ASTM D6046-24

Standard Classification of Hydraulic Fluids for Environmental Impact

SIGNIFICANCE AND USE
4.1 This classification establishes categories of hydraulic fluids which are distinguished by their response to certain standardized laboratory procedures. These procedures indicate the possible response of some environmental compartments to the introduction of the hydraulic fluid. One set of procedures measures the aerobic aquatic biodegradability (environmental persistence) of the fluids and another set of procedures estimates the acute ecotoxicity effects of the fluids.  
4.1.1 Although this classification includes categories for both persistence and ecotoxicity, there is no relationship between the two categories. They may be used independently of each other, that is, a hydraulic fluid can be categorized with respect to both sets of laboratory procedures, or to persistence but not ecotoxicity, or to ecotoxicity but not persistence.  
4.1.2 There is no relationship between the categories achieved by a hydraulic fluid for persistence and for ecotoxicity. The placing of a hydraulic fluid with regard to one set of categories has no predictive value as to its placement with regard to the other set of categories.  
4.2 The test procedures used to establish the categories of hydraulic fluids are laboratory standard tests and are not intended to simulate the natural environment. Definitive field studies capable of correlating test results with the actual environmental impact of hydraulic fluids are usually site specific and so are not directly applicable to this classification. Therefore, the categories established by this classification can serve only as guidance to estimate the actual impact that the hydraulic fluids might have on any particular environment.  
4.3 This classification can be used by producers and users of hydraulic fluids to establish a common set of references that describe some aspects of the anticipated environmental impact of hydraulic fluids which are incidental to their use.  
4.4 Inclusion of a hydraulic fluid in any category of this classi...
SCOPE
1.1 This classification covers all unused fully formulated hydraulic fluids in their original form.  
1.2 This classification establishes categories for the impact of hydraulic fluids on different environmental compartments as shown in Table 1. Fluids are assigned designations within these categories; for example PwL, Pwe, and so forth, based on performance in specified tests.  
1.3 This classification includes environmental persistence and acute ecotoxicity as aspects of environmental impact. Although environmental persistence is discussed first, this classification does not imply that considerations of environmental persistence should take precedence over concerns for ecotoxicity.  
1.3.1 Environmental persistence describes long term impact of hydraulic fluids to the environment. Environmental persistence is preferably measured by ultimate biodegradation but can also be measured by other means.  
1.3.2 Acute toxicity describes the immediate toxic impact of hydraulic fluids to the environment. Acute toxicity is preferably measured by the three trophic levels of aquatic organisms (Algae, Crustacea, and Fish).  
1.4 Another important aspect of environmental impact is bioaccumulation. This aspect is not addressed in the present classification because adequate test methods do not yet exist to measure bioaccumulation of hydraulic fluids.  
1.5 The present classification addresses the fresh water and soil environmental compartments. At this time marine and anaerobic environmental compartments are not included, although they are pertinent for many uses of hydraulic fluids. Hydraulic fluids are expected to have no significant impact on the atmosphere; therefore that compartment is not addressed.  
1.6 This classification addresses releases to the environment which are incidental to the use of a hydraulic fluid. The classification is not intended to address environmental impact in situations of major, accidental release...

General Information

• Status: Published
• Publication Date: 29-Feb-2024
• ICS: 75.120 - Hydraulic fluids
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.N0 - Hydraulic Fluids

Relations

• Replaces: ASTM D6046-18 - Standard Classification of Hydraulic Fluids for Environmental Impact
• Effective Date: 01-Mar-2024
• Referred By: ASTM D8324-21 - Standard Guide for Selection of Environmentally Acceptable Lubricants for the U.S. Environmental Protection Agency (EPA) Vessel General Permit
• Effective Date: 01-Mar-2024
• Referred By: ASTM D8431-22 - Standard Test Method for Detection of Water-soluble Petroleum Oils by A-TEEM Optical Spectroscopy and Multivariate Analysis
• Effective Date: 01-Mar-2024

Overview

ASTM D6046-24, titled Standard Classification of Hydraulic Fluids for Environmental Impact, is an international standard developed by ASTM International. This standard provides a comprehensive classification system for unused, fully formulated hydraulic fluids, focusing on their environmental impact. By using standardized laboratory procedures, ASTM D6046-24 enables the evaluation of two critical aspects: environmental persistence (primarily measured through biodegradability tests) and acute ecotoxicity (measured through toxicity tests on aquatic and soil organisms). This classification assists manufacturers, users, and regulators in assessing the potential environmental footprint of hydraulic fluids released incidentally during normal usage.

Key Topics

• Environmental Persistence:

  • Assesses the biodegradability of hydraulic fluids in aerobic aquatic environments (mainly fresh water).
  • Utilizes ultimate and primary biodegradation tests to classify fluids from highly biodegradable to persistent.

• Acute Ecotoxicity:

  • Measures the immediate toxic impact of hydraulic fluids on organisms spanning three trophic levels (algae, crustaceans, fish for water; plants, invertebrates for soil).
  • Classifies fluids based on their toxicity to these organisms using established laboratory methods.

• Environmental Compartments Covered:

  • Focuses on fresh water and soil environments.
  • Marine and anaerobic compartments are not currently addressed.
  • Bioaccumulation is noted as an important factor, but not included due to lack of sufficient test methods.

• Classification System:

  • Fluids are designated into categories such as Pw (persistence in water), Tw (toxicity in water), and Ts (toxicity in soil) based on test outcomes.
  • The system allows independent evaluation of both persistence and ecotoxicity.

• Limitations:

  • Laboratory tests do not directly simulate real environmental conditions.
  • Results serve as guidance, not absolute prediction of environmental behavior.
  • Standard does not address used hydraulic fluids, bioaccumulation, or accidental major releases.

