Nitrogen Containing Fertilizers Ammonia

Ammonia (NH3) is used as an applied fertilizer or as a building block for other fertilizer products. At room temperature it is a colorless, flammable gas with a pungent, suffocating odor. It becomes a clear, colorless liquid under increased pressure and is usually shipped as a compressed liquid in steel cylinders. Anhydrous ammonia is the form used primarily in refrigeration and agriculture. Ammonia is also stored as a refrigerated liquid under pressure and is injected into the soil or irrigation water as a gas after being exposed to air.

Ammonia dissolves in water to form ammonium hydroxide, a basic corrosive solution. Concentrations of ammonium hydroxide vary from 5% to 10% for household use and 25% or more for industrial use (1).

The American Conference of Governmental Industrial Hygienists (ACGIH) occupational exposure limits for ammonia are 25 ppm for 8-hour time-weighted average (TWA) and 35 ppm for short-term exposure (less than 15 minutes). Advice on the correct medical treatment for exposed persons must be available at all work areas (1).

The most common way for ammonia to enter the body is through the respiratory system (inhalation). Clinical results of ammonia inhalation can include coughing, hoarseness, wheezing, narrowing of throat, pulmonary edema, upper airway obstruction, chest pain, runny nose, tearing of the eyes, impaired vision, headache, and dizziness (2-4).

Ammonia irritates the skin and can cause chemical burns ranging from mild to severe, depending on the concentration of the ammonia solution or vapor and the length of time of the exposure. Concentrated vapor or solution may cause pain, redness of the skin, and blisters. Liquefied ammonia splashed or sprayed on skin can cause frostbite, tissue necrosis, or severe burns. These burns are caused by a freeze-dry effect that can freeze and desiccate large areas of skin and produce deep ulcerations if not properly and quickly decontaminated (5,6).

Ammonia, even at low concentrations, can irritate the eyes and cause burning, edema, photophobia, sloughing of the surface cells of the eye, and, in severe cases, blindness. Immediate burning in the mouth and throat occurs when ammonium hydroxide is swallowed, typically in a suicide attempt. Ingestion of concentrated solution can cause severe pain in the mouth, chest, and abdomen, swallowing difficulty, drooling, and vomiting. Burns and perforation of the esophagus or stomach can occur (6,7).

As the concentration of ammonia vapor increases, the symptoms of exposure become more severe. Acute exposures to ammonia can cause immediate burning of the eyes, nose, throat, and respiratory system and can result in death. Itchy eyes, coughing, and a burning nose are warning signs of potentially hazardous exposure levels. Continued short-term exposure may lead to tolerance of the ammonia scent, and workers may no longer be aware of ammonia's presence and potentially increasing and dangerous concentrations. The very young, the elderly, and people with pulmonary problems are at an increased risk from the effects of ammonia exposure (Table 14.1) (4-8).

Short-term exposures to ammonia do not often result in long-term or chronic health effects, except for eye injuries. Long-term effects are usually found with people who have repeated exposures to ammonia. These repeated ammonia exposures can have chronic effects on the lungs, nose, and eyes. Case reports have noted chronic inflammation of bronchi, airway hyperac-tivity, and chronic irritation of the eye membranes. Some authors reported

Table 14.1. Symptomatology at various exposure levels.

Ammonia concentration (ppm)

Effect on health

100

Concentration can be tolerated for several hours

400

Throat irritation

700 (visible cloud)

Eye injury, lung irritation, skin irritation

1700

Laryngospasm, coughing, glottal edema, labored

breathing

2500

A half-hour exposure can be fatal

5000 or greater

Death results from cardiorespiratory arrest

Source: Data from Lessenger (8).

Source: Data from Lessenger (8).

interstitial lung disease due to repetitive occupational exposure to ammonia. Consequences of chronic exposure may also include pneumonia, kidney damage, cataracts, glaucoma, ulceration and perforation of the cornea, and blindness (7,9).

Before working with ammonia, workers should be trained in its proper handling and storage and should know how to use proper personal protective equipment (7,9).

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