M’sians facing toxic mix of PM2.5 and ground-level ozone
PETALING JAYA: Malaysians are facing a double health threat from the haze.
Experts say fine particulate matter and ground-level ozone combine to heighten the risk of severe respiratory and cardiovascular illness.
Prof Dr Mohd Hasni Jaafar, an environmental health and toxicology specialist at Universiti Kebangsaan Malaysia, said simultaneous exposure to both pollutants could have overlapping effects through oxidative stress, inflammation and impaired respiratory function, potentially increasing the overall acute health burden, including on healthy adults.
The World Health Organisation (WHO) defines fine particulate matter (PM2.5) as particles with a diameter of 2.5 micrometres or less, which can be found in smoke and other sources of air pollution.
Mohd Hasni said ozone pollution occurs when ground-level ozone, a harmful gas, accumulates in the air after pollutants such as nitrogen oxides and volatile organic compounds react in the presence of sunlight.
High temperatures, he added, can accelerate the chemical reactions that produce ozone, particularly under favourable weather conditions.
“PM2.5 could penetrate deep into the lungs, triggering oxidative stress and inflammation.
“Certain fine and ultrafine particles, together with their associated chemical constituents, may also contribute to systemic inflammation and cardiovascular disturbances, including altered heart rate and increased cardiovascular stress.
“Ground-level ozone, a highly reactive oxidant gas, could rapidly irritate and injure the respiratory tract, causing throat irritation, coughing, chest tightness, pain during deep breathing and reduced lung function.
“At high concentrations, particularly during physical activity, ozone exposure may exacerbate asthma and other respiratory diseases and increase susceptibility to respiratory symptoms,” he said.
Earlier this week, the Health Ministry reported a 10.43% increase in upper respiratory tract infections (URTI) and a 26.47% rise in conjunctivitis cases amid the haze affecting parts of the country.
Data from 78 selected healthcare facilities nationwide showed that URTI cases rose from 3,509 in Epidemiological Week (EW) 39 to 3,875 in EW40.
A recent report by the European Union’s Copernicus Atmosphere Monitoring Service (CAMS) said heatwaves, wildfires and human-caused emissions had combined to expose 40% of the world’s population to extremely high levels of ozone pollution this year, with Asia the worst affected.
CAMS said heatwaves could accelerate the chemical reactions that produce ozone, while vegetation could also release compounds that contribute to its formation, with emissions potentially increasing at higher temperatures.
Mohd Hasni said although only a fraction of inhaled PM2.5 or its soluble constituents might enter the bloodstream, the exposure could contribute to systemic inflammation, oxidative stress and vascular dysfunction, potentially affecting kidney function.
Individuals with chronic kidney or pre-existing kidney disease might be particularly vulnerable to these effects, he added.
“The kidneys receive approximately 20%-25% of resting cardiac output and may therefore be exposed to circulating substances that enter the bloodstream,” he said.
Mohd Hasni added that other vulnerable groups include children, older adults, pregnant women, people with pre-existing respiratory or cardiovascular diseases and outdoor workers.
“Children and individuals with asthma or other respiratory conditions are particularly susceptible to ozone-induced airway irritation and reduced lung function,” he added.
Public health medicine specialist Datuk Dr Zainal Ariffin Omar said simultaneous exposure to PM2.5 and ground-level ozone is a concern because both pollutants could trigger inflammation and oxidative stress in the respiratory system.
Studies, he said, have also found greater reductions in lung function and an increased risk of respiratory hospital admissions following exposure to both pollutants.
“As such, the public must wear a well-fitted N95 mask when outdoors against PM2.5 and against ozone. The best defence is to stay indoors in an air-conditioned space with the windows closed,” he said.
Dr Zainal Ariffin also advised the public to limit strenuous outdoor activities, particularly during hot, sunny afternoons when ozone levels could be high.
Air purifiers fitted with high-efficiency particulate air (HEPA) filters could help reduce indoor particle concentrations, but standard HEPA filters do not effectively remove ozone gas, he added.
