1. Water Quality
  2. Water Quality Guidelines
  3. Guideline values
  4. Default guideline values
  5. Toxicant default guideline values for water quality in aquatic ecosystems

Toxicant default guideline values for water quality in aquatic ecosystems

​​Throughout the Water Quality Guidelines, we provide context and detailed guidance on how to use default guideline values (DGVs) correctly.

You can search for toxicant DGVs for the protection of aquatic ecosystems in freshwater and marine water.

Where possible, DGVs for toxicants have been derived using the species sensitivity distribution (SSD) approach, using methods described in the ANZECC & ARMCANZ (2000) guidelines for DGVs published in 2000 and Warne et al. (2018) for all DGVs published since 2000. Where the SSD approach could not be used, the less preferred ‘assessment-factor approach’ was used, following the method described in the ANZECC & ARMCANZ (2000) guidelines. Refer to Deriving guideline values for details.

Retrieval of default guideline values

Search results provide the DGVs and information to support them.

Medium — whether the DGV applies to freshwater or marine water.

Reliability classification — DGVs are classified as very high, high, moderate, low, very low or unknown. Classification is mainly based on the number and type (chronic, acute or a mix of both) of data used to derive the guideline value, as well as the fit of the statistical (SSD) model to the data (refer to details).

We have updated the reliability classification of all DGVs from the ANZECC & ARMCANZ (2000) guidelines to reflect the current classification (refer to Warne et al. 2018).

Publication date — year of publication of the DGV.

DGVs for different levels of species protection — where DGVs have been derived using the SSD method, guideline values are provided for 99, 95, 90 and 80% species protection. The DGV that is applicable to your situation depends on the current or desired condition of the ecosystem and the associated level of protection that is assigned. In most cases:

  • high ecological/conservation value system — apply 99% species protection DGV
  • slightly to moderately disturbed system — apply 95% species protection DGV
  • highly disturbed system — apply 90 or 80% species protection DGV.

Guideline values derived using the less preferred assessment-factor method cannot be related to a percentage of species protected; they are assigned an ‘unknown’ level of species protection. Refer to Level of protection for additional guidance on determining an ecosystem condition and associated level of protection.

Specific comments and general comments — for some toxicants, important context or guidance helps you to better understand the DGV and, in some cases, its implementation.

Downloadable files — we provide links to:

  • toxicant DGV technical briefs for details of the DGV, including background on the toxicant and its toxicity, available and final toxicity data, final DGVs and any associated caveats to their use, supporting information and references
  • toxicant data table, showing raw data that were considered acceptable for inclusion in the guideline value derivation dataset, and the associated toxicity test details
  • toxicant quality assessment worksheet, which provides the details of the quality assessment scores for each of the toxicity data values assessed for inclusion in the DGV derivation.

Reliability classification for default guideline values

The primary purpose of the reliability classification scheme for toxicant guideline values is to provide a quick and transparent way of indicating the general level of confidence in a guideline value. The classification scheme can be applied to both DGVs and site-specific guideline values.

Guideline values are assigned a level of reliability based on 4 factors:

  • method used to derive the guideline value (SSD or assessment factor)
  • number of species for which appropriate quality toxicity data are available (5 to 7, 8 to 14 or ≥ 15)
  • type of toxicity data (chronic, a mixture of chronic and converted acute, a mixture of chronic fresh and chronic marine data, or only converted acute values)
  • a visual assessment of the fit of the SSD to the toxicity data (good or poor).

There are 6 classes of reliability: very high, high, moderate, low, very low and unknown reliability (Table 1).

