Impact of Pollution on Health

Publié le 13 octobre 2023 – Mis à jour le 13 octobre 2023

Author
Valérie Bougaulta
a Université Côte d'Azur, UPR 6312 LAMHESS, EUR HEALTHY, Nice, France

Introduction

The practice of regular and consistent physical activity has long been recognised as an essential factor for good health and aging well [1]. Sportswomen and sportsmen are often considered in our society as a model of good health. For example, Olympic athletes and Tour de France cyclists have a longer life expectancy than the general population [2,3]. However, practicing a physical activity or a sport in unfavourable environmental conditions may not be without danger, even in apparently healthy people [4–6]. For example, many incidents and discomforts occurred during the 2019 athletics championships in Qatar, and isolated health concerns regularly occur during local sporting events, especially when the temperature is hot. During the 2021 Tokyo Olympics, medical teams were prepared and were able to take care of athletes whose core temperatures had sometimes risen to 42°C, potentially fatal for a non-trained person. Scientific research has accelerated in recent years on the effects of heat on the human body of elite athletes, the role and methods of acclimatization to avoid heat stroke (https://pubmed.ncbi.nlm.nih.gov/?term=athletes+heat). The place, dates and times of competitions may be affected by the weather in the future, as was already the case of the Tokyo marathon during the Olympic Games 2021 which was moved to the North of Japan to avoid the too intense heat.

Global warming, due to its obvious risks and effects on the health of the athletes, often masks the effects of atmospheric pollutants to the population, and yet it will be accompanied inexorably by a degradation of the quality of the air [7–10]. Air pollutants, with a few exceptions, are often odourless and colourless and unless they have an external indication (governmental association or individual sensor or World Health Organization, etc.) of their concentration in the atmosphere, few people know that they are exposed to them. However, they have a significant impact on health, causing premature deaths and an increase in emergency room admissions with each pollution episode and with years of exposure [11,12]. Megafires, for example, have been heralded as the future, with the accompanying considerable degradation of air quality, potentially deadly [13,14]. In 2019, Wildfires occurred in Australia during the Australian Open Tennis Tournament, and many players were unable to play due to coughs, nausea, and other various symptoms (https://www.bbc.com/news/world-australia-50497492). Some countries have dramatic concentrations of air pollutants, and sporting events continue to be organised, despite a lack of data on the future consequences on health (https://edition.cnn.com/2019/10/18/asia/delhi-marathon-pollution-intl-hnk-scli/index.html). In 2019, the Iron man in Nice (France), for example, occurred during a heat wave accompanied by an ozone pollution alert. Without resources to know what to do, the organisers reduced the distances randomly without scientific rational to avoid a cancellation (https://france3-regions.francetvinfo.fr/provence-alpes-cote-d-azur/alpes-maritimes/nice/canicule-parcours-ironman-france-nice-2019-raccourcis-1692562.html). Only during the Olympic Games, since at least those of Los Angeles in 1984, are preventative measures taken to reduce local production of pollutants during the event [15], such as reduced traffic [16], but this is not the case for athletes in other events or during the year and we cannot act on the acute pollution linked to natural events like mega fires, or volcanoes. The population of sportsmen and women, who represent a model of health, is too little studied, but is nevertheless a privileged target, because (1) they represent the model of good health in our societies, (2) they have capacities of adaptation and acclimatization often out of the ordinary and sometimes absent or failing in sick or sedentary people, (3) if the practice of a sport in a polluted environment becomes deleterious on their health, this would have dramatic consequences for the future of humanity, which would have the choice between becoming ill while practicing intense sport in an overly polluted environment or not doing so and being exposed to all the chronic diseases linked to sedentary life and pollution. Thus, some current epidemiological data indicate that the health benefits of physical activity (active transport in general) remain greater than the harms of air pollution [17], for example in European societies for healthy subjects. However, in countries where pollution is significant, there are no further benefice of exercise (at a mean ventilation of 63 l/min corresponding to 65% of maximum oxygen uptake) after 15 min (tipping point) and the air pollution health risks surpassed the exercise benefits after 75 min (break-even point) [6]. It should be noted that these studies are far from taking into account the duration and the intensity of the efforts of the sportsmen/women, in particular of endurance, and that often concerns particulate matter (PM) only. Children may also be more at risk of air pollution exposure even at levels slightly below air quality standards [18] and in polluted cities, especially with high level of ambient ozone [19], the most active children have an increased risk of developing respiratory problems, such as asthma compared to less active ones [20].

