AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

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.¹ 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

United States

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.

International

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. Chlorine has been reported to be used in conjunction with improvised explosive devices.

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  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

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.

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Lab Studies

• Arterial blood gas: The typical abnormality is hypoxia from bronchospasm or pulmonary edema.
• Obtain serum electrolytes, BUN, and creatinine after significant exposure, as metabolic acidosis and hyperchloremia may occur.

Imaging Studies

• Chest radiography
• • The chest radiograph findings are frequently normal initially but may exclude other causes of hypoxia in the differential.
  • The chest radiograph findings commonly lag behind the clinical findings of pulmonary edema.

Other Tests

• Pulse oximetry can be used as a measure of oxygenation.
• Handheld peak flow meters can be used to measure the degree of bronchospasm and follow the response to treatment.
• Pulmonary function testing may be helpful to measure the degree of airway obstruction or restriction.

Procedures

• Laryngoscopy or bronchoscopy can be used to evaluate the degree of damage caused by exposure.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Prehospital Care

• Take precautions to minimize exposure to toxins. In areas of large concentrations or enclosed environments, providers should use self-contained breathing apparatus.
• Remove victims from the toxic environment. Begin initial decontamination at the scene if the skin or eyes are involved. Copious amounts of water may be used. Remove the patient's clothing if it has been contaminated with liquid chlorine.
• Properly sealed chemical containers or material safety data sheets (MSDS) should accompany the patient if available.

Emergency Department Care

The most important aspect of treating patients exposed to chlorine gas is the provision of good supportive care. No antidotes are available. The medications listed below are adjuncts to rigorous attention to the airway patency, breathing, and circulation.

• Initial assessment
• • Remove the patient's clothing if it has been contaminated with liquid chlorine.
  • Evaluate the airway, breathing, and circulation. Provide supplemental oxygen (humidified if possible) as required by nasal cannula, face mask, nonrebreather mask, noninvasive positive pressure ventilation, or intubation. Poor oxygenation or laryngospasm may necessitate intubation. Positive pressure ventilation with positive end-expiratory pressure (PEEP) set at 5-10 mm Hg may improve oxygenation in patients with noncardiogenic pulmonary edema and allow for lower fraction of inspired oxygen settings to minimize the risk of oxygen toxicity.
• Decontamination
• • Wear appropriate protective gear during decontamination, especially if the exact toxin is not identified. Chlorine gas exposure represents a low risk for cross-contamination.
  • Irrigate the eyes and skin with copious amounts of water or saline if involvement is reported. Remove contact lenses (if present) prior to irrigation. If skin exposure is significant, wash with a mild soap and water.
  • Use a pH reagent strip capable of measuring the ranges 0-14 to assess any eye injury. Continue irrigation of the eye until the pH returns to near 7.
  • Evaluate the cornea with fluorescein staining under a slit lamp.
• Bronchospasm
• • Treat initial bronchospasm with beta agonists such as albuterol. Ipratropium may be added to the treatment.
  • Poor responses may require terbutaline or aminophylline.
  • Nebulized lidocaine (4% topical solution) may provide analgesia and reduce coughing.
• Sodium bicarbonate
• • In the past, several authors advocated nebulized sodium bicarbonate. Most recommendations are based on anecdotal experience, and little supporting clinical data are available.
  • The mechanism of action is believed to be the neutralization of hydrochloric acid formed in the airways. Theoretically, an exothermic reaction may occur.
  • Animal studies suggest nebulized sodium bicarbonate may cause chemical pneumonitis.
• Corticosteroids: Inhaled and parenteral steroids have been used with many patients exposed to chlorine gas, but no strong clinical evidence supports their use except in patients with an exacerbation of underlying reactive airway disease. Some animal studies demonstrate better lung compliance and arterial oxygen tension if treated with inhaled steroids within 30 minutes of exposure.
• Fluid management
  • Closely monitor the patient's fluid input and output because of the potential of pulmonary edema.
  • Fluid restriction may be required and diuretics may be used to treat impending pulmonary edema.
• Antibiotics
  • No evidence supports the use of prophylactic antibiotics.
  • Base decisions for administering antibiotics on clinical data supporting infection, typically pneumonia.
  • The choice of agent can be based on sputum Gram stain or cultures.

Consultations

• Request critical care or pulmonary consultation for most admissions.
• Toxicology or poison control center consultation is recommended.
• Obtain ophthalmologic consultation for patients with ocular involvement.

MEDICATION

Section 7 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

The goal of pharmacotherapy is to reduce morbidity and prevent complications.

