ammonia toxcicity

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Ammonia Toxicity Ahmad Al- Hajjar Aaalhajjar.c.e@gmail.com

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TABLE OF CONTENT 1. Introduction Sources of Exposure. Route of exposure. Ammonia excretion. Kinetics and Metabolism. Health effects of acute exposure Health effects of chronic exposure Animal and In-Vitro Data

Introduction :

Introduction • Ammonia is a compound of nitrogen and hydrogen with the formula NH 3. • It is a colourless gas with a characteristic pungent odour. • Although in wide use, ammonia is both caustic  and hazardous It is used in commercial cleaning products. • Because NH 3 boils at -33.34 °C the liquid must be stored under high pressure or at low temperature.

Sources of Exposure:

Sources of Exposure • Ammonia is released from a number of natural processes, and low levels are present in ambient air. • In Europe, agriculture is the largest source of ammonia. • In the UK, total ammonia emissions have been estimated at around 320,000 tones per year. • Ammonia is used either directly or indirectly in many industrial processes and as such exposure may occur in a range of industrial settings. • Ammonia is transported in bulk as a pressurized gas and spills or leaks after accidents are another potential source of exposure . • Domestically, exposure may occur from certain cleaning agents and dyes. Reaction of cleaning products may cause liberation of ammonia gas .

Route of exposure:

Route of exposure • Ammonia and ammonium hydroxide are corrosive and can rapidly penetrate the eye and may cause permanent injury. • Dermal exposure to ammonia or its solutions may result in irritation and, depending on the concentration, alkali burns. • Ingestion of ammonia solutions (ammonium hydroxide) • Chronic oral exposure to ammonia has not been characterized in humans. • the major route of exposure to ammonia is by inhalation.

Ammonia excretion:

Ammonia excretion • Ammonia reaching the circulation is principally excreted by humans as urinary urea. • excretion of absorbed ammonia in exhaled breath and faeces is not significant Small amounts of ammonia are excreted via the urine; the average daily excretion for human beings is approximately 2-3 μg, about 0.01 % of the total body burden. • Small amounts of unabsorbed ammonia may also be excreted from the gastrointestinal tract in the faeces.

Kinetics and Metabolism:

Kinetics and Metabolism • Ammonia dissolves in moisture in the air and on tissue or mucous membranes to form ammonium hydroxide, a strong base. • Absorbed ammonia is well distributed throughout body compartments and reacts with hydrogen ions, depending on the pH of the compartment to produce ammonium ions. • Ammonium ion is endogenously produced in the gut from the bacterial breakdown of nitrogenous constituents of food. • Almost all of this endogenous ammonium (approximately 99% of the 4 g produced daily) is absorbed by passive diffusion from the intestinal tract before entering the hepatic portal vein.

Cont.:

Cont. • Ammonium is produced in the intestines by bacteria and is efficiently absorbed from the gastrointestinal tract. • Dermal or ocular absorptions are considered not to contribute significantly to systemic ammonium following exposure • Ammonia is readily metabolized in the liver to urea or glutamine.

Health effects of acute exposure:

Health effects of acute exposure • Ammonia and ammonia solutions are irritant and corrosive and may be harmful by all routes of exposure. • Acute oral exposure rapidly results in pain, excessive salivation and burns to the mouth, throat and oesophagus. • Acute inhalation may initially cause upper respiratory tract irritation. Substantial exposures can cause burns in the oral cavity, nasopharynx, larynx and trachea, together with airway obstruction, respiratory distress and bronchiolar and alveolar oedema. • Ammonia or ammonia solutions are corrosive in contact with tissue, and splashes to the eye may result in serious injury.

Cont.:

Cont. The primary features after ammonia exposure are summarized in Table

Health effects of chronic exposure:

Health effects of chronic exposure • Effects following chronic oral exposure have not been defined in humans. Experiments in animals suggest osteoporosis, occurring secondary to chronic metabolic acidosis. • Chronic inhalation has been associated with increased cough, phlegm, wheeze and asthma. • Ammonia is considered not to be a human carcinogen. • Ammonia is considered not to be a human reproductive or developmental toxicant.

Animal and In-Vitro Data:

Animal and In-Vitro Data Inhalation repeated exposures (8 h/5 days a week for 30 days) to ammonia (223 ppm) produced no adverse clinical signs effects in rats, guinea pigs, rabbits, dogs and monkeys. Ingestion In one study, rabbits were given ammonium hydroxide (100 mg kg-1 bodyweight) as a 0.5-1% solution by oral gavages for up to 17 months. The key findings from this study included an initial fall in blood pressure, followed by an increase above the baseline and enlarged adrenal glands.

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