Mercury

7439-97-6

200.61

Transformation to methylmercury is the most important part of Hg
cycle in the environment. 
Hg is strongly bound to organic
matter is soil and sediment. - 
Inorganic Hg compounds are
methylized abiotically in the presence of methylcobalamine
(B12-CH3) and biotically with help of enzymes
(Hg2+ -> CH3Hg+ + /(CH3)2Hg) (Kaiser & Tölg 1980).

Organic Hg compounds kan be formed and break up chemically,
biochemically and through photosynthesis as well in atmosphere
as in aquatic environment: CH3Hg+ <-> (CH3)2Hg <-> Hg <-> Hg2+
(Anon 1989).

Inorganic Hg is mainly stored in kidneys (WHO 1976).

Organic Hg compounds decompose to inorganic Hg and accumulates in
kidneys (WHO 1976).

Methylmercury is absorbed in alimentary canal 90 - 100 %
after intake with food, whereas inorganic Hg is absorbed less
than 15 % (WHO 1976).

Brains seem to be very sensitive to methylmercury and for Hg
vapour  (Berlin 1986).

Methylmercury is very slowly decombosed mainly through
faeces (Berlin 1986).

Cat, inhalation, > 0.010 mg/m3 Hg vapor in air, effects on
reflexes (Nordberg 1981).

Rat, inhalation, NOEC, 0.003 mg/m3, Hg vapor (Nordberg 1981).

Toxic when 5 mg/kg in brains and in muscles of mink. 
Harp seal 
was killed at 25 mg/kg in 20 - 26 days (Virtanen & Nuuja 1987).

Inorganic bivalent Hg compounds and unstabile organic Hg
compounds induce damages in kidneys (Berlin 1986).

Methylmercury has effects on the central nervous system -
motoric and mental disorders etc. 
(Berlin 1986).

Classification: Group D: not enough evidence in animal
experiments (USEPA 1986).

Drosophila: slight mutagenicity (Perwak et al. 1985).

Teratogenic effects on fish and birds (Leonard et al. 1983).

LC50 0.051 ppm, 96hr, tadpoles of Rana hexadactyla (Khangarot et
al. 1985).

The 4-leaf stage plants (Pennisetum typhoideum, Medicago
sativa, Abelmoschus esculentum) were grown for 24 hours in
Knop's nutrient solution mixed with a known concentration
(1ppb, 10 ppb,...) of Hg solutions (HgCl2). 
Subtle damage in
terms of reduced chlorophyll content and reduction in standing
phytomass of the plants was observed at 1 ppb and visible
foliar symptoms at 10 ppb (Mhatre & Chaphekar 1984).

When the roots of onion bulbs had reached a length of about 15
mm the bulbs were transferred to glas jars containing the
experimental solution, where they were kept for 72 hours:
                     Lowest lethal dose for Allium cepa roots
1.Panogen 5            0.00125 mol/l (250 ppm Hg)
2.Panogen 8            0.00032 mol/l (64  ppm Hg)
3.Methyl mercury dicyanidamide 0.00025 mol/l (50 ppm Hg)
4.Methyl mercury hydroxide     0.00025 (50 ppm Hg)

                           Lowest C-mitotic dose
1.                      0.00000025 mol/l (0.05 ppm Hg)
2.                      0.00000080 mol/l (0.16 ppm Hg)
3.                      0.00000060 mol/l (0.13 ppm Hg)
4.                      0.00000025 mol/l (0.05 ppm Hg)
5.Phenyl mercury hydroxide 0.00000080 mol/l (0.16 ppm Hg)
6.Methoxyethyl mercury chloride 0.00000314 mol/l (0.63 ppm Hg)
(Ramel 1969).

LC50 0.36 mg/l, 96hr, Aplexa hypnorum (Holcombe et al. 1983). 
LC50 0.023 mg/l, 96hr, Lymnea acuminata (Khangarot et al. 1982).

LC50 0.16 mg/l, 96hr, Nais communis; LC50 0.29 mg/l, 96hr,
Ilyodrilus frantzi (Chapman & Mitshell 1986).