Context: A new large-scale study by Cambridge University researchers has found that long-term exposure to air pollution is linked to an increased risk of developing dementia.
Relevance of the Topic: Prelims: Major Pollutants and associated Health risks; ROS.
The data from the World Health Organisation (WHO) shows that 99% of the world’s population breathes air containing high levels of pollutants.
Long-term Air Pollution Exposure increases Dementia Risk: Highlights of the Study
| S. No. | Pollutants | Description | Associated Risks |
| 1. | PM 2.5 | Extremely fine particulate matter with a diameter of 2.5 micrometres or less. Predominantly produced by vehicle emissions and thermal power plants. | For every 10 micrograms per cubic metre (µg/m³) of long-term exposure to PM2.5, an individual’s relative risk of dementia would increase by 17% from the baseline. |
| 2. | Nitrogen dioxide (NO2) | Produced primarily due to the burning of fossil fuels by vehicles, thermal power plants, and various industrial processes. | For every 10 μg/m³ of long-term exposure to nitrogen dioxide, the relative risk of dementia increased by 3%. |
| 3. | Soot | Soot or Black Carbon comes from sources such as vehicle exhaust emissions and burning wood. | The study reported that dementia risk jumped by 13% for each 1 μg/m³ of long-term soot exposure. |
What is Dementia?
- Dementia is a term for several diseases that affect memory, thinking, and the ability to perform daily activities. The illness gets worse over time, and mainly affects older people.
- According to WHO, ~57 million people worldwide had dementia in 2021. The number is expected to increase to at least 150 million cases by 2050. The rise in air pollution, especially in developing countries, might lead to an even sharper rise in cases.
How Air Pollution causes Dementia?
- When pollutants are inhaled, the body’s immune system fights back through the release of Reactive Oxygen Species (ROS). ROS are the chemicals used by immune cells to neutralise foreign substances. When larger concentrations of pollutants are inhaled, greater amounts of ROS are released.
- However, ROS is damaging for the body’s cells as well. Therefore, as a natural counter-defence mechanism, the body produces another set of chemicals called antioxidants, that protect the cells against ROS.
- But Antioxidants are present in small quantities, and take time to build up. So, while they are able to effectively deal with smaller amounts of ROS, they are helpless when ROS is produced in large amounts.
- Thus, oxidative stress is caused by an imbalance between the production of Reactive Oxygen Species (ROS) and the body’s ability to detoxify them- leading to cellular damage from excess ROS.
- Both oxidative stress and resulting inflammation in the brain play a well-established role in the onset and progression of dementia. Air pollution triggers these processes through direct entry of pollutants to the brain or via the same mechanisms underlying lung and cardiovascular diseases.
These findings underscore the need for an interdisciplinary approach to dementia prevention. That means along with healthcare interventions, there is a need to strengthen urban planning, transport policy, and environmental regulation.