Article Text
PDF
Abstract
The upcoming Paris 2024 Olympic and Paralympic Games could face environmental challenges related to heat, air quality and water quality. These challenges will pose potential threats to athletes and impact thousands of stakeholders and millions of spectators. Recognising the multifaceted nature of these challenges, a range of strategies will be essential for mitigating adverse effects on participants, stakeholders and spectators alike. From personalised interventions for athletes and attendees to comprehensive measures implemented by organisers, a holistic approach is crucial to address these challenges and the possible interplay of heat, air and water quality factors during the event. This evidence-based review highlights various environmental challenges anticipated at Paris 2024, offering strategies applicable to athletes, stakeholders and spectators. Additionally, it provides recommendations for Local Organising Committees and the International Olympic Committee that may be applicable to future Games. In summary, the review offers solutions for consideration by the stakeholders responsible for and affected by the anticipated environmental challenges at Paris 2024.
- IOC
- Elite performance
- Water Sports
- Public health
- Hot Temperature
Statistics from Altmetric.com
WHAT IS ALREADY KNOWN
As seen at prior Olympic and Paralympic Games, a variety of location and sport-specific environmental challenges are experienced by athletes, stakeholders and spectators.
Paris will be no exception, with expected environmental challenges fluctuating and often combining within and between days of the Games period, presenting a variable challenge to maintain the health and performance of athletes, stakeholders and spectators.
Paris is a climate changed city and many of these environmental challenges have intensified over recent years (even since Paris was awarded the Games officially in September 2017).
WHAT ARE THE NEW FINDINGS
Extremes of heat, humidity, air and water pollution are likely at some point during Paris 2024, and although the environmental conditions could be fortuitously favourable from a Games perspective (eg, temperate, low rain fall, good air quality), this is unlikely and all attendees must be prepared appropriately and supported by evidence-informed Local Organising Committee/International Olympic Committee-facilitated infrastructure, logistics and policies.
There are a variety of evidence-informed recommendations that can be adopted by athletes, stakeholders and spectators to mitigate the negative health and performance effects of these environmental challenges.
Some athletes (eg, outdoor and/or endurance athletes) are more susceptible to the deleterious effects of these environmental challenges to their health and performance and could face combined environmental challenges (eg, triathletes could face heat, humidity, high ozone concentration and poor water quality).
Personal responsibility and organiser-delivered/facilitated infrastructure and policy are required to limit the negative effects of environmental extremes on the health and/or performance of all those attending Paris 2024.
Introduction
Unprecedented logistical and environmental challenges were faced at the Tokyo 2020 Olympic and Paralympic Games.1 These included heat,1 humidity2 and air quality3 from an environmental perspective and a myriad of logistical factors due to the COVID-19 pandemic.4 Similar or greater environmental challenges could be faced at the Paris 2024 Olympic and Paralympic Games (July–September 2024).5 Indeed, Paris is a city particularly affected by climate change,6 facing heat-related and air and water quality issues at many competition venues.7 Many of these factors have been shown to compromise the health of athletes,2 8 9 decrease elite athlete performance (mainly endurance and outdoor team athletes10 11) and/or affect the health of other attending stakeholders.12 Therefore, varied inter-related environmental and associated logistical challenges will be encountered at Paris 2024 by athletes, stakeholders (ie, volunteers, practitioners, on-site workers and journalists) and spectators, including, but not limited to: (1) varied physical and physiological event requirements; (2) diverse changeable environmental conditions; and (3) a myriad of athlete, stakeholder and spectator-specific factors (eg, sex, anthropometry, event/discipline/activity, competing/working/spectating, classification, acclimation status, medical history, type and severity of disability). Individualised (ie, based on the individual’s needs and specificities), practitioner-led and evidence-informed practice will be required to optimise athlete, stakeholder and spectator health, and performance at Paris 2024. Therefore, this evidence-based review, drawing extensively from recent recommendations and consensus reached by expert groups, will:
Outline specific environmental challenges that athletes, stakeholders and spectators may face at Paris 2024.
Provide athlete-centred, practice-led and evidence-informed solutions to meet the above challenges.
Provide stakeholder/spectator-centred, practice-led and evidence-informed solutions to meet the above challenges.
Provide recommendations for Local Organising Committee (LOC) and International Olympic Committee (IOC) ‘expert’ groups.
Adopted methods and approaches
Data were obtained from a variety of sources (as indicated) including personal communication with experts outside of the authorship. Recommendations were initially outlined by authors LM and LT and whenever possible align with existing consensus, meta-analysis, reviews and best practices (as cited). Refinement and consensus between authors were reached via four rounds of author revisions. These recommendations (summarised in figures 1 and 2) are realised through a combination of best practice guidelines (as cited) and author experience (including but not limited to substantial involvement with elite athletes, Olympic/Paralympic sport and a variety of non-Olympic/Paralympic elite sports: sport practitioners, sport researchers/scientists, sport clinicians and medical doctors, and members of international federations, governing bodies, LOCs and IOC Olympic/Paralympic ‘expert’ groups). Limitations of these approaches are provided within the relevant section.
