Mercury

Heavy metals and pesticides are bio-accumulated and under go bio-magnification. Mercury is the best example.
Source:
Pollutants in water bodies (organic forms of mercury), taken up by cyclops and other aquatic microorganisms primarily consumed by fish and finally by man. Minimata bay episode is an ideal incident to be quoted.
I. Inorganic – Calomel (Mercurous chloride). Used for opacity of cornea.
Yellow mercuric oxide – HgO and red mercuric oxide – HgI2 used as parasiticidal and counter irritant ointments.
II. Organic – Thiomersal / merthiolate, mercurochrome, phenyl mercuric acetate and nitrate used as antiseptic and fungicides. Mercurial seed dressings- specially fungicides.
Organic compounds are comparatively less toxic than inorganic forms. Mercury is readily absorbed through skin when ointments are applied. Also release of mercury vapours from one animal might affect other animals in the same shed [absorption through respiratory system]. Dogs, cats and cattle lick ointments. Red oxide of mercury is applied to horns and idols in villages.
Industrial effluents released into aquifers. Toxicity is due to conversion of mercurous salt into mercury and mercuric forms by catalase in RBCs within 15-20 minutes.
In the body mercury is stored in liver and kidneys. Excretion is in urine, faeces, saliva, sweat and milk. A little amount is retained in the tissues especially muscle and hair.
Action: Organic form acts by inhibiting ‘SH’ group of intramembranal and cellular proteins – thus forming mercaptides. Hepatotoxic, nephrotoxic and also neurotoxic as it crosses BBB and is immunosuppressive.
Inorganic form of mercury precipitates proteins and causes local corrosive action, has high affinity for phosphates, histidinyl and cysteinyl side chains of proteins, purines and porphyrins.
Clinical signs
Adult livestock
Violent gastro enteritis, diarrhoea, dehydration leading to shock, collapse and death.
Cattle – colic and sub normal temperature followed by death.
If animal lives, stomatitis and acute nephritis are seen.
In young animals – gastroenteritis is slight but nephritis and paralysis are predominant.
If absorption is through respiratory mucosa – dyspnoea and coughing, nasal discharge, fever, loss of appetite, bleeding of oral mucosa, (gingivitis) dermatitis and nephritis.
Lesions: Gastroenteritis, nephritis, edema of lungs, hydrothorax, hydropericardium, sub-pial edema and hemorrhages in epicardium and endocardium.
Diagnosis: Through history of, symptoms, lesions and detection of mercury in stomach, kidney and liver.
Rx: Chance of survival in acute poisoning is less. Prognosis is good if stomach is emptied in 10-15 minutes.
1. Raw white of egg to precipitate mercury followed by gastric lavage with saturated sodium bicarbonate solution.
2. Sodium thiosulfate 30 ml of 20% solution orally or I/V.
BAL is the drug of choice, dose same as that of arsenic.