Chemical Safety Assessment by Computer

Many countries have developed robust systems for the assessment and control of hazardous chemicals. In Europe the REACH regulations (Registration, Evaluation and Authorization and Restriction of Chemicals), came into force in 2007. REACH places obligations on all manufacturers, suppliers, and users of chemicals with regard to their environmental and human safety. The European Chemicals Agency (ECHA), was set up to administer REACH and other chemical legislation as it is introduced.

In the USA the Toxic Substances Control Act is undergoing review as the Safe Chemicals Act works its way through the system, aimed at strengthening the control of chemicals comparable to that of REACH in Europe. Other countries have or are bringing in tougher controls on chemicals to match those of REACH.

In Europe there are also separate regulations for pesticides, medicines, cosmetics and nano-materials. All of these regulations require many thousands of chemicals to be tested for environmental and human safety whilst at the same time trying to reduce or replace animal testing. One option in the armoury of alternative tests is the use of computer-based (in-silico) methods. In-silico methods include, expert systems, QSAR, and read-across, all as part of a “weight of evidence” approach to predictive toxicology.

The OECD issued a set of principles upon which toxicity predictions should be based. These are:

1) a defined endpoint
2) an unambiguous algorithm
3) a defined domain of applicability
4) appropriate measures of goodness-of-fit, robustness and predictivity
5) a mechanistic interpretation, if possible

These 5 principles must be met before in-silico predictions will be considered in a regulatory context.

Many software tools are now available for in-silico predictive toxicology, some commercial but some freely available such as the excellent OECD QSAR Toolbox ( )


All in-silico” predictive tools require expert judgement in order to obtain valid predictions. TfG has extensive experience in the use of the main publicly available tools, and actually participated in the development of some, through our involvement in a range of EU projects on this subject.

TfG can offer a “weight of evidence” package incorporating SAR, QSAR, read-across”, literature searching and expert judgement.