EDI statement
Our recommendations for Olympic and Paralympic athletes, as well as for all audiences, are developed with the aim of including and providing useful information to everyone. Our authors, including females and males and researchers with different backgrounds (young researchers, lecturers and professors), represent diverse perspectives from around the world.
Athlete recommendations and strategies to face environmental challenges at Paris 2024 Olympic and Paralympic Games. LOC, Local Organising Committee.
Spectators and stakeholders’ recommendations and strategies to face environmental challenges at Paris 2024 Olympic and Paralympic Games. LOC, Local Organising Committee.
Paris 2024: heat stress expectations and associated risks
Tokyo 2020 saw the hottest (hot/humid) Olympic and Paralympic Games on record.1 When Paris was awarded the Games (13 September 2017), summer heatwaves were exceptional yet have occurred every year since (excluding 2021). Indeed, temperatures are widely predicted to exceed 30°C regularly across the Games (see figure 3) and may reach 40°C should a heatwave comparable to 2022 occur.13 Moreover, average relative humidity in Paris during the summer months is around 70–80%.14
Temperature history and forecasts for Paris 2024.14 Average maximal temperature represents the daily maximal temperature over Olympic Games (OG) or Paralympic Games (PG) period. Worst expectations for Paris 2024.5 OG period: 27 July (first competition) to 11 August. PG period: 29 August (first competition) to 8 September.
Endurance (eg, road cycling, mountain biking, middle-distance running) and other sports with prolonged exposure to heat (eg, tennis, team sports) are scheduled for the afternoon and evening, when temperatures are expected to peak (temperatures >41°C observed after 19:00 hours in 2019). Thus, the likelihood of heat-related issues are significant. Additionally, staging some of Paris 2024 events in the city centre, such as triathlon, race walking and marathon, with limited shade and urban heat islands, could increase the potential for heat-related problems further.15 However, some precautions have already been taken for some events, with for example triathlon and marathon start times altered to 08:00 hours.
A proxy of likely Paris 2024 conditions5 were seen at the 2023 World Athletics Championships in Budapest (19–27 August), where temperatures reached 35°C and 90% relative humidity (wet-bulb globe temperature (WBGT) >33.5°C; index accounting for air temperature, humidity, radiant heat and air movement, with values >31°C representing a very high to extreme risk of heat illness). At both Tokyo 2020 and Budapest 2023, significant countermeasures were taken by the international federations, IOC expert groups, LOCs (events changing time and locations, often with relatively short notice2) and athletes/practitioners (behavioural and interventional thermoregulatory strategies employed16). However, logistical changes do not always yield the desired effects (eg, WBGT remained >30°C in Sapporo during the relocated Tokyo 2020 Olympic walk and marathon events), resulting in 50 athletes out of 368 (48 of these 50 showing signs and symptoms of exertional heat illness (EHI) being transferred to a medical station.2 Clearly, adapted policy can mitigate risks and the decline in athlete performance,17 but can fail if poorly planned and/or communicated. In addition, many Paralympic athletes are likely to be at greater risk of heat-related illnesses due to reduced thermoregulatory capacities (eg, reduced sweating capacity, lower convective surface area, additional sports equipment depending on their impairments18). Athletes/practitioners have a variety of long-term and short-term heat mitigation strategies to consider19 and ideally pilot/integrate into their event preparations.10
Although many athletes are most at risk of EHI because of their heat production during exercise, spectators and some stakeholders can also be affected by heat illness. At Paris 2024, a total of 45 000 volunteers and several million spectators20 will attend the Games. Many of these are often less ‘fit’ than athletes, with different age, weight and both known and unknown medical challenges (ie, obesity, cardiovascular and respiratory diseases), potentially reducing their resistance to heat21 while increasing their risk of heat-related illnesses and mortality during heatwaves.22 This is particularly true when they (and other stakeholders) are not acclimatised to the heat23 and have long heat stress exposure periods during spectating or other event responsibilities. If these long exposures are combined with inappropriate clothing (eg, is dark coloured, without sun projection and does not facilitate heat exchange), poor hydration practices and/or no sunscreen, among other factors outlined above, EHI becomes more likely.23 Untreated and/or unrecognised heat illness can be fatal in athletes, spectators and stakeholders, even without engaging in physical activity. For example, prior to the Tokyo Olympics a mascot from an amusement park died of heat stroke.
