• Shruti GOCHHWAL

Can Air Pollution Cause Neurological Disorders?

WHO estimates that air pollution causes nearly seven million premature deaths each year. This is more than that through HIV/AIDs, violence, malaria, alcohol, drugs, and traffic accidents.

This is because air pollution is responsible for increased mortality from heart diseases, strokes, lung cancer, chronic obstructive pulmonary diseases, and respiratory infections.

But does air pollution also cause neurological disorders like Alzheimer, and Parkinson’s? Let’s find out.

Alzheimer’s Disorder

Alzheimer’s disorder is a gradual form of dementia. It is a chronic continuing condition.

Dementia is an extensive term for conditions caused by diseases or brain injuries that affect thinking, memory, and behaviour. These changes can interfere with daily lifestyle.

Alzheimer’s disorder accounts for about 60 to 80 percent of dementia cases.

Usually, people with this disease get diagnosed after the age of 65. But, if it’s diagnosed earlier, it’s commonly known as early-onset Alzheimer’s disease.

Symptoms of Alzheimer’s include:

· Memory loss

· Trouble in problem-solving and planning

· Confusing places and times

· Vision changes

· Conversations and words become frustrating

· Judgment lapses

· Mood swings

· Loss in sense of initiative and spontaneity

· Repeating questions

· Trouble paying bills and handling money

Presently, there is no cure for Alzheimer’s. However, there are methods to slow down the progression of the disease.

Its symptoms are gradual and its effects on the brain are deteriorating, they cause a slow decline.

There is no expected outcome for people with Alzheimer’s. Few live a long time with little cognitive damage, while others may experience a more rapid onset of symptoms and faster disease progression.

Each person’s journey with Alzheimer’s varies.

Parkinson’s disorder

Parkinson’s disorder or Parkinsonism is a central nervous system (CNS) disorder that affects movement, often including tremors.

Caption: MRI scan of a fixed cerebral hemisphere.

Credits: Flickr

Nerve cell damage in the brain making dopamine levels to fall, causing Parkinson’s.

Its symptoms include lack of coordination, uncontrollable shaking or tremor, and speaking problems. However, these may vary and can worsen as the disease advances.

Other symptoms include:

  1. slowed movement (bradykinesia)

  2. problems standing up

  3. stiff limbs

Parkinson’s disorder itself doesn’t cause death. Rather, its symptoms can be fatal. For instance, injuries due to a fall or difficulties linked to dementia can be fatal.

Some people with Parkinson’s face problems swallowing. This causes aspiration pneumonia. It is caused when food, or other objects, are inhaled into the lungs.

How Pollution Impacts the Brain

Over the years, researchers have found links between pollution and neurological disorders like Alzheimer’s and Parkinson’s.

Inhaled pollutants get deposited in the lungs. They then enter the blood and attack the brain, which absorbs up to 50% of the oxygen we breathe.

This can lead to anxiety, dementia and other neurological disorders.

Lately, researchers from Penn State University explored possible links between pollution and neurological diseases.

This was done by observing the flow of cerebrospinal fluid (CSF).

CSF is a fluid that encloses the central nervous system, which forms the spinal cord and brain. It acts as a buffer that protects the CNS.

Role of CFS in Neurological disorders

Neurological conditions, like Alzheimer’s and Parkinson’s, are defined by the growth of faulty proteins due to CSF clearance in the body.

Pollution in the air that we breathe influences the CSF and, therefore, the connection with the brain.

Caption: Meningitidis in cerebrospinal fluid (CSF) seen by Gram stain.

Credits: Commons wikimedia

Researchers have already shown that a lower sense of smell is an early sign of neurological disorders.

For instance, a study published in Neurology found out that poor results in an odour identification test can predict Alzheimer’s before the typical symptoms appear.

Removing Sensory Nerves

Further, researchers removed the olfactory sensory nerves using zinc sulfate. These nerves are the sole part of the CNS that comes into direct contact with the outer environment.

Removing these sensory nerves damaged the ability to smell. Also, it reduced the flow of CSF from the nose.

Thus, it was concluded that pollution damages the olfactory sensory nerves. This causes a change in the production or flow of CSF.

As CSF is crucial for removing metabolic trash from the CNS, this plays a role in the development of neurological disorders.

In another study, researchers from the University of Columbia examined data of nearly 6,70,000 adults in Vancouver.

They calculated individual exposures to air and noise pollution, road proximity and green spaces at an individual’s residence.

In the follow-up period, the researchers noticed 4,101 cases of Parkinson’s disease, 13,270 cases of non-Alzheimer’s dementia, 660 cases of Multiple sclerosis (MS) and 1,377 cases of Alzheimer’s disease.

Specifically, for people with Parkinson’s disorder and non-Alzheimer’s dementia, staying close to a highway or major roads was linked with 7 per cent and 14 per cent increased risk of both disorders, respectively.

Due to the relatively low number of MS cases in Vancouver compared to the other disorders, the researchers could not link air pollution with an increased risk of MS.

They concluded that staying less than 150 meters from a highway or less than 50 meters from a major road is linked to a higher risk of getting dementia, Alzheimer’s, and Parkinson’s.

This is due to the increased exposure to air pollution near major roads and highways.

While accounting for green spaces, it was found that the effect of air pollution on neurological disorders was lesser.

This effect could be due to multiple factors. People who live near green spaces, are more likely to be physically fit and active and may also have more social interactions.

In current times, the high proportion of pollution is responsible for the growing prevalence of neurological disorders like Parkinson’s and Alzheimer’s disease.

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