PM2.5 linked to brain damage and dementia, stroke risk rises

Thailand continues to face an air pollution crisis caused by fine particulate matter, or PM2.5, a problem that recurs every year.

In recent periods, the severity of the problem has varied from area to area, both in terms of timing and the extent to which PM2.5 levels exceed the standard, particularly in major urban centres and industrial areas.

PM2.5 affects not only public health, but also the country’s economy and tourism.

PM2.5 outlook for the next seven days (April 23-29, 2026)

• 17 northern provinces: require special monitoring, as dust levels are expected to rise between April 23 and 25.
• Central and western regions: levels are expected to rise continuously throughout the week.
• Bangkok, surrounding provinces and the Northeast: the situation is expected to improve, with dust levels beginning to fall.

PM2.5 pollution tends to worsen during winter (November to February) and summer (March to April) because the dry weather and still air in both seasons allow PM2.5 to build up more easily.

This has a clear impact on public health, especially among vulnerable groups such as young children, older people, patients with respiratory diseases, and those with cardiovascular disease.

It also affects the wider economy and tourism because of poor visibility and health concerns.

PM2.5 causes neurological damage in multiple ways

Fine particulate matter that can be inhaled (PM2.5) has become one of the most widely reported pollution indicators in recent years.

Epidemiological studies have shown a strong association between PM2.5 and lung disease as well as cardiovascular disease.

Recent studies have shown that PM2.5 is also strongly associated with brain damage, particularly cerebrovascular injury (stroke) and neurological damage in the brain, including changes in brain function, dementia and psychiatric disorders.

PM2.5 can enter the lungs and the gut-microbiota-brain axis, triggering oxidative stress and systemic inflammation, or enter brain tissue directly through the olfactory nerve, ultimately damaging blood vessels and nerves in the brain.

Notably, there may be a period during which brain damage caused by PM2.5 can repair itself.

However, the exact pathophysiological mechanisms of brain injury and brain repair are not yet fully understood.

This article compiles and discusses the mechanisms of brain injury caused by PM2.5 and the self-repair process after injury, which may offer new ideas for the prevention and treatment of stroke and neurological brain disease.

The brain at every age is affected by PM2.5

Asst Prof Dr Surat Tanprawate, Assistant Dean and head of the Neurology Unit, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, said PM2.5 is small enough to enter the body through the respiratory system and bloodstream via key mechanisms such as the Lung-Gas-Blood Barrier and the Gut-Microbiota-Brain Axis.

Once inside the body, PM2.5 triggers oxidative stress in vascular cells, causing blood vessel dysfunction, inflammation and reduced elasticity of the blood vessels, which are key factors in stroke.

At the same time, evidence from animal experiments in which subjects were continuously exposed to PM2.5 through inhalation for 12 weeks found that PM2.5 can cause hardening of blood vessels in the brain.

Population-level studies have also found that increases in PM2.5 are associated with stroke incidence.

Every increase of 5 micrograms per cubic metre in PM2.5 raises the risk of paralysis and recurrent stroke by 24%, and increases severity to the point of death by as much as 30%, particularly among older people and patients with chronic diseases such as hypertension, diabetes and high blood lipids.

In addition, long-term exposure to airborne PM2.5 may be associated with lower cerebrospinal fluid (CSF) Aβ42 levels, a biomarker linked to amyloid plaque formation in the brain and a higher risk of Alzheimer’s disease.

A population study of 1,113 people aged 45-75 with normal brain health found that:

• One year of PM2.5 exposure was associated with a 10.1% decrease in CSF Aβ42 levels.
• Three years of PM2.5 exposure was associated with a 7.8% decrease in CSF Aβ42 levels.
• Five years of PM2.5 exposure was associated with a 7.6% decrease in CSF Aβ42 levels, but the result was not statistically significant.

Surat went on to say that a 2023 study published in a neurology journal confirmed that PM2.5 plays a major role in causing neurological damage in multiple ways, starting from childhood.

It may contribute to delayed brain development, lower intelligence or IQ, and risks related to learning, cognition and mood in adolescence, especially depression, which may raise suicide risk, as well as significantly increasing the risk of stroke and Alzheimer’s disease.

However, when PM2.5 levels are high, the public is advised to protect themselves by wearing face masks, installing air purifiers in bedrooms or at home, avoiding highly polluted areas, and refraining from all outdoor activities.

Main causes of PM2.5 in Thailand

However, the main causes of PM2.5 in Thailand stem from several complex factors, including forest fires, open burning and the burning of agricultural waste, as well as waste incineration, all of which are among the leading causes of air pollution.

In addition, transport systems in major urban areas with heavy traffic are another major source of PM2.5, while diesel vehicles have also been identified as a key contributor to air pollution.

Another factor that should not be overlooked is the industrial sector, as some factories continue to release air pollutants and are another cause of PM2.5.

On top of that, dry weather and still air also play an important role in allowing PM2.5 to accumulate more easily.

When these factors combine, they make Thailand’s PM2.5 situation an extremely challenging problem to solve.

At present, air pollution around the world is worsening, and exposure to fine particulate matter, or PM2.5, in the air has become a threat to human health and safety.

Animal experiments and epidemiological studies in Thailand and abroad have shown that exposure to PM2.5 can cause serious respiratory and cardiovascular disease, as well as damage the nervous system in many ways.

The main mechanisms identified include oxidative stress and neuroinflammation, changes in miRNA expression levels, autophagy, the PKA/CREB/BDNF signalling pathway, and abnormalities in the HPA axis.

The gut-microbiota-brain axis has also become a major focus of research in recent years.

The damage caused by exposure to PM2.5 does not arise from a single mechanism, but from a chain reaction.

The body’s ability to repair itself after PM2.5-related brain injury is also an issue that deserves further study.

Identifying the point at which repair or deterioration may occur in the injury process, together with early prevention and control, can significantly reduce the extent of brain damage.

However, because of the complexity and diversity of particulate matter components in the environment, and the unclear nature of their toxicity, research into brain injury caused by PM2.5 remains challenging.

Gaining a clearer understanding of how brain injury occurs and of the mechanisms that have yet to be fully studied remains a task for the future.