Applications

• Product Development and Labeling:

  • Manufacturers of hydraulic fluids use ASTM D6046-24 to design, formulate, and label products according to their environmental impact classification.
  • Facilitates transparent communication of biodegradability and toxicity characteristics to end-users and stakeholders.

• Regulatory Compliance:

  • Assists compliance with environmental regulations and eco-label programs focused on reducing ecological risks associated with hydraulic fluids.

• Purchasing and Specification:

  • Enables engineers, purchasing managers, and environmental managers in industries such as construction, forestry, transportation, and manufacturing to specify fluids that minimize environmental risks.
  • Provides a common reference for selecting and comparing hydraulic fluids based on anticipated environmental impact.

• Sustainability Initiatives:

  • Supports corporate and governmental sustainability policies by helping identify and use hydraulic fluids that degrade more readily in the environment and exhibit lower toxicity to local ecosystems.

Related Standards

• ASTM D4175: Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants.
• ASTM D5864: Test Method for Determining Aerobic Aquatic Biodegradation of Lubricants.
• ASTM D6006: Guide for Assessing Biodegradability of Hydraulic Fluids.
• ASTM D6081: Practice for Aquatic Toxicity Testing of Lubricants.
• OECD 301 Series: Tests for ready biodegradability (e.g., CO₂ Evolution, Modified MITI).
• OECD 201, 202, 203, 207, 208: Acute toxicity protocols for algae, aquatic invertebrates, fish, earthworms, and terrestrial plants.
• US EPA Methods: Aerobic Aquatic Biodegradation, Seed Germination, Acute Toxicity for Daphnids and Fish.
• ISO 9439: Ultimate Biodegradability in Water - Determination of released carbon dioxide.

In summary, ASTM D6046-24 standardizes the classification of hydraulic fluids regarding environmental persistence and ecotoxicity, offering a practical framework for evaluating and reducing environmental impact in hydraulic fluid selection and management. This enhances responsible product stewardship and encourages a sustainable approach to hydraulic fluid use in sensitive environmental settings.

