How air pollution fogs the mind and affects the brain “It’s the silent killer lurking in the background” By Dr Amit Srivastava

Every year, as the summer season ebbs and the sudden fall in temperatures heralds winter, there is a precipitous peak in air pollution in most parts of north India, particularly in the National Capital Region (NCR).

Everybody is seen squabbling over the thick smog in the horizon, with local administrations taking desperate short-term measures like temporarily shutting down schools, curbing traffic, construction work and diesel guzzling units and other points of combustion, smoke and dust across the NCR.

However, what we need to realise is that the air pollution levels are markedly high all throughout the year even though we only take temporary action to tide over those few “dangerous days”, when visibility gets hit, our eyes start burning, and it gets difficult to breathe for children, elderly and the asthmatics.

Actually, it’s important to ponder over it seriously throughout the year.

Apart from the acute health hazards that the air pollution poses, it’s the long-term effects that are of major concern.

It is naive of us to assume that all is well once the smog dissipates.

The respiratory system, the skin and eyes gets more acutely affected as they directly come in contact with the pollutants, though chronic inflammation and cancers are also known to be triggered as a long-term effect in these organs.

Another indirect health hazard is the surge in the number of fatal road accidents due to the thick smog in the Delhi-NCR region that stays all through the day and reduces the visibility to dangerous levels.

More importantly, the brain and the cardiovascular system bear the long-term brunt of air pollution. As a neurologist, I would concentrate on the adverse effects of air pollution on our nervous system.

Air pollution comprises a diverse mixture of particulate matter (PM), gases (for example, ground-level ozone, carbon monoxide, sulphur oxides, nitrogen oxides), organic compounds (polycyclic aromatic hydrocarbons and endotoxins) and metals (vanadium, nickel, and manganese) mixed in the outdoor and indoor air.

Of these components, particle pollution and ground-level ozone are the most widespread health threats.

While diverse environmental factors have been implicated in neuroinflammation leading to CNS pathology, air pollution may rank as the most prevalent source of environmentally induced inflammation and oxidative stress.

Air pollution is an omnipresent concoction of environmental toxin capable of assaulting the central nervous through diverse pathways.

While many types of cells in the brain respond to the exposure to air pollution, research reports indicate that microglia and capillaries in the brain may be critically responsible for the damage.

Air pollution is also associated with diverse CNS diseases, including brain stroke, Alzheimer’s disease and other types of dementia, chronic depression and Parkinson’s disease.

1) A stroke can be defined as the sudden blocking of brain’s blood supply or when a blood vessel bursts, resulting in loss of oxygen to the brain that, in turn, injures or kills brain cells resulting in paralysis, loss of memory and language, balance problem, etc.

Latest studies indicate air pollution as a leading risk factor for stroke worldwide.

A study, published in The Lancet Neurology, finds that air pollution is associated with about a third of the global stroke burden. This includes environmental and household air pollution, researchers say.

Interestingly, they also reported on the top five risk factors for stroke in certain countries. In the United Kingdom and United States, high blood pressure, high BMI, low-fruit intake, low-vegetable intake and smoking were responsible.

But in both India and China, high blood pressure, low-fruit and vegetable- intake, air pollution, high sodium intake were the top reasons in that order.

The basic mechanism of action could be the pro-inflammatory triggers in the pollutants that cascades the damage to the brain vessels.

2) Air pollution is also responsible for affecting the cognition and memory of people causing dementia and also leading to chronic depression.

Dementia describes a set of symptoms that can include memory loss and difficulty in thinking, and it is one of the leading cause of morbidly in many countries.

The exact cause of the condition is unknown, but there are factors known to increase your risk – and breathing in toxic air could now be one of them.

Newer evidence suggests that pollution exposure can harm the brain, accelerating cognitive ageing, and may even increase risk of Alzheimer’s disease and other forms of dementia.

The link between air pollution and dementia is still hazy, but many epidemiological studies from around the world, new findings from animal models and human brain imaging studies, and increasingly sophisticated techniques for modelling PM2.5 exposures have raised alarms.

Researchers at the University of Toronto in Canada reported in The Lancet that among 6.6 million people in the province of Ontario, those living within 50 meters of a major road – where levels of fine pollutants are often 10 times higher than just 150 metres away – were 12 per cent more likely to develop dementia than people living more than 200 metres away.

Animal models have shown deposits of beta – Amyloid, the same plaque like substance implicated in human Alzheimer’s disease, in the brains of affected animals living in polluted areas.

3) Environmental exposure to manganese is shown to trigger neurodegenerative condition like the Parkinson’s disease. Lewy body deposits, similar to human patients of Parkinson’s disease, were seen in the brain of experimental animals.

4) Also, recent research has linked air pollution to hypertension and diabetes mellitus type 2. It’s important to realise that hypertension and diabetes are the two most common risk factors for a number of diseases including strokes.

Exposure to air pollutants, particularly traffic air pollutants were significantly associated with increased risk of type 2 diabetes mellitus and hypertension.

In a long-term large cohort of American women (the Sisters Study), Long-term PM2.5 and NO2 (nitric oxide) exposures were associated with higher blood pressure.

Research in Germany has proven that women who are exposed to environmental pollutants like nitrogen oxide and sulphur dioxide during preconception or the first few weeks of pregnancy during the first trimester can drastically increase the chance of developing gestational diabetes. It has also been shown that exposure to ozone later in pregnancy can also increase the chance of developing GDM as well as type 2 later in life.

Air pollution is a major health hazard that affects the brain as much as other vital systems of the body.

It is the harbinger for many a diseases which cause major morbidity and mortality, whose treatment incurs massive economic burden on the society. It is a silent killer lurking in the background.

So, tackling air pollution to prevent the myriad diseases it is linked with, is of paramount priority for the physical, mental and economic well-being of the society.

Name : Dr. Amit Srivastava
Qualification : MBBS ,MD (Medicine),DM (Neurology)
Department: Senior Consultant PSRI Institute of Neuro Sciences

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