File on intoxications due to Carbon Monoxide (CO)
Carbon monoxide is a colourless and odourless gas. Its density is close to that of air. Its presence is due to incomplete combustion of any combustible: wood, Calor ® gas, coal, petrol, heating oil, natural gas, petroleum or propane. It rapidly spreads in the environment. It has the same effect as an extremely toxic asphyxiating gas which is absorbed by the body in a few minutes and infiltrates the haemoglobin.
|
Carbon Monoxide (CO) is the polluting gas which is the most produced in the world , in far greater volumes than all other polluting gases put together. Moreover it is particularly treacherous as it is a colourless and odourless gas and is thus undetectable. Its lethal effects in confined premises are well-known. It is formed during the combustion of carbonaceous substances (hydrocarbons, coal, wood) and is very toxic when its concentration reaches a certain threshold. CO penetrates the circulatory system via the lungs and is absorbed by the haemoglobin (red corpuscles) 200 times more rapidly than oxygen. As the CO accumulates in the blood, the body is more and more deprived of oxygen. Long term exposure to a weak concentration of CO may lead to permanent brain or heart damage. A head ache may be a first symptom.
Carbon monoxide is inhaled from the air and absorbed by the lungs while breathing. Its toxic characteristics are caused when it is combined with haemoglobin, a protein which normally vehicles oxygen in the blood. This combination leads to the development of a relatively stable compound called carboxyhaemoglobin (COHb) which prevents the haemoglobin from conveying the oxygen to the tissues. Because there is a far greater affinity between Haemoglobin and CO than with oxygen, when you breathe air containing CO, it will infiltrate the haemoglobin first, thus taking the place of the oxygen. CO can also combine with other proteins such as myoglobin (present in muscle tissue) and certain cytochromes. The development of carboxyhaemoglobin is can be stopped either by eliminating the CO from the respiratory system by placing the person in a sound environment or by making him breathe oxygen possibly under high pressure (hyperbaric therapy). In the majority of case incidents result from :
When accidents occur an accumulation of errors and other factors mentioned above are often to blame. All types of appliances, whatever the type of combustible used, are a source of Carbon monoxide which varies in quantity according to the type of combustible and the quality of combustion:
Under-privileged families run a greater risk of CO intoxication because their heaters may be in poor condition. The maintenance of their heaters and of their ventilation systems may be neglected because of lack of money. There is frequently more than one victim usually a whole family of parents and children. Cases of mass intoxication regularly occur in large shops, restaurants, churches, or ice-skating rinks causing the death of several victims of all ages. Specific climatic conditions, low atmospheric pressure and fog for example, or exceptional conditions, very bad weather and severe cold entail greater risks especially because of widespread use of makeshift heating systems to make up for a deterioration of the usual heating system used (electric generator, petroleum stove, brazier.). In the case of the 1999 December storm in France , the risks were increased: chimney flues or extractor fans were ripped out, greater use of electric generators inside premises (although they should normally be used outside) because of power cuts. Certain regions are particularly vulnerable; for example in the North of France when it is foggy, there are a great number of simultaneous intoxications sometimes justifying emergency measures. Source : French Direction Générale de la Santé
As soon as the level of CO exceeds the threshold of 50 ppm, precautions must be taken especially for vulnerable persons: children, pregnant women, persons suffering from anaemia, heart conditions, respiratory problems, asthma, chronic bronchitis or emphysema. The threshold of 50 ppm has thus been chosen to determine the first level of alert for the CO mètre. Up till now surveillance of the level of CO in the air indoors has been limited to work places. There is no agreed limit concerning levels of CO in ordinary buildings. However the World Health Organisation has proposed guidelines using levels of concentration of CO in the air with levels of carboxyhaemoglobin in the blood taking into account the length of exposure and the level of alveolar ventilation. The equation which is most commonly used is the Coburn-Forster- Kane equation. In view of the well known toxic effects of CO on our health and the link with the level of carboxyhaemoglobin (COHb), the World Health Organisation considers that a level of COHb amounting to 2.5% was the maximum accepted level for the safety of the population. Guidelines have thus been established ensuring that the limit of 2.5% should not be exceeded even if the person is taking moderate or slight physical exercise.
