O3 exposure impaired pulmonary function and increased dyspnea regardless of breathing route, and although nasal breathing slightly attenuated overall post-exercise lung function decline, it did not protect against O3-induced pulmonary impairment and increased breathing discomfort during exercise.
Key Findings
Results
Ozone exposure at 0.40 ppm impaired multiple measures of pulmonary function during exercise regardless of breathing route.
O3 exposure reduced FEV1, FVC, PEF, FEF25-75, and FEV1/FVC (all p < 0.05)
Participants were recreationally active adults (n=13, 6 females) with no history of cardiovascular or pulmonary disease or exercise-induced bronchoconstriction
Exercise was performed at 90% of power at the first ventilatory threshold for 30 minutes
Study used a double-blind crossover design with four experimental visits
Results
No breathing route by environment interaction was observed for O3-induced pulmonary function impairment.
No statistically significant breathing route × environment interaction was found for any spirometric measure
This indicates nasal breathing did not provide protection against O3-induced lung function decrements specifically
Both nasal and oral breathing conditions showed pulmonary function impairment under O3 exposure
Results
Oral breathing produced modestly greater post-exercise reductions in lung function measures than nasal breathing regardless of environmental condition.
Oral breathing was associated with greater post-exercise reductions in FEV1, PEF, FEF25-75, and FEV1/FVC compared to nasal breathing
This effect was observed regardless of whether participants were breathing room air or O3
The differences were described as 'modest' by the authors
FVC was not among the measures showing a breathing route difference
Results
Nasal breathing was associated with greater breathing effort and air hunger during exercise compared to oral breathing.
Nasal breathing produced significantly greater breathing effort and air hunger (p < 0.05)
Dyspnea was assessed using the Multidimensional Dyspnea Profile every 5 minutes during exercise
This increased breathing discomfort occurred regardless of environmental condition (room air or O3)
O3 exposure also increased dyspnea regardless of breathing route
Methods
The study used a double-blind crossover design with four experimental conditions combining two breathing routes and two environmental conditions.
Four conditions: nasal breathing with room air, nasal breathing with 0.40 ppm O3, oral breathing with room air, oral breathing with 0.40 ppm O3
13 recreationally active participants completed all four visits
Mean V̇O2peak was 45.8 ± 5.3 mL/kg/min
Spirometry was assessed before and after each trial
Exercise intensity was set at 90% of power at the first ventilatory threshold for 30 minutes of low-intensity cycling
What This Means
This research suggests that breathing through the nose during exercise does not protect the lungs from the harmful effects of ozone air pollution. The study had 13 healthy, recreationally active adults cycle at a moderate intensity for 30 minutes while breathing either through their nose or mouth, under either clean air or ozone-polluted air (at 0.40 parts per million, a level that can occur in polluted urban environments). Researchers measured lung function before and after exercise and tracked breathing discomfort throughout. Ozone caused measurable declines in lung function—including how much air people could forcefully exhale—regardless of whether participants breathed through their nose or mouth.
Interestingly, while nasal breathing did slightly reduce the overall post-exercise drop in lung function compared to mouth breathing (an effect seen in both clean and polluted air conditions), it did not specifically shield against the additional lung function damage caused by ozone. On top of that, nasal breathing actually made exercise feel harder to breathe through, with participants reporting more air hunger and breathing effort during nasal compared to oral breathing. This tradeoff means that any marginal lung protection from nasal breathing came at the cost of greater breathing discomfort.
This research matters because many people exercise outdoors in areas with air pollution and may wonder if breathing through their nose offers protection. These findings suggest that while nasal breathing has some general benefits for lung function during exercise, it does not meaningfully guard against ozone's harmful respiratory effects. People with respiratory sensitivities should be aware that ozone exposure during exercise can impair lung function regardless of how they breathe, and may want to consider avoiding outdoor exercise on high-ozone days.
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Silveira A, Comeau A, Skirrow M, Brindley J, Boulianne S, Hansen-Barkun C, et al.. (2026). The impact of breathing route on pulmonary and sensory responses to ozone exposure during exercise in adults.. Physiological reports. https://doi.org/10.14814/phy2.71071