4. Impact of Mercury and Its Toxicity on Health and Environment: A General Perspective

Mercury, which has been used since ancient times can also cause severe threats to human health and the environment. It exists in various forms (like metallic, inorganic, and organic), and each carries its own health burden. Its ability to be transported long distances is an environmental threat that can affect far-away ecosystems and wildlife. Notable mercury-related incidents such as Minamata, Iraq, Grassy Narrows, Kodaikanal, and others shook the world. In addition, its widespread industrial use poses a high risk of exposure. Major threats posed in healthcare are artisanal and small-scale gold mining (ASGM), scientific applications, and electrical industries. Mercury enters the human body both through inhalation and/or ingestion, inducing a range of detrimental cellular changes. It binds with the sulfhydryl and selenohydryl groups on albumin present in the plasma, disrupting receptors, and intracellular signals. It induces the production of free radicals and alters cellular redox potential. Additionally, it can disrupt cellular signaling pathways, involved in cell growth, differentiation, and apoptosis. Its permeability across the blood–brain barrier makes it severely neurotoxic, especially CH₃-Hg (methylation mainly caused by microbes) binds to thiol-containing molecules like cysteine to form CH₃-Hg-Cys and readily crosses the blood–brain barrier, damages the cerebellum and visual cortex. Mercury can induce post-translational changes affecting protein biosynthesis. Besides, the digestive, respiratory, muscular, and renal systems are also affected. Mercury produces oxidative stress, triggers autoimmunity and damages DNA, mitochondria, and lipid membranes. Its disposition in the CNS suggests its potential role in the pathogenesis of multiple sclerosis, Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), and glial tumors. Several methods for controlling mercury pollution exist but the use of nano-adsorbents and bioremediation are most common. As a holistic approach, phasing out mercury use, replacing it with suitable substitutes, proper waste disposal, continuous monitoring and evaluation, and enforcing strict legislation seems to be a practical option. WHO and the national governments have provided the restrictions and permissible limits for mercury use. Worth mentioning is the implementation of the Minamata Convention to control and reduce global mercury emissions and releases.