Description

• Kinetics and metabolism
  nitric acid or HNO₃ is corrosive at the site of contact and does not elicit systemic toxicity
•  on contact with body tissues, nitric acid is rapidly broken down into its constituent ions

Health effects of acute exposure

HNO₃is irritating and corrosive to all tissues with which it comes into contact
acute inhalation of nitric acid vapour can lead to symptoms such as ocular and nasal
irritation, sore throat, cough, chest tightness, headache, ataxia and confusion
in severe cases, pulmonary oedema may develop hours or days following exposure
acute ingestion may cause burns to the oesophagus and stomach which can cause
ulceration, haemorrhage and perforation. Abdominal pain, nausea, salivation, vomiting,
diarrhoea and haematemesis may occur, and some cases may be fatal
dermal exposure may result in deep burns, blisters and permanent scarring
ocular exposure may cause corneal burns, lacrimation, photophobia and blindness

Health effects of chronic exposure

chronic inhalation exposure to nitric acid can cause respiratory irritation, leading to
bronchitis and airways hyper reactivity and erosion of dental enamel
dermal exposure to low concentrations of nitric acid can result in dermatitis
strong inorganic acid mists found in occupational settings, which may include (but not
limited to) nitric acid, are carcinogenic to humans, causing cancer to the larynx and
possibly lung

Nitric acid

• Summary of Health Effects

ConcentratedHNO₃ is highly corrosive to all tissues with which it may come into contact
and exposure can occur via all routes (ingestion, inhalation, dermal and ocular
absorption .
The toxicity of nitric acid is due to its effects at the point of contact; it readily dissociates into
simple ions and therefore systemic effects are unlikely.
Inhalation exposure to HNO₃ is a common occupational hazard as it readily forms a
vapour at room temperature. Symptoms of an acute inhalation exposure toHNO₃ include
a burning sensation, dry nose and throat, cough, chest pain, shortness of breath, headache
and difficulty breathing . An acute exposure to a high dose of concentrated HNO₃ can
cause pulmonary oedema, which has a latency period between 3 and 30 hours and can
potentially be fatal.

Long term inhalation exposure to HNO₃ can lead to chronic respiratory irritation such as
bronchitis and may also lead to dental erosion as the HNO₃ deposits on the teeth and
erodes the outer coating of the enamel.
Inhalation of strong inorganic acid mists, which may include nitric acid, causes cancer of the
larynx; the evidence suggests exposure may also associated with lung cancer in humans [5].
Ingestion of nitric acid can cause burns to the lips, tongue, mouth, throat and stomach. Other
symptoms can include abdominal pain, nausea, vomiting and diarrhoea . In severe cases,
the ingestion of a high dose of HNO₃ may be fatal .
Dermal exposure to HNO₃ can result in severe burns, blisters and permanent scarring
depending upon the concentration of the acid and the duration of exposure. Ocular exposure
can cause severe eye burns, pain and redness which may lead to permanent injury and
possibly blindness.

• Kinetics and Metabolism

HNO₃ is a contact irritant that causes adverse effects at the site of exposure. The
corrosive effects of nitric acid are due to the low pH. Aqueous solutions and vapours of nitric
acid readily dissociate into hydrogen and nitrate ions.
Following inhalation exposure HNO₃ reacts immediately with respiratory mucous
membranes and does not appear to be absorbed after oral exposure . Exposure to HNO₃ does not give rise to systemic toxicity as it is broken down at the point of contact and
therefore causes adverse effects only at the site of exposure .