INTRODUCTION	Section 2 of 11
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Background: The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the US Government.

The respiratory and mucous membrane irritant effects of chlorine have been well known for many years. John Doughty, a New York City schoolteacher, first suggested use of chlorine gas as a chemical warfare agent during the American Civil War. This proposal was never acted upon during that war. Chlorine gas was officially introduced into the chemical warfare arsenal in 1915 at Ypres, Belgium. An estimated 93,800 tons of chlorine gas was produced during World War I, with more than half produced by Germany.

Accounts of chlorine attacks at Ypres describe an olive-green cloud rolling over the Allied positions, following the ground contours, and sinking into the trenches. Soldiers seeking safety in those trenches were overcome by the gas and experienced tearing eyes, vomiting, and difficulty breathing. They abandoned their trenches and suffered great losses from artillery and rifle fire.

Chlorine was abandoned as a warfare agent when the use of gas masks was introduced and more effective compounds were created and deployed. Total gas casualties in World War I were estimated at almost 1.3 million troops.

Chlorine liquid is presently used in cleaning agents (eg, bleach, disinfectants), in water purification, and in the manufacture of items such as plastics. It is used in the following industries: pesticide, refrigerant, paper and pulp, textile, metallurgy, pharmaceutical, cosmetic, battery, water and sewage purification, and food processing. More than 200 significant industrial accidents involving chlorine have occurred since World War I.

Pathophysiology: Chlorine is a greenish yellow gas that is heavier than air in its pure form. It is an oxidizing agent that is highly reactive with water and liberates hypochlorous acid, hydrochloric acid, and oxygen-free radicals, which are toxic to tissues. Chlorine is considered to have intermediate solubility and can exert irritant effects throughout the respiratory tract. The most common site of injury is at the mucous membrane, where water concentrations are highest. The specific sites of chlorine's effects include the eye conjunctiva, nasal mucosa, pharynx, larynx, trachea, and bronchi.

Chlorine has a strong, pungent odor and stinging, burning effect on the skin and mucous membranes. Because its odor threshold of 0.08 ppm is below the level associated with toxicity, the sense of smell usually provides adequate warning that chlorine is in the vicinity. This may allow escape and avoidance of serious toxicity. Chlorine is also soluble in alkalis, alcohols, and chlorides. Chlorine is not combustible, but as an oxidizer, it may react violently with many materials, including fuels.

Inhalation toxicity is a function of the dose received and is dependent on the concentration of gas and duration of exposure. The permissible exposure level set by the Occupational Safety and Health Administration (OSHA) is 1 ppm. The Immediately Dangerous to Life or Health (IDLH) concentration determined by the National Institute for Occupational Safety and Health (NIOSH) is 25 ppm. Exposure to 15 ppm causes throat irritation. Exposure to more than 50 ppm is dangerous, and exposure to 1000 ppm is fatal, even with short exposures. The lowest reported lethal concentration is 430 ppm for 30 minutes. In a study by D' Alessandro et al, exposure to 1 ppm for 60 minutes created significant changes in forced expiratory volume in 1 second (FEV1), forced expiratory flow (FEF) after 25-75% of vital capacity has been expelled, and specific airway resistance in healthy subjects and in subjects with airway hyperresponsiveness. These changes appear to be transient.

Household mixing of sodium hypochlorite (bleach) cleaning agents with ammonia produces chloramine gas. This gas interacts with water in the mucous membranes, producing ammonia and hypochlorous or hydrochloric acid. Typically, this occurs in an enclosed environment such as a restroom, which may allow greater exposure to occur. Chlorine gas also may be released in the household by mixing sodium hypochlorite with acidic cleaning agents (toilet bowl cleaners).

Frequency:

• In the US: Chlorine and chloramine poisoning are common in the United States. Chlorine is listed as the most common inhalational irritant, and in 1989 data from the San Francisco Bay Area Regional Poison Control Center, chlorine was cited in almost one third of the morbidity cases following acute irritant exposure involving both adults and children. Toxic effects after inhalation exposure are usually mild to moderate, and death is uncommon. Large amounts of chlorine are produced in the industrial sector, and potential exists for accidental or deliberate release.

• Internationally: The same potential for release that exists in the United States is present worldwide. In addition, chlorine can be used in sabotage, warfare, and terrorist actions. A disgruntled employee introduced chlorine liquid into the air filtration system in a department store, causing evacuation of the store, but no injuries occurred. One terrorist incident involved the release of chlorine on board a ferry.

Mortality/Morbidity: Mortality is a rare consequence of chlorine gas exposure. During the first battle at Ypres, 800 deaths were reported and almost 3000 personnel were incapacitated out of 15,000 troops. A study of the American Expeditionary Force in World War I revealed a total of 1843 patients exposed to chlorine gas with an average admission time of 60 days.
Morbidity from moderate and severe exposures is typically caused by noncardiogenic pulmonary edema. This may occur within 2-4 hours of exposure to moderate chlorine concentrations (25-50 ppm) and within 30-60 minutes of severe exposures (>50 ppm).

Chlorine has been implicated as a cause of reactive airway disease syndrome (RADS). Patients may have bronchial hyperreactivity after inhalational injury. It has been reported to occur after a single, high-dose exposure or after repeated low-level exposure. Most exposures, however, do not result in long-term effects. Patients with pre-existing obstructive disease can have a worsening of symptoms after chlorine exposure.

	CLINICAL	Section 3 of 11
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Pictures Bibliography

History: The patient may experience symptoms based on the exposure. Exposure possibilities include acute low levels, acute high levels, and chronic low levels.

• Acute exposure (low levels): Most poisonings fall into this category and are caused by household exposure to low-concentration cleaning products.

• Eye tearing, nose and throat irritation

• Sneezing

• Excess salivation

• General excitement or restlessness

• Acute exposure (high levels): Symptoms as above as well as the following:

• Dyspnea: Upper airway swelling and obstruction may occur.

• Violent cough

• Nausea and vomiting (with the smell of chlorine in emesis)

• Lightheadedness

• Headache

• Chest pain or retrosternal burning

• Muscle weakness

• Abdominal discomfort

• Dermatitis (with liquid exposure): Corneal burns and ulcerations may occur from splash exposure to high-concentration chlorine products.

• Chronic exposure

• Acne (chloracne)

• Chest pain

• Cough

• Sore throat

• Hemoptysis

Physical:

• Tachypnea

• Cyanosis (most prevalent during exertion)

• Tachycardia

• Wheezing

• Intercostal retractions

• Decreased breath sounds

• Rales (pulmonary edema)

• Nasal flaring

• Aphonia, stridor, or laryngeal edema

• Ulceration or hemorrhage of the respiratory tract

• Rhinorrhea

• Lacrimation, salivation, and blepharospasm

• Chloracne or tooth enamel corrosion (with chronic exposure)

• Redness, erythema, and chemical burns to the skin from dose-dependent exposure to liquid

Causes:

• Occupational exposures constitute the highest risk for serious exposure to high-concentration chlorine.

• Other exposures occur during industrial or transportation accidents.

• Wartime exposure is rare but always possible.

• Household exposure occurs during swimming pool maintenance or inappropriate mixing of bleach cleaning agents with acids or ammonia products.