One of the most heinous issues of concern in contemporary times is climate change and its disastrous effects on the global environment. The consequences of climate change is an impending reality that has physical, mental, emotional and social effects on people worldwide. However, trying to understand the affect climate change has on human health and how it triggers mental illness is a complex task; scientists, nonetheless, have begun to decipher the connection between the two.

One might think that air pollution due to climate change is not related to brain health but what if the two are interrelated? Research increasingly suggests that there is a strong link between climate change/air pollution exposure and risk of mental disorders like dementia, mainly Alzheimer’s and Parkinson’s.

Dementia, unlike Alzheimer’s and Parkinson’s, is not a specific disease. It is a set of symptoms that are connected to different disorders and adversely affect the brain, resulting in memory loss, difficulty communicating, and loss of motor skills, personality changes, paranoia and hallucinations. Dementia can be caused by a wide variety of reasons, even by a blow to the head. The most common form of dementia is Alzheimer’s.

Recent studies suggest that air pollution is persistently increasing in the developing world, especially in countries like China and India while at the same time, global population is ageing and rates of dementia are likely to increase consequently.

Health and diseases related to the brain, like any organ, are affected by several factors, both internal and external. These factors are mostly subdivided into genetic and environmental influences. Most often, the environmental and genetic influencers interact. Here is a rundown of what factors relating to climate change cause dementia and how:

Air Pollution

Air pollution is a complex mixture of gases mostly, carbon dioxide, ozone, nitrogen, sulfur oxides and metals such as lead and manganese; volatile organic compounds and particulate matter from vehicles and industries also add up to air pollution. While several of the constituents are linked with diseases and illnesses, evidence shows particulate matter is one of the causes of several heart diseases such as cardiovascular diseases, including decreased level of oxygen to the heart (myocardial ischemia), heart failure, arrhythmia, stroke, and blood clots (venous thrombosis).

Studies now hold that air pollution has become one of the major causes of neurodegenerative disease. Most of the evidence has been accumulated from postmortem studies that compare brain tissue of residents living in cities exposed to severe air pollution with the brain tissue of people living in cities exposed to low air pollution. Most of these individuals did not have any neurologic disease or symptoms before demise, but died sudden deaths.

This evidence reveals inflammation in the residents living in polluted cities, along with Alzheimer’s type brain tissue pathology, in comparison with people living in cities with cleaner air. Pathology consisted of inflammatory marks, inflammatory endothelium activation, amyloid-betan accumulation, oxidative stress etc. A lot of particulate matter was found in red blood cells, blood vessels, and inflammatory cells inside brain tissues around the blood vessels. Disruption of blood-brain barrier amongst residents of cities exposed major air pollution was also observed.

Countries with an ageing population and a high rate of brain diseases are generally the ones exposed to highly polluted air with limited infrastructure to diagnose and treat brain diseases such as dementia. Some contemporary studies prove, yet again, that people exposed to high levels of air pollution, specifically fine particles reflect higher risk for dementia and pre-dementia, also known as mild cognitive deficiency.

A study, conducted in Taiwan, drew a sample of almost 100,000 people and proved that with every unit increase to particle pollution exposure, risk of development of dementia increased by over 100 percent. This is a clear confirmation of the claim that air pollution, one of the major contributors of climate change, plays a vital role in increasing the risk of dementia, and brain related diseases.

How climate change, specifically air pollution causes Dementia -Alzheimer’s and Parkinson’s

There are two ways through which air particles and pollution can enter your body. One is the sense of smell which is extremely potent. A direct link of the nose and brain through the nasal nerve makes it very easy for dirt particles to travel all the way up your brain. Along with particles, pollution also brings nasty heavy metals, that are life threatening.

Consequently, the brain’s homegrown immune system is disrupted. The microglia cells that clean waste, reduce dead neurons and enhance synaptic links by clearing pathogens, fail to fulfill their duty. Instead of oxidative chemicals killing pathogens, chemicals merely gather and dismantle brain activity. The impairment caused by this, is what we witness in patients suffering from dementia, mostly Alzheimer’s and Parkinson’s disease.

Pollution particles are also inhaled via lungs- moving past the defense system of the body, the particles pass into the bloodstream, triggering the immune reaction which in turn circulates molecules, cytokins and inflammation in the bloodstream. Low-level chronic inflammation occurs, interacting with blood-brain barrier and damaging it.

PCBs &other Organic Pollutants

PCBs are chemicals that were used for several years in a range of materials such as paints, insulators, lubricants etc. Due to the cancer, causing toxins found in PCBs, they were banned in the US back in 1977. Consequently, PCBs were found to be interfering with thyroid hormone function and brain development, since they weren’t broken down easily. There have been numerous studies where the toxicity of PCBs and its harmful effects have been proven on the developing brain leading to cognitive decline/dementia. Every study on the topic validated a link between adult PCB exposure and dementia, cognitive impairment.

One of the studies revealed significant dependent reduction in terms of memory functions and attention span, amongst women. Another, similar research found that older people who regularly consumed fish from the Great Lakes, suffered from memory and learning impairments.

These specific studies give more evidence and further reinstate the argument that environmental chemicals play a vital role in increasing the risk of brain diseases, not only in developing countries such as China and India, that are more exposed to pollutants, but also the West.