Table 1 Details of the reliability classification for toxicant guideline values (adapted from Warne et al. 2018)
Derivation method Type of toxicity dataNumber of dataModel fitReliability
Species sensitivity distributionChronic≥ 15GoodVery high
≥ 15PoorModerate
8–14GoodHigh
8–14PoorModerate
5–7GoodModerate
5–7PoorLow
Combined chronic and converted acute
or
Combined chronic fresh and chronic marine
≥ 15GoodModerate
≥ 15PoorLow
8–14GoodModerate
8–14PoorLow
5–7GoodModerate
5–7PoorLow
Converted acute≥ 15GoodModerate
≥ 15PoorLow
8–14GoodModerate
8–14PoorLow
5–7GoodLow
5–7PoorVery low
Assessment factorChronic or converted acute< 5Not applicableUnknown

The reliability of a guideline value helps indicate whether it would benefit from the acquisition and incorporation of more toxicity data into the derivation. Higher reliability guideline values can be derived using the method described in Warne et al. (2018).

Ecotoxicity data needed for the derivation can be obtained from:

  • more recent data in the literature, including more recent water quality guideline value documents or their equivalent from other jurisdictions
  • generating new data.

Refer to Warne et al. (2018) for more details on the reliability classification.

Improved guideline values can be submitted, via the third-party guideline value derivation process, for national consideration and endorsement as DGVs.

Application of default guideline values

Our DGVs are mostly derived according to risk assessment principles using data from laboratory tests in clean water. They represent the current best estimates of the concentrations of toxicants that should have no significant adverse effects on the aquatic ecosystem.

DGVs focus on direct toxic effects of individual toxicants. Where possible, a hierarchy of chemical measurements (that is, total, dissolved, then bioavailable fractions) should be used for comparison with the DGVs. Preferably, you would do this assessment together with the measurement of other lines of evidence, using a weight-of-evidence process.

The reliability of a guideline value helps indicate how you should use that guideline value. Guidance for how to use the DGVs based on their reliability classification is provided in Table 2. This would also apply to site-specific guidelines values.

Table 2 Guidance on the use of default guideline values (DGVs) according to their reliability
DGV reliability Adequate for assessing water quality? Use guidance
Very highYesUse these DGVs in the context of the accompanying supporting information.
Use with other lines of evidence if possible or needed.
HighYesUse these DGVs in the context of the accompanying supporting information.
Use with other lines of evidence if possible or needed.
ModerateYesUse these DGVs in the context of the accompanying supporting information.
Use with other lines of evidence to account for the lower reliability of the DGVs and improve overall confidence in the assessment.
Supplement the DGV derivation with additional chronic toxicity data if possible to improve the DGVs’ reliability.
LowNoUse only as interim values, with a plan to improve DGV reliability or derive site-specific guideline values by acquiring relevant additional chronic toxicity data to enable derivation of a moderate reliability guideline value at the least.
If used, use with other lines of evidence to sufficiently account for the lower reliability of the DGVs and improve the overall confidence in the assessment.
Document the justification for using these DGVs.
Very lowNoUse only as interim values, with a plan to improve DGV reliability or derive site-specific guideline values by acquiring relevant additional chronic toxicity data to enable derivation of a moderate reliability guideline value at the least.
If used, use with other lines of evidence to sufficiently account for the lower reliability of the DGVs and improve the overall confidence in the assessment.
Document the justification for using these DGVs.
UnknownNoUse only as interim values, with a plan to improve DGV reliability or derive site-specific guideline values by acquiring relevant additional chronic toxicity data to enable derivation of a moderate reliability guideline value at the least.
If used, use with other lines of evidence to sufficiently account for the lower reliability of the DGVs and improve the overall confidence in the assessment.
Document the justification for using these DGVs.

DGVs in the Water Quality Guidelines classified as very high, high or moderate represent an adequate screening point for assessing water quality in conjunction with other relevant lines of evidence (weight of evidence).

Sometimes, an assessment of water quality using a high or very high reliability DGV in the absence of other lines of evidence may be appropriate. For example, where the DGV is significantly above the measured environmental concentrations.

DGVs classified as either low, very low or unknown reliability should only be used as interim values with a commitment to improving their reliability or deriving site-specific guideline values.

