Chlorine gas poisoning

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Chlorine poisoning
Other namesChlorine gas toxicity
SpecialtyEmergency medicine

Chlorine gas poisoning is an illness resulting from the effects of exposure to chlorine beyond the threshold limit value.

Signs and symptoms[edit]

The signs of acute chlorine gas poisoning are primarily respiratory, and include difficulty breathing and cough; listening to the lungs will generally reveal crackles. There will generally be sneezing, nose irritation, burning sensations, and throat irritations. There may also be skin irritations or chemical burns and eye irritation or conjunctivitis. A person with chlorine gas poisoning may also have nausea, vomiting, or a headache.[1][2][3]

Chronic exposure to relatively low levels of chlorine gas may cause pulmonary problems like acute wheezing attacks, chronic cough with phlegm, and asthma.[2]


While celebrating the end of examinations in the spring of 1943, sixth form students at Kesteven and Grantham Girls School spilled ink onto parquetry:[4]

Knowing that soap and water was useless, what was to be done? Surely, this time we would be expelled. Then someone thought of our star scientist – Margaret Roberts would know what would remove the now-spreading black stain. Her remedy was that it should be sprinkled with bleaching-powder and then have hydrochloric acid poured on (stolen from the lab). I scrubbed away furiously, and sure enough, the boards began to recover.

But the next moment I was almost overcome by the fumes and had to rush out of doors, quite blue in the face – no one knew that the lethal mixture would give off chlorine gas. Our violent coughing and splutterings alerted the staff, who were too genuinely concerned about us to be angry at the mess.

— Lorna Smith, classmate of future British Prime Minister Margaret Thatcher (née Roberts)

Occupational exposures constitute the highest risk of toxicity and common domestic exposures result from the mixing of chlorine bleach with acidic washing agents such as acetic, nitric and phosphoric acid or ammonia. They also occur as a result of the chlorination of table water. Other exposure risks occur during industrial or transportation accidents. Wartime exposure is rare.[2][3]

Dose toxicity[edit]

Humans can smell chlorine gas at ranges from 0.1–0.3 ppm. According to a review from 2010: "At 1–3 ppm, there is mild mucous membrane irritation that can usually be tolerated for about an hour. At 5–15 ppm, there is moderate mucous membrane irritation. At 30 ppm and beyond, there is immediate chest pain, shortness of breath, and cough. At approximately 40–60 ppm, a toxic pneumonitis and/or acute pulmonary edema can develop. Concentrations of about 400 ppm and beyond are generally fatal over 30 minutes, and at 1,000 ppm and above, fatality ensues within only a few minutes."[2]


The concentration of the inhaled gas and duration of exposure and water contents of the tissues exposed are the key determinants of toxicity; moist tissues like the eyes, throat, and lungs are the most susceptible to damage.[5]

Once inhaled, chlorine gas diffuses into the epithelial lining fluid (ELF) of the respiratory epithelium and may directly interact with small molecules, proteins and lipids there and damage them, or may hydrolyze to hypochlorous acid and hydrochloric acid which in turn generate chloride ions and reactive oxygen species; the dominant theory is that most damage is via the acids.[2][3][6][7]


Test performed to confirm chlorine gas poisoning and monitor patients for supportive care include pulse oximetry, testing serum electrolyte, blood urea nitrogen (BUN), and creatinine levels, measuring arterial blood gases, chest radiography, electrocardiogram (ECG), pulmonary function testing, and laryngoscopy or bronchoscopy.[3]


There is no antidote for chlorine poisoning; management is supportive after evacuating people from the site of exposure and flushing exposed tissues. For lung damage caused by inhalation, oxygen and bronchodilators may be administered.[7]


There is no way to predict outcomes. Most people with mild to moderate exposure generally recover fully in three to five days, but some develop chronic problems such as reactive airway disease. Smoking or pre-existing lung conditions like asthma appear to increase the risk of long term complications.[1]


In 2014, the American Association of Poison Control Centers reported about 6,000 exposures to chlorine gas in the US in 2013, compared with 13,600 exposures to carbon monoxide, which was the most common poison gas exposure;[8] the year before they reported about 5,500 cases of chlorine gas poisoning compared with around 14,300 cases of carbon monoxide poisoning.[9]

Society and culture[edit]

In War[edit]

Industrial accidents[edit]

In the USA[edit]

There have been many instances of mass chlorine gas poisonings in industrial accidents.

