Harris et al. 2024, Ozone and maximal exercise in endurance athletes

Controlled chamber trial in trained endurance athletes. At a peak real-world ozone level (170 ppb), end-exercise oxygen uptake, minute ventilation and tidal volume each fell by around 3 to 4% during maximal cycling; submaximal exercise was unaffected. A small effect, at maximal effort only, but evidence that high ozone measurably limits hard efforts even in fit people. Moderate.