Athlete-centred heat mitigation strategies
Long-term heat mitigation strategies
Two weeks of heat acclimation (ie, artificial exposure)/acclimatisation (ie, natural exposure) (HAc) provides the most robust performance and health protective effects during exercise in the heat.10 Typically, this entails undertaking 14 days of daily exercise (60–90 min) with a core temperature ≥38.5°C.24 If active HAc is not possible for any/all sessions, other methods increasing core and skin temperatures, sweating and skin blood flow,10 24 such as passive HAc (eg, postexercise sauna ≥80°C and/or hot water immersion ≥40°C for ≥40 min25), can be adopted for any/all sessions.26 Passive HAc can be used to preserve the quality of the active part of an athlete’s training (or those with extensive technical and tactical training requirements such as team sport athletes). This method is particularly useful to ‘top-up’ HAc during an athlete’s taper to avoid interference with the consolidation of adaptations procured through their final preparation/training phases (it may also be useful for non-endurance athletes, such as shorter distance or explosive events26). With long-term HAc, heart rate and core temperature during exercise decrease, although from predominately non-elite samples, but similar responses are observed with elite athletes.27 Self-reported HAc adoption resulted in fewer race withdrawals (ie, 19% vs 30%) and better performance (eg, ranked better; 18th vs 28th position) at several World Championship race walking and running road race events.17 28 Meta-analytical review of performance improvements (mainly in endurance sports) suggests improvements of ~15% with short-term HAc (ie, <7 exposures), ~21% with medium-term HAc (ie, 8–14 exposures) and ~22% with long-term HAc (ie, >15 exposures27). While short-term HAc can procure relevant adaptations, these are not as complete as long-term HAc and thus do not convey the same magnitude of health and performance benefits while their positive effects return to baseline (eg, decay) more quickly.27 Given that 5–7 days of reacclimation are sufficient to regain acclimation after 2–3 weeks without heat exposure (after initial 2 weeks’ HAc), potential HAc periodisation would include 2 weeks’ HAc several weeks before competition, followed by 2 weeks of normal training (including some active/passive heat exposures) and 1 week of reacclimation before competitions,29 provided the athletic taper is not compromised. Moreover, adaptations from HAc are not detrimental to endurance performance during temperate competition,30 although whether they are advantageous has been debated.31 Although these recommendations are mainly aimed at improving performance in endurance sports or situations involving prolonged exposure to heat, HAc may be beneficial for non-endurance and non-outdoor events (for both Olympic and Paralympic athletes18), where it will improve thermal tolerance and comfort to heat stress during non-athletic activities of daily life and between heats of non-endurance competition, without detriment to athletic performance.26 32
Short-term pre-event or competition-day focused strategies
To limit heat strain on the day of competition, several focused strategies can be used.33 Precooling (~2–7.1%) and mid-cooling (~3.2–11.9%) can improve exercise performance in the heat34 35 across endurance and team sports,36 yet precooling is detrimental for short-duration explosive efforts.37 Although much of these data rely on non-elite athletes,35 both precooling and mid-cooling are now used by many elite athletes at major events (ie, 80% of athletes adopted precooling and/or 93% used mid-cooling at the Doha 2019 IAAF World Athletics Championships38; 77% of athletes used precooling or mid-cooling at Tokyo Paralympic Games16). These strategies can include various combinations of internal (eg, ice slurry/ice cold water ingestion), external (eg, immersion, ice vest, ice cold hat, ice filled towel and other cold exposures) and perceptual (eg, menthol mouth rinse) strategies.33 When and how they are used are event and athlete specific whilst often limited by event rules and practice realities (eg, time and resource available). Illustrated evidence-informed examples for endurance and team sport athlete recommendations can be found elsewhere.33 39 In brief, precooling and mid-cooling strategies are piloted away from competition and integrated into an athlete’s precompetition and during competition routine (eg, a phase change ice vest worn when a team sport player warms up before a game and at half time alongside ice slurry ingestion and ice towel application; ice slurry ingestion and ice towels in the ‘call room’ prior to and during road races). With all cooling manoeuvres, it is important to consider any unwanted side effects (eg, gastrointestinal (GI) disturbance, altered sweat response, disrupted pacing from central to peripheral sensation integration) and how altering thermal sensations through body cooling may alter heat-related illness risk; however, if done appropriately, the favourable core to skin temperature gradient elicited from effective mid-cooling should reduce heat-related illness risk.38 Postexercise cooling can be used to accelerate acute athletic recovery, such as delayed-onset muscle soreness.33
