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. Chronic exposure to relatively low levels of chlorine gas may cause pulmonary problems like acute wheezing attacks, chronic cough with phlegm, and asthma.
Causes
While celebrating the end of examinations in the spring of 1943, sixth form students at Kesteven and Grantham Girls School spilled ink onto parquetry: 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.
Dose toxicity
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."
Mechanism
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. Once inhaled, chlorine gas diffuses into the epithelial lining fluid 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.
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.
Outcomes
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.
There have been many instances of mass chlorine gas poisonings in industrial accidents.
In 2005 in South Carolina freight train derailed, releasing an estimated of chlorine. Nine people died, and at least 529 persons sought medical care.
In 2004 in Texas a freight train accident released of chlorine gas and other toxic chemicals. Forty-four persons were injured, including three who died.
In 2002 in Missouri, a flex hose ruptured during unloading a train car at a chemical plant, releasing approximately of chlorine gas. Sixty-seven persons were injured.
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.
In 2020, on 6th of March, an incident occurred at EPCL Port Qasim, Karachi, where over 50 people were hospitalized as a result of Chlorine gas leakage. No casualties were reported though.
