ASTM E1242-23

Standard Practice for Using Octanol-Water Partition Coefficient to Estimate Median Lethal Concentrations for Fish Due to Narcosis

SIGNIFICANCE AND USE
5.1 This procedure can be used to limit the need for screening tests prior to performing a test for estimating the LC50 of a non-reactive and non-electrolytic chemical to the fathead minnow. By eliminating the screening test, fewer fish need be tested. The time used for preparing and performing the screening test can also be saved. The value obtained in this procedure can be used as the preliminary estimate of the LC50 in a full-scale test.  
5.2 Estimates can be used to set testing priority of groups of non-reactive and non-electrolytic chemicals.  
5.3 If the estimated value is more than 0.3 times the experimental value, the mechanism of action is probably narcosis. If less, the effect concentration is considered to reflect a different mechanism of action.  
5.4 This practice estimates a maximum LC50, that is, non-reactive and non-electrolytic chemicals are at least as toxic as the practice predicts, but may have a lower LC50 if acting by a more specific mechanism. Data on a chemical indicating a lower toxicity than predicted should be considered suspect or an artifact because of limited solubility of the test material.
SCOPE
1.1 This practice covers a procedure for estimating the fathead minnow (Pimephales promelas) 96-h LC50 of nonreactive (that is, covalently bonded without unsaturated residues) and nonelectrolytic (that is, require vigorous reagents to facilitate substitution, addition, replacement reactions and are non-ionic, non-dissociating in aqueous solutions) organic chemicals acting solely by narcosis, also referred to as Meyer-Overton toxicity relationship.2  
1.2 This procedure is accurate for organic chemicals that are toxic due to narcosis and are non-reactive and non-electrolytic. Examples of appropriate chemicals are: alcohols, ketones, ethers, simple halogenated aliphatics, aromatics, and aliphatic substituted aromatics. It is not appropriate for chemicals whose structures include a potential toxiphore (that structural component of a chemical molecule that has been identified to show mammalian toxicity, for example CN is known to be reponsible for inactivation of enzymes, NO2 for decoupling of oxidative phosphorylation, both leading to mammalian toxicity). Examples of chemicals inappropriate for this practice are: carbamates, organophosphates, phenols, beta-gamma unsaturated alcohols, electrophiles, and quaternary ammonium salts.  
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Dec-2022
• ICS: 07.080 - Biology. Botany. Zoology
• Technical Committee: E50 - Environmental Assessment, Risk Management and Corrective Action
• Drafting Committee: E50.47 - Biological Effects and Environmental Fate

Relations

• Refers: ASTM E943-08 - Standard Terminology Relating to Biological Effects and Environmental Fate
• Effective Date: 01-Mar-2008
• Refers: ASTM E729-96(2007) - Standard Guide for Conducting Acute Toxicity Tests on Test Materials with Fishes, Macroinvertebrates, and Amphibians
• Effective Date: 01-Oct-2007
• Refers: ASTM E1023-84(2007) - Standard Guide for Assessing the Hazard of a Material to Aquatic Organisms and Their Uses
• Effective Date: 01-Oct-2007

Overview

ASTM E1242-23: Standard Practice for Using Octanol-Water Partition Coefficient to Estimate Median Lethal Concentrations for Fish Due to Narcosis provides a standardized procedure for estimating the 96-hour median lethal concentration (LC50) of organic chemicals, specifically for the fathead minnow (Pimephales promelas). This practice applies to non-reactive and non-electrolytic organic chemicals that act through narcosis, as described by the Meyer-Overton toxicity relationship.

The method leverages the octanol-water partition coefficient (Kow), a widely used metric in environmental chemistry for assessing the hydrophobicity of chemicals, to estimate toxicity. This approach helps minimize the need for preliminary screening tests, conserving both time and biological resources in aquatic toxicology studies.

Key Topics

• Scope of Application:

  • Relevant for organic chemicals that are non-reactive, non-electrolytic, and whose primary toxicity mechanism is narcosis.
  • Examples of applicable chemicals include alcohols, ketones, ethers, simple halogenated aliphatics, aromatics, and aliphatic-substituted aromatics.
  • Excludes chemicals with toxiphores-structural components known for specific mammalian toxicity (e.g., cyanides, nitro groups, carbamates, organophosphates).

• Methodology:

  • Utilizes the octanol-water partition coefficient (Kow) to estimate a maximum 96-h LC50 value.
  • The estimation acts as a preliminary toxicity value before undertaking full-scale aquatic toxicity tests.

• Significance and Use:

  • Reduces the need for screening tests, thus limiting the number of fish required.
  • Saves time in aquatic toxicity assessments.
  • Assists in prioritizing the testing of chemical groups and can indicate if a chemical likely acts via the narcosis mechanism.

• Interpretation of Results:

  • If the estimated LC50 significantly exceeds measured LC50 values (by more than 0.3 times), narcosis is likely the main mode of action.
  • Lower experimental values than predicted may indicate alternative toxicity pathways or artifacts such as low solubility.

