With less than 3 weeks to go until the inauguration of the 2026 Milan-Cortina Olympics, snow cannons are already blasting the alps with artificial snow — nearly a million cubic meters just to host the competitions. But while attention has focused on snow production, the scientific community is urging a broader view: The real health risk for athletes could be the air they breathe inside indoor ice rinks.

Artificial Snowmaking at Olympic

The organizing committee plans to produce 2.4 million cubic meters of artificial snow, using 948,000 cubic meters of water, including 580,000 cubic meters at the Livigno site alone (a high-altitude ski village on the Swiss border). This industrial-scale operation has drawn protests from environmental groups and concern from the International Ski and Snowboard Federation, whose president, Johan Eliasch, has criticized “unexplained delays” in production.

But artificial snow is not just water and cold. To allow freezing at higher temperatures — down to -3 °C instead of the usual -7 °C normally required — the ski industry has been using a microscopic aid for decades: bacteria that help water become ice.

The discovery dates back to 1975, when Steve Lindow, PhD, then a student at the University of California, Berkeley, identified a bacterium, Pseudomonas syringae, with an extraordinary ability: proteins on its surface organize water molecules into crystalline structures, triggering ice formation — a strategy the bacterium uses in nature to attack plants, damaging tissues with intracellular ice crystals.

The most widely used commercial product contains bacteria grown through fermentation, freeze-dried, and irradiated, then added to water in snowmaking systems. According to manufacturers, it can yield up to 40% more snow. Before bacteria, the industry experimented with silver iodide, copper, and mercury, all of which were abandoned due to toxicity concerns.

Is Artificial Snow Safe?

Are these bacteria a health risk? Evidence from a 2010 French study, published in Science of the Total Environment and conducted by the French Agency for Food, Environmental and Occupational Health & Safety offers reassurance. The research analyzed four exposure scenarios and reached a conclusion that P syringae is not pathogenic to humans. Levels of bacterial endotoxins in artificial snow do not exceed those found naturally in falling snow.

The only group identified as being at low potential risk were workers who prepare the additive mixtures, particularly during mixing and tank-cleaning processes. The study recommends using personal protective equipment: goggles, gloves, and masks. Athletes skiing on artificial snow, however, face no greater risk than those skiing on natural snow.

One uncertainty remains. A 2008 study in Applied and Environmental Microbiology identified three lipopeptides with antifungal and hemolytic activity in the P syringae strains used in Snomax, a common snowmaking additive. The authors emphasized that “the occurrence of these bioactive metabolites should be considered” when using the bacterium to produce snow. This concern is more environmental — due to its possible fungicidal effect — than human health, but it has prompted research to search for variants of the bacterium devoid of these compounds.

Indoor Rink Air Risks

While artificial snow appears largely safe, the same cannot be said for the air breathed inside indoor ice rinks. Here the scientific literature is unequivocal: Indoor rinks represent a documented health risk, especially for frequent users — athletes, coaches, and maintenance staff.

The main culprit is ice-resurfacing machines that run on propane or gasoline. A 1993 Canadian study published in the American Journal of Public Health measured pollutant concentrations in seven indoor rinks during 2 hour hockey games. Carbon monoxide (CO) ranged from 4 to 117 ppm, whereas nitrogen dioxide (NO₂) concentrations reached 342 to 2729 ppb. For each hour of exposure to 1 ppm of CO, players’ blood CO levels increased by an average of 0.53 ppm. The study recommended maximum exposure limits of 20 ppm for CO and 250 ppb for NO₂ over 1-hour periods.

Outbreaks, Poisonings, and Chronic Effects

These findings are not merely theoretical. In January 2011, in New Hampshire, a group of hockey players suddenly developed acute respiratory symptoms, including cough, shortness of breath, hemoptysis, and chest pain. A previously healthy 19-year-old was hospitalized with oxygen saturation reduced to 88%-91% (normal > 95%) and bilateral lung infiltrates. The cause was traced to dangerously high NO₂ concentrations, compounded by a malfunctioning ventilation system.

In Finland, a 2007 study documented for CO poisoning outbreaks that involved more than 300 people at ice rinks. Common causes were high emissions from propane-powered machines, small arena volumes, and inadequate ventilation. The study also revealed more subtle effects: Among young hockey players, rhinitis (18.3%) and cough (13.7%) during or after training were significantly associated with personal exposure to NO₂.

Concerns deepen when athletes’ long-term respiratory health is examined. A 2024 systematic review analyzed studies of elite cross-country skiers and hockey players: 27% of skiers and 14% of hockey players were diagnosed with asthma, with even higher percentages reporting respiratory symptoms and exercise-induced bronchoconstriction.

A 2003 study in the European Respiratory Journal examined 88 elite hockey players: 24% showed bronchial hyperresponsiveness, and 15% had established asthma. Sputum analysis revealed mixed neutrophilic and eosinophilic inflammation — a pattern suggesting a specific “ athlete’s asthma” distinct from classic allergic asthma.

Finally, a 2004 study of elite female hockey players documented a progressive decline in lung function over 4 years of training. Players who moved from rinks with low particulate concentrations to rinks with high levels showed a significant drop in respiratory function. Damage predominantly affected small airways, suggesting a remodeling process that might not be fully reversible.

Why Athletes Are Especially Vulnerable

Athletes’ vulnerability has a clear physiologic basis. During intense exercise, lung ventilation increases dramatically — cross-country skiers can exceed 100 l/min. The switch from nasal to mouth breathing bypasses natural warming and filtration mechanisms, allowing large volumes of cold, dry, and potentially polluted air reach the lower airways directly.

Cold air causes loss of water and heat from the respiratory tract, triggering an inflammatory cascade. Studies on skiers have documented neutrophil infiltration of the airways, epithelial damage visible at bronchoscopy, and neutrophilic and lymphocytic inflammation with remodeling in biopsy samples. When exposure to CO, NO₂, and fine particulate matter from combustion engines in indoor rinks is added, the mix becomes truly harmful.

Prevention and Research Recommendations

A 2012 review in the British Journal of Sports Medicine outlined several preventive strategies:

• Air quality: Increase ventilation and replace fossil-fuel machines with electric ones. The organizing committee for the 2010 Vancouver Olympics adopted this measure first, and Milan-Cortina is moving in that direction as well.
• Heat-and-moisture-exchange (HME) devices: HME devices recycle heat and humidity from exhaled air, warming inspired air from -10 °C to more than 19 °C. A 2023 study of elite cross-country skiers and biathletes found these devices effectively prevent bronchoconstriction, but added resistance and ice buildup make them difficult to use in competition.
• Temperature limits: The International Ski Federation sets a minimum temperature of -20 °C for cross-country skiing competitions. Athletes have asked for more conservative limits, recognizing extreme cold exposure as an occupational health risk.
• Pharmacotherapy: For athletes with asthma or bronchial hyperresponsiveness, montelukast has shown specific protection against bronchoconstriction caused by inhaling rink air contaminated with fine particulate matter. Studies suggest the respiratory damage may be mediated by leukotrienes.
• Systematic monitoring: The Olympic committee recommends a multilayered approach to improve air quality in arenas: continuous monitoring, rapid response when thresholds are exceeded, regular equipment maintenance, and staff training.

This story was translated from Univadis Italy, part of the Medscape Professional Network.