Cooling methods can be complemented by nutrition and hydration strategies to limit hypohydration to ≤2%40 and to optimise electrolyte and carbohydrate feeding41 which must be preplanned according to individual responses, tolerances and race-specific needs. Behavioural strategies such as adapted pacing strategies are often naturally used in the heat,42 but specific and practised pacing and tactical strategies could contribute to prevent decreased performance.43 Such pacing-related practice and ultimately race execution could be particularly challenging for Paralympic athletes with compromised peripheral-to-central feedback processes and/or thermoregulation44 or with intellectual impairments when executing defined pacing strategies. Ideally, all these interventions complement prior long-term HAc33 and must be integrated into an environment-specific competition-day plan, undergoing extensive piloting reflective of the most challenging competition-day scenario. Other strategies on competition day include clothing (ie, light-coloured, loose-fitting, sun-protective clothing), sunscreen (ie, sun protection factor ≥25 using a water-based organic chemical sun filter), modified warm-up practices (ie, lower duration and/or intensity) and shade.24
Stakeholders and spectator-centred heat mitigation strategies
Unlike most athletes, stakeholders and spectators may not be adequately aware of and/or prepared specifically for the weather at Paris 2024. Yet, potentially underpublicised and misunderstood heat-related risks may challenge stakeholders/spectators. For example, they are likely to stand/sit in a hot environment for several hours with limited or no natural/artificial shade, with compact viewing areas increasing heat and humidity and decreasing airflow, which together compromise evaporative cooling.23 These risks present further in urban sports where artificial urban materials frequently reach temperatures ranging from 50°C to 80°C under intense solar radiation.45 The HAc and cooling methods recommended for athletes (described earlier) are certainly of value to non-athletes, even if their implementation is sometimes complicated and requires certain precautions with at-risk populations. Advising spectators to: (1) limit their exposure to the heat by controlling time spent outside in hot temperatures46; (2) wear appropriate clothing (including sunglasses and well-ventilated caps/hats) and sunscreen, as described above24; (3) stay properly hydrated and carry non-alcoholic drinks to the venue; (4) avoid overcrowded areas (eg, the last kilometre of races) and urban materials (eg, concrete, brick, metal surfaces) where possible; and (5) protect themselves from high solar exposure using shaded areas with cooler surfaces including green and blue spaces (eg, trees and buildings, provided their surfaces remain cool and are not directly exposed to radiation23) all appear prudent. Additionally, those taking medications should understand their possible undesirable interaction effects on thermal tolerance/responses (eg, altered thermoregulatory control46). Comprehensive and individualised precautions, to be discussed with medically qualified personnel, should also be taken by people with obesity, cardiovascular disease, respiratory disease, diabetes and those ≥60 years old, who are particularly susceptible to thermal stress and related illnesses.47
Recommendations for LOC and IOC ‘expert’ groups
In the event of extreme competition-day heat, the priorities of the organisers, medically qualified personnel and the LOC will be to avoid an unmanageable number of heat-related problems for athletes, stakeholders and spectators. This approach should encompass prevention, management and treatment of heat-related illnesses. Prevention involves implementing evidence-informed education and effective communication strategies about heat risks, cooling strategies and benefits of HAc, as provided by IOC, World Athletics and World Triathlon at previous events.24 In previous events held in hot/humid environments, such as the Doha 2019 World Athletics Championships (ie, WBGT 23–31°C), 37% of athletes (ie, marathon runners and race walkers) did not have a dedicated heat preparation period17 despite the predicted and observed conditions markedly increasing their vulnerability to heat-related illnesses and performance decrements. Clearly showing that not all elite athletes adopt evidence-informed preparation strategies,17 in part due to a variety of barriers (eg, climate, cost, knowledge) which are discussed elsewhere.39 During Paris 2024, organisers will have to work closely with the meteorological services and set up on-site weather stations to provide detailed yet understandable weather forecasts. Detailed forecasts (including worst-case scenarios) will be imperative for long-term planning (ie, weeks prior to the event) to develop effective pre-event mitigation strategies and short-term/real-time decision-making (ie, days and hours leading up to the event) for competition-day athlete, stakeholder/spectator and LOC decision-making alongside practical recommendations.
