Sodium hydroxide does not readily form a vapour and inhalation exposure is only likely to occur to aerosols. Three case reports suggest that sodium hydroxide aerosols may cause severe irritation of the respiratory tract. In one case, permanent lung injury resulted. Due to its corrosive nature, sodium hydroxide aerosols could cause pulmonary edema (severe, life- threatening lung injury). A worker, exposed to hot mists of sodium hydroxide in a confined space, experienced tightness of chest, dyspnea (difficult breathing) and cough during each exposure. The symptoms resolved when exposure stopped. Irreversible obstructive lung disease resulted when an individual applied about 5 L of a 5% sodium hydroxide solution with a brush in a small room with very limited ventilation. Severe lung injury occurred in a man who inhaled in an aerosol given off when water was poured on sodium hydroxide pellets.

Sodium hydroxide is extremely corrosive and is capable of causing severe burns with deep ulceration and permanent scarring. It can penetrate to deeper layers of skin and corrosion will continue until removed. The severity of injury depends on the concentration of the solution and the duration of exposure. Burns may not be immediately painful; onset of pain may be delayed minutes to hours. Several human studies and case reports describe the corrosive effects of sodium hydroxide. A 4% solution of sodium hydroxide, applied to a volunteer's arm for 15 to 180 minutes, caused damage which progressed from destruction of cells of the hard outer layer of the skin within 15 minutes to total destruction of all layers of the skin in 60 minutes. Solutions as weak as 0.12% have damaged healthy skin within 1 hour. Sodium hydroxide dissolved the hair and caused reversible baldness and scalp burns when a concentrated solution (pH = 13.5) dripped onto a worker's head and treatment was delayed for several hours.

Sodium hydroxide is extremely corrosive. The severity of injury increases with the concentration of the solution, the duration of exposure, and the speed of penetration into the eye. Damage can range from severe irritation and mild scarring to blistering, disintegration, ulceration, severe scarring and clouding. Conditions which affect vision such as glaucoma and cataracts are possible late developments. In severe cases, there is progressive ulceration and clouding of eye tissue which may lead to permanent blindness.

There are no reported cases of industrial workers ingesting sodium hydroxide solutions. Non-occupational ingestion has produced severe corrosive burns to the esophageal tissue, which has in some cases progressed to stricture formation. Should ingestion occur, severe pain; burning of the mouth, throat and esophagus; vomiting; diarrhea; collapse and possible death may result.

SKIN: Owing to its corrosive nature, repeated or prolonged skin contact would be expected to cause drying, cracking, and inflammation of the skin (dermatitis).

INHALATION: A worker, exposed for 2 hours daily over 20 years to mists from boiling a solution of sodium hydroxide in 2 large containers in a small room with inadequate ventilation, developed severe obstructive airway disease. It was concluded that the massive and prolonged exposure induced irritation and burns to the respiratory system eventually leading to the disease. The authors noted that chronic exposure had not previously been reported, probably since the strong and immediate irritation would normally deter workers from further exposure. Actual exposures to sodium hydroxide aerosols were not measured and the authors could not definitely exclude late onset asthma as a cause of the man's condition.

A report of workers exposed to sodium hydroxide aerosol for at least 16 months, was confounded by the presence of high concentrations of Stoddard solvent and other solvent vapours, as well as other chemicals.

There was no trend of increased mortality in relation to duration (up to 30 years) or intensity of exposure (0.5 mg/m³ to 1.5 mg/m³) among 291 workers exposed to sodium hydroxide dust during the production of flakes or beads of concentrated sodium hydroxide from chlorine cell effluent. This study is limited by the small population size.

Sodium hydroxide has been implicated as a cause of cancer of the esophagus in individuals who have ingested it. The cancer may develop 12 to 42 years after the ingestion incident. Similar cancers have been observed at the sites of severe thermal burns. These cancers may be due to tissue destruction and scar formation rather than the sodium hydroxide itself.

A case-control study reported an association between renal cancer and history of employment in the cell maintenance area of chlorine production. The major exposures in this work were presumed to be to asbestos and sodium hydroxide. An association was made between renal cancer and sodium hydroxide exposure. This study is limited by factors such as small numbers of exposed workers, multiple exposures, reliance on work histories and is not considered sufficiently reliable.

There is no human or animal information available.

There is no human or animal information available.

No information available.

It does not accumulate.