Ahad, 14 Oktober 2012

Keracunan Raksa



      The growing scarcity of high quality ore bodies on the earth surface has caused many companies to explore and developed mines in more extreme condition in a higher, deeper, hotter or colder environments. Old time gold mining use mercury to extracts gold from host rocks. Gold in ore dissolved selectively in liquid mercury. When heated, the liquid mercury evaporates leaving behind the pure gold. This technique of gold extraction is termed as ‘patio process’ and still continue to be used in the less developed countries. Small scale miners in Brazil and Indonesia use the mercury amalgamation process extensively and have produces millions of ounces of gold while discharging hundreds of tons of mercury to the environments every year. Mercury toxicity has been documented extensively in the small scale gold miners and in humans whom consume fish from the polluted area (Goldfrank L.R. et al. 1994).

      Mercury combines easily with metals such as silver, gold and tin to form alloy called amalgams. These amalgams are routinely used in dental fillings. Exposure to the mercury vapor or dust in dental practice occurs commonly from various sources including instruments that mix amalgam (mechanical algamators), sterilizing instruments, contaminated with amalgam, handling, storing, cleaning mercury or amalgam. Elemental mercury is also used in cantor tubes, thermometers, sphygmomanometers where exposure can occur following breakage or an incorrectly handled spill or repair (Notani, S.P. 1980).

           Mercury toxicity is related to its ability to form covalent bonds with sulfhydryl group, diffusely disrupting enzymes systems in multiple organs. Adverse health effects may results from exposure to any of the 3 different form of mercury that is elemental (Hgº ) , mercuric ( Hg   ) or organic mercury compound such as methyl mercury.  Elemental or metallic mercury can exist as a solid, liquid or vapor state. With increasing temperature, elemental mercury vaporizes and can be inhaled into the lung.

            Elemental mercury vapor is readily absorbed into the lung and transported via red blood cells to the brain and other organs. Mercury is distributed in the brain gray matter and accumulates in the brainstem nuclei and in various parts of the cerebellum. Elemental mercury is not absorbed in the normal gastrointestinal tract and ingestion of elemental contaminated mercury dust is not a significant route of exposure.

Mercuric salt are used as tissue fixative in pathology laboratory. Mercuric salt exposures are less common than elemental mercury exposure in the hospitals. Organic mercury in the form of methyl mercury or alkyl mercury compounds is encountered mainly in seafood and may confound attempts at biologic monitoring for elemental mercury at the workplace. Phenylmercuric acetate was used as one of the most common biocides (for mold and mildew). It is previously use in interior paints (Lunberg I. & Hakansson, M. 1985).

For long term mercury exposure,  a person may reveal subtle personality changes. Tremors, gingivitis, rash or bronchospasm may present. Inhalation of elemental mercury vapors (quicksilver, Hgº) can initially cause caugh, chills, fever and shortness of breath and may progress to pulmonary edema, respiratory failure and death if exposure is substantial. With large inhalational exposure, acute pulmonary toxicity occurs. An erosive bronchitis or bronchiolitis with interstitial pneumonitis can result which usually develop within hours of exposure. Chest X-ray revealed acute interstitial pneumonitis, along with patchy atelectasis and emphysema (U.S. Department of Health and Human Services. 1992).

Following low level long term exposure to environmental mercury or mercuric salts, a range of Central Nervous System effect may be seen. At lowest levels, syndrome of weakness, fatigue, anorexia and gastrointestinal disturbances may be manifested which is termed as micromercurialism. With increasing exposure, there’ll be tremors, initially occurring in the fingers, eyelids and lips. Progression to generalized tremors accompanies more extensive Central Nervous System effect, including memory loss, insomnia, excitability and depression. Subtle and explosive personality disturbances are classically described. Inadvertent enteral exposure routes of mercuric salt results in profound gastrointestinal toxicity and renal tubular dysfunction. Chronic exposure to mercuric salt may leads to sensitization phenomenon with bronchospasm and dermatitis.

Organic mercury may adversely affects the CNS and causes tremors, shyness, emotional lability, nervousness, memory deficit and diminution of psychomotor skills. Contact with phenylmercuric acetate will cause childhood form of mercury toxicity, i.e. acrodynia. Symptoms associated with acrodynia include fever, splenomegaly, irritability, insomnia, personality changes, generalized weakness and erythematous rashes with peeling on the hands, feet and nose. These symptoms are somewhat similar to Kawasaki’s disease. The differences is the facts that acrodynia has no adverse effecs on the coronaries arteries while that is the hall mark for Kawasaki’s disease (Lunberg I. & Hakansson, M. 1985).











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