Exposure to synthetic chemicals comes in three main forms – by mouth, through the nose and lungs, and through the skin. Those that we commonly breathe include solvents, exhaust fumes, cigarette smoke and aerosol droplets. In addition to these, many people are exposed to fumes at work – from industrial processes, photocopier machines or dry cleaning solvents, for example. Those living in industrial areas, or near rubbish incinerators, are exposed to other airborne chemicals from these sources. The third source listed above – the skin – is far less important. The number of synthetic chemicals that get into our bodies through the skin is relatively small, but solvents such as white spirit can enter in this way, as can oils and solvents used in cosmetics.

Someone eating an average diet and drinking unfiltered tap water is likely to ingest at least a hundred different synthetic chemicals every day. Exposure to airborne chemicals will vary more widely, depending on where people live, what work they do, how well-ventilated their homes are, and what sort of household products they use. A smoker in the house will increase the variety and quantity of air pollutants considerably. In all, we are probably exposed to at least two hundred different synthetic chemicals every day – and some people will encounter many more.

WHAT CAUSES CHEMICAL SENSITIVITY?

Why are some people apparently made ill by everyday synthetic chemicals? There are two types of explanation on offer, which can be summed up as ‘allergic explanations’ and ‘deficiency explanations’. The first type of theory proposes that these people make an inappropriate immune response (allergic response) to certain synthetic chemicals, in the same way that a hay-fever sufferer reacts adversely to pollen. The second type of explanation suggests that these people have some sort of defect that makes them less able to cope with environmental chemicals. It is usually assumed that this

is a deficiency in the enzymes that detoxify foreign chemicals. We will look at the evidence – such as it is – for each of these explanations.

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