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: D6046 − 24
Standard Classification of
Hydraulic Fluids for Environmental Impact
This standard is issued under the fixed designation D6046; 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* classification is not intended to address environmental impact
in situations of major, accidental release. Nothing in this
1.1 This classification covers all unused fully formulated
classification should be taken to relieve the user of the
hydraulic fluids in their original form.
responsibility to properly use and dispose of hydraulic fluids.
1.2 This classification establishes categories for the impact
1.7 This classification does not cover any performance
of hydraulic fluids on different environmental compartments as
properties of a hydraulic fluid which relate to its performance
shown in Table 1. Fluids are assigned designations within these
in a hydraulic system.
categories; for example PwL, Pwe, and so forth, based on
1.8 This standard does not purport to address all of the
performance in specified tests.
safety concerns, if any, associated with its use. It is the
1.3 This classification includes environmental persistence
responsibility of the user of this standard to establish appro-
and acute ecotoxicity as aspects of environmental impact.
priate safety, health, and environmental practices and deter-
Although environmental persistence is discussed first, this
mine the applicability of regulatory limitations prior to use.
classification does not imply that considerations of environ-
1.9 This international standard was developed in accor-
mental persistence should take precedence over concerns for
dance with internationally recognized principles on standard-
ecotoxicity.
ization established in the Decision on Principles for the
1.3.1 Environmental persistence describes long term impact
Development of International Standards, Guides and Recom-
of hydraulic fluids to the environment. Environmental persis-
mendations issued by the World Trade Organization Technical
tence is preferably measured by ultimate biodegradation but
Barriers to Trade (TBT) Committee.
can also be measured by other means.
1.3.2 Acute toxicity describes the immediate toxic impact of
2. Referenced Documents
hydraulic fluids to the environment. Acute toxicity is prefer-
2.1 ASTM Standards:
ably measured by the three trophic levels of aquatic organisms
D4175 Terminology Relating to Petroleum Products, Liquid
(Algae, Crustacea, and Fish).
Fuels, and Lubricants
1.4 Another important aspect of environmental impact is
D5291 Test Methods for Instrumental Determination of
bioaccumulation. This aspect is not addressed in the present
Carbon, Hydrogen, and Nitrogen in Petroleum Products
classification because adequate test methods do not yet exist to
and Lubricants
measure bioaccumulation of hydraulic fluids.
D5864 Test Method for Determining Aerobic Aquatic Bio-
1.5 The present classification addresses the fresh water and
degradation of Lubricants or Their Components
soil environmental compartments. At this time marine and
D6006 Guide for Assessing Biodegradability of Hydraulic
anaerobic environmental compartments are not included, al-
Fluids
though they are pertinent for many uses of hydraulic fluids.
D6081 Practice for Aquatic Toxicity Testing of Lubricants:
Hydraulic fluids are expected to have no significant impact on
Sample Preparation and Results Interpretation
the atmosphere; therefore that compartment is not addressed.
E943 Terminology Relating to Biological Effects and Envi-
ronmental Fate
1.6 This classification addresses releases to the environment
E1440 Guide for Acute Toxicity Test with the Rotifer Bra-
which are incidental to the use of a hydraulic fluid. The
chionus
This classification is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.N0 on Hydraulic Fluids. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2024. Published April 2024. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1996. Last previous edition approved in 2018 as D6046 – 18. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D6046-24. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6046 − 24
TABLE 1 Overview of Extended Classification
Toxic Substances Control Act (TSCA), Good Laboratory
Categories of Environmental Impact Practice Standards, Final Rule, U.S. Federal Register, 40
Environmental
Environmental CFR Part 792, August 17, 1989
Compartment
Ecotoxicity Bioaccumulation
Persistence
2.6 Other Standards:
Fresh Water Pw Tw Bw
MENVIQ 92.03/800—D.mag. 1.1, March 1992
Marine Pm Tm Bm
Soil Ps Ts Bs 29 CFR 1910 OSHA Regulated Carcinogens and Potential
Anaerobic Pa Ta Ba
Carcinogens
3. Terminology
2.2 ISO Standards: 3.1 Definitions:
International Standard ISO Test 9439:1990 Technical Corri- 3.1.1 For definitions of terms used in this classification not
gendum 1, Water Quality—Evaluation in An Aqueous given below, refer to Terminology D4175.
Medium of the “Ultimate” Biodegradability of Organic 3.1.2 acute ecotoxicity, n—the propensity of a material to
Compounds—Method by Analysis of Released Carbon produce adverse behavioral, biochemical, or physiological
Dioxide effects in non-human organisms or populations in a short
period of time, usually not constituting a substantial portion of
2.3 OECD Standards:
the life span of the organism.
OECD 301B CO Evolution Test (the Modified Sturm Test)
OECD 301C Modified MITI Test (I)
3.1.3 aerobic, adj—(1) taking place in the presence of
OECD 301F Manometric Respirometry Test
oxygen, (2) living or active in the presence of oxygen.
OECD 201 Alga, Growth Inhibition Test
3.1.4 anaerobic, adj—(1) taking place in the absence of
OECD 202 Daphnia sp., Acute Immobilisation Test and
oxygen, (2) living or active in the absence of oxygen.
Reproduction Test
3.1.5 biodegradation, n—the process of chemical break-
OECD 203 Fish, Acute Toxicity Test
down or transformation of a material caused by organisms or
OECD 207 Earthworm Acute Toxicity Test
their enzymes.
OECD 208 Terrestrial Plants Growth Test
3.1.5.1 Discussion—Biodegradation is only one mechanism
2.4 US EPA Tests:
by which materials are transformed in the environment.
Aerobic Aquatic Biodegradation Test, 40 CFR 796.3100
3.1.6 ecotoxicity, n—the propensity of a material to produce
(Also available as EPA publication 560/6-82-003, number
adverse behavioral, biochemical, or physiological effects in
CG-2000)
non-human organisms or populations.
Toxic Substances Control Act (TSCA), 40 CFR Parts 796
and 797—Environmental Effects Testing Guidelines, Fed-
3.1.7 effect load XX (ELXX), n—a statistically or graphically
eral Register, Vol 50, No. 188, September 27, 1985, p.
estimated loading rate of test material that is expected to cause
one or more specified effects in XX % of a group of organisms
2.5 Environmental Canada Test Methods: under specified conditions for a specified time.
Biological Test Method: Acute Lethality Test Using Rain- 3.1.7.1 Discussion—This terminology should be used for
