Formaldehyde
·
Dormol, fannoform, formalin,
formalith, formic aldehyde, formol, lysoform, methanal, methyl aldehyde,
methylene oxide, morbicid, oxomethane, oxymethylene.
· Colourless gas with strong pungent
smell.
· Formalin is an aqueous solution of
formaldehyde containing 37 to 40% formaldehyde and 10 to 15% methanol.* This is
however generally referred to as 100% formalin. Therefore 10% formalin would
actually mean a 1: 10 dilution of such a commercial preparation and contains
3.7% formaldehyde. Formalin is a clear, colourless liquid with a pungent odour.
Some formaldehyde aqueous solutions can be amber to dark brown or even reddish
in colour.
· Formaldehyde is also available as a
solid polymer, para-formaldehyde, in a powder or flaked form containing from 90
to 93% formaldehyde, and as its cyclic trimer, trioxane.
·
Industrial/Household: Formaldehyde
is used in fertilisers, pesticides, sewage treatment, paper-making,
preservatives, embalming fluids, disinfectants, foam insulation, urea and
melamine resins, artificial silk and cellulose esters, explo-sives, particle
board, plywood, air fresheners, cosmetics, fingernail polishes, water-based
paints, tanning and preserving hides, and as a chemical intermediate. It is
also used as a preservative and coagulant in latex rubber, and in photograph
developing processes and chrome printing.
·
Medical/Veterinary: Therapeutically,
formaldehyde has been used to treat massive haemorrhagic cystitis and hydatid
cysts of the liver. It has also been used in veterinary medicine. Formaldehyde
is sometimes used to sterilise dialysis machines. Dialysis patients using
dialyser machines sterilised with formaldehyde receive a small dose with each
treatment. The most frequent sequelae is a type of autoim-mune haemolytic
anaemia; rarely, peripheral eosinophilia may occur. Severe hypersensitivity
reactions have been observed in a few of these dialysis patients, though the
exact relationship of this to formaldehyde-sterilised equipment is unclear.
Currently other sterilisers are in use such as a mixture of hydrogen peroxide
and peracetic acid.
·
Formaldehyde is a common contaminant
of smoke and is even present to a significant extent in tobacco smoke. Burning
wood, cigarette smoking, and other forms of incomplete combustion emit
formaldehyde. Addicts some-times dip cigarettes of tobacco or cannabis in
formaldehyde (“amp” or “dank”) before smoking, in the belief that this produces
a hallucinogenic effect and “body numbness”. It is a dangerous practice and can
result in encephalopathy, pulmonary oedema, rhabdomyolysis and coma.
Formaldehyde is a protoplasmic poison and potent caustic. It
causes coagulation necrosis, protein precipitation, and tissue fixation. Due to
conversion in the body to formic acid there is usually profound metabolic
acidosis, and this is aggravated by the concomitant presence of methanol (a
common additive in formalin solutions) which is also broken down to formic
acid. Delayed absorption of methanol might occur following ingestion of
formalin if the formaldehyde causes fixation of the stomach.
·
Inhalation—cough, lacrimation, dyspnoea, chest pain,
wheezing, rhinitis, anosmia, tracheitis, bronchitis, laryngospasm, pulmonary
oedema, headache, weak-ness, dizziness, and palpitations.
·
Ingestion—severe abdominal pain, vomiting, diarrhoea,
haematemesis, tachypnoea, hypotension, cyanosis, altered mental status, and
coma. Seizures, jaundice, albuminuria, haematuria, anuria, and metabolic
acidosis have also been reported. Ulceration of mouth, oesophagus, and stomach
is common. Strictures and perforation are possible delayed complications. Renal
failure is a frequent complication in severe poisoning. Hepatotoxicity has been
reported. Skin and mucous membrane may appear whitened. If the patient survives
for more than 48 hours, the prognosis is good.
·
Dermal exposure—dermatitis, brownish discolouration of the
skin, urticaria, and pustulovesicular eruptions, may develop from dermal
exposure. Concentrated solutions can cause coagulation necrosis.
·
Ocular exposure—irritation, lacrimation, and conjuncti-vitis
may develop with exposure to vapours. Eye expo-sure to solutions with high
formaldehyde concentrations may produce severe corneal opacification and loss
of vision. Inhalation or ingestion of formaldehyde has not been found to affect
vision in humans or animals.
·
Formaldehyde is a known carcinogen in animals, and
epidemiologic data among humans are mounting in implicating the chemical in
human carcinogenesis. There are reports of increased incidence of
nasopha-ryngeal cancers in individuals occupationally exposed to formaldehyde.
Some epidemiologic studies have found a slightly elevated risk for lung cancer
mortality with formaldehyde exposure. Suggestive association between
occupational exposure to formaldehyde and deaths from breast cancer was seen in
one case-control study.
