What is Mercaptan Toxicity?
Mercaptans, also known as thiols, are certain types of chemicals that contain sulfur and often have a strong and disagreeable smell. These chemicals are used in a variety of industrial processes, including refining oil, producing chemicals, and making pesticides. Workers in these industries might come into contact with mercaptans in several ways, like breathing them in, touching them, or swallowing them while they are producing, handling or storing materials that contain mercaptans.
One type of mercaptan, called methyl mercaptan or methanethiol, can interfere with an important part of our cells’ power producers, the mitochondria. Specifically, methyl mercaptan can affect a key enzyme called cytochrome c oxidase in the fourth part of a process called the mitochondrial electron transport chain. This, in turn, can reduce the levels of a molecule called intracellular adenosine triphosphate (ATP) within our cells, which is essentially cells’ energy source. This is particularly harmful for organs with high energy needs, like our brain and heart.
If someone is exposed to methyl mercaptan for an extended period of time, it can lead to a condition called metabolic acidosis. This happens mainly because the interference with ATP production forces our cells to produce energy in a less efficient, oxygen-free way, leading to an increase in the production of lactic acid.
What Causes Mercaptan Toxicity?
Common ways you might come into contact with a substance called mercaptan could be through your job, environment, or by accident. Mercaptans are a type of compound that have sulfur in it and are mainly used to create a ‘smell’ in natural gas, propane, and other fuel gases. They do this so people can sense any leaks by just smelling it. You might have heard about these odor-making substances known as methyl mercaptan and ethyl mercaptan, also known as ethanethiol. Under normal circumstances, these mercaptans are safe when present in small quantities. However, exposure to large amounts due to accidents, work-related incidents, or misuse can be harmful.
Intentional poisoning with mercaptan is unusual. According to safety guidelines known as the Acute Exposure Guideline Level (AEGL) for humans, which are based on experiments with rats, exposure to mercaptan should not exceed 120 parts per million (ppm) for 10 minutes. Sudden inhalation of mercaptans can cause slowed or stopped breathing, and extremely high exposure can cause seizures, paralysis, heart attack, coma, and even death. It’s also worth noting that the United States Department of Homeland Security (DHS) has categorized methyl mercaptan as a potential large-scale chemical weapon.
Risk Factors and Frequency for Mercaptan Toxicity
Getting accurate numbers on mercaptan toxicity is difficult because there isn’t a lot of data available and cases often go unreported. Mercaptan toxicity is pretty rare and we don’t have a lot of scientific literature that records specific statistics about how common it is. Even so, we can make a few general observations. It’s more common for workers in the natural gas and fuel gas industry to be exposed to mercaptans. On the other hand, cases where people intentionally misuse or abuse products that contain mercaptan are randomly scattered and not well-documented.
Signs and Symptoms of Mercaptan Toxicity
Exposure to mercaptans, a type of chemical, can lead to what is known as mercaptan toxicity. The symptoms and severity can vary a lot, depending on factors like the type of mercaptan, how one was exposed, the concentration, how long one was exposed, and physical factors unique to each person. It’s important to spot the symptoms quickly and get medical help promptly to manage and treat it effectively.
Depending on the characteristics and conditions of exposure, mercaptans can affect several body systems, including the respiratory, cardiovascular, nervous, gastrointestinal, renal, and hepatobiliary (liver and bile ducts) systems. Not just that, these chemicals can bring about dermatological (skin-related) or hematological (blood-related) health issues.
- Respiratory system: Breathing in high concentrations of mercaptans may irritate the nose, throat, and air passages, which may cause difficulties in breathing, coughing, chest tightness, and wheezing. Long-term exposure can even cause narrowing of the bronchial tubes, bronchitis, and fluid build-up in the lungs.
- Cardiovascular system: Mercaptans can affect how blood vessels expand or contract, which in turn can lead to unstable blood pressure and poor blood flow to the body’s periphery. On top of that, these chemicals can interfere with the endothelial layer (inner lining of blood vessels) and damage heart functions, potentially causing severe cardiovascular issues.
- Nervous system: Mercaptan toxicity may cause symptoms like headaches, dizziness, confusion, and problems with thinking. The chemicals can also interfere with neurotransmitter systems and neuronal (brain and nerve cell) function, which can lead to abnormal behavior and potentially have long-lasting impacts on the nervous system.
- Gastrointestinal system: Mercaptans can cause irritation to the gastrointestinal lining and upset digestive processes, leading to symptoms like nausea, vomiting, belly pain, and diarrhea.