bow Trout, Report EPS 1/9, Environment Canada, July hydraulic fluids instead of the standard effect concentration
1990 (ECXX) when the hydraulic fluid is not completely soluble
Biological Test Method: Reference Method for Determining under test conditions.
Acute Lethality of Effluents to Rainbow Trout, Reference
3.1.8 environmental compartment, n—a subdivision of the
Method EPS 1/RM/13, Environment Canada, July 1990
environment based on physical or chemical properties, or both.
Biological Test Method: Growth Inhibition Test Using the
3.1.8.1 Discussion—Examples of environmental compart-
Freshwater Alga Selenastrum capricornutum, Report EPS
ments are aerobic fresh water, aerobic marine, aerobic soil, and
1/RM/25, Environment Canada, November 1992
anaerobic media. The results of test procedures may be applied
Biological Test Method: Acute Lethality Test Using Daphnia
to environmental compartments, but the test systems do not
spp., Report EPS 1/RM/11, Environment Canada, July
constitute an environmental compartment.
3.1.9 fresh water environment, n—the aerobic, fresh water
Biodegradability of Two-Stroke Cycle Outboard Engine Oils
environmental compartment.
in Water, CEC L-33-A-93, Co-Ordinating European
3.1.10 good laboratory practices (GLP), n—guidelines for
Council, 1994 (Formerly L-33-T-82)
the management of laboratory experiments which are pub-
lished by regulatory agencies or other recognized groups and
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
are concerned with the organizational process and the condi-
4th Floor, New York, NY 10036, http://www.ansi.org. All standards referenced are
tions under which laboratory studies are planned, performed,
from the OECD Guidelines for Testing of Chemicals.
4 monitored, recorded, and reported.
Available from Organization for Economic Cooperation and Development
(OECD), 2, Rue Andre Pascal, S-75775, Paris CEDEX 16, France. May also be 3.1.10.1 Discussion—The major GLPs used are
found in U.S. Federal Register, Vol 50, No. 188, September 27, 1965, paragraph
796.3260.
Available from U.S. Government Printing Office, Washington, DC.
6 7
Available from CEC, Madou Plaza, Place Madou 1, B-1030 Brussels, Belgium. Available from Ministere de l’Environment, Gouvernment du Quebec.
D6046 − 24
USEPA–TSCA, USFDA, OECD, and to some extent the MITI 3.1.19 terrestrial (or soil) environment, n—the aerobic en-
version from Japan for submissions in Japan. vironmental compartment which is found in and on natural
soils.
3.1.11 inhibition load XX (ILXX), n—a statistically or
graphically estimated loading rate of test material that is
3.1.20 theoretical CO , n—the amount of CO which could
2 2
expected to cause a XX % inhibition of a biological process in theory be produced from the complete oxidation of all the
(such as growth or reproduction) which has an analog as
carbon in a material.
opposed to a digital measure.
3.1.21 theoretical O , n—the amount of oxygen which
3.1.11.1 Discussion—An example of a digital measure
would theoretically be required to completely oxidize a mate-
would be alive or dead. This terminology should be used for
rial.
hydraulic fluids instead of the standard inhibition concentration
3.1.22 ultimate biodegradation, n—degradation achieved
(ICXX) when the hydraulic fluid is not completely soluble
when a material is totally utilized by microorganisms resulting
under test conditions.
in the production of carbon dioxide (and possibly methane in
3.1.12 inoculum, n—spores, bacteria, single-celled
the case of anaerobic biodegradation), water, inorganic
organisms, or other live materials that are introduced into a test
compounds, and new microbial cellular constituents (biomass
medium.
or secretions or both).
3.1.13 lethal load XX (LLXX), n—a statistically or graphi-
3.1.23 ultimate biodegradation test, n—a test which esti-
cally estimated loading rate of test material that is expected to
mates the extent to which the carbon in a material is converted
be lethal to XX % of a group of organisms under specified
to CO or methane, either directly by measuring the production
conditions for a specified time.
of CO or methane, or, for aerobic biodegradation, indirectly
3.1.13.1 Discussion—This terminology should be used for
by measuring the consumption of O .
hydraulic fluids instead of the standard lethal concentration
3.1.23.1 Discussion—The measurement of new biomass is
(LCXX) when the hydraulic fluid is not completely soluble
usually not attempted.
under test conditions.
3.1.24 water accommodated fraction (WAF), n—the pre-
3.1.14 loading rate, n—the ratio of test material to aqueous
dominately aqueous portion of a mixture of water and a poorly
medium used in the preparation of a water accommodated
water-soluble material which separates in a specified period of
fraction (WAF) and in interpretation of the results of a toxicity
time after the mixture has undergone a specified degree of
study with a poorly water soluble lubricant or lubricant
mixing and includes water, dissolved components, and dis-
component.
persed droplets of the poorly water soluble material.
3.1.15 mechanical dispersion, n—a mixture produced by the
3.1.24.1 Discussion—The chemical composition of the
application of mechanical shearing forces to a multi-phase
WAF depends on the ratio of poorly soluble material to water
system, one component of which is water, so as to distribute
in the original mixture as well as the details of the mixing
one or more of the materials uniformly throughout the mass of
procedure.
the water with the water existing as a continuous phase.
3.1.25 wppm—an abbreviation for part per million by
3.1.16 pre-adaptation, n—the pre-incubation of an inocu-
weight.
lum in the presence of the test material and under conditions
4. Significance and Use
similar to the test conditions.
3.1.16.1 Discussion—The aim of pre-adaptation is to im-
4.1 This classification establishes categories of hydraulic
prove the precision of the test method by decreasing variability
fluids which are distinguished by their response to certain
in the rate of biodegradation produced by the inoculum.
standardized laboratory procedures. These procedures indicate
Pre-adaptation may mimic the natural processes which cause
the possible response of some environmental compartments to
changes in the microbial population of the inoculum leading to
the introduction of the hydraulic fluid. One set of procedures
more rapid biodegradation of the test material but not to a
measures the aerobic aquatic biodegradability (environmental
change in the final extent of biodegradation.
persistence) of the fluids and another set of procedures esti-
mates the acute ecotoxicity effects of the fluids.
3.1.17 primary biodegradation, n—degradation of the test
4.1.1 Although this classification includes categories for
material by microorganisms resulting in a change in its
both persistence and ecotoxicity, there is no relationship