Air pollution is a generic term, but the chemical compositions and types of pollutants are extremely varied, and it seems that the mechanisms of action of each are different. While some are irritants to the airways, others may be carcinogenic. Air pollutants may be gas (Ozone (O3), nitric oxide (NO), sulfur oxide (SOx), carbon monoxide (CO)) or particulate matter. They may be of primary source, from human or natural origin, or secondary, formed by a photochemical reaction, such as O3 formed through the reaction of sunlight, NO, especially dioxide (NO2) and volatile organic compounds [21]. Particulate matter is a very large category of molecules characterized by the size of the PM, their composition, mass, shape and electrical charge. Generally, they are characterized by their size, PM10 and PM2.5, being generally measured in the atmospheres of the cities worldwide, and with PM1 and ultra-fine particles (PM0.1) being the most studied in health studies. As the inhaled dose, whatever the pollutant, depends on its concentration, the ventilation of the subject, and the duration of exposure, people exercising are particularly exposed to the deleterious effect of pollutants. Indeed, sport and physical activity, through an increase in the person’s breathing, may increase the risk of penetration of pollutants in the airways, lungs, blood, and organs [22,23]. The ventilation a rest is around 6 l/min, it may increase to around 50 l/min in healthy people exercising at light to moderate intensity and 100 l/min in young physically active people at high intensities, but may be sustained for a few hours well above 100 l/min and more than 200 l/min over a few minutes in young elite endurance athletes. There is an insufficient number of studies that can allow us to conclude on the short- or long-term risks of exposure to different pollutants in athletes of different sports, the regulations to be adopted, to identify healthy people at risk, and also the management and prevention plans to be adopted (nutrition, medication…) [23–25]. The international sports federations have tried to regulate, for many years, the conduct of competitions in cold or hot temperatures, taking into account the WBGT [26–28] (https://www.ccsam.ca/competitive-skiing/event-information/event-cancellation-policy-2/) . In case of a health threat, they have the possibility to cancel or postpone competitions, and these policies are currently well applied. In case of high pollution level, there is no rule at all, and we don’t know what to do.

Several scientific publications have very recently underlined the lack of studies on the effects of the different pollutants on the respiratory health of healthy people performing an exercise. Only ozone has been studied, especially by Californian teams in the 80s, and shows an obvious impact on pulmonary function and respiratory difficulties. In view of the Los Angeles Olympic Games in 1984, research was carried out, in particular because of the recurrent high ozone concentrations in this region [29,30]. Ozone is the pollutant that usually accompanies heat waves and is of particular concern for the future. Worryingly, it may be locally more difficult to reduce ozone concentrations than those of PM for example (by reducing traffic for example). After the COVID-19 lockdown period, PM and NO2 emissions (mainly related to reduced traffic), were drastically reduced in Europe and China [31]. On the other hand, ozone increased in the same cities studied [31]. In healthy non asthmatic non allergic adults, it may provoke severe falls in lung volumes, sometimes around 50% during light to moderate exercise, and even more in asthmatics [23–25,32]. As a consequence, rare studies showed that up to 40% of a group of healthy well-trained athletes may stop exercise when performed in the presence of ozone concentrations similar to episodes of pollution observed in Europe, due to a severe respiratory discomfort [32–34]. Some rare studies of concern suggest that regular inhaled corticosteroid treatments may have no effect on airway response to ozone [35–37], and may even worsen symptoms and fall in lung function when exposed to ozone in people with respiratory pathologies[38,39]. This is of particular concern because inhaled corticosteroid therapy is the preferred treatment for inflammation in many lung or airway diseases (asthma, chronic obstructive pulmonary disease), but also for athletes having exercise-induced bronchoconstriction (“exercise induced asthma”) [40]. It is now well-known that endurance sport may favor the development of such diseases due to the high-level of ventilation but also inhalation of pollutants [41]. In a disturbing way too, only a few studies exist but report the complete inefficiency of inhaled Beta2-agonist (Salbutamol, albuterol) to reverse the fall in lung function due to ozone when exercising in elite non-asthmatic cyclists [42,43]. This medication is the rescue medication or taken as a preventive measure by many asthmatics, whether or not they are athletes, and particularly before exercise to avoid an attack of exercise-induced asthma. The mechanisms of the fall in lung function due to ozone and of asthma crisis may be different and it may explain why inhaled medication is less effective during ozone peaks and why asthmatics lose control of their disease, leading to emergency room visits and death for some.

LAMHESS’s (Université Côte d’Azur, France) associate colleagues, who work for the World Athletics Medical Commission, have continuously measured pollution in athletics stadiums around the world since 2019 and aim to see the effects on the health and performance of athletes, but also to plan the schedules and dates of sports events accordingly. Our laboratory (LAMHESS) is also represented regularly in international working groups on sport, health and pollution, including the International Olympic Committee (IOC) medical commission. LAMHESS aspires to bring together researchers from around the world working on pollution, health and performance to accelerate the production of knowledge in regular athletes, elite or not. This network is nascent but will allow the standardization of studies between countries because the multidisciplinary nature of studies requires toxicologists, atmospheric chemists, epidemiologists, sports science specialists, physiologists, specialized doctors, nutritionists, international sports federations, etc. Our studies will relate on the one hand to field measurements, with measurement of the pollutants and physiological variables in situations of exercise by practitioners, and on the other hand will relate to exposure in inhalation chambers to better understand the mechanisms of each pollutant. We will look at a wide range of parameters such as the mechanisms of action of various pollutants, including various types (gas, particulate, etc.), and composition, why some subjects are sensitive and others not, what is the recommendation threshold for air pollutants according to their properties for postponing or cancelling a mass or elite sporting event, what are the management and prevention plans, etc. The risk of not accelerating the pace of these studies is to find ourselves without a solution to save people sensitive to pollutants (the current medication being insufficient for some pollutants) and to see an increase in the number of deaths or respiratory or other diseases among athletes during events, training or in recreation courses. For now, when an acute air pollution episode is announced in Europe (in general level 2 or 3), sensitive people (adults and children) with asthma or chronic disorders are currently told not to do physical activity in order to avoid emergencies and death. With the air pollution accompanying global warming, it is likely to affect more and more people and finally what will we do? Force everyone to stop doing sports, knowing the harmful impact of physical inactivity?
 

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