Mercuryand its compounds are highly toxic to humans, especially to the developing
nervous system. They are also harmful to ecosystems and wildlife populations.
Microbial metabolism of deposited mercury can create methylmercury, which has
the capacity to collect in organisms (bioaccumulate) and to concentrate up food
chains (biomagnify), especially in the aquatic food chain. Methylmercury is a
well-documented neurotoxicant, which may in particular cause adverse effects on
the developing brain. It readily passes both the placental barrier and the
blood-brain barrier; therefore, exposures during pregnancy are of highest
concern. It may also cause adverse effects on the cardiovascular system,
thereby leading to increased mortality. Methylmercury compounds are considered
possible carcinogenic to humans according to the International Agency for Research
on Cancer. Furthermore, inhalation of elemental mercury vapour causes symptoms
such as tremors, insomnia, memory loss, neuromuscular changes, and headaches.
Kidney and thyroid may be affected.
Mercuryin the atmosphere is divided into three inorganic forms i.e. the elemental mercury reactive gaseous
mercury and particulate mercury. Hg0 is the main chemical speciation of
atmospheric mercury, which constitutes the majority of the mercury in the atmosphere
over 95%. As Hg0 has very low solubility in water and its chemical reaction
rate is very slow with other components in the atmosphere such as the strong
oxidant O3, H2O2, OH and NO3 radicals Hg0 has a long atmospheric lifetime and can be transported through the atmosphere
over thousands of kilometers.
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