physical or chemical properties, or both.
between the two categories. They may be used independently
3.1.17.1 Discussion—The extent to which the results of a
of each other, that is, a hydraulic fluid can be categorized with
primary biodegradation test correspond to the biological con-
respect to both sets of laboratory procedures, or to persistence
version of the test material will depend on the attribute which
but not ecotoxicity, or to ecotoxicity but not persistence.
is being measured.
4.1.2 There is no relationship between the categories
3.1.18 primary biodegradation test, n—a test which follows
achieved by a hydraulic fluid for persistence and for ecotoxic-
the disappearance of a test material by measuring some
ity. The placing of a hydraulic fluid with regard to one set of
attribute of the material.
categories has no predictive value as to its placement with
3.1.18.1 Discussion—The extent to which the results of a
regard to the other set of categories.
primary biodegradation test correspond to the biological con-
version of the test material will depend on the attribute which 4.2 The test procedures used to establish the categories of
is being measured. hydraulic fluids are laboratory standard tests and are not
D6046 − 24
TABLE 2 Environmental Persistence Classification—Aerobic
intended to simulate the natural environment. Definitive field
Fresh Water
studies capable of correlating test results with the actual
environmental impact of hydraulic fluids are usually site
NOTE 1—Test methods are given in Table 4.
specific and so are not directly applicable to this classification.
Ultimate Biodegradation Test Results
Persistence
Therefore, the categories established by this classification can
Designation
% Theoretical CO % Theoretical O
2 2
serve only as guidance to estimate the actual impact that the
For Hydraulic Fluids Containing Less Than 10 % by weight O
hydraulic fluids might have on any particular environment.
Pw1 greater than or equal to greater than or equal to
4.3 This classification can be used by producers and users of 60 % in 28 days 67 % in 28 days
Pw2 greater than or equal to greater than or equal to
hydraulic fluids to establish a common set of references that
60 % in 84 days 67 % in 84 days (12
describe some aspects of the anticipated environmental impact
(12 weeks) weeks)
of hydraulic fluids which are incidental to their use.
Pw3 greater than or equal to greater than or equal to
40 % in 84 days 45 % in 84 days
4.4 Inclusion of a hydraulic fluid in any category of this
(12 weeks)
Pw4 less than 40 % in 84 days less than 45 % in 84 days
classification does not imply that the hydraulic fluid is suitable
(12 weeks) (12 weeks)
for use in any particular hydraulic system application.
Persistence Ultimate Biodegradation Test Results
4.5 The composition of hydraulic fluids may change with
Designation % Theoretical CO or % Theoretical O
2 2
use and any change could influence the environmental impact
For Hydraulic Fluids Containing 10 % by weight or More O
of a used hydraulic fluid. Therefore, the classification of a
Pw1 greater than or equal to 60 % in 28 days
hydraulic fluid may change upon use depending on the type
Pw2 greater than or equal to 60 % in 84 days (12 weeks)
and extent of the use.
Pw3 greater than or equal to 40 % in 84 days (12 weeks)
Pw4 less than 40 % in 84 days (12 weeks)
5. Basis of Classification
Persistence Primary Biodegradation, Test Results
Designation % Loss of Starting Material
5.1 This classification consists of two groups of tests, one
For All Hydraulic Fluids
group addressing the environmental persistence of hydraulic
fluids (Category P) and one group addressing acute ecotoxicity Pw-C greater than or equal to 80 % in 21 days
Pw4 less than 80 % in 21 days
of hydraulic fluids (Category T). The ecotoxicity categories are
further divided into two environmental compartments, aerobic
soil (Ts) and aerobic fresh water (Tw). At this time categories
for environmental persistence are limited to aerobic fresh water
other elemental components of the hydraulic fluid and subtract-
(Pw).
ing that percentage from 100. For purposes of this classifica-
5.2 All testing shall use as its starting point the unused fully
tion determination of carbon, hydrogen, and nitrogen by Test
formulated hydraulic fluid.
Methods D5291 and subtraction of that total from 100 is
5.3 The classification of hydraulic fluids for environmental acceptable. Direct determination of elemental oxygen by neu-
persistence is defined by the hydraulic fluid’s biodegradability tron activation is also acceptable.
as measured in tests for ultimate biodegradation. Primary 5.3.1.2 Table 2 has been constructed assuming that 60 % of
biodegradation measures the degradation of the hydraulic fluid the carbon in the hydraulic fluid goes directly to CO during
only, without any precise measurement of the remaining biodegradation and that the remaining carbon is converted to
materials. Therefore it is not suitable to address long term biomass.
environmental persistence. Pre-adaptation of inoculum for a 5.3.2 Class Pw1 includes hydraulic fluids which would be
period of up to two weeks is allowed for all categories. The expected to be the least persistent in the environment. It may be
classification system is given in Table 2. assumed that such a fluid would rapidly and extensively
5.3.1 Table 2 is divided into three parts. Part A, for biodegrade in an aerobic aquatic environment which contains
hydraulic fluids with elemental analyses indicating a contents microbial life and the conditions necessary for it.
of less than 10 % by weight oxygen, has separate requirements 5.3.2.1 Although a minimum production of 60 % theoretical
for tests which measure % theoretical CO and % theoretical CO or greater up to but not including 100 % theoretical CO
2 2 2
O . For these hydraulic fluids the different numerical results for or consumption of the technically equivalent fraction of
the two different types of ultimate biodegradability tests are theoretical O leads to a strong implication that the hydraulic
technically equivalent. Part B for hydraulic fluids with elemen- fluid will rapidly and extensively biodegrade, such a finding
tal analyses indicating a contents of 10 % by weight or more does not unequivocally rule out the possibility that the biodeg-
oxygen has the same numerical result for both types of ultimate radation produces recalcitrant metabolites not normally found
biodegradation test and these numerical results are also tech- in nature. Recalcitrant metabolites could constitute a persistent
nically equivalent. The difference between hydraulic fluids residue of the hydraulic fluid that may remain in the environ-
containing little oxygen and fluids containing relatively abun- ment. It is also possible that a very small fraction of the
dant oxygen is related to the use of the oxygen present in the original hydraulic fluid, perhaps an additive, could not be
base stocks by the microor
...

