Page 675 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

640 SECTION | IX Gases, Solvents and Other Industrial Toxicants

VetBooks.ir Anhydrous ammonia has an 8-h time-weighted average discharge, keratoconjunctivitis, corneal opacity, atrophic
rhinitis, dyspnea, hemoptysis, hoarse voice, dysphagia,
maximum acceptable exposure of 25 ppm, a short-term
reduced production values, and possibly increased rates
exposure limit of 35 ppm, and an immediately dangerous
to life and health level of 500 ppm. of respiratory infections. Higher exposures can result in
severe pulmonary disease and possibly acute respiratory
Toxicokinetics and Toxicodynamics distress.
NH 3 is highly water soluble and thus tends to primarily
Diagnostic Testing
affect the upper respiratory tract, mucous membranes, and
the eye (Close et al., 1980; O’Kane, 1983; Robinson Air monitoring is the most effective form of diagnostic
et al., 1990; Chao and Lo, 1996; Brautbar et al., 2003; testing.
Makarovsky et al., 2008). However, deeper structures
may be affected if the upper respiratory tract scrubbing is Postmortem Findings
overwhelmed. Irritation and possibly corrosion of the respiratory tract,
particularly the upper tract, and exposed surfaces of the
Pathophysiology eye dominate the gross findings. Histological findings
NH 3 is irritant and/or corrosive depending on the concen- may include hyperplasia of the bronchiolar and alveolar
tration. NH 3 reacts with tissue water to produce ammo- epithelium.
nium hydroxide, a strong alkali (Close et al., 1980;
Robinson et al., 1990; Chao and Lo, 1996; Brautbar et al., Treatment
2003; Makarovsky et al., 2008). The reaction is exother- The immediate treatment priority is the prompt removal
mic and capable of producing significant tissue burns. of the patient from the source of exposure. Rescuers
Ammonium hydroxide produces typical alkaline liquefac- need to take great care not to become casualties in such
tion necrosis. Alkali liquefaction necrosis results in dee- circumstances. Copious skin and eye irrigation should be
per tissue damage than that caused by an acid of similar performed for at least 20 min (taking care to avoid hypo-
pH reserve. In addition, ammonium hydroxide tissue thermia). Patients should then be treated for acute respi-
breakdown liberates water, aiding the further conversion ratory distress and/or burns. In animal production
of NH 3 to ammonium hydroxide. Mild exposure primarily facilities, the best treatment is to improve ventilation
affects the upper respiratory tract and eyes, whereas more and to reduce the accumulation of animal wastes within
severe exposure may affect the entire respiratory tract. the facilities.
The degree of damage to the respiratory tract is dependent
on the depth of inhalation, duration of exposure, concen- Prognosis
tration, and the pH change of the tissue fluids. Even mild
The prognosis depends on the severity, depth, and chronic-
levels of exposure can reduce pulmonary clearance and
ity of respiratory tract injury. Reactive airway diseases and
potentially increase the risk of infections of the respira-
asthma are common following NH 3 exposures. Chronic
tory tract. Within animal facilities, ammonia is generally
respiratory sequelae may occur with severe exposures.
adsorbed by dust particles, which enable deeper penetra-
tion of the lung compared with gaseous NH 3 (Kim et al., Prevention
2008). In such circumstances, the toxicological thresholds
for adverse effects may be lower than for gaseous NH 3 . Improved ventilation and removal of wastes is the most

Liquid anhydrous ammonia ( 33 C) freezes tissue on effective form of prevention within intensive animal facil-
contact and can produce deep, irreversible skin damage ities. The use of air monitors (personal and space) and
(Amshel et al., 2000; Latenser and Lucktong, 2000; personal protective equipment has reduced human casual-
Lessenger, 2004; Welch, 2006). ties. Veterinarians and farmers should have a very high
degree of suspicion regarding areas where high levels of
NH 3 might be present, particularly enclosed spaces.
Vulnerable Populations
Improved security of liquid anhydrous ammonia storage
Individuals with preexisting lung disease, reactive airway facilities has been recommended.
syndromes, and/or asthma are at significantly greater risk.
Smoke Inhalation
Clinical Presentation
Clinical signs associated with relatively low-level expo- Overview, Uses, and Sources of Exposure
sures pertain to eye and upper respiratory tract irritation: Smoke inhalation injury results from a combination of
shallow breathing, excessive lacrimation, nasal exposure to gaseous combustion products, particulate