Applications

• Aquatic Toxicology:

  • Efficiently estimate acute toxicity of organic chemicals to fish, particularly fathead minnows, using physicochemical data rather than resource-intensive bioassays.
  • Provides a screening tool for environmental risk assessment by regulatory agencies, environmental consultants, and research laboratories.

• Chemical Prioritization:

  • Supports prioritizing substances for further detailed investigation by offering preliminary toxicity assessments.
  • Helps identify chemicals that may pose higher ecological risks due to narcosis-based toxicity.

• Environmental Risk Management:

  • Assists in early-stage hazard assessments and environmental impact studies.
  • Facilitates compliance with environmental safety regulations and standards in chemical manufacturing and use.

Related Standards

• ASTM E729: Guide for Conducting Acute Toxicity Tests on Test Materials with Fishes, Macroinvertebrates, and Amphibians
• ASTM E943: Terminology Relating to Biological Effects and Environmental Fate (withdrawn 2023)
• ASTM E1023: Guide for Assessing the Hazard of a Material to Aquatic Organisms and Their Uses
• ASTM E1147: Test Method for Partition Coefficient (N-Octanol/Water) Estimation by Liquid Chromatography (withdrawn 2013)

Practical Value

Utilizing the guidelines in ASTM E1242-23 streamlines aquatic toxicity testing for certain organic chemicals, enhancing efficiency in laboratory studies and supporting informed decision-making in environmental assessment and chemical management. Using Kow as a predictive tool simplifies the process of estimating fish toxicity, providing cost-effective and ethical alternatives to traditional bioassays. This standard is essential for professionals in environmental toxicology, regulatory compliance, and risk management seeking reliable and internationally recognized practices.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1242 − 23
Standard Practice for
Using Octanol-Water Partition Coefficient to Estimate
Median Lethal Concentrations for Fish Due to Narcosis
This standard is issued under the fixed designation E1242; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers a procedure for estimating the
E729 Guide for Conducting Acute Toxicity Tests on Test
fathead minnow (Pimephales promelas) 96-h LC50 of nonre-
Materials with Fishes, Macroinvertebrates, and Amphib-
active (that is, covalently bonded without unsaturated residues)
ians
and nonelectrolytic (that is, require vigorous reagents to
E943 Terminology Relating to Biological Effects and Envi-
facilitate substitution, addition, replacement reactions and are
ronmental Fate (Withdrawn 2023)
non-ionic, non-dissociating in aqueous solutions) organic
E1023 Guide for Assessing the Hazard of a Material to
chemicals acting solely by narcosis, also referred to as Meyer-
Aquatic Organisms and Their Uses
Overton toxicity relationship.
E1147 Test Method for Partition Coefficient (N-Octanol/
1.2 This procedure is accurate for organic chemicals that are
Water) Estimation by Liquid Chromatography (With-
toxic due to narcosis and are non-reactive and non-electrolytic.
drawn 2013)
Examples of appropriate chemicals are: alcohols, ketones,
ethers, simple halogenated aliphatics, aromatics, and aliphatic
3. Terminology
substituted aromatics. It is not appropriate for chemicals whose
3.1 Definitions:
structures include a potential toxiphore (that structural compo-
3.1.1 acute toxicity—where an adverse effect such as mor-
nent of a chemical molecule that has been identified to show
tality is measured after organisms exposed to a compound for
mammalian toxicity, for example CN is known to be reponsible
a relatively short period, usually not constituting a substantial
for inactivation of enzymes, NO for decoupling of oxidative
portion of their life span.
phosphorylation, both leading to mammalian toxicity). Ex-
3.1.2 narcosis, n—a reversible state of stupor,
amples of chemicals inappropriate for this practice are:
unconsciousness, or arrested activity produced by the influence
carbamates, organophosphates, phenols, beta-gamma unsatu-
of chemicals on critical sites within membranes or by disrupt-
rated alcohols, electrophiles, and quaternary ammonium salts.
ing the normal functioning of certain proteins by means of
1.3 This international standard was developed in accor-
nonspecific binding of organic chemical(s) to hydrophobic
dance with internationally recognized principles on standard-
sites. Death results if exposure is not terminated after a length
ization established in the Decision on Principles for the
of time which varies with concentration.
Development of International Standards, Guides and Recom-
3.1.3 octanol-water partition coeffıcient (K ), n—referred
ow
mendations issued by the World Trade Organization Technical
to as P in some literature.
Barriers to Trade (TBT) Committee.
3.1.4 toxiphore, n—a chemical structure substituent group
that when present gives rise to an adverse effect in exposed
organisms.
This practice is under the jurisdiction of ASTM Committee E50 on Environ-
mental Assessment, Risk Management and Corrective Action and is the direct
responsibility of Subcommittee E50.47 on Biological Effects and Environmental
Fate.
Current edition approved Jan. 1, 2023. Published February 2023. Originally For referenced ASTM standards, visit the ASTM website, www.astm.org, or