The elimination of CO from the body depends on the amount of oxygen in the air and the atmospheric pressure. The curve below shows the amount of time it takes for levels of COHb to drop in ambient air, in pure oxygen and in a hyperbaric chamber.
Usual rate of elimination of carboxyhaemoglobin :
Elimination of gas is ,just as intoxication by CO, a particularly slow process especially under normal conditions: normal atmospheric pressure and 21% volume of oxygen in the air. Under these conditions, it takes 4h30 for the concentration of COHb to be halved. The process may be speeded up by increasing the concentration of oxygen or, better still, by placing the victim in a hyperbaric chamber with more than 2000mm of mercury during 12 to 30 minutes. This process increases the level of oxygen in the blood and speeds up the separation of CO and haemoglobin. A short time after exposure, the concentration levels of residual carboxyhaemoglobin (COHb) can be calculated with the following nomogram:
There are two different types of intoxication : - Acute intoxication which calls for immediate action on behalf of emergency services and with symptoms of dizziness, fainting, muscular impotence, even a coma or death. - Chronic intoxication, which causes head aches, nausea, mental confusion. It is difficult to detect and can cause in the long run cardiac and respiratory problems. This type of intoxication has recently been suspected of impairing the normal brain development of children and particularly their intellectual abilities. The clinical signs are not specific: headaches, dizziness, faintness, nausea, dyspnoea, problems with eye sight, sense of smell and taste, difficulties with sleep, memorisation and concentration, pains in the chest, abdomen and muscles may be observed to varying degrees. CO has been described as a 'great imitator' because CO intoxication often produce erroneous diagnoses of influenza, gastro-enteritis or other mild disorders. Moreover CO intoxication is frequently revealed through the discovery of a latent heart or cerebral condition. The fact that ready made explanations can be given to explain the observed symptoms no doubt leads to an underestimation of the number of CO intoxications of patients with 'known' vascular problems. Three particular clinical conditions ought to be pointed out: pregnant women (high risk for the foetus), children under the age of two (unusual behaviour, for example screaming), elderly persons (unspecific symptoms could be wrongfully ascribed to old age). Taken individually, symptoms may not therefore confirm intoxication. It seems unreasonable to ask for a report of suspected cases merely on a clinical basis as it would no doubt entail a large number of pointless investigations. However the clinical signs should lead the doctor to suspect CO intoxication and to look for other signs in order to confirm CO intoxication. In all similar situations the air exhaled by the patient should be tested with a carboxymeter (the carboxymeter is a specifically used to detect carbon monoxide).
Each year in France 6000 persons are victims of an intoxication due to Carbon monoxide and 300 of them die. Anybody can be a victim of this type of intoxication which often occurs when carrying out daily activities, such as turning on the heater or hot water. Acute intoxication calls for urgent action. The chronic type of intoxication is much more difficult to detect. It is therefore essential that everyone, medical professionals, social workers, heating specialists or retailers, but also each individual should be vigilant in detecting this type of intoxication which is still not widely known. Accidents vary enormously depending on the social and geographical backgrounds. Thus in the Pas de Calais region alone, Carbon monoxide causes 40 deaths and 1000 hospitalizations a year.
A measuring device such as the CO Metre® Pro enables the user to :
The use of the device can provide other types of information: tobacco is an important source of CO. In certain public places like offices, badly ventilated premises it is sometimes possible to identify levels of up to 30 ppm. Similarly in car traffic, particularly in tunnels or underground car parks, important levels of CO can be found. A device which allows continual monitoring of CO levels such as the Coach, will moreover monitor appliances which are potential sources of CO in the home.
Contact the anti poison centre or toxico vigil centres in your region. The addresses and 'phone numbers can be found at the following addresses :
Carbon monoxide intoxications are not subject to official reports. The 1985 official instructions incite the 'Directions Departementales des Affaires Sanitaires et Sociales' (regional health authorities) to inform the DGS (the official government health authority) of accidental cases of intoxication but the transmission of this information remains very partial. Make sure your heater is regularly serviced by qualified professionals. In France, NanoSense recommends the Proxiserve group:
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
01.41.41.00.02
