Acute exposure

Inhalation

Human volunteers exposed to concentrations of 10-20 mg/l (approximately 5,000-10,000 ppm) complained of coughing, and 'smarting' of the eyes and nose. At 30 mg/l (15,960 ppm) there was continuous lacrimation, and marked coughing which could be tolerated but with much discomfort. The atmosphere became 'intolerable and suffocating' at 40 mg/l (21,280 ppm). With an increase in the ventilation rate, simulating work activity, the adverse effects became noticeable at lower concentrations (Lester and Greenberg, 1951).

Dermal

Human volunteers exposed to ethanol using a modified Draize test reported little or no irritation. A 21-day continuous patch test did not show any adverse effects until day 13. Erythema, and hardening were the worst effects reported over the 21-day test period (Phillips et al., 1972). It may be concluded that no adverse effects are expected on acute dermal exposure to ethanol.

Splash contact with ethanol causes an immediate burning sensation with reflex closure of the eyelids. The eye may be painful but this is transient with a residual foreign body sensation. Ethanol contact may cause corneal injury and loosening of the epithelium, however, recovery is rapid and complete (Grant and Schuman, 1993).

Human volunteers exposed to concentrations of 10-20 mg/l (approximately 5,000-10,000 ppm) complained of 'smarting' of the eyes and nose. At 30 mg/l (15,960 ppm) there was continuous lacrimation, which could be tolerated but with much discomfort (Lester and Greenberg, 1951; Grant and Schuman, 1993).

Ingestion

Ethanol is predominantly a CNS depressant. At first it depresses the areas of the brain associated with highly integrated functions, leading to animated behaviour and disinhibition (Osborn, 1998). As the blood ethanol concentration increases there is successive impairment of neural activity and sedation. At high blood concentrations there is loss of protective reflexes, coma, and risk of death from respiratory depression.

The clinical effects following exposure to ethanol correlate well with blood concentration as outlined below. However, as the toxicity of ethanol is also related to the route and rate of absorption and the tolerance of the individual, the blood ethanol concentration should be interpreted with care. Death has occurred at relatively low blood ethanol concentrations, following aspiration of stomach contents.

• Mild intoxication (associated with blood ethanol concentrations <1,500 mg/l): Altered mood, disinhibition and slight incoordination.

• Moderate intoxication (associated with blood ethanol concentrations 1,500-3,000 mg/l): Nystagmus, diplopia, dysarthria and ataxia. Involvement of the autonomic nervous system may also lead to hypotension and hypothermia. Hypoglycaemia and lactic acidosis can occur. There may be flushing, tachycardia, sweating and incontinence. Increasing CNS depression occurs with drowsiness, progressing to stupor and coma. Sedation with loss of the gag reflex leaves the patient at risk of aspirating the stomach contents. Rhabdomyolysis (skeletal muscle breakdown) has been reported in a patient immobilised by ethanol for four hours (Hewitt and Winter, 1995).

• Serious intoxication (associated with blood ethanol concentrations of >3,000 mg/l): Coma, convulsions, respiratory depression and cardiovascular collapse. Concentrations in the range 5-7 g/l are associated with fatalities, usually leading to death from respiratory depression (Gibson et al., 1985; Charness et al., 1989; Osborn, 1998; Bevan, 2001). A concentration as high as 11,270 mg/l has been survived with aggressive supportive management (Berild and Hasselbalch, 1981).

As a result of inter-individual variation, and differences in route of exposure, rate of absorption, degree of tolerance of the individual, and medical predispositions, the blood ethanol concentration may not always correlate with toxicity. A group of patients presenting to a detoxification centre with massively elevated ethanol levels (range 3,000-5,000 mg/l), were reported to be conscious and able to respond appropriately (Redmond, 1983; Redmond, 1986). However, these cases are considered exceptional. The fatal oral dose for ethanol is quoted at 5,000 mg/kg in a non-ethanol tolerant adult (Osborn, 1998).

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