, and, in some cases, lung cancer.

New studies also show that air pollution plays a role in reproductive disorders, childhood developmental disorders, neurological conditions, and type 2 diabetes.

The results of the monitoring program implemented by Santé publique France show a significant association between rising pollution levels—such as PM2.5 particles—and an increase in the number of deaths. Indeed, the Gazel’Air study used data from the Gazel cohort (coordinated by Inserm’s UMS 11 unit) to establish, for the first time in France, the link between 25 years of exposure to air pollution, mortality, and indicators of cardiovascular disease (CVD), respiratory disease, and diabetes in a study population of over 20,000 volunteer EDF-GDF workers followed from 1989 to 2015.

In this study, increased concentrations of PM, nitrogen dioxide (NO₂), and benzene were associated with an increased risk of all-cause non-accidental mortality. Thus, a 10 µg/m³ increase in PM2.5 was associated with a 15% increase in the risk of total non-accidental mortality. This risk was subsequently used in the quantitative health impact assessment (EQIS) for mainland France.

This assessment showed that in our country, nearly 40,000 people die each year from air pollution, corresponding to a loss of 7.6 months of life expectancy.