Carbon monoxide (CO) is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels, including gas, oil, wood, and coal. It is only when fuel does not burn fully that excess CO is produced, which is poisonous. When CO enters the body, it stops the blood from bringing oxygen to cells, tissues, and organs. CO is poisonous as you cannot see it, taste it, or smell it but CO can kill quickly without warning. The Health and Safety Executive (HSE) statistics show every year in the UK around 15 people die from CO poisoning caused by gas appliances and flues that have not been correctly installed, maintained or those that are poorly ventilated. Some levels that present do not kill but can cause serious harm to health if breathed in over a prolonged period, with extreme cases causing paralysis and brain damage because of prolonged exposure to CO. Therefore, understanding the danger of CO poisoning as well as educating the public to take appropriate precautions could inevitably reduce this risk.
How is CO generated?
CO is present in several different industries, such as steel works, manufacturing, electricity supply, coal and metal mining, food manufacturing, oil and gas, production of chemicals and petroleum refining to name a few.
CO is produced by incomplete combustion of fossil fuels such as gas, oil, coal, and wood. This happens where there is a general lack of burner maintenance, insufficient air – or the air is of insufficient quality to allow complete combustion. For example, the efficient combustion of natural gas generates carbon dioxide and water vapour. But if there is inadequate air where that combustion takes place, or if the air used for combustion becomes vitiated, combustion fails and produces soot and CO. If there is significant water vapour in the atmosphere, this can reduce the burning efficiency still further and speed up CO production.
Incorrect or poorly maintained appliance such as cookers, heaters or central boiler are the most common cause of carbon monoxide exposure. Other causes include blocked flues and chimneys as this can prevent carbon monoxide form escaping leading to dangerous levels accumulating. Burning fuel in an enclosed or unventilated environment such as running a car engine, petrol-powered generator or barbecue inside a garage or tent can lead to similar CO accumulation. Faulty or blocked car exhausts can lead to inefficient combustion and hence a leak or blockage within the exhaust pipe can cause an excess of CO to be produced. Some vehicles and properties may have flues or exhausts blocked after heavy snowfall which may lead to a build-up of carbon monoxide. A different cause of CO poisoning may result from some chemicals, paint fumes and some cleaning fluids and paint removers contain methylene chloride (dichloromethane), which when inhaled the body breaks this substance down into carbon monoxide leading to possible co poisoning. Though to be fair, since methylene chloride is a listed 1B carcinogen, its breakdown to CO may not be the worst of a subject’s subsequent health problems. Another common cause of low-level CO poisoning is smoking, and smoking shisha pipes can be particularly bad, especially indoors. This is because shisha pipes burn charcoal and tobacco, which can lead to a build-up of carbon monoxide in enclosed or unventilated rooms.
High concentrations of CO
In some cases, high concentrations of CO may be present. Environments that this may occur include a house fire, therefore the fire service are at risk of CO poisoning. In this environment there can be as much as 12.5% CO in the air which when the carbon monoxide rises to the ceiling with other combustion products and when the concentration hits 12.5% by volume this will only lead to one thing, called a flashover. This is when the whole lot ignites as a fuel. Apart from items falling on the fire service, this is one of the most extreme dangers they face when working inside a burning building.
How does CO affect the body?
Due to the characteristics of CO being so hard to identify, I.e., colourless, odourless, tasteless, poisonous gas, it may take time for you to realise that you have CO poisoning. The effects of CO can be dangerous, this is because CO prevents the blood system from effectively carrying oxygen around the body, specifically to vital organs such as the heart and brain. High doses of CO, therefore, can cause death from asphyxiation or lack of oxygen to the brain. According to statistics from the Department of Health, the most common indication of CO poisoning is that of a headache with 90% of patients reporting this as a symptom, with 50% reporting nausea and vomiting, as well as vertigo. With confusion/changes in consciousness, and weakness accounting for 30% and 20% of reports.
Carbon monoxide can severely affect the central nervous system and those with cardiovascular disease. As CO prevents the brain from receiving sufficient levels of oxygen it has a knock-on effect with the heart, brain, and central nervous system. along with symptoms including headaches, nausea, fatigue, memory loss and disorientation, increasing levels of CO in the body go on to cause lack of balance, heart problems, cerebral edemas, comas, convulsions and even death. Some of those who are affected may experience rapid and irregular heartbeats, low blood pressure and arrhythmias of the heart. Cerebral edemas caused because of CO poisoning are especially threatening, this is because they can result in the brain cells being crushed, thereby affecting the whole nervous system.
