In recent years there has been an ever-increasing tendency for the media and many pressure groups to publicise negative reports on synthetic chemicals, using emotive words such as “toxic”, “dangerous”, “nasty” and “polluting”. Even accepting the official legal (EU) definition of “toxic”, very few of the chemicals under attack are truly toxic, but the main point is that the reports usually focus on the hazard(s) identified with the chemical in question.
Identification of the hazards is important, but it is only the first step in a broader process. If only the hazard is known, the information is almost useless, partly because all chemicals have a hazard associated with them. Water, for example, has an inhalation hazard; sodium chloride (common salt) increases blood pressure to dangerous levels at fairly low doses. It is possible to identify a hazard for any chemical, given a high enough concentration and an appropriate route of exposure.
Once the hazard has been identified, the next (and most important) stage is to determine the level of exposure. This enables calculation of the risk involved in its use:
RISK = HAZARD x EXPOSURE
Risk is much more important than hazard. To give two examples from everyday life where we almost subconsciously calculate risk:
1) Crossing the road. Here is an obvious hazard – getting hit, possibly killed, by a moving vehicle. If you only take the hazard into consideration, you would never cross a road – ever! This would clearly be nonsensical, and we all calculate the risk and choose a safe moment to cross. This is exactly the same principle as that which should be applied to the use of chemicals.
2) Taking paracetamol. Each day, millions of people take paracetamol tablets as a headache cure. Paracetamol is a chemical, and it is hazardous. As few as 12 standard tablets can cause irreversible liver damage and a slow, agonising death. So why do people expose themselves to such a dangerous chemical? The answer is because exposure to the lower levels contained in the one or two tablets typically consumed have no significant adverse effect. Low exposure reduces the risk to an acceptable level.
Telling people not to use a chemical because of its hazard is, therefore, highly misleading. If we were not to use chemicals solely based on their hazards, we would have to exist in a total vacuum!
There is also the common occurrence of “implied hazard”. For example, there are many accounts of the use of propylene glycol in cosmetic products, where the article claims that this is used as antifreeze as though this obviously, therefore, makes the compound unsuitable for cosmetic use. This is a common internet myth and, in fact, it is ethylene glycol that is used in antifreeze! However, the principle remains the same and, whilst skin contact with neat propylene glycol is not recommended, it is only slightly irritating (although it can increase the transport of other, less desirable compounds through the skin) but it is not particularly hazardous. At the much lower concentrations used in personal care products, the irritation potential is reduced to insignificance. There is no correlation between its (alleged) use in antifreeze and its use in cosmetics. This principal applies equally to other ingredients that are used in cosmetics and also in other applications.
Unfortunately, the scientific community must shoulder some responsibility for this situation. There are many examples of studies that have identified a hazard that has been publicised by the authors before any attempt has been made to assess the risk. In the absence of the correct context provided by the risk assessment, the media are free to revel in the negative connotations – bad news is always better than good news!
In summary, whilst the hazard can be useful information, it bears no relation to reality until the risk is assessed. If the approach we adopt to risk in our everyday lives was applied to the use of chemicals, the world may be a slightly better, less neurotic place!