hg toxicity
TRANSCRIPT
MERCURY TOXICITY
Toxicity Source Human action Side effects Adverse effects
Contents
Mercury poisoning (also known as hydrargyria or mercurialism) is a type of metal poisoning caused by exposure to mercury or its compound mercury (Hg).
Mercury is a heavy metals means a metal of relatively high density, or of high relative atomic weight.
Heavy metal occurring in several forms, all of which can produce toxic effects in high enough doses.
INTRODUCTION
More about Mercury Mercury, or quicksilver, was known in ancient times as
hydrargyros, hence it’s chemical symbol ‘Hg’. Mercury is the only metal that is liquid at room
temperature and pressure. Mercury is an extremely rare element, but occurs in
deposits throughout the world mostly as cinnabar (or mercuric sulphide).
Like water, mercury can evaporate and become airborne. Because it is an element, mercury does not break down
into less toxic substances. Once mercury escapes to the environment, it circulates in
and out of the atmosphere until it ends up in the bottoms of lakes and oceans.
Mercury can be found as the elemental metal or in a wide variety of organic and inorganic compounds.
Depending on its chemical form, mercury may travel long distances before it falls to earth with precipitation or dust.
Uses of Mercury
Felting and Hat-making Fluorescent lamps Mercury batteries Thermometers and thermostats Vacuum pumps, Barometers, Electric rectifiers and switches Printer and photocopy toners. Mercury-vapor lamps (for sterilizing water and
instead of steam in boilers of some turbine engines.) Amalgamation (to dissolve silver or gold to form
an amalgam, as in tooth fillings) This process has been largely supplanted by the cyanide process, in which gold or silver is dissolved in solutions of sodium or potassium cyanide.
Sources of Mercury Non-ferrous metal manufacturing, mining
and alumina production are the largest sources of mercury emissions.
Precious metal mining (which can emit mercury to water or land),
Cement manufacturing (which may emit mercury into the air) and
Chemical manufacturing, which can emit of mercury to land and into water.
Fossil fuel power plants may also emit mercury into the air by burning fuels such as coal, oil, and petrol.
Our landfills and sewage also contribute to mercury being released into our soil and water.
Small amounts of mercury can be released into the air in the exhaust fumes of cars, buses and motorbikes.
Relative sources of mercury exposure
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FORM OF MERCURY
EXISTS IN THREE CHEMICAL FORM Elemental mercury
Inorganic mercury
Organic mercury
ELEMENTAL MERCURY
Most volatile .Exist in liquid/vapor form. Inhaled and absorbed into
lungs(80%) and GIT(0.01%) and can cross the blood brain barrier or reach the placenta.
Most common form amalgam restoration.
Exposure to this form can occur due to accidental spillage of mercury in dental office.
Elemental mercury is used in thermometers, barometers, and pressure-sensing devices.
Hg˚ released from amalgam & inhaled with 80%uptake in the lung
Hg˚ distributes and throughout body and nervous system
Hg˚ breaks down to inorganic mercury (Hg˝)
Hg ˝ accumulates in the nervous system , liver and kidney
INORGANIC MERCURY
Normally mined as inorganic sulfide oreMainly in liquid form Can also exist in other form than sulfide Irritating in nature Main route of entry is through lung(80%)Due to absence of fully formed blood brain barrier
it has been found in neonatal brain. Inorganic mercury form complexed with gluthione
in the liver and secreted in the bile cysteine mercury or gluthione mercury complex.
Inorganic mercury was used in the past in laxatives, skin-lightening creams and soaps, and in latex paint.
ORGANIC MERCURY
Mainly in the form of methyl mercury (CH3Hg+ )
Main route of entry is absorption though GIT(95-98%) though food.
Used in fungicide and pesticide.
Found in vegetables , fruits and grains.
Toxic in nature.
Effects on Humans
Depending on its chemical form (elemental, inorganic or organic) mercury is able to cause a myriad of adverse health effects including :
Neurotoxicity (elemental mercury, methyl-mercury),
Nephrotoxicity (elemental mercury, mercuric salts such as mercuric chloride),
Teratogenicity (methyl-mercury) – abnormalities in physiological development, including birth defects
Death (elemental mercury, methyl-mercury).