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: D6046 − 18 D6046 − 24
Standard Classification of
Hydraulic Fluids for Environmental Impact
This standard is issued under the fixed designation D6046; 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 classification covers all unused fully formulated hydraulic fluids in their original form.
1.2 This classification establishes categories for the impact of hydraulic fluids on different environmental compartments as shown
in Table 1. Fluids are assigned designations within these categories; for example PwL, Pwe, and so forth, based on performance
in specified tests.
1.3 This classification includes environmental persistence and acute ecotoxicity as aspects of environmental impact. Although
environmental persistence is discussed first, this classification does not imply that considerations of environmental persistence
should take precedence over concerns for ecotoxicity.
1.3.1 Environmental persistence describes long term impact of hydraulic fluids to the environment. Environmental persistence is
preferably measured by ultimate biodegradation but can also be measured by other means.
1.3.2 Acute toxicity describes the immediate toxic impact of hydraulic fluids to the environment. Acute toxicity is preferably
measured by the three trophic levels of aquatic organisms (Algae, Crustacea, and Fish).
1.4 Another important aspect of environmental impact is bioaccumulation. This aspect is not addressed in the present classification
because adequate test methods do not yet exist to measure bioaccumulation of hydraulic fluids.
1.5 The present classification addresses the fresh water and soil environmental compartments. At this time marine and anaerobic
environmental compartments are not included, although they are pertinent for many uses of hydraulic fluids. Hydraulic fluids are
expected to have no significant impact on the atmosphere; therefore that compartment is not addressed.
1.6 This classification addresses releases to the environment which are incidental to the use of a hydraulic fluid. The classification
is not intended to address environmental impact in situations of major, accidental release. Nothing in this classification should be
taken to relieve the user of the responsibility to properly use and dispose of hydraulic fluids.
1.7 This classification does not cover any performance properties of a hydraulic fluid which relate to its performance in a hydraulic
system.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
This classification is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.N0 on Hydraulic Fluids.
Current edition approved Oct. 1, 2018March 1, 2024. Published October 2018April 2024. Originally approved in 1996. Last previous edition approved in 20172018 as
D6046 – 17.D6046 – 18. DOI: 10.1520/D6046-18.10.1520/D6046-24.
*A Summary of Changes section appears at the end of this standard
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TABLE 1 Overview of Extended Classification
Categories of Environmental Impact
Environmental
Environmental
Compartment
Ecotoxicity Bioaccumulation
Persistence
Fresh Water Pw Tw Bw
Marine Pm Tm Bm
Soil Ps Ts Bs
Anaerobic Pa Ta Ba
1.9 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:
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D5291 Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants
D5864 Test Method for Determining Aerobic Aquatic Biodegradation of Lubricants or Their Components
D6006 Guide for Assessing Biodegradability of Hydraulic Fluids
D6081 Practice for Aquatic Toxicity Testing of Lubricants: Sample Preparation and Results Interpretation
E943 Terminology Relating to Biological Effects and Environmental Fate
E1440 Guide for Acute Toxicity Test with the Rotifer Brachionus
2.2 ISO Standards:
International Standard ISO Test 9439:1990 Technical Corrigendum 1, Water Quality—Evaluation in An Aqueous Medium of the
“Ultimate” Biodegradability of Organic Compounds—Method by Analysis of Released Carbon Dioxide
2.3 OECD Standards:
OECD 301B CO Evolution Test (the Modified Sturm Test)
OECD 301C Modified MITI Test (I)
OECD 301F Manometric Respirometry Test
OECD 201 Alga, Growth Inhibition Test
OECD 202 Daphnia sp., Acute Immobilisation Test and Reproduction Test
OECD 203 Fish, Acute Toxicity Test
OECD 207 Earthworm Acute Toxicity Test
OECD 208 Terrestrial Plants Growth Test
2.4 US EPA Tests:
Aerobic Aquatic Biodegradation Test, 40 CFR 796.3100 (Also available as EPA publication 560/6-82-003, number CG-2000)
Toxic Substances Control Act (TSCA), 40 CFR Parts 796 and 797—Environmental Effects Testing Guidelines, Federal Register,
Vol 50, No. 188, September 27, 1985, p. 39321
2.5 Environmental Canada Test Methods:
Biological Test Method: Acute Lethality Test Using Rainbow Trout, Report EPS 1/9, Environment Canada, July 1990
Biological Test Method: Reference Method for Determining Acute Lethality of Effluents to Rainbow Trout, Reference Method
EPS 1/RM/13, Environment Canada, July 1990
Biological Test Method: Growth Inhibition Test Using the Freshwater Alga Selenastrum capricornutum, Report EPS 1/RM/25,
Environment Canada, November 1992
Biological Test Method: Acute Lethality Test Using Daphnia spp., Report EPS 1/RM/11, Environment Canada, July 1990
Biodegradability of Two-Stroke Cycle Outboard Engine Oils in Water, CEC L-33-A-93, Co-Ordinating European Council, 1994
(Formerly L-33-T-82)
Toxic Substances Control Act (TSCA), Good Laboratory Practice Standards, Final Rule, U.S. Federal Register, 40 CFR Part 792,
August 17, 1989
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.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org. All standards referenced are from
the OECD Guidelines for Testing of Chemicals.
Available from Organization for Economic Cooperation and Development (OECD), 2, Rue Andre Pascal, S-75775, Paris CEDEX 16, France. May also be found in U.S.
Federal Register, Vol 50, No. 188, September 27, 1965, paragraph 796.3260.
Available from U.S. Government Printing Office, Washington, DC.
Available from CEC, Madou Plaza, Place Madou 1, B-1030 Brussels, Belgium.
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2.6 Other Standards:
MENVIQ 92.03/800—D.mag. 1.1, March 1992
29 CFR 1910 OSHA Regulated Carcinogens and Potential Carcinogens
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this classification not given below, refer to Terminology D4175.
3.1.2 acute ecotoxicity, n—the propensity of a material to produce adverse behavioral, biochemical, or physiological effects in
non-human organisms or populations in a short period of time, usually not constituting a substantial portion of the life span of the
organism.
3.1.3 aerobic, adj—(1) taking place in the presence of oxygen, (2) living or active in the presence of oxygen.
3.1.4 anaerobic, adj—(1) taking place in the absence of oxygen, (2) living or active in the absence of oxygen.
