Phosphine gas is a highly toxic chemical compound. Pure phosphine is colorless and odorless, but commercial grades often smell like garlic or decaying fish due to impurities. It is a potent respiratory poison, posing an immediate danger to human health at concentrations as low as 50 parts per million (ppm).
How Phosphine Affects the Body
Upon inhalation, phosphine is rapidly absorbed into the bloodstream through the lungs, distributing quickly throughout the body. Its primary toxic effect involves disrupting cellular respiration within the mitochondria, the energy-producing centers of cells. Phosphine interferes with the electron transport chain, inhibiting cytochrome oxidase, a crucial enzyme for ATP synthesis. This leads to a severe energy deficit, impairing cellular function and causing cell death in vital organs.
The gas also acts as a redox toxin, inducing oxidative stress by generating reactive oxygen species (ROS) within cells. An excess of these unstable molecules can damage cellular components such as DNA, RNA, proteins, and mitochondria, contributing to widespread cellular injury. Organs with high oxygen demands, including the brain, heart, kidneys, and liver, are particularly susceptible to this damage. This cellular poisoning can lead to severe organ dysfunction and death.
Recognizing Exposure Symptoms
Symptoms of phosphine gas exposure can manifest within the first few hours, with severity depending on the exposure level. Initial mild to moderate symptoms include headaches, dizziness, fatigue, and drowsiness. Gastrointestinal distress is common, presenting as nausea, vomiting, abdominal pain, and diarrhea. Individuals may also experience thirst, muscle pain, and chills.
As exposure continues, respiratory symptoms become prominent, including cough, chest tightness, and shortness of breath. Pulmonary edema, a dangerous accumulation of fluid in the lungs, can occur, sometimes with a delayed onset of up to 72 hours. Severe exposure can lead to cardiovascular complications such as low blood pressure, rapid heart rate, and life-threatening heart rhythms. Neurological effects, including tremors, convulsions, and seizures, may also develop, potentially progressing to coma.
Where Phosphine is Encountered
Phosphine gas is primarily encountered where it is intentionally generated or used. A significant use is as a fumigant in agriculture and pest control, protecting stored agricultural products such as grains, tobacco, nuts, and seeds from insects and rodents. Fumigant pellets containing metal phosphides, like aluminum phosphide, release phosphine gas upon contact with moisture or stomach acid in pests.
Beyond agriculture, phosphine is involved in various industrial processes. It is used in semiconductor manufacturing as a doping agent to modify electrical properties. The gas also finds application in producing certain chemicals, flame retardants, and metal alloys. Less commonly, phosphine can be an unintentional byproduct in illicit drug manufacturing, such as methamphetamine.
What to Do After Exposure
Immediate action is crucial if phosphine gas exposure is suspected. First, move away from the contaminated area to fresh air. Contact emergency services promptly, providing details about the exposure incident. Any contaminated clothing should be carefully removed to prevent continued exposure.
There is no specific antidote for phosphine poisoning; medical treatment focuses on supportive care to manage symptoms and maintain vital functions. This may involve administering oxygen for breathing difficulties and monitoring cardiac and respiratory function. If safe, ventilate the affected area to disperse the gas. All individuals with suspected significant exposure should be transported to a medical facility for evaluation, as some severe symptoms, such as pulmonary edema or liver damage, may have a delayed onset.