Side effect of mercury
ALLERGY
TOXICITY
ALLERGY
Allergy responses represent an antigen-antibody reaction marked by itching, rashes, sneezing, or other symptoms
Contact dermatitis or Comb's type IV hypersensitivity reaction represent the most likely physiologic side effect to dental amalgam
TOXICITYTOXIC EFFECT ON MERCURY
FORM OF MERCURY
ELEMENTAL INORGANIC METHYL MERCURY
ROUTE OF EXPOSURE
INHALTION ORAL ORAL –FISHCONSUMPTION
TARGET ORGAN CNS , KidneyPeripheral nervous system
KIDNEY, PNS CNS
LOCAL CLINICAL SIGN
Lung ;bronchial irritation
GI-irritationSkin – irritation ulceration
SYSTEMIC EFFECTS
Kidney-proteinuriaCNS –mood changePNS - Tremors
Kidney – proteinuria,Tubular necrosisIs PNSTREMORSNUMBNESS
Developmental Effects in fetus And newborn.CNS IN ADULT TREMORS PARAESTHESIA
PSYCHOLOGICAL DISTURBANCES
Fits of anger short term memory loss low self –esteem loss of self control sleepiness.A person may also suffer from the loss
of ability to learn new thing or things that require memorization
ORAL CAVITY PROBLEMs
Inflammation of the mouth loss of bone around teeth ulcerated gums and other
areas in the mouth Darkening of gums taste of metal Bleeding gums
RESPIRATORY PROMBLEMS -Weakness and problems with breathing - Emphysema -persistent cough
NEUROLOGICAL PROBLEMS -headaches -vertigo -tinnitus - twitching in various areas of the body (eyelid, feet etc.)
G.I.T PROBLEMS -Cramps -inflamed colon -diarrhea C.V.S PROMBLEMS -Weak pulse -increase B.P -Chest pain/feeling of pressure in the chest area
Hg Damage Development of CNS In The Fetus During The Prenatal period
Mercury poisoning can result in several diseases, including:- Acrodynia (pink disease) Hunter- Russell syndrome MINAMATA DISEASE
Acrodynia (Pink disease) Considered to be a mercury allergy
Erythema of the palms soles Edema of hand and feet Desquamating rash Hair loss Diaphoresis Tachycardia, hypertension Photophobia Irritability,
Constipation/Diarrhea Anorexia Insomnia Poor muscle tone
HUNTER-RUSSELL SYNDROME
Syndrome is characterized by paresthesia,
visual field constriction, ataxia, impaired hearing, and speech impairment.
The term Hunter-Russell syndrome derives from a study of mercury poisoning among workers in a seed packing factory in Norwich, England in the late 1930s who breathed methyl mercury that was being used as a seed disinfectant and preservative.
MINAMATA DISEASE
Minamata disease is an example of organic toxicity. In 1952 Minamata Bay, a factory discharged inorganic
mercury into the water. The mercury was methylated by bacteria and subsequently ingested by fish.
In 1953 fisherman and farmers showed symptoms-neurological damage and fetal deformity.
Disease diagnosed in 1956 - linked to fish consumption 1957 fishing banned in area1959- mercury identified as cause1960 source identified - factory effluent.
Symptoms were:- 1.ataxic gait 2.convulsions 3.numbness in mouth & limbs 4.constriction in the visual field 5.difficulty in speaking.
Adverse effects
Acute perioral and facial paresthesias Visual-field constriction Respiratory distress and nonspecific dermatitis
Babies exposed in utero are affected by low birth weight, seizure disorders, profound developmental delay, incomplete visual loss (including tunnel vision) or total blindness, and hearing loss.
Neurologic damage in the form of diffuse and widespread neuronal atrophy is most severe in patients exposed in utero.
Even prenatal exposure at low concentrations can cause subtle, but detectable, decrements in the areas of motor function, language, and memory.
Children so affected may have long-term stigmata, including motor impairment, visual loss, hearing loss, developmental delay, and seizure disorders.
Dental amalgam are still widely used by the dental profession in most parts of the world.
Some countries, like Sweden, Canada and Germany, UK have either banned or imposed serious limitations on amalgam usage.
WHO states mercury levels in biomarkers such urine, blood , hair do not represent levels in critical organs and tissues.
The American Dental Association Council on Scientific Affairs has conclude that both amalgam and composite materials are considered safe and effective for tooth restoration.
CONCLUSION