approved in 1988. Last previous edition approved in 2014 as E1242 – 97(2014). contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
DOI: 10.1520/E1242-23. Standards volume information, refer to the standard’s Document Summary page on
Lipnick, Robert L., “Validation and Extension of Fish Toxicity QSARs and the ASTM website.
Interspecies Comparisons for Certain Classes of Organic Chemicals,” QSAR in The last approved version of this historical standard is referenced on www.ast-
Toxicology and Xenobiochemistry, Elsevier, 1985. m.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1242 − 23
4. Summary of Practice 6.2 Obtain the octanol-water partition coefficient (K ), by
ow
measurement (see Test Method E1147), from a literature
4.1 The hydrophobicity of a non-reactive and non-
source or by estimation based on structure. Since the K
ow
electrolytic organic chemical as quantified by log of the
value is critical to calculating the LC50, it is important to
octanol-water partition coefficient is substituted into an experi-
obtain a measured value rather than depending completely on
mentally deri
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E1242 − 97 (Reapproved 2014) E1242 − 23
Standard Practice for
Using Octanol-Water Partition Coefficient to Estimate
Median Lethal Concentrations for Fish Due to Narcosis
This standard is issued under the fixed designation E1242; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers a procedure for estimating the fathead minnow (Pimephales promelas) 96-h LC50 of nonreactive (that
is, covalently bonded without unsaturated residues) and nonelectrolytic (that is, require vigorous reagents to facilitate substitution,
addition, replacement reactions and are non-ionic, non-dissociating in aqueous solutions) organic chemicals acting solely by
narcosis, also referred to as Meyer-Overton toxicity relationship.
1.2 This procedure is accurate for organic chemicals that are toxic due to narcosis and are non-reactive and non-electrolytic.
Examples of appropriate chemicals are: alcohols, ketones, ethers, simple halogenated aliphatics, aromatics, and aliphatic
substituted aromatics. It is not appropriate for chemicals whose structures include a potential toxiphore (that structural component
of a chemical molecule that has been identified to show mammalian toxicity, for example CN is known to be reponsible for
inactivation of enzymes, NO for decoupling of oxidative phosphorylation, both leading to mammalian toxicity). Examples of
inappropriate chemicals chemicals inappropriate for this practice are: carbamates, organophosphates, phenols, beta-gamma
unsaturated alcohols, electrophiles, and quaternary ammonium salts.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E729 Guide for Conducting Acute Toxicity Tests on Test Materials with Fishes, Macroinvertebrates, and Amphibians
E943 Terminology Relating to Biological Effects and Environmental Fate (Withdrawn 2023)
E1023 Guide for Assessing the Hazard of a Material to Aquatic Organisms and Their Uses
E1147 Test Method for Partition Coefficient (N-Octanol/Water) Estimation by Liquid Chromatography (Withdrawn 2013)
3. Terminology
3.1 Definitions:
This practice is under the jurisdiction of ASTM Committee E50 on Environmental Assessment, Risk Management and Corrective Action and is the direct responsibility
of Subcommittee E50.47 on Biological Effects and Environmental Fate.
Current edition approved Oct. 1, 2014Jan. 1, 2023. Published December 2014February 2023. Originally approved in 1988. Last previous edition approved in 20082014
as E1242 – 97(2008). DOI: 10.1520/E1242-97R14.(2014). DOI: 10.1520/E1242-23.
Lipnick, Robert L., “Validation and Extension of Fish Toxicity QSARs and Interspecies Comparisons for Certain Classes of Organic Chemicals,” QSAR in Toxicology
and Xenobiochemistry, Elsevier, 1985.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1242 − 23
3.1.1 acute toxicity—where an adverse effect such as mortality is measured after organisms exposed to a compound for a relatively
short period, usually not constituting a substantial portion of their life span.
3.1.2 narcosis—narcosis, n—a reversible state of stupor, unconsciousness, or arrested activity produced by the influence of
chemicals on critical sites within membranes or by disrupting the normal functioning of certain proteins by means of nonspecific
binding of organic chemical(s) to hydrophobic sites. Death results if exposure is not terminated after a length of time which varies
with concentration.
3.1.3 octanol-water partition coeffıcient (K )),—n—referred to as P in some literature.
ow
3.1.4 toxiphore—toxiphore, n—a chemical structure substituent group that when present gives rise to an adverse effect in exposed
organisms.
3.2 For definitions of other terms used in this standard, refer to Guide E729, Terminology E943, and Guide E1023.
4. Summary of Practice
4.1 The hydrophobicity of a non-reactive and non-electrolytic organic chemical as quantified by log of the octanol-water partition
coefficient is substituted into an experimentally derived equation and an approximate 96-h log LC50 for fathead minnow is
calculated. This value is a maximum value. The actual LC50 could be lower, but should not be higher.
4.2 For d
...