Across competition venues, diverse microclimate environments are seen in part through an array of competition surfaces, related built environments and spectator seating/standing. These hyperlocal and location-specific data must be representative of the real-world/real-time competition environment that will be encountered by the athlete and other stakeholders/spectators at each specific venue24; ideally accurate predictions to enable planned rather than reactive decision-making. Policies and procedures for schedule and venue changes to lower heat-related risk should be planned and shared widely in advance to athletes’ staff, to ease their integration into athlete competition-day preparations. During competitions, organisers should provide freezers for ice jackets and drinks in the start/finish/competition areas and refuelling zones, to aid athlete cooling and encourage teams to monitor athlete core temperature through ingestible telemetric thermometer pills (although adoption is costly and may be out of reach for some athletes/federations). Moreover, for athletes as well as stakeholders and spectators, shaded areas, readily accessible water fountains and ice dispensers, sunscreen, caps, umbrellas and air blowers should be provided,23 38 in addition to enabling them to carry non-alcoholic drinks freely to, within and between venues. Organisers should ensure that appropriate clothing, as described above, is provided for volunteers and other stakeholders who are wearing additional mandatory items such as bibs. Heat can, in a situation-dependent manner, affect spectators and Games volunteers to a greater extent47 than athletes (due to longer exposure times) and evidently in potentially greater numbers.48 Education and specific training for medical services, but also for volunteers and spectators about heat stroke detection, will be essential for early recognition (ie, signs and symptoms) and effective treatment. Heat stroke management and treatment protocols require medically qualified personnel (ie, four caregivers for one patient) and organisers to be well equipped for rapid cooling (ie, cold water baths) before hospital transfer,49 for both athletes and other at-risk stakeholders and spectators. For quick transfer of collapsing athletes, a wheelchair to starters ratio of 1:5 is recommended.17 Rectal temperature probes will be necessary to assess core temperature accurately and continuously. Lowering core temperature will mainly require immersion in cold water. In Tokyo 2020, >20 tonnes of ice were used at the competition venues and ~2200 kg/day for the Athlete Village Polyclinic.24 A similar, if not higher, quantity should be pre-emptively planned for Paris 2024. Use of a point-of-care blood analysis device is also recommended for conducting blood sodium and blood glucose analysis to differentially diagnose the collapsed athlete’s medical condition to transfer only people requiring hospitalisation.49
Paris 2024: air pollution expectations and associated risks
As the Athlete Village at Paris 2024 will not have air-conditioning, it is plausible fans and open windows will be a predominant method of cooling and that athletes will spend considerable time outside in shaded and naturally ventilated areas. Therefore, while pollution per se may be lower in Paris compared with Tokyo, total exposure could be markedly higher in Paris (see table 1 for specific comparisons). Marathon runners, walkers and triathletes may face heightened risks, especially since these events typically occur in the early morning when particulate matter (PM) concentrations peak due to rush hour traffic. In addition to endurance sports, athletics and outdoor team sports (among several other) events entail particular risk, as they will take place during pollution peaks (ie, ozone (O3) and PM, in the afternoon and evening) in stadiums located near major roads.
Annual mean of air pollutants in Paris in 2022 compared with World Health Organization (WHO) recommendations and Tokyo 2021
Air quality is determined by the concentrations of various pollutants, most notably by nitrogen dioxide (NO2), O3 and PM with a diameter of less than 10 (PM10) or 2.5 (PM2.5) μm. O3 is generally the dominant pollutant on sunny, warm days, with a uniform regional distribution, while PM and NO2 tend to display a more localised distribution depending on meteorological conditions, vehicle traffic and other emission sources. The 2008 Beijing Olympic and Paralympic Games took place in a highly air-polluted location, although air quality improved during the Games.50 This led to considerable interest in the effects of air quality on athletes’ health and performance prior to Beijing.8 The air quality is less a concern in Paris than Beijing. However, as with most capital cities in Western Europe, yearly air quality in Paris is above WHO-recommended levels (table 1 51), with O3 concentrations above those observed in Tokyo in 2021,52 although the situation has improved over the last 10 years (eg, −30% in NO2). Moreover, O3 concentrations are increased during extreme climate events (eg, 2022 Paris heatwave) and exacerbated with associated anticyclonic events while PM concentration may be increased by specific events such as wildfires.53 Other compounding factors include the increase in transport-related pollution during the Games,54 especially around highways and similar motor transport congestion areas. Although a planned reduction in traffic at the competition venues could lead to a reduction in PM concentrations, this could also lead to adverse effects such as an increase in O3 concentrations.52