- Renal and liver system: Exposure to mercaptans can adversely affect kidney and liver function. This can lead to issues in excreting toxins and waste products, influencing electrolyte balance. The liver might also show signs of toxicity, disturbances in metabolic processes, and impairment in the detoxification pathways.
- Dermatological effects: Direct contact with mercaptans can lead to skin irritation and chemical burns. These reactions can happen when the skin comes into contact with mercaptans or through exposure to contaminated clothes or equipment.
- Hematological effects: High-level mercaptan exposure can cause oxidative damage to red blood cells and lead to their rupture. If this is severe, symptoms of anemia like fatigue, weakness, or shortness of breath may manifest.
Testing for Mercaptan Toxicity
To diagnose mercaptan toxicity, doctors usually carry out a full check-up, ask about exposure to toxic substances, and run a few lab tests. Mercaptan toxicity, unfortunately, doesn’t have a specific test to diagnose it, so the lab tests are mainly done to see if the body’s functions are affected.
When assessing your health, your doctor will ask about any recent accidental exposures to harmful substances and your work history. This is because the symptoms of mercaptan toxicity vary a lot and can be hard to pinpoint, making it difficult to diagnose quickly.
Depending on how you were exposed, you might experience symptoms like coughing, wheezing, shortness of breath, feeling nauseous, vomiting, stomach pain, headache, confusion, skin irritation, and chemical burns.
Lab tests, like a complete blood count and comprehensive metabolic panel, can give an idea of how severe the mercaptan toxicity is. These tests help check for anemia (low red blood cell count), acute liver injury, or acute kidney injury with possible changes in electrolyte levels. An arterial blood gas test can be used if you have breathing problems or lower than normal levels of oxygen in your blood. This test helps to check how effectively the lungs are moving oxygen into the blood and removing carbon dioxide from the blood. It can also identify any imbalances in the body’s acid/base level caused by exposure to mercaptan. If available, a urinalysis (urine test) may be used to check for mercaptan by-products.
While imaging or scans don’t play a big role in diagnosing mercaptan toxicity, they can be useful in more severe cases to identify signs of toxic impact on particular organs. These scans can also help the doctor rule out other causes of the symptoms that are not related to mercaptan toxicity.
Treatment Options for Mercaptan Toxicity
Currently, there’s no specific drug or treatment for mercaptan toxicity, which is the harmful effects caused by exposure to a group of chemicals called mercaptans. If someone experiences mild to severe symptoms after exposure to mercaptans, the focus is on treating the symptoms and giving supportive care. Quick consultation with a medical toxicologist or local poison control center is advised, especially in unusual cases or those with unclear symptoms.
The first step in managing mercaptan toxicity is to remove the person from the source of exposure. This may involve steps like using an emergency service to get away from the exposure site, or placing the person in an isolation setting to limit further exposure. Clothes that might be contaminated should be taken off carefully and kept in sealed bags, following facility protocols. If someone has swallowed the toxic substance, they should rinse their mouth.
It’s always important to understand and follow protocols for managing any kind of exposure to toxins. Using personal protective equipment (PPE) is vital to ensure safety for the person exposed and for those caring for them.
If the skin has been exposed to mercaptans, it’s crucial to clean the affected area. Removing contaminated clothes and washing the skin thoroughly with soap and water can help get rid of the remaining mercaptan. If the eyes have been exposed, rinse them with clean water for at least 15 minutes. Healthcare facilities often have eye wash stations for this purpose. If it’s not possible to use an eye wash station, a device called a Morgan lens can be used. To know how long to wash the eyes, it can be helpful to measure the pH level in the eyes, both before and after cleaning.
Routinely checking blood pressure, heart rate, breathing rate, and oxygen level is essential for deciding the appropriate treatment. An electrocardiogram (ECG) which is a heart test, might be needed if there are signs of a heart rhythm problem. These signs could include feeling lightheaded, fainting, having heart palpitations, or chest pain.
Intravenous fluids may be used to keep the body hydrated and to correct any imbalances in electrolytes, which are minerals needed by our bodies. If there are breathing problems, medications to open up the airways might be helpful. Some people might need additional oxygen, a type of breathing support known as non-invasive ventilation, or help in managing their airway.
Mild to moderate nausea and vomiting can be reduced with anti-nausea medications. Pain can be relieved using nonsteroidal anti-inflammatory drugs (NSAIDs) or opioid medications, depending on how severe the pain is. Antihistamines, which are drugs that reduce the effects of a chemical in the body that cause allergic reactions, can be used for itching and inflammation.
Severe skin burns or irritations may need topical treatments and wound care. In case of kidney or liver problems related to the exposure, these issues would be managed following standard medical protocols.
