Archives of Toxicology

, Volume 67, Issue 5, pp 365–368 | Cite as

Degradation of methyl and ethyl mercury by singlet oxygen generated from sea water exposed to sunlight or ultraviolet light

  • Ikuo Suda
  • Mari Suda
  • Kimiko Hirayama
Short Communication


Photodegradation of methyl mercury (MeHg) and ethyl Hg (EtHg) in sea water was studied by sunlight or ultraviolet (UV) light exposure, and by determining inorganic Hg produced by degradation. Sea water containing 1 μM MeHg or EtHg was exposed to sunlight or UV light. N-Acetyl-l-cysteine was added to the solution for preventing Hg loss during the light exposure. MeHg and EtHg in sea water were degraded by sunlight (>280 nm), UV light A (320–400 nm) and UV light B (280–320 nm), though the amounts of inorganic Hg produced from MeHg were 1/6th to 1/12th those from EtHg. Inorganic Hg production was greater with increasing concentration of sea water. Degradation of MeHg and EtHg by the UV light A exposure was inhibited by singlet oxygen (1O2) trappers such as NaN3, 1,4-diazabicyclo[2,2,2]octane, histidine, methionine and 2,5-dimethylfuran. On the other hand, inhibitors or scavengers of Superoxide anion, hydrogen peroxide or hydroxyl radical did not inhibit the photodegradation of alkyl Hg. These results suggested that (1O2) generated from sea water exposed to sunlight, UV light A or UV light B was the reactive oxygen species mainly responsible for the degradation of MeHg and EtHg.

Key words

Methyl mercury Ethyl mercury Reactive oxygen Photodegradation Sunlight 





methyl mercury


ethyl mercury


superoxide anion


hydrogen peroxide

· OH

hydroxyl radical


singlet oxygen






Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Asada K (1990) Light and oxygen environments in the biosphere and their effects on the evolution of organisms. J Act Oxyg Free Rad 1: 28–37Google Scholar
  2. Eto K, Oyanagi S, Itai Y, Tokunaga H, Takizawa Y, Suda I (1992) A fetal type of Minamata Disease: an autopsy case report with special reference to the nervous system. Mol Chem Neuropathol 16: 171–186PubMedGoogle Scholar
  3. Inoko M (1981) Studies on the photochemical decomposition of organomercurials-methyl mercury (II) chloride. Environ Pollut (Series B) 2: 3–10CrossRefGoogle Scholar
  4. Konishi T, Takahashi H (1983) Direct determination of inorganic mercury in biological materials after alkali digestion and amalgamation. Analyst 108: 827–834CrossRefPubMedGoogle Scholar
  5. Suda I, Hirayama K (1992) Degradation of methyl and ethyl mercury into inorganic mercury by hydroxyl radical produced from rat liver microsomes. Arch Toxicol 66: 398–402PubMedGoogle Scholar
  6. Suda I, Takahashi H (1986) Enhanced and inhibited biotransformation of methyl mercury in the rat spleen. Toxicol Appl Pharmacol 82: 45–52CrossRefPubMedGoogle Scholar
  7. Suda I, Takahashi H (1992) Degradation of methyl and ethyl mercury into inorganic mercury by other reactive oxygen species besides hydroxyl radical. Arch Toxicol 66: 34–39PubMedGoogle Scholar
  8. Suda I, Totoki S, Konishi T, Takahashi H (1990) Biotransformation of alkyl mercury by active oxygen producing systems. Comprehensive Studies on Minamata Disease 16 [Suppl]: 39–49Google Scholar
  9. Suda I, Totoki S, Takahashi H (1991) Degradation of methyl and ethyl mercury into inorganic mercury by oxygen free radical-producing systems: involvement of hydroxyl radical. Arch Toxicol 65: 129–134PubMedGoogle Scholar
  10. Suda I, Totoki S, Uchida T, Takahashi H (1992) Degradation of methyl and ethyl mercury into inorganic mercury by various phagocytic cells. Arch Toxicol 66: 40–44PubMedGoogle Scholar
  11. Takahashi H, Shibuya Y, Fukushima Y (1978) Photochemical degradation of methylmercury. Comprehensive Studies on Minamata Disease, Middle Reports 4: 7–10Google Scholar
  12. Takizawa Y, Minagawa K, Hisamatsu S (1981) Studies on mercury behaviour in man's environment: (report V) photodegradation of methylmercury in the atmosphere by ultraviolet rays with sterilization. Jpn J Pub Health 28: 313–320Google Scholar
  13. Yasutake A, Hirayama K (1990) Selective quantification of inorganic mercury in tissues of methylmercury-treated rats. Bull Environ Contam Toxicol 45: 662–666CrossRefPubMedGoogle Scholar

Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • Ikuo Suda
    • 1
  • Mari Suda
    • 1
  • Kimiko Hirayama
    • 2
  1. 1.Kyushu National Agricultural Experiment StationMAFFNishigoshi KumamotoJapan
  2. 2.Kumamoto University College of Medical ScienceKumamotoJapan

Personalised recommendations