Background

Carbon monoxide is a colourless, tasteless, odourless, non-irritating gas produced during incomplete combustion of gas or fossil fuels due to there being insufficient oxygen present. In the home, incorrectly installed, poorly maintained and ventilated cooking and heating appliances, such as those using gas, coal, wood or paraffin are the main sources of carbon monoxide. As well as these domestic sources, the most significant exposure to carbon monoxide comes from cigarette smoking and car exhausts.

Production of carbon monoxide increases when cars are moving slowly hence levels of carbon monoxide in the atmosphere are higher near busy roads during peak times when the flow of traffic is slow. Carbon monoxide production increases when the engine is cold, as catalytic converters take time to reach the operating temperature and thus petrol engine cars in closed garages are dangerous even with a catalytic converter. Levels may also increase in winter due to periods of still cold air as this affects the dispersal of carbon monoxide, as it is usually rapidly dispersed away from roads and destroyed by photochemical reactions over a period of months.

In smokers, cigarettes are the major source of carbon monoxide. The amount of carbon monoxide in the blood of smokers is greater than that caused from breathing in contaminated air, even in polluted areas.

When breathed in, carbon monoxide enters the blood through the lungs and attaches to the body's oxygen carrier, haemoglobin. This reduces the amount of oxygen that can be carried round the body. Carbon monoxide also impairs the release of such oxygen as it is transported. Exposure to higher concentrations for a short period of time can cause headaches, dizziness, nausea, vomiting, confusion, collapse and coma. When individuals are removed from the source of carbon monoxide these symptoms usually subside. Exposure to lower concentrations of carbon monoxide for a longer period may affect learning, manual dexterity, driving performance and attention level.

People who have diseases that affect the delivery of oxygen to the heart or brain, such as those with coronary heart disease, angina or anaemia are particularly at risk from carbon monoxide poisoning as the amount of oxygen being carried to the heart or brain is further reduced by carbon monoxide.

Carbon monoxide is transported across the placenta which reduces the oxygen supply to the baby. Therefore exposure to elevated levels of carbon monoxide during pregnancy may result in a decrease in birth weight and possibly behavioural problems. Such effects are more likely in smokers because smoking is a significant source of carbon monoxide.

Key Points     Production and Uses

• Carbon monoxide - Production and Uses
  Added/updated: 24 November 2009