Some studies have suggested that a type of vitamin B12 called cobinamide might help in treating mercaptan toxicity. At least in laboratory studies, cobinamide appears to counteract the effects of mercaptans, possibly by binding directly with the mercaptan and reducing the stress on the body’s cells. However, more research is needed in this area.
What else can Mercaptan Toxicity be?
If someone is showing signs of being poisoned by mercaptan, a toxic gas, it’s important for doctors to consider other health issues that might be causing similar symptoms. These could include:
- Respiratory tract infections
- Chemical pneumonia (also known as pneumonitis)
- Problems with the digestive system (also known as gastrointestinal disorders)
- Exposure to other harmful gases or substances.
Carbon monoxide poisoning, another dangerous gas, is also something doctors should be mindful of, especially if the person might have been exposed to dangerous gases. Doctors might order a blood test to check for levels of carbon monoxide, as it’s a common poisoning hazard.
What to expect with Mercaptan Toxicity
The outlook for someone exposed to mercaptan — a type of hazardous compound — varies depending on the specific type of mercaptan involved, how long and in what manner they were exposed, the person’s general health condition, how well decontamination functions, the advice of a medical toxicologist (a doctor who specializes in treating poisonings), and how quick and appropriate the medical help is.
Generally speaking, the outlook for someone exposed to mercaptan is good as long as they receive the necessary care right away. Many people experience mild to moderate symptoms that go away on their own or with treatment. However, the condition may get more serious in cases of severe mercaptan exposure or if the person was exposed for a prolonged period, more so if it significantly affects their whole body. If the person goes into severe respiratory distress (serious trouble breathing), experiences fluctuations in their heart rate and blood pressure, or develops complications affecting the brain or nervous system, these could indicate a very serious condition that must be managed intensively by healthcare professionals.
Being in the hospital for a long time to manage mercaptan poisoning can carry risks similar to those for any other condition that requires a hospital stay. These include deep vein thrombosis (a blood clot in a deep vein), pneumonia (a type of lung infection), hospital-acquired infections, and complications related to being on a ventilator (a machine that helps with breathing).
But patients who have a mild poisoning can usually be safely monitored in an area such as the emergency department. This can prevent unnecessary risks associated with a hospital stay. If a medical toxicologist is consulted, they can help guide the care of the patient in the most appropriate way, which could lead to fewer complications and lower healthcare costs.
Possible Complications When Diagnosed with Mercaptan Toxicity
The most serious lung problem that can result from exposure to mercaptans is Acute Respiratory Distress Syndrome (ARDS). ARDS is a critical condition where you start having trouble breathing and get low levels of oxygen in your blood very quickly.
Mercaptans can also impact your heart, potentially causing abnormal heart rhythms, lack of blood flow to the heart muscle, and heart failure. In people without prior heart issues, a sudden heart failure can occur. For those with existing heart conditions, their heart failure may worsen. Extremely severe cases might even experience cardiac arrest due to causes related to heart rhythm, heart failure, or lack of blood flow to the heart.
Gastrointestinal issues associated with exposure to mercaptans are usually due to severe loss of fluids from the body because of vomiting or diarrhea.
The nervous system can also be affected by toxicity from mercaptans. People may experience confusion, seizures, and even falling into a coma. Longer-term exposure can lead to future neurological issues and disturbances in behavior.
Contact with mercaptans can cause irritation to the skin. This can be anything from mild rashes to serious chemical burns. If this occurs, consulting with professionals who specialize in wound care or a burns center can provide helpful guidance for managing the situation.
Known Complications from mercaptan exposure:
- Acute Respiratory Distress Syndrome (ARDS)
- Dysrhythmias (abnormal heart rhythms)
- Myocardial ischemia (lack of blood flow to heart muscle)
- Heart failure (either sudden in people without prior issues or worsening in people with existing conditions)
- Cardiac arrest from heart rhythm issues, heart failure, or lack of blood flow to the heart
- Gastrointestinal fluid losses from vomiting or diarrhea
- Altered mental status, seizures, or coma
- Future neurological and behavioral issues due to chronic exposure
- Skin rashes or serious chemical burns from direct contact
Preventing Mercaptan Toxicity
It’s very important to prevent contact with mercaptans in the future. Ways to achieve this can include setting up safety protocols and educating people on the correct way to use, store and handle substances that contain mercaptans. This is especially important for people who work with these substances as part of their job.
Both employers and employees should be educated about the possible dangers, the right protective gear to use, and what to do in case of an emergency. This knowledge can help reduce the risk of accidents and improve overall safety in the workplace.
