Toxicology has been described as the science of poisons. While partly true, it is more than that. It is a scientific discipline with roots in pharmacology, medicine, pathology and areas of biology that involves the study of the adverse effects (if any) of chemicals on living organisms. One of its roles is to attempt to predict whether toxicity observed in model systems, such as animals or in in vitro tests, is likely to be expressed in humans if they are exposed to the chemical in question. Regulatory toxicology is the application of toxicological knowledge and expertise by governments and their agencies to the control of chemical substances in order to protect human and animal health, and the well-being of the wider environment. Substances are classified on their main uses, for example into human and veterinary pharmaceuticals, pesticides and biocides and so on. These divisions are arbitrary and sometimes a substance may have one or more uses. For example, substances of the avermectin class are used as crop protection agents and are thus classed as pesticides (or plant protection products), but these same substances may also be used as parasiticides in human and veterinary medicines and are then classed as human or veterinary pharmaceuticals.

How chemicals are regulated depends on their uses and, in most areas of regulation, on their benefits versus any potential risks arising from knowledge of their toxic properties – their hazards. Sometimes these benefits are relatively easy to identify, although quantifying the benefits may be more problematic. For example, pharmaceutical products used in the treatment of human cancer frequently have toxic properties, but the benefits, the treatment and possibly the cure of the disease are self-evident, and if the benefits are deemed to outweigh the risks, then their clinical use will be permitted. On the other hand, some substances, for example environmental pollutants, might pose toxicological hazards with associated risks but offer no significant benefits to those potentially exposed. Do we then consider the benefits of the objects that create the pollutants, such as motor vehicles and power stations? Workers in chemical industries may be exposed to potentially toxic chemicals, and it is easy to conclude that such substances should be prohibited. However, what if the substance is a precursor for some other material or substance on which broader society is dependent? How do we regulate this type of chemical and its exposure?

Regulation of chemicals is not new. At the time of Henry VIII of England, physicians were concerned over what they regarded as ‘adulterated drugs’ being supplied and used by apothecaries. Henry enacted the first English law (1540) to control medicines and authorised physicians to inspect the premises of apothecaries to examine their products. Prior to the establishment of the European Union (EU) and its predecessor organisations, and in many cases for some time after, countries that are now members of the EU regulated chemicals on the basis of their own laws. This frequently meant that the level of regulation differed widely from country to country. In some European countries, regulation was regarded as strict, while in others it was viewed as being more relaxed. As a consequence, various classes of chemical have gradually been brought under the umbrella of regulation at the EU level, either directly by the intervention of EU agencies or indirectly by the application of harmonised regulatory requirements for enactment by EU member states. This has resulted in a comprehensive web of legislation and regulatory requirements covering most classes of chemical, including human and veterinary pharmaceuticals, pesticides, biocides and industrial chemicals, as well as various types of pollutant.

In this book, we have attempted to describe the regulation of chemicals in the EU, largely based on their toxic properties. Of course, chemicals are also regulated on the basis of other properties, such as their flammability and their ability to cause explosions. While these aspects cannot be overlooked, this is a book about regulatory toxicology, so we have not focussed on these other areas. We have, though, invited authors regarded as experts in their own speciality areas to contribute chapters to this book. Without such experts, there would be no book!

As editors, we would like to thank all of our contributors for their time and expertise, and to apologise for the myriad editorial requests and changes that we have inflicted on them. We are very grateful indeed for their efforts and understanding. We would also like to thank our colleagues at the Royal Society of Chemistry for their magnificent efforts in putting all of this together. They have been patient and understanding, and we are most grateful to them too.

Timothy C. Marrs

Kevin N. Woodward