IF YOU have ever squinted through a brown haze and thought, "this can't be good for me," you were right. The link between polluted air and lung damage is well-established.
However, emerging science suggests that fine particulate matter does not just settle in your respiratory tract; it enters your bloodstream and causes chronic neuroinflammation. In other words, it could target your brain.
So we had to ask: Can breathing dirty air actually lower your intelligence?
Verdict:
TRUE
Breathing polluted air over a long period of time is genuinely linked to a decline in memory, reasoning and mental sharpness, and in children it may actually reduce IQ scores, according to a growing pile of peer-reviewed research that your lungs would rather you not read.
The main troublemaker is something called PM2.5, which stands for fine particulate matter and refers to tiny airborne particles so small they can slip past your body's defences, travel up through your nose and make their way directly into your brain.
Once there, they trigger inflammation in brain tissue, which over time may interfere with the brain's ability to store memories, solve problems and think clearly.
The concern is greatest for children, whose brains are still under construction and have considerably less tolerance for this kind of uninvited renovation.
A 2024 meta-analysis published in Environmental Health, which looked at data from 4,860 children across North America, Europe and Asia, found that for every additional microgram of PM2.5 per cubic metre of air that children were exposed to, their performance IQ scores dropped by a measurable 0.39 points.
That may not sound like much, but it adds up, and Malaysia's current air quality means the exposure is not occasional.
The risk starts even before a child takes their first breath.
Research published in PMC found that babies whose mothers were exposed to high levels of pollutants released during the burning of peat and organic matter were more likely to have lower IQ scores by the time they reached age five.
This is particularly relevant in Malaysia seeing that the haze has returned in force.
IQ scores in affected children were between 4.31 and 4.67 points lower at age five, and brain scans of children in high and low pollution exposure groups showed real, measurable differences in brain structure.
Adults are not off the hook either, just slower to feel it.
A study that tracked nearly 9,000 adults over 15 years in the UK found that people living with higher levels of air pollution showed faster declines in both memory and the ability to plan and organise their thoughts.
The researchers worked out that the memory decline linked to pollution exposure was roughly equivalent to what you would expect from ageing an extra one and a half years, while the impact on planning and reasoning was closer to four additional years of ageing.
For Malaysians, this is not an abstract concern.
According to the 2025 World Air Quality Report, Malaysia's national average PM2.5 level was 16 micrograms per cubic metre in 2025, which is more than three times the World Health Organisation's recommended safe limit of 5 micrograms per cubic metre.
Kuala Lumpur sat at 15.7 micrograms per cubic metre as an annual average, and that is before accounting for the seasonal haze spikes that periodically turn the Klang Valley sky the colour of old dishwater.
Now for the BUT, because there is always a but.
One bad haze day is not going to cost you your wits as the research is about years of sustained exposure, not a week of squinting through smoke from Kalimantan.
What it does tell you is that clean air is not just a quality of life issue but a brain health issue, and that the haze Malaysians have largely learned to shrug off every year may be doing more than irritating their throats.
For parents keeping children indoors on days when the Air Pollutant Index goes red, the science suggests that is not an overreaction and may be one of the more sensible things you can do for a small, still-developing brain.
So the next time you find yourself staring at your laptop unable to finish a sentence, take comfort in knowing that it might not be entirely your fault. And perhaps invest in a good air purifier.
Sources:
1. https://link.springer.com/
2. https://www.ncbi.nlm.nih.gov/
3. https://pmc.ncbi.nlm.nih.gov/
4. https://pmc.ncbi.nlm.nih.gov/
