Ammonia Hazards and Safety: Understanding Exposure Risks

Ammonia: Upper Respiratory Irritant and Health Risks

Certain substances primarily affect the upper respiratory tract, without impacting the lower respiratory tract (throat or bronchi). Due to their extraordinary solubility in water, these substances are completely absorbed by the nose and throat, allowing air to reach the lungs practically pure. Ammonia is a prime example of such an irritant.

Ammonia: Chemical Profile and Characteristics

Formula: NH₃
Synonym: Anhydrous Ammonia

Characteristics: A colorless gas with a pungent, hot, and suffocating odor. It can be liquefied under pressure.

Sources of Exposure

• Chemical Manufacturing: Used in the manufacture of fertilizers, as a solvent in textiles, leather, pulp, and paper manufacturing, and as a stabilizer in rubber production.
• Organic and Inorganic Synthesis: Utilized in the synthesis of nitric acid, urea, plastics, resins, synthetic fibers, explosives, rocket fuels, cyanides, amides, dyes, amines, and household cleaners.
• Mining Applications: Employed in extracting and purifying metallurgical ore, scrap processing, annealing, atomic hydrogen welding, and within the electronics and steel industries.
• Oil Refining: Functions as a neutralizing agent, in the manufacture and recovery of catalytic cracking, and for the extraction of paraffins from lubricating oils.
• Refrigeration: Used in refrigeration units, ice plants, and for the storage of frozen products.

Routes of Entry

Ammonia can affect the body if inhaled or if it comes into contact with the eyes or skin. Ingestion can also lead to adverse effects.

Health Effects and Pathology

Ammonia vapor is a strong irritant to the eyes (especially the cornea), respiratory tract, and skin. Inhalation of concentrations from 2500 to 6500 ppm can cause breathlessness, chest pain, and pulmonary edema, the latter of which can be fatal. Consequences may include bronchitis or pneumonia. Residual reductions in lung function have been observed.

Tolerance to generally irritating ammonia concentrations may be acquired through adaptation, a phenomenon frequently observed among workers accustomed to exposure.

Liquid anhydrous ammonia can cause severe eye injuries or blindness, and lead to first and second-degree skin burns, which are often serious and can be fatal if extensive.

Environmental Exposure Limits

The time-weighted average (TWA) allowable limit for ammonia is 20 ppm (14 mg/m³).

The short-term exposure limit (STEL) is 35 ppm (24 mg/m³).

Clinical Presentation

Acute Effects

Ammonia is a strong irritant to the eyes, respiratory tract, and skin. Acute exposure can cause burning and tearing, runny nose, cough, chest pain, respiratory failure, and even death. It can also lead to severe and delayed breathing difficulties. Skin exposure to high gas concentrations can cause burns and blisters. Direct contact with liquid ammonia can cause severe burns to the eyes and skin. Similarly, contact of the eyes, nose, throat, and skin with ammonia solutions can cause serious burns.

Chronic Effects

Repeated exposure to ammonia gas can cause chronic irritation of the eyes and upper respiratory tract.

Environmental Control Measures

• Process enclosure
• Local exhaust ventilation
• General dilution ventilation

Personal Protective Measures

• Waterproof clothing
• Gloves
• Face shields and other protective clothing necessary to prevent skin contact
• Emergency showers should be installed where there is a risk of workers' bodies being exposed to ammonia.