Health effects associated with various pollutants are contingent on factors such as their nature (ie, O3 and PM may affect different populations), concentration and duration of exposure. Millions of spectators may be exposed to air pollution at Paris 2024, increasing their risks of respiratory and cardiovascular diseases, morbidity and mortality,55–57 although these risks increase in the case of long-term exposure. In addition to affecting spectators, effects could be exacerbated for athletes. In a systematic review of randomised controlled trials, specific evidence of O3 exposure having deleterious effects on respiratory symptoms and lung function while exercising was reported, without such effects for other pollutants.58 Further, some individuals were more susceptible to these effects than others.59 Indeed, some athletes (particularly endurance athletes) appear very susceptible even at low concentrations of O3.59 Despite this variance, generally a dose–response is seen with higher concentrations eliciting more severe negative symptomology in endurance athletes. Together, these data suggest air pollution (especially in sensitive athletes) deleteriously affects athlete health8 and performance (eg, maximal or optimal performance capacity across a variety of sports60). Mechanistically, acute air pollution exposure (with pollutant specificity) can reduce oxygen delivery to tissues, increase oxidative stress and inflammation61 and increase respiratory-related symptomology (eg, asthma, lung inflammation and nose and throat irritation62) alongside eye discomfort and skin sensitivity.8 Moreover, athletes with exercise-induced bronchoconstriction (mainly endurance athletes63) may be more sensitive to the effects of some pollutants when exercising.64 In addition, in the context of the Summer Olympic Games, infectious respiratory illnesses represent up to 50% of acute symptom medical consultations,65 largely due to known risks associated with travelling and mass gatherings (>15 000 expected athletes at the 2024 Olympic and Paralympic Games66) alongside unfavourable changes in immunity and microbiota states through intensive physical training.67 Air pollution may increase the risk of respiratory virus infections and severity, concerning to athletes and the general population.55
Athlete-centred air pollution mitigation strategies
Hung et al 68 recently suggested acute strategies to mitigate air pollution effects by limiting the total inhaled dose during training (ie, reduce exposure by time, exercise in the morning, reduce the intensity). Here, O3 peaks should be avoided in the afternoon and early evening, when pollutant levels are at their highest, and high-intensity training should be relocated (including relocation inside) when required (facilitated by monitoring pollution levels and following organisers’ advice) and feasible (eg, resource and facility availability). Considering air pollution could negatively affect many athletes, consideration prior to the games of alternative facilities outside the Paris area to avoid pollution peaks, as well as familiarisation to alternative sessions (eg, running on a treadmill rather than outside), appears prudent. Athletes and staff should be guided by the LOC’s recommendations, regarding pollutant concentration, to adapt their training time and location.
Before and after training and competition, some strategies exist to limit PM inhalation by reducing exposure within accommodation and/or during transport and should be used by everyone (ie, those who take part in outdoor competitions, but also indoors). These include closing vehicle windows, using cabin filters, turning on air-conditioning (although the Paris 2024 Athlete Village will not have air-conditioning) and wearing a face mask (ie, N95, KN95 and FFP2 masks can remove 14–96% of PM depending on the mask, and its correct use69), especially when local PM concentrations are high. Masks may also reduce infection propagation. It should be noted that wearing a mask can cause dyspnoea in high temperatures, especially if people are active.70 O3 acclimatisation (ie, repeated exposures to O3) could be used in athletes before competition.3 71 Typically, arriving 4–7 days in advance of their competition and/or living in a country with similar conditions may help athletes to acclimate, mitigating to some degree the acute effects on respiratory symptoms, lung function and physiological parameters of performance.72 However, there is a lack of evidence on the use of acclimatisation for athletes with asthma. Nutrition strategies such as consuming antioxidant supplementation68 73 could also be used, although there is a lack of data exploring pollutant supplement-specific effects. In one of the limited data sets in this space, Hung et al 68 suggested consuming vitamin C (250–600 mg) and vitamin E (75–100 mg), and beta carotene (25 mg) the week before events to limit air pollution effects on performance.
Given that respiratory illnesses are prevalent in athletes, and that air pollutants may trigger respiratory symptoms (eg, asthma symptoms) in a dose-dependent manner,8 precautions to limit acute respiratory illness should be adopted, such as physical distancing, hand washing, alcohol-based hand sanitiser and face masking (for PM or virus infections).
Stakeholders and spectator-centred air pollution mitigation strategies
Due to the large number of visitors expected at Paris 2024, congested transport systems are likely, increasing travel time to competition venues and exposure to pollution for all stakeholders and spectators (ie, high concentrations of PM in metro stations). As for athletes, mitigation strategies against PM such as closing vehicle windows, using cabin filters, turning on air-conditioning and wearing a face mask (as described above) could/should be used. Planification of spectator’s journeys (ie, time and route) should be determined in advance to limit time in places with poor air quality. To limit PM exposure during the day, spectators should also maximise their time in less polluted places (eg, parks, green and blue spaces when PM or NO2 is high, indoor well-ventilated modern spaces with closed windows when O3 is high) between competitions. Since air pollution could exacerbate acute respiratory illness symptoms, strategies such as limiting time spent in confined spaces and overcrowded areas (eg, bus and subway), and preventive treatments and up-to-date vaccination before travelling to these types of events46 could constitute potential solutions for limiting respiratory illnesses which would be exacerbated by high air pollution.
