- Tuesday | 09 Oct, 2018
- Mahmood A. Khwaja, Hafsa Bashir, Shiza Durrani
- Research Reports,Project Publications
Mercury is naturally occurring element in environment and humans are exposed to it through food, water and air (Labban et al., 2018). It is a very toxic substance which represents a global and major threat to human health, including in the form of methyl mercury in fish and seafood resources, ecosystems and wildlife (EU, 2017). The agency of toxic substances and disease registry (ATSDR) ranked mercury as the 3rd most toxic element (ATSDR, 2011).
Mercury is used in dentistry as a filling material to fill tooth cavities caused by decay of tooth. The material is called Dental amalgam or silver filling and has been practiced since last 150 years. Silver amalgam is a mixture consisting of 50 % elemental mercury and powdered silver, tin, and copper. The reason for being used in dentistry; is its strength, durability, cost effectiveness and its properties that allow it to bind and react together to the other particle to form amalgam (FDA, 2017).
Among others, humans are exposed to mercury in its form as methyl mercury, as well as during placement or removal of dental mercury restorations. However, the exposure is dependent upon the number and size of restoration, composition, chewing habits, food texture, grinding, brushing of teeth, and many other physiological factors (Labban et al., 2018). Recent studies revealed that new high strength MRI’s result in increased and rapid mercury leakage from teeth (Kennedy, 2018). Wi-Fi signals has also been reported to be dangerous resulting in mercury release from mercury dental fillings (Sayer Ji, 2018).
Studies have shown the harmful effects of mercury over children. Ginsberg et al. (2004) found growing fetuses and children as most vulnerable to mercury exposure as adults, due to their immature detoxification mechanisms and immune system. It was found that higher level exposure to mercury was resulted in damaging brain, nerves and kidneys. Fok et al (2007) studied that mercury could efficiently cross the placenta and hence fetal exposure to mercury was recorded higher in blood of fetus than in mother. Mercury could also pass through the blood-brain barrier and accumulate in the central nervous system in an organic form (Philbert et al., 2000). It was found that mercury exposure at critical neuro-developmental periods, such as during the prenatal stage and early childhood, could induce persisting motor, sensory, and behavioral impairment (Karagas et al., 2012; Perera and Herbstman, 2011). Adams et al. (2007) highlighted the increased prevalence of autistic behavior in children with mercury filling than the controlled group which resulted in higher concentration for excretion of coproporphyrine- responsible for mercury intoxication (Nataf et al., 2006; Geier and Geier, 2006; Geier and Geier, 2007 (a,b). Mutter and Yeter (2008) observed higher exposure at early stages leads to Kawasaki disease (KD) in children.
To protect human health and environment from emissions/releases from mercury and mercury compounds, 140 global governments after long negotiations, in acted & adopted Minamata Convention on Mercury. To-date more than 128 countries, including Pakistan have signed the convention and 96 governments have already ratifiedand is in force now. Article 4, paragraph 3 Annex A part II states “phase down the use of dental amalgam - now specified by 2020” (UNEP, 2013).