A new study has raised serious concerns about the risk to athletes' performance and the health of spectators across Paris, ahead of the 2024 Olympic and Paralympic Games.
An analysis of historical air quality monitoring data for Paris and surrounding areas over previous summers suggests that concentrations of respiratory irritant ozone and pollen will reach high levels during the Olympic Games, which begin on Friday, July 26.
Athletes can be affected by environmental factors, even if they are in generally good physical condition, the researchers say. Breathing polluted air during exercise may pose health risks, depending on exposure levels and underlying long-term conditions, they say.
They say endurance athletes are particularly susceptible to allergies.
To try to estimate the potential impact of air quality on athletes and spectators during the Games, the researchers reviewed historical hourly data between July and September for air pollutants (2020-2023) and pollen (2015-2022).
This data was collected from 50 permanent automated monitoring stations of the Airparif network for the Paris region, and from sensors in the Bio-Aerial Surveillance Network (RNSA).
The researchers focused on levels of ozone (O3), nitrogen dioxide (NO2), and fine particulate matter (PM2.5) at a distance of 12.5 m (the city of Paris) to 50 m (the entire region).
The World Health Organization (WHO) recommends that air quality thresholds (AQT) of 15 μg/m3 per 24 hours for PM2.5, 25 μg/m3 per 24 hours for nitrogen dioxide, and 100 μg/m3 per 8 hours for ozone levels should not be exceeded for more than 3-4 days per year.
The researchers calculated that the average daily maximum PM2.5 particulate matter between July and September was 11 μg/m3 at traffic monitoring stations, which is below the daily air quality threshold recommended by the World Health Organization.
Average daily nitrogen dioxide levels ranged from 5 μg/m3 in rural areas to 17 μg/m3 in urban areas.
Near traffic control stations, this rose to 40 μg/m3, exceeding the air quality standard recommended by the World Health Organization.
Peaking in both cases around 08:00 and 20:00 local time, ambient ozone levels exceeded the WHO recommended air quality standard for 20 days of the month, peaking at 16:00 local time.
Inhaling ozone can cause inflammation of the airways, which can lead to airway narrowing, coughing, and shortness of breath.
The researchers acknowledge several limitations to their findings, most notably the lack of direct measurements at individual Olympic venues, as not all venues have dedicated sensors. The data also did not take into account unexpected changes in traffic during the Games.
But they noted that "although there is a lack of evidence to suggest an additive effect of ozone and PM2.5 on the association between pollutants and mortality, larger effects of air pollutants were observed when temperatures were warmer."
They explained that the data suggests that it is unlikely to be a problem for healthy people, but it may affect those who may be more at risk due to their advanced age or underlying conditions.