Edouard Bastarache on sat 14 jun 03
Hey Snail,
something to chew on:
Ammonia
Toxicology :
Ammonia is mainly absorbed by the respiratory tract. Absorption by other
routes is negligeable.
A-Toxicokinetics :
I-Absorbtion
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).
II-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.
III-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.
IV-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.
B-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, whimpering 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.
C-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.
D-Chronic effects :
Repeated or prolonged exposure can generate a certain tolerance, i.e. the
irritating odor and effects will be felt at higher concentrations.
D-Sensitization :
Available data do not show that ammonia can cause cutaneous or respiratory
sensititzation
Justification of effects :
Some reports mention cutaneous eruption (urticaria) following the 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.
E-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.
F-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.
G-Effects on breast milk :
It is detected in human mother's milk.
Justification of effects :
Ammonia is a natural component of this milk.
H-Cancinogenic effects :
There was no data concerning a cancerogenic effect found in the consulted
documentary sources.
I-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 exchanges
of chromatid-sisters in workers of a manufacture of artificial fertilizers
simultaneously exposed to several chemicals among which ammonia.
J-Lethal concentration 50 :
Rat : 2 000 ppm for 4 hours.
Mouse : 2 115 ppm pour 4 hours.
Mouse : 3 360 ppm pour 4 hours.
Rat : 7 338 ppm pour 4 hours.
Rat : 7 715 ppm pour 4 hours.
Rabbit : 3,5 g/m³ pour 4 hours.
Cat : 3,5 g/m³ pour 4 hours.
K-First Aid :
I-Inhalation :
In the event of inhalation of gas, bring the worker in a ventilated place
and place her/him in semi-seated position. If she/he does not breathe, give
her/him artificial respiration. In the event of respiratory difficulties,
give her/him oxygen. Transfer immediately her/him to the nearest medical
emergency department. The symptoms of pulmonary oedema may appear after a
delay of several hours and are worsened by the 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
L-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.
M-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
III-Danger Immédiat pour la Vie et la Santé(DIVS), (IDLH)=
300 ppm
Edouard Bastarache M.D. (Occupational & Environmental Medicine)
Author of « Substitutions for Raw Ceramic Materials »
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
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.
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