Trot out the bogey word ''chemical'' and play on the punters' ignorance.

The test tube that morphs into a cigarette and its 4000 chemicals is an image we can't miss at the moment, part of the government-sponsored message that smoking is bad. It is depressing that such a message is needed after several years of ghoulish snaps from the autopsy department decorating cartons of the product.

However, there appears to be another message conveyed in the 4000 chemicals campaign, which must have been thoroughly researched before it was ever unleashed. This suggestion appears to be: if you want to scare the public, one conduit into their subliminal fears is the imagery of science.

The use of the word chemical as a negative and the image of the test tube suggest that the advertising agency believe these constitute negatives in the minds of what might be called ordinary people.

The test tube, that transparent phallus, conjures images of laboratories, mad professors and Frankenstein, or at least an unpleasant experience with high school science.

There is a continued reluctance among Australian students to study science and maths at a high level and a consequent shortage of many science-based professionals.

And then there is the use of the word ''chemical'' as a bogey. The high priests of the clean, green and totally pure mantra have long warned us of what are termed ''chemicals'', high among these being pesticides or other production residues in food.

A couple of years ago, a friend, stridently antagonistic to most aspects of Western medicine and a practitioner of what is curiously known as ''natural medicine'', was deeply concerned about my health and a bottle of some herbal compound appeared in the mail.

Touched by her concern, I soon found swallowing the recommended doses of the stuff caused a reaction worse than the ailment it was supposed to remedy. I told her this, suggesting that I could be allergic to some chemical compound in the herbs. Her response: ''There's no chemicals in it; it's all natural.'' A perfect example of public confusion over what constitutes a chemical.

In recent decades, one of the fastest-growing packaged beverages has been bottled water. Consider the idiocy of being able to pump this substance into plastic bottles and then sell vast quantities of it in a city with one of the most protected water supplies in the world. As my father once said, if you market it the right way, some people will buy sugar-coated dog shit.

Apart from water being sold in a container made of a highly complex chemical compound, the content, water, is nothing other than a chemical, a compound of two hydrogen atoms and one oxygen.

The bottle itself is likely to be polyethylene terephthalate, commonly known as PET. An article in the US government publication Environmental Health Perspectives in November last year offered evidence PET may release what are called endocrine disruptors under conditions of common use, affected by storage temperature and duration. Endocrine disruptors act like the body's own hormones, causing disruptions in the function and sometimes leading to mutations and diseases including some cancers.

There is no research yet that drinking bottled water from these containers leads to any such ailments. It is certainly less than the fear surrounding the plastic substance BPA (Bisphenol A), also used in some polycarbonate water bottles and even baby feeding bottles, which has been much more conclusively proven as an endocrine disruptor. But it is curious that such suggestions are linked to a product touted as purer than what we get from a tap.

It is also worth stating that the research leading to discoveries of threats to our health and the means to mitigate them are almost inevitably carried out in laboratories using chemicals.

As for the bogey word ''chemical'', apart from being 55 to 70 per cent made up of the chemical water, most of the rest of our bodies are chemicals, too, as is just about all of what we eat, including toxins.

These toxins are not just the product of science because many commonly consumed vegetables contain them, including pesticides, as part of their defence systems. Celery, potatoes and other root vegetables are examples, and the levels of toxins are not reduced by eating organic varieties.

As for bottled drinking water, many are now aware of BPA and an acquaintance told me this week she always ensures her water bottles are BPA free - she said this after coming back from smoking a cigarette.

Geoff Strong is an Age senior writer.