Running through hazy conditions means breathing in more polluted air just when the body is working hardest, increasing exposure to fine particles such as PM2.5. (AI-generated pic) PETALING JAYA: You've probably seen it lately - the sky turns a dull grey, there is a faint smell of smoke in the air, yet runners are still out on jogging tracks.

With races and training continuing through haze season, it is worth asking whether trying to stay fit could sometimes mean taking on more risk than we realise.

Haze from vegetation fires carries tiny particles known as PM2.5, measuring 2.5 micrometres or less - about 30 times thinner than a human hair. These particles can travel deep into the lungs and reach the alveoli, the tiny air sacs where oxygen passes into the bloodstream.