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Air pollution, the most prevalent form of pollution worldwide, is associated with a wide range of neurological disorders, including neurodegenerative conditions, stroke, autism, depression, and developmental delay. There is accumulating evidence on the association between air pollution and headache disorders, especially migraine. Many classical and non-classical air pollutants have been associated with headache, including particulate matter, nitrogen dioxide, sulfur dioxide, ozone, carbon monoxide, as well as polycyclic aromatic hydrocarbons and volatile organic compounds. There has also been research on the impact of biomass fuels on health-related symptoms, including headache, which form an important source of air pollution in our country. The exact mechanisms underlying headache pathophysiology vis-à-vis air pollution are not precisely defined but include triggering of neuroinflammation and activation of the transient receptor potential ankyrin 1 (TRPA1)-associated pathways. Evidence from different regions of the world indicates a significant association between headache incidence and prevalence, and occurrence of air pollution. Despite growing data, research on adverse effects of air pollution on headache disorders remains limited, and appropriate outcome measures are not holistically defined in these studies. Due to the rapid advancement of the scourge of air pollution, there is a pressing need to expand the arena of research, specifically focused on pathological mechanisms, impact on health and quality-of-life parameters, as well as broader global ramifications.

Background: Among the primary environmental issues affecting global health, air pollution is considered the leading cause of concern. Globally, around 800,000 deaths were attributed to air pollution according to WHO. Evidence suggests that there has been a strong association of air pollution with stroke. Approximately, 25% of stroke mortality was due to air pollution according to a study in 2013. Objective: The aim of this review was to analyze the association between stroke, intracerebral hemorrhage, and subarachnoid hemorrhage and air pollution and its burden globally with a special focus on South Asia along with its association with the COVID-19 pandemic. Results: There is growing research data linking air pollution to cardiovascular disorders including stroke. Short-term and long-term air pollution exposures have been shown to increase stroke incidence in epidemiological data. Air pollution, both gaseous and particle, show a strong and tight temporal relationship with stroke hospitalizations and death. The link between ICH and SAH to air pollution is less strong and less well studied as compared to ischemic stroke. Stroke and air pollution both are highly prevalent in South Asia. It is possible that the high prevalence of stroke in south Asia may be linked to the high frequency of air pollution in addition to other conventional risk factors. Decreased stroke admissions and mortality and reduced cardiovascular mortality reported during coronavirus disease 2019 (COVID) lockdown may be attributable to decreased levels of air pollution. Conclusion: Even though air pollution poses a significant threat to human health, a great number of countries still fail to achieve internationally agreed air quality standards. Air pollution should be recognized among the most significant controllable risk factors for cardiovascular and cerebrovascular disease prevention and treatment.

Man and environment have a strong connection with each other for their functioning. Environmental toxins which can be natural or manmade result in the loss of this balance by causing systemic inflammatory response within the human body, with the brain being the most affected target end-organ. These problems are more prominent in Third World countries, where environmental regulations laws are either relaxed or non-existent. These neurotoxins play a very important aetiological role in the manifestation of various neurodegenerative diseases, neurodevelopmental disorders and psychiatric disorders. Environmental neurotoxicity results from inhibition of mitochondrial activity, excess oxidative stress leading to neuroinflammation, and promoting apoptosis and neuronal cell death. Having the know-how of these neurotoxins will provide insight into the process of neurodegeneration and will result in further designing of studies to delve into processes and mechanisms of neuronal regeneration and axonal sprouting. This review highlights the various central nervous system disorders associated with exposure to environmental neurotoxins and discusses the way forward to prevent or halt the process of neurodegeneration.

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