Thursday, 6 April 2017

Benzene, soft drinks and secondhand smoke

Science-Based Medicine reports on a court case in which the Nigerian Bottling Company was prosecuted (and lost) for selling soft drinks to the UK which had too much benzene in them.

This sounds pretty scary on the face of it, but the dose is in the poison. There is benzene in water and there is benzene in soft drinks, but very little. For some reason, the UK has a much lower limit than the international standard and a lower limit than Nigeria. Its 150 mg/kg limit for benzoic acid is a quarter of the Codex limit.

The product was tested on import into the UK and found to exceed their limit on benzoic acid (note – this refers to benzoic acid, not benzene):
The UK standards limit benzoic acid in soft drinks to a maximum of 150 mg/kg. Both Fanta and Sprite have benzoic levels of 200 mg/kg which is lower than the Nigerian regulatory limit of 250 mg/kg when combined with ascorbic acid and 300 mg/kg without ascorbic acid and also lower than the 600 mg/kg international limit set by Codex.
So the product was compliant with Nigerian and international limits, but over the stricter limit for the UK. 

The company said that it bottled the drinks to comply with Nigerian law and that they were not intended for export. The judge didn't accept this and suggested that the drinks were not 'fit for human consumption' even though they would be legal in many countries, including her own.

However, the main thing that interested me in the article was how much benzene people breathe in day-to-day life, presumably safely.

The WHO, as stated above, estimates that the average person is exposed to 250-400 micrograms of benzene per day. You will inhale 32 micrograms when you fill up your car, and 40 micrograms from driving for one hour. Smokers inhale 2-7 thousand micrograms a day, and passive exposure to smoke contributes an estimated 50 micrograms per day.

This suggests that amount of benzene you inhale from breathing secondhand smoke is well within the limit of what you would expect in a normal day.

But hang on, I thought that benzene in secondhand smoke was a mortal threat? I remember a TV advert put out by the Department of Health in 2006 as part of its campaign to prepare people for the smoking ban which featured someone who purported to be a scientist talking about how toxic benzene is and how awful it would be if benzene fumes got in the air. She even put on a gas mask.

She was then told that cigarette smoke contains benzene and, rather than asking a scientific question like 'How much?', she screwed her face up and said 'that's horrible'. The advert ended with the message: 'Where there's smoke, there's poison.'

You don't suppose the government was trying to deceive us in some way, do you?

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