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Jul, 09 2005
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Ammonia

Ammonia

Molecular Formula : H3N


Uses and sources of emission :

Ammonia is used mainly in the manufacture of fertilizers and of many other products in a very large variety of fields. It is used as a cooling gas in the industry of industrial refrigeration.
One can also find it as a cooling gas in arenas, and as an air contaminant in breeding settings (examples: pigsties, henhouses).
Ammonia is also found as liquid ammonia which is in fact gaseous ammonia dissolved in water (solution of ammonia at 28% or ammonia at 28%).

Hygiene and Safety :
I-Appearance :

Ammonia is a colourless gas with a characteristic and prickly odor. It is a suffocating gas at high concentration.

II-Exposure Characteristics :

Exposure to ammonia in the work environment occurs mainly as a gas, because of its very low boiling point and its great volatility. The exposure to liquified ammonia generates a significant gas concentration because of its very low boiling point and its high volatility.
The exposure to liquified ammonia is increasingly frequent because of its use in refrigeration systems. Moreover, concentrated aqueous ammonia solutions can emit ammonia vapors at high levels of concentration.

III-Exposure to the gas :
The prickly odor characteristic of ammonia can be detected at 16,7 ppm, which is in the same order of magnitude as the VEMP, 25 ppm or 17 mg/m³; at a VECD of 35 ppm or 24 mg/m³; at an IDLH value of 300 ppm or 209 mg/m³ and at the lower limit of explosiveness at 13 % or 13 000 ppm; so that it can be a sign of adequate warning before the exposure becomes dangerous.
An olfactive fatigue occurs following repeated exposures, therefore the odor cannot be an adequate sign of warning to an exposure exceeding the VEMP or the VECD. However, the olfactive threshold is sufficiently low to prevent a situation of IDLH.

IV-Exposure to the liquid :

Ammonia is a liquid at -33,35°C. In the liquid state, it is thus necessary to take into account all the aspects which comprise the exposure to a liquid at low temperature.

Immediately dangerous to life or health (IDLH) : 300 ppm

V-Inflammability and explosiveness :

A-Inflammability :

The fire hazard caused by ammonia is relatively low, it must be put in contact with materials or a surface having a temperature of 651°C before igniting itself
However the presence of oil or other combustible materials can increase the fire hazard by lowering this temperature of autoignition. Ammonia can ignite in contact with strong oxidants.

B-Explosiveness :

Ammonia requires a concentration of at least 15% and the presence of a source of ignition to explode.
Ammonia can explode in contact with strong oxidants.


Toxicology :

I-Toxicokinetics :

A-Absorbtion
Ammonia is mainly absorbed by the respiratory tract. Absorption by other routes is negligeable.During a short-time exposure (up to 2 minutes) at concentrations varying between 57 and 500 ppm, 83 à 92 % of the inhaled dose is retained in the respiratory tract (mouth, lungs, etc.), among volunteers. Following longer exposures (30 minutes) among seven (7) volunteers exposed at 500 ppm, it has been reported that the retention of ammonia in the mucous membranes of the nasopharynx diminishes to 23 % when equilibrium is achieved (after10 à 27 minutes).
B-Distribution :
The few data available in man suggest that only small amounts are absorbed into the blood circulation. Blood ammonia is distributed throughout the body where it plays an important role the synthesis of proteins and in maintaining the acid-base equilibrium.
C-Metabolism :
Ammonia is an essential constituent of the human body. It is produced during digestion and rapidly metabolized into glutamine and urea, mainly by the liver.

D-Excretion :
The major part of ammonia (70-80%) dissolved in the mucous membranes of the upper respiratory tract was excreted unchanged in the expired air following inhalation at 500 ppm during 10 to 27 minutes by volunteers. Ammomia absorbed by the body is excreted by the kidneys as urea and ammonia compounds. Less than 1% of the 4 grams of ammonia produced daily by the intestinal tract is excreted in the feces. A certain amount may also be excreted in sweat.
II-Acute Effects :
Irritation and corrosion :

Ammonia being absorbed very little by the body, its effects are limited to its irritating and corroding capacity to the eyes, the skin and the respiratory tract.
Ammonia as a gas is irritating and corrosive to the skin, the eyes and the higher respiratory tract (nose and throat). The severity of symptoms may vary according to the conditions of exposure (duration of contact, concentration of the product, etc).
The first signs of exposure are discomfort, dry nose, watering and a burning sensation in the eyes.
Exposure to high concentrations may cause irritation of the skin, damage to the cornea, cough, pain in the chest, respiratory problems (dyspnea i.e. shortness of breath) and suffocation.
In severe cases, one observes laryngeal oedema which may evolve to pulmonary oedema and death by asphyxiation. The symptoms of pulmonary oedema (mainly cough and other respiratory difficulties) often appear after a delay which may go up to 48 hours. Physical exertion may worsen these symptoms.
Rest and medical surveillance are consequently essential.
Accidental exposure to high concentrations can also cause a bronchial irritation syndrome
(RADS, Reactive Airways Dysfunction Syndrome, an asthma-like condition or asthma without a latency period).
Very high concentrations may lead to corrosion of the skin, eyes and upper respiratory tract.
Contact with liquified ammonia gas can cause frostbites as well as corrosion of the eyes and the skin, following a direct contact.

