HAZY skies have brought with them a claim that breathing in polluted air can take a toll on a man's fertility.
The claim was raised in a Threads post and has since prompted questions from the public.
Can exposure to the haze affect male fertility?
Verdict:
TRUE
Exposure to haze may lower sperm quality and potentially affect male fertility, although the impact varies with the level and duration of exposure as well as a man's overall health.
A check by MyCheck.my found that air pollution, including haze, has been associated with changes in how well sperm swim, how many there are, their shape and the integrity of their DNA.
Universiti Kebangsaan Malaysia (UKM) Faculty of Medicine senior biochemistry lecturer Dr Faizul Jaafar said recent research showed that prolonged exposure to haze and high levels of air pollution could put male fertility and sperm quality at risk.
He said this could reduce semen volume, sperm concentration and motility, as well as the percentage of normally shaped sperm.
Air pollution may also raise the sperm DNA fragmentation index (DFI), according to Dr Faizul.
A higher DFI signals genetic damage to sperm, which he said could hurt the chances of pregnancy.
Haze pollutants such as fine particulate matter (PM2.5), ozone and nitrogen dioxide trigger oxidative stress that damages sperm DNA and disrupts sperm production in the testes, he explained.
Dr Faizul also highlighted motorcyclists and food delivery riders, who spend long hours outdoors and may be exposed to higher levels of pollution.
While studies looking specifically at how haze affects this group are still needed, he said continuous daily exposure to polluted air could potentially affect sperm quality.
He also raised concerns over recent findings that he said showed more than 30% of young men had low semen quality.
This can happen without obvious signs, he added, as a man may look physically healthy while unknowingly having sperm quality problems.
Universiti Putra Malaysia (UPM) urology department head, urologist and medical lecturer Dr Mohamad Fairuz Mohamad Sharin said high levels of pollutants such as carbon monoxide and nitrogen may contribute to a rise in abnormal sperm.
According to him, air pollution could also raise surrounding temperatures, which may in turn disrupt sperm production.
"If we look at it, the surrounding temperature now can even reach 30 to 33 degrees Celsius. Naturally, the male reproductive organs, the testes, are located outside the body. This is different from women, whose reproductive organs and egg production are inside the body.
"A man's testes need a temperature about two to four degrees Celsius lower than our core body temperature to produce sperm better.
"That is why the older generation often said men are more fertile during cold or rainy weather. From a biological point of view, there is a basis to it because lower temperatures can help produce better sperm," said Dr Mohamad Fairuz.
Scientific studies from the region point in the same direction, though with some caution.
A 2024 Chiang Mai University study published in JBRA Assisted Reproduction examined men in northern Thailand, where seasonal haze from agricultural burning is a yearly problem.
In years with better air quality, researchers found no harmful link between fine particulate levels and sperm quality.
During years with heavier PM2.5 pollution, however, they recorded a negative link with sperm concentration, motility and shape.
That effect was most noticeable for exposure about three months before semen samples were collected.
On a wider scale, a 2025 review in BMC Urology that pooled 17 studies covering more than 24,000 participants concluded that air pollution can impair sperm parameters.
Sources:
2. https://pmc.ncbi.nlm.nih.gov/
3. https://doi.org/10.1186/