Another way CO affects the body is through the respiratory system. This is because the body will struggle to distribute air around the body because of carbon monoxide due to the deprivation of blood cells of oxygen. As a result, some patients will experience a shortness of breath, especially when undertaking strenuous activities. Every-day physical and sporting activities will take more effort and leave you feeling more exhausted than usual. These effects can worsen over time as your body’s power to obtain oxygen becomes increasingly compromised. Over time, both your heart and lungs are put under pressure as the levels of carbon monoxide increase in the body tissues. As a result, your heart will try harder to pump what it wrongly perceives to be oxygenated blood from your lungs to the rest of your body. Consequently, the airways begin to swell causing even less air to enter the lungs. With long-term exposure, the lung tissue is eventually destroyed, resulting in cardiovascular problems and lung disease.
Chronic exposure to carbon monoxide can have extremely serious long-term effects, depending on the extent of poisoning. In extreme cases, the section of the brain known as the hippocampus may be harmed. This part of the brain is accountable for the development of new memories and is particularly vulnerable to damage. Figures have shown that up to 40% of people who have suffered from carbon monoxide poisoning experience problems such as amnesia, headaches, memory loss, personality and behavioural changes, loss of bladder and muscle control, and impaired vision and coordination. Some of these effects do not always present themselves immediately and can may take several weeks or may be highlighted after more exposure. Whilst those who suffer from long-term effects of carbon monoxide poisoning recover with time, there are cases in which some people suffer permanent effects. This may occur when there has been enough exposure to result in organ and brain damage.
Unborn babies are at the highest risk of carbon monoxide poisoning, since foetal haemoglobin mixes more readily with CO than adult haemoglobin. As a result, the baby’s carboxy haemoglobin levels become higher than the mothers. Babies and children whose organs are still maturing are at risk of permanent organ damage. Additionally, young children and infants breathe faster than adults and have a higher metabolic rate, therefore, they inhale up to twice as much air as adults, especially when sleeping, which heightens their exposure to CO.
How to identify
In the event of carbon monoxide poisoning there are a number of treatments, these depend on the levels of exposure, and the age of the patient.
For low levels of exposure seeking medical advice from your GP is best practice.
However, if you believe that you have been exposed to elevated levels of CO then your local A&E would be the most suitable place to go. Although your symptoms will usually indicate whether you have CO poisoning, for adults a blood test will confirm the amount of carboxyhaemoglobin in your blood. For children this will lead to an underestimate of the peak exposure since children will metabolise the carboxyhaemoglobin faster. Carboxyhaemoglobin (COHb) is a stable complex of carbon monoxide that forms in red blood cells when carbon monoxide is inhaled, using up the capacity of the red blood cell to transport oxygen.
The effects of CO poisoning can include breathlessness, chest pain, seizures and loss of consciousness which may lead to death or physical problems that can occur, depending on how much CO is in the air. For example:
|CO volume (parts per million (ppm)||Physical Effects|
|200 ppm||Headache in 2–3 hours|
|400 ppm||Headache and nausea in 1–2 hours, life threatening within 3 hours.|
|800 ppm||Can cause seizures, severe headaches and vomiting in under an hour, unconsciousness within 2 hours.|
|1,500 ppm||Can cause dizziness, nausea, and unconsciousness in under 20 minutes; death within 1 hour|
|6,400 ppm||Can cause unconsciousness after two to three breaths: death within 15 minutes|
Around 10 to 15% of people who obtain serve CO poisoning go on to develop long-term complications. These include brain damage, vision and hearing loss, Parkinsonism – an illness that isn’t Parkinson’s disease but has similar symptoms, and coronary heart disease.
There are several treatments for CO poisoning, these include rest, standard oxygen therapy or hyperbaric oxygen therapy.
Standard oxygen therapy is provided in hospital in the event you have been exposed to a prominent level of carbon monoxide, or you have symptoms that suggest exposure. This process includes being given 100% oxygen through a tight-fitting mask. Normal air contains around 21% oxygen. Continuous breathing of concentrated oxygen enables your body to quickly replace carboxyhaemoglobin. For best results, this type of therapy is continued until your carboxyhaemoglobin levels decrease to less than 10%.
The alternative treatment is that of hyperbaric oxygen therapy (HBOT), this treatment consists of flooding the body with pure oxygen, helping it overcome the oxygen shortage caused by carbon monoxide poisoning. However, there is currently not enough evidence about the long-term effectiveness of HBOT for treating severe cases of carbon monoxide poisoning. Although standard oxygen therapy is usually the recommended treatment option, HBOT may be recommended in certain situations – such as, if there’s been extensive exposure to carbon monoxide and nerve damage is suspected. The treatment provided is decided upon purely on a case-by-case basis.