Read Across (from Analogs/Categories)
“Read across” is a technique of filling data gaps. To “read across” is to apply data from a tested chemical for a particular property or effect (cancer, reproductive toxicity, etc.) to a similar untested chemical. The read across technique is often applied within groups of similar chemicals assembled for assessment using either analog approach (grouping based on a very limited number of chemicals) or category approach (grouping based on a larger number of chemicals). In an analog/category approach, not every chemical needs to be tested for every endpoint.

Source: EPA, Glossary of Terms, Methods of Toxicity Testing and Risk Assessment
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Grouping of substances and read-across approach
Substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or "category" of substances. Application of the group concept requires that physicochemical properties, human health effects and environmental effects or environmental fate may be predicted from data for reference substance(s) within the group by interpolation to other substances in the group (read-across approach). This avoids the need to test every substance for every endpoint. Preferably, a category should include all similar substances. REACH Annex XI, Section 1.5. sets out the requirements for the application of this strategy.

Source: REACH Regulation, Annex XI (Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), establishing a European Chemicals Agency, amending Directive 1999/45/EC and repealing Council Regulation (EEC) No 793/93 and Commission Regulation (EC) No 1488/94 as well as Council Directive 76/769/EEC and Commission Directives 91/155/EEC, 93/67/EEC, 93/105/EC and 2000/21/EC) - OJ L 396 30.12.2006, page 376.

See also: ECHA


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