|Other names||Chlorine gas toxicity|
Chlorine gas poisoning is an illness resulting from the effects of exposure to chlorine beyond the threshold limit value.
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.
While celebrating the end of examinations in the spring of 1943, sixth form students at Kesteven and Grantham Girls School spilled ink onto parquetry:
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.
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."
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 (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.
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.
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.
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.
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; the year before they reported about 5,500 cases of chlorine gas poisoning compared with around 14,300 cases of carbon monoxide poisoning.
There have been many instances of mass chlorine gas poisonings in industrial accidents.
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".