Drug Category: Bronchodilators

Beta-receptor agonists that relax airway smooth muscles, causing an increase in airway diameter; specifically, the beta2-receptor is targeted.

Drug Category: Anticholinergics

Believed to work synergistically with bronchodilators.

Drug Category: Methylxanthines

Historically used to treat asthma but lost favor because of newer treatment strategies, toxic effects, and narrow therapeutic windows.

Drug Category: Topical anesthetic

Inhaled topical anesthetics have been used to reduce cough and may reduce pain associated with chlorine inhalations.

Drug Category: Corticosteroids

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. Corticosteroids modify the body's immune response to diverse stimuli.  

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Further Inpatient Care

• Pulmonary edema may present in a delayed fashion after chlorine gas exposure.
• • Patients who present asymptomatic and remain asymptomatic 6 hours after exposure may be discharged with appropriate instructions and in the presence of reliable family members.
  • Admit patients who present with symptoms that continue for 6 hours after exposure for an observation period of at least 24 hours. If asymptomatic at 24 hours, patients may be discharged with appropriate follow-up care.
  • Consider patients exposed to large concentrations in an enclosed environment, those with underlying cardiopulmonary disorders, and children for admission and observation, even if initially asymptomatic.

Further Outpatient Care

• Discharge medications are not applicable since only asymptomatic patients should be discharged from the ED.
• Cases of chronic reactive airway disease after acute exposures to chlorine gas are described in the literature. Consider referring patients for pulmonary function testing.

Transfer

• Consider transfer to a higher level of care when patients cannot be treated locally. The major concern is the treatment of noncardiogenic pulmonary edema that may require positive pressure ventilation.

Deterrence/Prevention

• Proper labeling and avoiding mixing chemicals facilitate prevention. Household cleaning products should not be mixed. Using proper precautions when handling swimming pool chemicals reduces risks. Adequate ventilation is necessary when handling any potentially noxious chemical.
• On a larger scale, chemical warfare treaties between countries and the safe transportation and handling of industrial chlorine compounds facilitate deterrence.
• Training prehospital and hospital providers in the management of chemical casualties can improve the treatment provided to exposed personnel while minimizing personal risks. Hospitals can establish mass casualty plans and perform drills to ensure that preparations are adequate in the event of a large-scale industrial accident.

Complications

• Short-term effects
• • Bacterial superinfection resulting in bronchitis or pneumonia may present 3-5 days after chlorine gas exposure. Search for infection if the patient fails to recover from chlorine gas toxicity in 3-4 days.
  • Pleural effusions associated with pulmonary edema are possible.
• Long-term effects: Long-term complications from exposure are rare, but some reports of chronic reactive airway disease following exposure exist. Other authors attribute these consequences to bacterial superinfection or smoking.

Prognosis

• Most individuals exposed to chlorine gas recover without significant sequelae. Even exposure to high-concentration chlorine gas is unlikely to result in significant, prolonged pulmonary disease.

Patient Education

• Educate patients on the risks associated with the improper handing of chlorine pool chemicals and the improper mixing of household cleaning chemicals.
• For excellent patient education resources, visit eMedicine's Bioterrorism and Warfare Center and Procedures Center. Also, see eMedicine's patient education articles Chemical Warfare, Personal Protective Equipment, and Bronchoscopy.

MISCELLANEOUS

Section 9 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Medical/Legal Pitfalls

• Discharging a patient prior to resolution of symptoms that may indicate impending pulmonary edema
• Failure to ascertain a possibility of chlorine gas exposure through occupational history or mixed household chemicals
• Failure to consider bacterial superinfection in patients who are not responding to several days of appropriate therapy
• Failure to monitor patients in a setting in which respiratory support is immediately available, or failure to transfer patients to a facility with appropriate respiratory support capability

Special Concerns

• Superheated chlorine gas from an industrial fire or chemical warehouse explosion may carry the danger of direct thermal injury to the mucous membranes of the eyes, mouth, and respiratory tract in addition to the chemical effects.