Recommendations for LOC and IOC ‘expert’ groups
Unlike heat, which is near ubiquitously measured, pollution data require targeted attention to limit athletes’ exposure. Organisers need to closely monitor air quality forecasts (accurate predictions would enable planned rather than reactive decision-making) and real-time assessments in key locations such as the Olympic and Paralympic Village, competition venues and training facilities with low-cost wearable air pollution sensors (an objective sensor evaluation has been provided by South Coast Air Quality Management District - http://www.aqmd.gov/aq-spec/sensors) and/or with permanent air pollution sensors, similar to the one installed by World Athletics at the Nice Stadium (France). Daily communication, including PM and O3 concentrations and recommendations mainly based on WHO guidelines, of specific locations (especially for PM) and times to be avoided due to poor air quality will be paramount for the well-being of athletes, stakeholders and spectators. Educating athletes, stakeholders and spectators about the risks and mitigation strategies, employing informative infographics, such as presented in figures 1 and 2, may help raise awareness. Organising committees can also minimise exposure to pollution by providing access to indoor training facilities when pertinent, facilitating efficient athlete transport to minimise time spent in heavily polluted areas (with high PM concentration) and considering alternative venues or rescheduling options in the case of major weather events.68 LOC should also consider preventive measures to limit localised PM concentration peaks by favouring low/no emission vehicles, encouraging access with public transport and reinforcing the restriction of vehicles near competition venues. Distribution of masks (N95, KN95, FFP2) may also be planned in case of PM concentration peaks at competition venues and in the Olympic and Paralympic Village for athletes, stakeholders and spectators.
Paris 2024: water quality and temperature expectations and associated risks
Since the announcement of open water swimming (OWS) events in the Seine River (in late 2017), concerns have loomed over the water quality,74 where swimming has been prohibited since 1923 (although some events such as Paris triathlon and ‘Traversée de Paris à la nage’ have recently taken place). Water events at the Olympic Games have already had to contend with water pollution, most notably at the 2016 Rio Games,75 but the situation at Paris 2024 is unprecedented due to heavily urbanised waterways, resulting in degraded water quality (high concentration of faecal bacteria76). In 2023, merely a year before Paris 2024, water quality on event sites was deemed unacceptable for 12 out of 27 days during the Olympic and Paralympic periods according to thresholds established by World Triathlon and World Aquatics, which rely on bacterial indicator organisms (ie, Enterococci >400 cfu/100 mL and Escherichia coli >1000 cfu/100 mL). Even more concerning, E. coli levels reached 2567 and 2759 cfu/100 mL, respectively, on the days of the men and women’s triathlon events (ie, 6–7 August). During summer 2023, poor water quality led to the cancellation of the OWS World Cup event (6 August) and modification of the paratriathlon test event to a duathlon (19 August) in the Seine River, due to exceptional heavy rain and a default to sewer valves opening directly into the Seine. During heavy rainfall events, more likely due to climate change (figure 4) such as on 28 July 2023 (when 48 mm of rain occurred), E. coli levels spiked to 8464 cfu/100 mL, posing a significant health and performance risk to athletes.9 Likely illnesses from faecal bacteria include GI symptoms,77 eye and skin infections and respiratory illnesses.78 Aquatic athletes are at risk of water ingestion during competition (ie, during 15–40 min of swimming, 75% of the triathletes reported water ingestion79), exposing them to a myriad of potential pathogens. Regarding on-water events (eg, canoeing, kayaking and rowing), these are taking place outside of major cities, in places where there are fewer heavily urbanised waterways, making the risks associated with poor water quality lower.
Average precipitation during Olympic Games (OG) period (27 July to 11 August) since 1900.
