Air pollution

For most people, the benefits of running outweigh the harm of polluted air; on bad days, change where, when and how hard you run.

• Check the air quality index: when it is in the unhealthy range, shorten or ease the session, or train indoors. With asthma or a heart condition, be more cautious and follow your doctor’s advice.
• Stay away from busy roads: pollution drops sharply within 100 to 200 m of heavy traffic, so choose parks and quiet streets.
• Run early in the morning: ozone peaks on hot, sunny afternoons, traffic fumes at rush hour.
• Hard sessions make you breathe far more air: save them for cleaner days.

Coughing, chest tightness or unusual breathlessness: stop, and see a doctor if it persists.