What is Phosgene Toxicity?
Phosgene, a chemical compound, was first created over 200 years ago by a scientist named John Davy. During World War I, people referred to it as ‘Choky Gas’ or ‘CG.’ Nowadays, it’s common in industrial settings. Phosgene is an airborne substance that doesn’t mix with water and can cause strong irritation. It can lead to a condition known as chemical pneumonia, an inflammation of the lungs caused by inhaling or aspirating toxic substances. It can also cause Acute Respiratory Distress Syndrome (ARDS), a severe lung condition that prevents enough oxygen from getting to the lungs and into the blood, which sometimes can’t be easily fixed.
What Causes Phosgene Toxicity?
Researchers are currently studying phosgene’s potential use as a biological weapon, especially in places where its production is not regulated. Phosgene is a type of gas that can exist in its natural state at room temperature, or be stored as a liquid if the temperature is below 8.2 degrees Celsius. It is estimated that over 12 million metric tons of phosgene are produced worldwide every year.
Looking at this by country, China produces 37% of the world’s supply of phosgene, followed by Europe with 31%, and North America with 20%. Recently, the Environmental Protection Agency (EPA) found 123 potential sites across the U.S. where a large number of people could be exposed to phosgene either in case of an accident at the plant where it is produced, or if these places were targeted in a biological attack. Because phosgene is heavier than air, if there was a leak or release, it would tend to gather in low-lying, poorly ventilated or enclosed areas.
Phosgene has a distinct odor that some people describe as musty or similar to the smell of freshly cut grass or hay. However, only about 10% of people can detect this smell when the concentration is at 2 parts per million. Because of its subtle smell and the fact that humans are generally not very good at detecting it, phosgene is considered particularly dangerous.
Risk Factors and Frequency for Phosgene Toxicity
Phosgene, a chemical which used to be common in military settings, is now typically used in many manufacturing processes. It’s found in things like producing dyes, pesticides, livestock feed chemicals, pharmaceuticals, and other organic materials. Sometimes, it might even be released as a byproduct from activities like paint decomposition or welding.
People who are exposed to large house or industrial fires might also risk phosgene poisoning. This is because when products containing chlorine burn, they can create phosgene. However, it’s important to note that there isn’t much recent data on phosgene toxicity. Most of the information we have comes from anecdotes, case studies, simulations, and estimations.
Signs and Symptoms of Phosgene Toxicity
Phosgene is a substance that, depending on its concentration, can cause various symptoms. If the concentration is low, people might not notice its sharp, suffocating smell. Common symptoms include headache, nausea, fatigue, burning sensations, teary eyes, eye redness, eye pain, sore throat, wheezing, and a cough. Interestingly, people who smoke might start to dislike tobacco smoke after being exposed to phosgene.
There can also be lung and heart symptoms such as a feeling of choking, tightness in the chest, shortness of breath, and chest pain. The onset of symptoms typically occurs within 2 to 24 hours after exposure. But phosgene doesn’t dissolve in water very well, so symptoms can sometimes appear more than 24 hours later. In some cases, symptoms have been delayed for up to 72 hours and brought on by physical exertion.
The most common vital signs include fast breathing, low blood pressure, and a low level of oxygen in the blood. However, these may not be evident at the beginning of the illness. A physical exam might show a productive cough with pink, frothy spit, swelling or redness in the throat, and abnormal breathing sounds. This cough could be accompanied by wheezing when listening to the patient’s lungs. Patients who are struggling to breathe may look blue (cyanotic). If a person inhales a lot of phosgene, it can cause a serious condition where the voice box spasms rapidly (laryngospasm).
Testing for Phosgene Toxicity
If you’ve been exposed to phosgene – a toxic chemical gas – beyond the safe limit of 50 ppm/min or if you’re not sure of the concentration of it that you’ve inhaled, it’s important to seek medical care immediately. This is also necessary if you’ve been exposed to liquid phosgene near your face or throat, or if you’re experiencing breathing problems.
At the hospital, doctors use multiple methods to monitor the impact of excessive phosgene exposure, which can lead to a serious condition called acute hypoxemic respiratory failure. This condition happens when your lungs can’t supply your body with the oxygen it needs.
Various tests are done to track how the disease is progressing. These tests include measuring your vital signs like heart rate, multiple physical examinations over time, as well as lab tests and imaging scans like X-rays. Lab tests may require samples such as your blood, to count the total number of your blood cells, to check the levels of various chemicals in your body and to check for two specific heart health indicators, troponin and Brain Natriuretic Peptide (BNP).
In some patients with phosgene toxicity, lab tests showed higher than normal white blood cell count (leukocytosis), lower than normal potassium (hypokalemia) and sodium (hyponatremia) levels. Usually, troponin and BNP levels are normal unless there is a heart problem.
For patients with lung problems, doctors measure the oxygen and carbon dioxide levels in their blood (arterial blood gas measurements). They also get chest X-rays to check for signs of lung damage. This may show ‘fluffy’ patches on both lungs and congestion around hilar region (area where blood vessels and airways enter and leave your lung). An electrocardiogram (ECG), a test that measures the heart’s electrical activity, may also be performed. In most scenarios it shows fast heart rate (sinus tachycardia), but in severe cases, it might show signs of strain on the right side of the heart.
