Benzene – isn’t it only found in chemistry sets?
You may think you have never handled a significant volume of benzene? Wrong. When you fill your petrol tank you may at the same time handle a litre of benzene, which is volatile carcinogenic substance easily capable of causing exposure. Benzene is a classic example of how differently cancer-causing chemicals are seen depending on where they are. In the laboratory, even a small amount of benzene is regarded as a carcinogenic compound and there are strict restrictions on its use, and efforts are made to change it to a safer alternative.
Benzene here is as an example of the volatile aromatic hydrocarbons found in many solvents and liquid fuels. Other related compounds are xylene and toluene, but they are not carcinogenic like benzene.
The most important outdoor source of benzene (C6H6) is petrol, and so benzene gains access to our environment both by direct volatilization and by incomplete burning. Other sources include oil refineries, the use of solvents containing benzene (usually as an impurity), and incomplete burning processes.
The most important indoor source of benzene is tobacco smoking, but there are other sources, e.g. kerosene lamps and kerosene stoves without flue. Some cleaning agents, waxes, paints and glues may have technical solvents with benzene present as an impurity.
Exposure levels and health effects
Average exposure levels in European cities vary from 3 μg/m3 to 18 μg/m3, but the variation is huge and maximal concentrations may be around 200 μg/m3. The yearly average limit value in European Union is 5 μg/m3.
Benzene causes leukaemia. This can be stated with confidence because some factory workers used to be exposed to very high concentrations for decades. The present lowest outdoor levels are not a cause for concern, but the values at the upper range are problematic.
Should something be done?
Most people are exposed through outdoor air from traffic emissions, if there are no specific sources, but it is also possible to be exposed to benzene from food, drink or via skin.
Since benzene is a carcinogenic substance, the exposure should be minimized as much as possible. The risk assessment is hampered by the fact that benzene only needs to be listed as an ingredient, if the product contains more than 1%. Therefore it is difficult to know the real concentration in the products.
Benzene is a prime example of a substance that is known to be carcinogenic, but nonetheless people are exposed to it every day. It is unlikely to cause any real danger except in occupational use, but there is no absolute certainty. Certainly it should not have any place as a cleaning agent for use in the homes.
One level up: The air that we breathe
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