PETALING JAYA, Aug. 20 -- As Malaysians once again experience a resurgence in haze pollution and deteriorating air quality, many have begun taking precautions against its more visible health effects.

While coughing, sore throats and irritated eyes may prompt people to take action, some of the more concerning pollutants associated with haze are invisible to the naked eye and may not always factor into how people protect themselves.

Known as PM2.5, these microscopic fine particles - particulate matter (PM) measuring 2.5 micrometres or less in diameter - are small enough to penetrate deep into the lungs and potentially trigger adverse health effects beyond the respiratory system.

Invisible threat

The World Health Organisation (WHO) defin...