Treatment Options for Phosgene Toxicity
If a person has been exposed to phosgene, a type of dangerous gas, there are some important steps that should be taken to ensure their safety. First, if phosgene is present on someone’s clothing, it can continue to cause harm, so the clothing should be removed promptly and put into two plastic bags for safe disposal. It’s particularly important to help the person stay calm if they’ve inhaled a large amount of phosgene because excessive physical activity or distress might worsen their lung symptoms.
Low doses of medications such as morphine or benzodiazepines might be given to help ease anxiety. It’s important to quickly evaluate and protect the person’s airway, breathing, and circulation. If the person’s oxygen levels are low or they’re showing signs of breathing trouble, they should be provided with oxygen supplementation immediately. Recent studies have shown that noninvasive positive airway pressure, a type of breathing support, can improve outcomes in people exposed to phosgene.
Experts suggest this breathing support should be started early or considered in individuals who have been exposed to extremely high quantities of phosgene gas, the exact amount of exposure is unknown, or liquid phosgene has come in contact with the face. If this support is not enough, endotracheal intubation (placing a tube into the windpipe to maintain an open airway) might be performed. The use of corticosteroids, a type of medication that helps decrease inflammation, hasn’t been proven to benefit those exposed to this gas. However, the decision to use these medications is left to the doctor responsible for the care of the patient.
If individuals need prolonged ventilatory support, suffer from severe lung symptoms, or need management that requires unsafe ventilator settings, they might benefit from extracorporeal membrane oxygenation. This is a treatment that provides cardiac and respiratory support by removing carbon dioxide from the blood and returning it with oxygen. Medications that relax the lung muscles, known as inhaled beta-adrenergic agonists, may be used if the person experiences bronchospasm, which is a sudden tightening or constriction of the muscles in the lungs.
What else can Phosgene Toxicity be?
When considering lung-related illnesses that feature low oxygen levels alongside signs of central blood vessel blockage, with or without lung tissue inflammation, medical professionals should also consider the possibility of phosgene-induced lung injury. Similar conditions may include:
- Lung bruising
- Infectious pneumonia
- Aspiration pneumonitis (inhaling toxic substances)
- Fluid accumulation in the lungs due to heart problems (such as in acute decompensated congestive heart failure)
- Bleeding in the lung
Historical data, a physical examination, and lab analysis can help distinguish between lung bruising and acute fluid accumulation in the lungs due to heart problems. A high fever, an increase of white cells in the blood, and a persistent, phlegmy cough could indicate infectious pneumonia. Likewise, past incidents and physical examination could help identify aspiration pneumonitis, and if so, antibiotics could be part of the treatment approach.
What to expect with Phosgene Toxicity
If you’ve been exposed to less than 50 mcg/min of phosgene (a poisonous gas), you don’t necessarily need to be evaluated by a healthcare professional. However, if you’ve been exposed to amounts between 50 and 150 mcg/min, if you don’t know how much you’ve been exposed to, or if you’re experiencing respiratory symptoms, you should get checked out at a healthcare facility.
After being evaluated by a healthcare professional, you might be allowed to go home if you’re not showing signs of damage from the poison or lung swelling (pulmonary edema). This could be the case after 8 hours of careful observation. If after this time, the healthcare professional isn’t satisfied that you’re ready to be discharged, they’ll recommend further medical monitoring.
If lung swelling kicks in within 2 to 6 hours, it suggests a severe injury. In this case, you may need to be transferred to a facility equipped with Extracorporeal Membrane Oxygenation (ECMO), a machine that essentially does the work of your heart and lungs. This is to prepare for a severe and stubborn form of lung injury known as refractory Acute Respiratory Distress Syndrome (ARDS).
If you manage to survive the initial toxic exposure, the good news is that you’re likely to completely recover over time. In most cases, it takes 1 to 2 years to get back to normal.
Possible Complications When Diagnosed with Phosgene Toxicity
People who survive initial exposure to phosgene gas may feel out of breath when exercising and may struggle with physical activity for several months. Those who have a history of smoking generally fare worse after inhaling phosgene.
Common Impact:
- Shortness of breath
- Poor tolerance for exercise
- Harsher impacts for smokers
Recovery from Phosgene Toxicity
After a stay in the hospital, part of the recovery process should involve visits to occupational health therapists. Regular lung function tests should also be carried out to keep track of your healing progress.
Preventing Phosgene Toxicity
Phosgene is mainly found in workplaces. Workers in industries dealing with phosgene use special badges that detect exposure. Hence, healthcare providers should ask patients if they have been exposed to phosgene and if they wear these badges. These badges must be worn as near to the mouth and nose as possible. However, they only provide an estimated detection of phosgene and may not accurately reflect the amount a person has inhaled. Therefore, healthcare providers rely on their expertise to assess a patient’s health.
The Environmental Protection Agency (EPA) conducted air tests in California and did not find any alarming levels of phosgene- under 31.8 parts per trillion (ppt), especially in the Los Angeles basin. The Occupational Safety and Health Administration, The National Institute for Occupational Safety and Health (NIOSH), and the American Conference of Governmental Industrial Hygienists (ACGIH) have advised that exposure to phosgene should be kept under 0.1 parts per million (ppm). This limit helps in places where phosgene detection badges are in use.