3.1.5 biodegradation, n—the process of chemical breakdown or transformation of a material caused by organisms or their
enzymes.
3.1.5.1 Discussion—
Biodegradation is only one mechanism by which materials are transformed in the environment.
3.1.6 ecotoxicity, n—the propensity of a material to produce adverse behavioral, biochemical, or physiological effects in
non-human organisms or populations.
3.1.7 effect load XX (ELXX), n—a statistically or graphically estimated loading rate of test material that is expected to cause one
or more specified effects in XX % of a group of organisms under specified conditions for a specified time.
3.1.7.1 Discussion—
This terminology should be used for hydraulic fluids instead of the standard effect concentration (ECXX) when the hydraulic fluid
is not completely soluble under test conditions.
3.1.8 environmental compartment, n—a subdivision of the environment based on physical or chemical properties, or both.
3.1.8.1 Discussion—
Examples of environmental compartments are aerobic fresh water, aerobic marine, aerobic soil, and anaerobic media. The results
of test procedures may be applied to environmental compartments, but the test systems do not constitute an environmental
compartment.
3.1.9 fresh water environment, n—the aerobic, fresh water environmental compartment.
3.1.10 good laboratory practices (GLP), n—guidelines for the management of laboratory experiments which are published by
regulatory agencies or other recognized groups and are concerned with the organizational process and the conditions under which
laboratory studies are planned, performed, monitored, recorded, and reported.
3.1.10.1 Discussion—
The major GLPs used are USEPA–TSCA, USFDA, OECD, and to some extent the MITI version from Japan for submissions in
Japan.
3.1.11 inhibition load XX (ILXX), n—a statistically or graphically estimated loading rate of test material that is expected to cause
a XX % inhibition of a biological process (such as growth or reproduction) which has an analog as opposed to a digital measure.
3.1.11.1 Discussion—
An example of a digital measure would be alive or dead. This terminology should be used for hydraulic fluids instead of the
standard inhibition concentration (ICXX) when the hydraulic fluid is not completely soluble under test conditions.
3.1.12 inoculum, n—spores, bacteria, single-celled organisms, or other live materials that are introduced into a test medium.
Available from Ministere de l’Environment, Gouvernment du Quebec.
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3.1.13 lethal load XX (LLXX), n—a statistically or graphically estimated loading rate of test material that is expected to be lethal
to XX % of a group of organisms under specified conditions for a specified time.
3.1.13.1 Discussion—
This terminology should be used for hydraulic fluids instead of the standard lethal concentration (LCXX) when the hydraulic fluid
is not completely soluble under test conditions.
3.1.14 loading rate, n—the ratio of test material to aqueous medium used in the preparation of a water accommodated fraction
(WAF) and in interpretation of the results of a toxicity study with a poorly water soluble lubricant or lubricant component.
3.1.15 mechanical dispersion, n—a mixture produced by the application of mechanical shearing forces to a multi-phase system,
one component of which is water, so as to distribute one or more of the materials uniformly throughout the mass of the water with
the water existing as a continuous phase.
3.1.16 pre-adaptation, n—the pre-incubation of an inoculum in the presence of the test material and under conditions similar to
the test conditions.
3.1.16.1 Discussion—
The aim of pre-adaptation is to improve the precision of the test method by decreasing variability in the rate of biodegradation
produced by the inoculum. Pre-adaptation may mimic the natural processes which cause changes in the microbial population of
the inoculum leading to more rapid biodegradation of the test material but not to a change in the final extent of biodegradation.
3.1.17 primary biodegradation, n—degradation of the test material by microorganisms resulting in a change in its physical or
chemical properties, or both.
3.1.17.1 Discussion—
The extent to which the results of a primary biodegradation test correspond to the biological conversion of the test material will
depend on the attribute which is being measured.
3.1.18 primary biodegradation test, n—a test which follows the disappearance of a test material by measuring some attribute of
the material.
3.1.18.1 Discussion—
The extent to which the results of a primary biodegradation test correspond to the biological conversion of the test material will
depend on the attribute which is being measured.
3.1.19 terrestrial (or soil) environment, n—the aerobic environmental compartment which is found in and on natural soils.
3.1.20 theoretical CO , n—the amount of CO which could in theory be produced from the complete oxidation of all the carbon
2 2
in a material.
3.1.21 theoretical O , n—the amount of oxygen which would theoretically be required to completely oxidize a material.
3.1.22 ultimate biodegradation, n—degradation achieved when a material is totally utilized by microorganisms resulting in the
production of carbon dioxide (and possibly methane in the case of anaerobic biodegradation), water, inorganic compounds, and
new microbial cellular constituents (biomass or secretions or both).
3.1.23 ultimate biodegradation test, n—a test which estimates the extent to which the carbon in a material is converted to CO
or methane, either directly by measuring the production of CO or methane, or, for aerobic biodegradation, indirectly by measuring
the consumption of O .
3.1.23.1 Discussion—
The measurement of new biomass is usually not attempted.
3.1.24 water accommodated fraction (WAF), n—the predominately aqueous portion of a mixture of water and a poorly
water-soluble material which separates in a specified period of time after the mixture has undergone a specified degree of mixing
and includes water, dissolved components, and dispersed droplets of the poorly water soluble material.
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3.1.24.1 Discussion—
The chemical composition of the WAF depends on the ratio of poorly soluble material to water in the original mixture as well as
the details of the mixing procedure.
3.1.25 wppm—an abbreviation for part per million by weight.
3.1.25 Definitions and terms not given in this classification may be found in the Compilation of ASTM Standard Definitions, 1990
or Terminology E943.
4. Significance and Use
4.1 This classification establishes categories of hydraulic fluids which are distinguished by their response to certain standardized
laboratory procedures. These procedures indicate the possible response of some environmental compartments to the introduction
