Inhalation toxicity studies: OECD guidelines in relation to REACH and scientific developments.

The OECD Health Effects Test Guidelines (TGs) provide guidance concerning the use of methods for the identification and characterization of hazards from chemical substances. These TGs are largely based on tests in routine use for many years and are known to yield information relevant to various types of toxicity. They have proven their value in practice and will remain of paramount importance for decades to come. However, the TGs describe mostly animal assays, and there is an increasingly strong urge to reduce animal testing on ethical grounds. In addition, assessment procedures are generally considered too slow and too rigid, which has resulted in elaborate testing of a relatively small number of chemicals, while virtually nothing is known about the vast majority of compounds. The major objectives of Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) are to improve the knowledge about the properties and use of chemicals and to speed up the procedure of risk assessment. The REACH text contains information requirements that can be met by OECD TGs but REACH also provides rules for adaptation of the standard testing regime. Also, various components of "Intelligent Testing Strategies" are described in order to limit animal testing. This paper briefly describes the OECD TGs for inhalation toxicity studies, including those in preparation, and their role in future hazard identification. This will be discussed in relation to the evaluation of the safety of thousands of chemicals in a relatively short period of time and scientific developments, including the use of alternatives to animal testing.