14737 IUPAC Gold Book - hazard quotient 10.1351/goldbook.14737 14737 current initialism: HQ 1 Ratio of toxicant exposure (estimated or measured) to a reference value regarded as corresponding to a threshold of toxicity; often this is determined as the predicted environmental concentration (PEC) divided by the predicted no-effect concentration (PNEC). If the hazard quotient exceeds unity, the toxicant may produce an adverse effect, but normally this will require an HQ of several times unity; an HQ of less than one indicates that no adverse effects are likely over a lifetime of exposure. predicted environmental concentration https://goldbook.iupac.org//terms/view/14944 predicted no-effect concentration https://goldbook.iupac.org//terms/view/14945 PAC, 2009, 81, 829. 'Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)' on page 895 (https://doi.org/10.1351/PAC-REC-08-07-09) https://goldbook.iupac.org/terms/view/14737/html https://goldbook.iupac.org/terms/view/14737/json https://goldbook.iupac.org/terms/view/14737/plain Citation: 'hazard quotient' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14737 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-04-21T15:08:11+00:00