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  Chest radiograph of a 36-year-old chemical worker 2 hours postexposure to chlorine inhalant. She had severe resting dyspnea during the second hour, diffuse crackles/rhonchi on auscultation, and a partial pressure of oxygen of 32 mm Hg breathing room air. The radiograph shows diffuse pulmonary edema without significant cardiomegaly (used with permission from Medical Aspects of Chemical and Biological Warfare, Textbook of Military Medicine. 1997: 256).
	View Full Size Image
Media type:  X-RAY

Media file 2:  A section from a lung biopsy (hematoxylin and eosin stain; original magnification X 100) from a 36-year-old chemical worker taken 6 weeks postexposure to chlorine. At that time, the patient had no clinical abnormalities and a partial pressure of oxygen of 80 mm Hg breathing room air. The section shows normal lung tissues without evidence of interstitial fibrosis and/or inflammation (used with permission from Medical Aspects of Chemical and Biological Warfare, Textbook of Military Medicine. 1997: 256).
	View Full Size Image
Media type:  Photo

Media file 3:  Chemical Terrorism Agents and Syndromes. Signs and symptoms. Chart courtesy of North Carolina Statewide Program for Infection Control and Epidemiology (SPICE), copyright University of North Carolina at Chapel Hill.
	View Full Size Image
Media type:  Image

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

1. D'Alessandro A, Kuschner W, Wong H, Boushey HA, Blanc PD. Exaggerated responses to chlorine inhalation among persons with nonspecific airway hyperreactivity. Chest. Feb 1996;109(2):331-7. [Medline].
2. Baxter PJ. Gases. In: Hunter's Diseases of Occupations. 1994:213-235.
3. Beckett WS. Inorganic gases. In: Textbook of Clinical Occupational and Environmental Medicine. 1994:838-843.
4. Blanc PD, Galbo M, Hiatt P, Olson KR. Morbidity following acute irritant inhalation in a population-based study. JAMA. Aug 7 1991;266(5):664-9. [Medline].
5. Demeter SL, Cordasco EW. Reactive airway disease after chlorine gas exposure [letter; comment]. Chest. Sep 1992;102(3):984. [Medline].
6. Gjonaj ST, Lowenthal DB, Dozor AJ. Nebulized lidocaine administered to infants and children undergoing flexible bronchoscopy. Chest. Dec 1997;112(6):1665-9. [Medline].
7. Glindmeyer HW, Lefante JJ, Freyder LM, et al. Relationship of asthma to irritant gas exposures in pulp and paper mills. Respir Med. May 2003;97(5):541-8. [Medline].
8. Graham DR. Noxious gases and fumes. In: Textbook of Pulmonary Disease. 1994:901-916.
9. Horton DK, Berkowitz Z, Kaye WE. The public health consequences from acute chlorine releases, 1993-2000. J Occup Environ Med. Oct 2002;44(10):906-13. [Medline].
10. Joy RJ. Historical aspects of medical defense against chemical warfare. In: Textbook of Military Medicine: Medical Aspects of Chemical and Biologic Warfare. 1997:87-109.
11. Kennedy SM, Enarson DA, Janssen RG, Chang-Yeung M. Lung health consequences of reported accidental chlorine gas exposures among pulpmill workers. Am Rev Respir Dis. Jan 1991;143(1):74-9. [Medline].
12. Moore BB, Sherman M. Chronic reactive airway disease following acute chlorine gas exposure in an asymptomatic atopic patient. Chest. Sep 1991;100(3):855-6. [Medline].
13. Nelson LS. Simple asphyxiants and pulmonary irritants. In: Goldfrank's Toxicologic Emergencies. 1998:1529-1530.
14. Parrish JS, Bradshaw DA. Toxic inhalational injury: gas, vapor and vesicant exposure. Respir Care Clin N Am. Mar 2004;10(1):43-58. [Medline].
15. Rabinowitz PM, Siegel MD. Acute inhalation injury. Clin Chest Med. Dec 2002;23(4):707-15. [Medline].
16. Schonhofer B, Voshaar T, Kohler D. Long-term lung sequelae following accidental chlorine gas exposure. Respiration. 1996;63(3):155-9. [Medline].
17. Segal E, Lang E. Toxicity, Chlorine Gas. eMedicine Journal [serial online]. 2000. [Full Text].
18. Smart JK. History of chemical and biologic warfare: An American perspective. In: Textbook of Military Medicine: Medical Aspects of Chemical and Biologic Warfare. 1997:9-86.
19. Traub SJ. Respiratory agent attack (toxic inhalational injury). In: Ciottone GR. Disaster Medicine. 3^rd ed. Philadelphia, PA: Mosby Elsevier; 2006:573-575/ chap 93.
20. Urbanetti JS. Toxic inhalational injuries. In: Textbook of Military Medicine: Medical Aspects of Chemical and Biologic Warfare. 1997:247-270.
21. Vinsel PJ. Treatment of acute chlorine gas inhalation with nebulized sodium bicarbonate. J Emerg Med. May-Jun 1990;8(3):327-9. [Medline].
22. Wadbrook PS. Advances in airway pharmacology. Emerging trends and evolving controversy. Emerg Med Clin North Am. Nov 2000;18(4):767-88. [Medline].

Article Last Updated: Jul 3, 2008