III-Dose-effects relationship :



Concentration in (ppm)
Probable effects following acute exposure
17 Olfactory detection limit.
20-25 Discomfort among non-accustomed workers.
25 (VEMP), (Quebec’s time weight average exposure limit.)
32-50 (5 min.) Nose dryness, slight irritation of the nose and throat.
35 (VECD), (Quebec’s short term exposure limit.)
135 (5 min.) Eye irritation, watering. Irritation of nose and throat.
300 IDLH, « Immediately dangerous to life or health »
500 (30 min.) Severe irritation of the respiratory tract.
2 000-3 000 Severe cough.
2 500-7 000 (30 min.) Respiratory troubles, bronchospasm, pulmonary oedema.
5 000-10 000 (30 min.) Rapid death by suffocation or by accumulation of fluids in the lungs.


IV-Chronic effects :

Repeated or prolonged exposure can generate a certain tolerance, i.e. the irritating odor and effects will be felt at higher concentrations.

V-Sensitization :

Available data do not show that ammonia can cause cutaneous or respiratory sensitization

Justification of effects :
Some reports mention cutaneous eruption (urticaria) following exposure to the vapors of ammonia and asthma-like reactions following exposure to concentrations between 8 to 15 ppm of ammonia. However, these reports do not make it possible to link these effects with a mechanism of allergic nature.

VI-Effects on development :

No data concerning an effect on the development was found in the consulted documentary sources

Justification of effects :
Ammonia is produced by the body. It is also an essential constituent for the normal development of human beings. An exposure in the work environment is not very likely to lead to an increase in the blood ammonia level and thus, it does not represent a hazard to development.

VII-Effects on reproduction :

No data concerning the effects on reproduction was found in the consulted documentary sources.

Justification of effects :
Ammonia is normally produced by the body. It is also an essential constituent for the normal development of human beings. An exposure in the work environment is not very likely to lead to an increase in the blood ammonia level and thus, it does not represent a hazard for reproduction.

VIII-Effects on breast milk :

It is detected in human mother's milk.
Justification of effects : Ammonia is a natural component of this milk.

IX-Cancinogenic effects :

There was no data concerning a cancerogenic effect found in the consulted documentary sources.

X-Mutagenic effects :

The data do not make it possible to make an adequate evaluation of the mutagenic effect.

Justification of effects :
A study mentions a light increase in chromosomal aberrations and sister chromatid exchanges in workers of a manufacture of artificial fertilizers simultaneously exposed to several chemicals among which ammonia.


First Aid :

I-Inhalation :

In the event of inhalation of gas, bring the worker in a ventilated place and place him in semi-seated position. If he does not breathe, give him artificial respiration. In the event of respiratory difficulties, give him oxygen. Transfer immediately him to the nearest medical emergency department. The symptoms of pulmonary oedema may appear after a delay of several hours and are worsened by physical exertion. Rest and medical supervision are consequently essential.

II-Contact with eyes :

Rinse the eyes copiously with water for at least 20 minutes. See a doctor.

III-Contact with skin :

Quickly withdraw contaminated clothing by using suitable gloves. Abundantly rinse skin with water. See a doctor.
In the event of a frostbite, apply lukewarm water, rinse abundantly and see a doctor



Quebec’s exposure limits :

I-Valeur d'exposition moyenne pondérée (VEMP), (TLV-TWA)=
25 ppm
17 mg/m³
II-Valeur d'exposition de courte durée (VECD), (TLV-STEL)=
35 ppm 24 mg/m³


Prevention :


When engineering measures and modifications of working methods are not sufficient enough to reduce the exposure to this chemical, the wearing of individual protection equipment may be necessary. These protection gears must be in conformity with regulation.

I-Respiratory tract :

Wear a respiratory protection apparatus if the concentration in the work environment is higher than VEMP (25 ppm or 17 mg/m³) or than the VECD (35 ppm or 24 mg/m³).

II-Skin :

Wear skin protection. The selection of skin protection equipement depends on the nature of the work to be carried out.

III-Eyes :

Wear protection for the eyes if there is a risk of splashes. The selection of ocular protection depends on the nature of the work to carry out and, if it is necessary, on the type of apparatus of respiratory protection used.










Edouard Bastarache M.D. (Occupational & Environmental Medicine)
Author of « Substitutions for Raw Ceramic Materials »
Sorel-Tracy
Quebec
[email protected]
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html





References :
1-CSST-Quebec, Repertoire Toxicologique, 2003
2-Toxicologie Industrielle et Intoxications Professionnelles, Lauwerys R.
last edition.
3-Sax’s Dangerous Properties of Industrial Materials, Lewis C., last edition.
4-Clinical Environmental Health and Toxic Exposures, Sullivan J.B and Krieger G.R.,
last edition.


by Edouard Bastarache




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