of the hydraulic fluid. One set of procedures measures the aerobic aquatic biodegradability (environmental persistence) of the fluids
and another set of procedures estimates the acute ecotoxicity effects of the fluids.
4.1.1 Although this classification includes categories for both persistence and ecotoxicity, there is no relationship between the two
categories. They may be used independently of each other, that is, a hydraulic fluid can be categorized with respect to both sets
of laboratory procedures, or to persistence but not ecotoxicity, or to ecotoxicity but not persistence.
4.1.2 There is no relationship between the categories achieved by a hydraulic fluid for persistence and for ecotoxicity. The placing
of a hydraulic fluid with regard to one set of categories has no predictive value as to its placement with regard to the other set of
categories.
4.2 The test procedures used to establish the categories of hydraulic fluids are laboratory standard tests and are not intended to
simulate the natural environment. Definitive field studies capable of correlating test results with the actual environmental impact
of hydraulic fluids are usually site specific and so are not directly applicable to this classification. Therefore, the categories
established by this classification can serve only as guidance to estimate the actual impact that the hydraulic fluids might have on
any particular environment.
4.3 This classification can be used by producers and users of hydraulic fluids to establish a common set of references that describe
some aspects of the anticipated environmental impact of hydraulic fluids which are incidental to their use.
4.4 Inclusion of a hydraulic fluid in any category of this classification does not imply that the hydraulic fluid is suitable for use
in any particular hydraulic system application.
4.5 The composition of hydraulic fluids may change with use and any change could influence the environmental impact of a used
hydraulic fluid. Therefore, the classification of a hydraulic fluid may change upon use depending on the type and extent of the use.
5. Basis of Classification
5.1 This classification consists of two groups of tests, one group addressing the environmental persistence of hydraulic fluids
(Category P) and one group addressing acute ecotoxicity of hydraulic fluids (Category T). The ecotoxicity categories are further
divided into two environmental compartments, aerobic soil (Ts) and aerobic fresh water (Tw). At this time categories for
environmental persistence are limited to aerobic fresh water (Pw).
5.2 All testing shall use as its starting point the unused fully formulated hydraulic fluid.
5.3 The classification of hydraulic fluids for environmental persistence is defined by the hydraulic fluid’s biodegradability as
measured in tests for ultimate biodegradation. Primary biodegradation measures the degradation of the hydraulic fluid only, without
any precise measurement of the remaining materials. Therefore it is not suitable to address long term environmental persistence.
Pre-adaptation of inoculum for a period of up to two weeks is allowed for all categories. The classification system is given in Table
2.
5.3.1 Table 2 is divided into three parts. Part A, for hydraulic fluids with elemental analyses indicating a contents of less than 10
wt % 10 % by weight oxygen, has separate requirements for tests which measure % theoretical CO and % theoretical O . For these
2 2
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TABLE 2 Environmental Persistence Classification—Aerobic
Fresh Water
NOTE 1—Test methods are given in Table 4.
Ultimate Biodegradation Test Results
Persistence
Designation
% Theoretical CO % Theoretical O
2 2
For Hydraulic Fluids Containing Less Than 10 Wt % O
For Hydraulic Fluids Containing Less Than 10 % by weight O
Pw1 greater than or equal to greater than or equal to
60 % in 28 days 67 % in 28 days
Pw2 greater than or equal to greater than or equal to
60 % in 84 days 67 % in 84 days (12
(12 weeks) weeks)
Pw3 greater than or equal to greater than or equal to
40 % in 84 days 45 % in 84 days
(12 weeks)
Pw4 less than 40 % in 84 days less than 45 % in 84 days
(12 weeks) (12 weeks)
Persistence Ultimate Biodegradation Test Results
Designation % Theoretical CO or % Theoretical O
2 2
For Hydraulic Fluids Containing 10 Wt % or More O
For Hydraulic Fluids Containing 10 % by weight or More O
Pw1 greater than or equal to 60 % in 28 days
Pw2 greater than or equal to 60 % in 84 days (12 weeks)
Pw3 greater than or equal to 40 % in 84 days (12 weeks)
Pw4 less than 40 % in 84 days (12 weeks)
Persistence Primary Biodegradation, Test Results
Designation % Loss of Starting Material
For All Hydraulic Fluids
Pw-C greater than or equal to 80 % in 21 days
Pw4 less than 80 % in 21 days
hydraulic fluids the different numerical results for the two different types of ultimate biodegradability tests are technically
equivalent. Part B for hydraulic fluids with elemental analyses indicating a contents of 10 wt % 10 % by weight or more oxygen
has the same numerical result for both types of ultimate biodegradation test and these numerical results are also technically
equivalent. The difference between hydraulic fluids containing little oxygen and fluids containing relatively abundant oxygen is
related to the use of the oxygen present in the base stocks by the microorganisms. Further information is given in Appendix X1.
5.3.1.1 Oxygen content of hydraulic fluids is most commonly determined by difference, that is, by determining the other elemental
components of the hydraulic fluid and subtracting that percentage from 100. For purposes of this classification determination of
carbon, hydrogen, and nitrogen by Test Methods D5291 and subtraction of that total from 100 is acceptable. Direct determination
of elemental oxygen by neutron activation is also acceptable.
5.3.1.2 Table 2 has been constructed assuming that 60 % of the carbon in the hydraulic fluid goes directly to CO during
biodegradation and that the remaining carbon is converted to biomass.
5.3.2 Class Pw1 includes hydraulic fluids which would be expected to be the least persistent in the environment. It may be
assumed that such a fluid would rapidly and extensively biodegrade in an aerobic aquatic environment which contains microbial
life and the conditions necessary for it.
5.3.2.1 Although a minimum production of 60 % theoretical CO or greater up to but not including 100 % theoretical CO or
2 2
consumption of the technically equivalent fraction of theoretical O leads to a strong implication that the hydraulic fluid will
rapidly and extensively biodegrade, such a finding does not unequivocally rule out the possibility that the biodegradation produces
recalcitrant metabolites not normally found in nature. Recalcitrant metabolites could constitute
...