·
Asthma and dermatitis in sensitive individuals.
·
Possible disturbances in memory, mood, and sleep; headache,
and fatigue. Seizures may also be induced.
·
Occupational exposure at recommended limits is not thought
to present a reproductive risk. Formaldehyde exposure among female hospital
workers did not correlate with an increase in spontaneous abortion in one
study, but did correlate in another.
·
Formaldehyde is a potent genotoxin and has been reported to
be active in many short-term genetic tests, including the Ames Salmonella assay
and other assays for mutation using bacteria, chromosome aberrations and sister
chromatid exchanges in vitro and in vivo, and many assays detecting direct
effects on DNA.
·
About 30 to 50 ml of 100% formalin (liquid) ; more than 100 ppm (gas). Ingestion of as little as 30 ml of
37% (approximately 2 tablespoons) formaldehyde solution (formalin) has been
reported to cause death in an adult. Exposure to air concen-trations as low as
2 ppm can cause eye and upper respiratory irritation. Dermal exposure to
formalin can result in irritation (acute),
or allergic dermatitis (chronic) in
susceptible individ-uals. Exposure to solutions of 2 to 10% may result in
blisters, fissures, and urticaria.
· Formaldehyde plasma levels are not
widely available, but may help in dialysis monitoring.
· Monitor acid base status in
symptomatic patients.
· Monitor liver function tests.
· Monitor haematocrit and haemoglobin
concentration in dialysis patients repeatedly exposed parenterally to
formal-dehyde.
· Monitor blood methanol levels after
significant formalin ingestion.
· Pulmonary function testing and nasal
and bronchial provo-cation tests may be recommended in patients with signs and
symptoms of reactive airways dysfunction following inhalation of formaldehyde.
· The presence of a small amount of
endogenously derived formate in human urine is normal; however, formate derived
from the metabolism of formaldehyde, several other indus-trial compounds
(methanol, halomethanes, acetone) and some pharmaceutical compounds may elevate
the urine formate concentration above the normally expected values.
· Urinary formic acid levels were
shown to be subject to a great deal of individual variation and did not
correlate with known exposures to formaldehyde. Formic acid is not a suitable
biomarker for formaldehyde exposure.
·
Dilution with milk or water as a first-aid measure may help
reduce corrosive effects. Emesis is contraindicated. Activated charcoal may be
of benefit.
·
Gentle gastric aspiration with a soft nasogastric tube (if
the victim is seen within 1 hour of ingestion).
·
Sodium bicarbonate IV.
·
Haemodialysis.
·
Ethanol infusion will help counteract methanol toxicity.
·
Monitor electrolytes, fluids, acid-base, and renal
func-tion.
·
Dopamine or noradrenaline for hypotension
·
Watch for signs of gastrointestinal haemorrhage and
perforation.
·
Early endoscopy to assess the degree of injury.
·
Inhalation exposure: Administer 100% humidified
supplemental oxygen, perform endotracheal intubation, and provide assisted
ventilation as required. Administer inhaled beta adrenergic agonists if
bronchospasm develops. Maintain adequate ventilation and oxygena-tion with
frequent monitoring of arterial blood gases and/or pulse oximetry. If a high
FIO2 is required to maintain adequate oxygenation, mechanical
ventilation and positive-end-expiratory pressure (PEEP) may be required;
ventilation with small tidal volumes (6 ml/ kg) is preferred if ARDS develops.
·
Exposed skin and eyes should be flushed with copious amounts
of water. Patients with ocular exposure to significant concentrations of
formaldehyde should be evaluated by an ophthalmologist.
·
Removal of patient from exposure.
·
Symptomatic measures.
·
Preventive measures include exhaust
ventilation at place of work, use of goggles, face shields, gloves, and aprons.
·
Odour of formalin around the mouth
and nostrils, and in the stomach contents.
·
Inflammatory oedema of oesophagus,
larynx, and lungs.
·
Stomach (and sometimes the proximal
small intestine) may show signs of “fixation” of tissues. Histological details
may be well preserved.
·
Kidneys may reveal microscopic
evidence of tubular necrosis.
·
Autopsy
Diagnosis: To confirm the presence of formalde-hyde in the gastric
contents, a small quantity of the latter is dissolved in resorcinol in a test
tube and sulfuric acid is gently poured along the sides of the tube. A red to
violet coloured ring will develop at the junction of the two solu-tions.
·
Most reported cases of acute poisoning are either accidental
or suicidal in nature. Chronic poisoning is invariably due to occupational
exposure.
·
Some Indian studies conducted in embalming rooms of medical
colleges revealed fairly high formaldehyde concentra-tion of ambient air,
stressing the need for fixing standard limits of exposure in work places in
India like in the West.
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