In addition to water quality, the Seine River temperature can now reach 27.5°C during summer heatwaves (~27.7°C for 10 days in 2003 and above 26°C every year since 201780). Although these temperatures permit triathlon and OWS competitions (World Aquatics permitted temperature range: 16–31°C; World Triathlon: 12–32°C), ‘hot’ water could be of concern for aquatic athletes (potentially exacerbated by combined exposure to poor-quality water). In triathlon, wet suits are not permitted with water >20°C (distance ≤1500 m) and >18°C in OWS. Water temperatures exceeding 20°C can contribute to the enforcement of the rule outlined previously (ie, wet suits not allowed), resulting in an increased skin surface area exposed to poor water quality. Additionally, elevated water temperatures pose an increased risk of hyperthermia due to compromised evaporative heat loss through immersion during swimming81 and greater radiant heat gain with black wet suits in OWS.9
Athlete-centred water quality mitigation strategies
As with air pollution, athletes will have to minimise exposure to poor water quality82 by training in clean water venues (ie, indoors or by monitoring water quality) which will also limit inadvertent consumption of poor-quality/polluted water. This latter item could further be improved by rehearsing and optimising feed zone practice. Athletes should also be aware of the high probability of logistical changes such as postponement (eg, due to a weather event) or course modifications (eg, alternative courses and entry/exit points82). Regarding hyperthermia risks, in addition to the cooling strategies detailed in part 1, athletes should limit fully suited time.9
Recommendations for LOC and IOC ‘expert’ groups
At Tokyo 2020, water quality prior to the Olympic Games was poor, leading to the modification of the paratriathlon test event to a duathlon (swim section replaced by a second run) in 2019. However, the organisers managed to remedy this for the Tokyo 2020 Olympic and Paralympic Games by maintaining water quality in the Odaiba Bay within the required safety thresholds. This was accomplished by using a triple layer barrier system to block bacteria from entering the precise area where the swim competition was seen. Moreover, the city of Tokyo updated its sewer system to increase its capacity to divert overflow sewage from flowing directly into the Bay, as can occur during heavy rainfall; clearly, a complex and costly solution requiring years of thought and execution. Due to the major threat posed by heavy rainfall to water quality at Paris 2024, the city of Paris has endeavoured to make similar progress to Tokyo in making the Seine swimmable over the last decade (ie, €1.4 billion invested over 10 years83). However, organisers will not know how effective these new strategies (eg, a 50 000 m³ tank under construction to intercept urban run-off83) will be in the event of heavy rainfall before the Olympic Games. As with air pollution, organisers must be ready to adapt the programme and venues in the case of major weather events. Furthermore, in addition to providing athletes with daily water quality data and recommendations, education by the LOC, aimed at enhancing risk comprehension, awareness and familiarity with mitigation strategies (via infographic as presented in figure 1) will be instrumental in mitigating potential water quality issues. In case of heavy rainfall and transiently polluted water, access to clean water swimming facilities should be provided for athlete training.
Limitations
The quality and level of evidence, as well as the risk of bias, were not formally assessed, which may affect the reliability of our recommendations. The recommendations provided are based on expert consensus, meta-analysis, reviews and best practices, but despite the diversity of the author panel, potential biases may exist, reflecting predominant views and possibly overlooking alternative approaches. Additionally, the generalisability of these recommendations to locations other than Paris is uncertain due to varying environmental and cultural factors.
Conclusion
Most athletes, regardless of their sport, will likely be affected by environmental challenges at the Paris 2024 Olympic and Paralympic Games, whether within and/or outside of their training and competition. Endurance athletes appear to be particularly susceptible to the adverse effects of environmental factors. However, it is essential to acknowledge that all athletes, to varying degrees, may experience impacts on their health and performance due to environmental conditions. Some athletes, such as triathletes, could face a combination of factors such as heat, high O3 concentration and poor water quality.
These challenges will affect athletes and spectators, Games volunteers, practitioners and a myriad of other stakeholders. All of these will require both personal and organiser-delivered/facilitated strategies to limit negative environmental effects. Finally, some events are beyond the scope of this Paris-centric review, such as the sailing events held in Marseille, and the surfing events held in Tahiti.
Furthermore, it is imperative to recognise that future summer sports events will, at some point, experience extreme environmental challenges (eg, Los Angeles 2028 Olympic and Paralympic Games will occur a few hundred miles from the hottest ever recorded temperature on earth). The experiences and lessons learnt from addressing environmental challenges at Paris 2024 can serve as valuable templates for future sporting events worldwide (as did Doha 2019 and Tokyo 2020), or guidance for the general public (eg, with the ambition to make the Seine swimmable). The comprehensive local warnings and recommendations provided to organising committees (table 2; figures 1 and 2) could offer invaluable guidance for mitigating environmental impacts in diverse locales hosting major competitions.
Recommendations for IOC and LOC to face heat, air pollution, poor water quality and hot water
Ethics statements
Patient consent for publication
Ethics approval
Not applicable.
References
Footnotes
X @@LoisMougin, @VBougault, @ephysiol, @@margomountjoy, @@bstephenson311, @_SKCarter, @@LJJ_nutrition, @@steve_mears, @@DrLeeTaylor
Contributors LM, SM and LT conceptualised the article. LM and LT wrote the article, with VB, SR, MLM, BS, LJJ, SM and SC providing critical input. SC designed and created the figure, with LM and LT providing content and critical input. All authors contributed to drafting or revising the manuscript and approved the final version to be published. LT (l.taylor2@lboro.ac.uk) is the guarantor.
Funding LM is a doctoral researcher funded by a Vice-Chancellor's Fellowship at Loughborough University, with funding aligned to the Sports for Climate Action and Nature (SCAN) cluster.
Competing interests MLM is Deputy Editor of BJSM, and on the Editorial Board of the BJSM Injury Prevention and Health Promotion Journal. SR is Associate Editor of BJSM. LJJ and SM have current/previous fundings from the food/nutrition industry.
Provenance and peer review Not commissioned; externally peer reviewed.