  • In 2005 in South Carolina a freight train derailed, releasing an estimated 11,500 US gallons (44,000 l; 9,600 imp gal) of chlorine. Nine people died, and at least 529 persons sought medical care. [12]
  • In 2004 in Texas a freight train accident released 90,000 pounds (41,000 kg) of chlorine gas and other toxic chemicals. Forty-four people were injured, including three who died. [13]
  • In 2002 in Missouri, a flex hose ruptured during unloading a train car at a chemical plant, releasing approximately 16,900 pounds (7,700 kg) of chlorine gas. Sixty-seven persons were injured.[1]


  • In 2015 In Nigeria, the explosion of a chlorine gas storage tank at a water treatment plant in Jos killed 8 people.[14]
  • In 2017 chlorine gas was released in Fort McMurray, Alberta, Canada, after chemicals were mixed improperly at a water treatment plant. In 2020 the Regional Municipality of Wood Buffalo was fined $150,000 (CAD) for the incident. [15]
  • In 2017, in Iran, at least 475 people, including nine firemen, suffered respiratory and other symptoms after a chlorine gas leak in the southwestern Iranian province of Khuzestan.[citation needed]
  • In 2020, on 6th of March, an incident occurred at EPCL (Engro Polymer and Chemicals Limited) Port Qasim, Karachi, where over 50 people were hospitalized as a result of Chlorine gas leakage. No casualties were reported.[16]


  1. ^ a b c Jones R, Wills B, Kang C. Chlorine gas: an evolving hazardous material threat and unconventional weapon. West J Emerg Med. 2010 May;11(2):151-6. PMID 20823965 PMC 2908650
  2. ^ a b c d e White CW, Martin JG. Chlorine gas inhalation: human clinical evidence of toxicity and experience in animal models. Proc Am Thorac Soc. 2010 Jul;7(4):257-63. Review. PMID 20601629 PMC 3136961
  3. ^ a b c d Gerald F O'Malley, GF et al. Chlorine Toxicity Medscape Drugs & Diseases, Ed. Dembek, ZF. Updated: Dec 11, 2015
  4. ^ Moore, Charles (19 April 2013). "A side of Margaret Thatcher we've never seen". The Daily Telegraph. Retrieved 25 July 2017.
  5. ^ CDC Basic Facts Page last reviewed April 10, 2013. Page last updated April 10, 2013
  6. ^ Squadrito GL, Postlethwait EM, Matalon S. Elucidating mechanisms of chlorine toxicity: reaction kinetics, thermodynamics, and physiological implications. Am J Physiol Lung Cell Mol Physiol. 2010 Sep;299(3):L289-300. Review. PMID 20525917 PMC 2951076
  7. ^ a b Agency for Toxic Substances and Disease Registry via the CDC. Medical Management Guidelines: Chlorine Page last reviewed: October 21, 2014. Page last updated: October 21, 2014
  8. ^ Mowry JB, et al 2014 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 32nd Annual Report. Clin Toxicol. 2015;53(10):962-1147. PMID 26624241. Page 1089
  9. ^ Mowry JB, et al. 2013 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 31st Annual Report. Clin Toxicol. 2014 Dec;52(10):1032-283. PMID 25559822 PMC 4782684 Page 1225
  10. ^ David Cloud for the New York Times. May 21, 2007 7 U.S. Soldiers Die in Iraq, 6 in Sweep of Baghdad
  11. ^ "Syria fails to remove all chemical weapons as deadline passes". Financial Times. 27 April 2014. Retrieved 12 September 2014.
  12. ^ CDC Public Health Consequences from Hazardous Substances Acutely Released During Rail Transit --- South Carolina, 2005; Selected States, 1999--2004
  13. ^ United States. National Transportation Safety Board. (2006). Collision of Union Pacific Railroad train MHOTU-23 with BNSF Railway Company train MEAP-TUL-126-D with subsequent derailment and hazardous materials release, Macdona, Texas, June 28, 2004. National Transportation Safety Board. OCLC 75276300.
  14. ^ Michael Olukayode for Bloomberg News. July 25, 2015 Nigeria Says 8 People Dead After Inhaling Chlorine Gas in Jos
  15. ^ The Canadian Press. September 11, 2020 Regional Municipality in Northern Alberta Fined for Releasing Chlorine Gas
  16. ^ "Over 50 hospitalised after chemical leak at Karachi Engro factory | SAMAA". Samaa TV. Retrieved 2020-03-06.

Public Domain This article incorporates public domain material from the Centers for Disease Control and Prevention document: "Public Health Consequences from Hazardous Substances Acutely Released During Rail Transit --- South Carolina, 2005; Selected States, 1999--2004".

External links[edit]