If low, very low or unknown reliability DGVs are used, then the justification for their use must be provided. Due to the lower confidence in the low, very low or unknown reliability DGVs, additional lines of evidence need to be used in conjunction with these DGVs when assessing water quality.

DGVs should always be used in the context of all accompanying supporting information, for example:

  • In most cases, DGVs classified as either moderate, low, very low or unknown will have certain data limitations that could be addressed by acquiring more chronic toxicity data
  • Very high and high reliability DGVs can have specific limitations, which should have been documented, and that may need to be taken into account. Examples of this are provided in Warne et al. (2018).

See also:

Additional guidance on how a DGV should be applied:

You should note that jurisdictions may specify alternative requirements for the use of DGVs, or even site-specific guideline values, based on the guideline value reliability or other information.

DGVs should not be used as blanket values for Australia and New Zealand because ecosystem types vary widely, even on a smaller scale. Variability amongst ecosystems and associated water quality can affect toxicant transport and degradation, bioavailability and toxicity.

In some cases, you can refine DGVs to account for local water quality characteristics, such as water hardness, dissolved organic carbon concentration and naturally elevated background concentrations.

We provide guidance on how to compare DGVs or site-specific guideline values to monitoring data.

When there is no default guideline value for a toxicant

It might be deemed appropriate to derive a site-specific guideline value where there is no DGV for a toxicant.

You could derive a site-specific guideline value using either reference-site data (e.g. 80th percentile of background or reference-site data) or biological-effects data.

In some cases, it might be more beneficial and cost-effective to derive a DGV that can be applied to your site, and then propose it for inclusion in the Water Quality Guidelines.

If these options are deemed to be unnecessary or infeasible, then it is possible to use any available toxicity data for the toxicant of concern to derive an interim guideline value, using the OECD (1992, 1995) approach of deriving environmental concern levels. This is similar to the assessment-factor approach used for DGVs when there are insufficient data to use the SSD method. Larger assessment factors are applied as datasets get smaller, reflecting the decreasing scale of confidence in the values. Also, the toxicity data may not have been screened and quality assessed in a consistent manner, although the quality assessment process detailed by Warne et al. (2018) can be used.

OECD (1992) recommendations for deriving environmental concern levels for use as interim guideline values (with our additional recommendations to enhance guidance) are to apply:

  • 1000 to the lowest acute LC50 value, EC50 value or QSAR estimate within a dataset on only one or two aquatic species (for only one to two chronic data, it is recommended to apply a factor of 200)
  • 100 to the lowest acute LC50 value, EC50 value or QSAR estimate within a dataset comprising, at a minimum, algae, crustaceans and fish, or
  • 10 to the lowest chronic no observable effect concentration (NOEC) value or QSAR estimate within a dataset comprising, at a minimum, algae, crustaceans and fish (in the ANZECC & ARMCANZ 2000 guidelines, a factor of 20 was applied to such datasets),

where LC50 = median lethal concentration; EC50 = half maximal effective concentration; QSAR = quantitative structure–activity relationship; NOEC = no observable effect concentration.

In cases where toxicity data or a guideline value are missing for marine water but available for freshwater, it may be appropriate to use the freshwater data or guideline value as an interim guideline (Batley et al. 2018), taking into account any known salinity effects.

We emphasise that development of interim guideline values is the least preferred option. Interim guideline values are not meant to substitute for site-specific guideline values or DGVs, and should only be used as a temporary measure while more robust guideline values are derived. Be aware that, depending on the issue, some jurisdictions may not accept the use of interim guideline values.

References

ANZECC & ARMCANZ 2000, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra.

Batley, GE, van Dam, RA, Warne, MStJ, Chapman, JC, Fox, DR, Hickey, CW & Stauber, JL 2018, Technical Rationale for Changes to the Method for Deriving Australian and New Zealand Water Quality Guideline Values for Toxicants, Australian Government Department of Agriculture and Water Resources, Canberra.

OECD 1992, Report of the OECD Workshop on Extrapolation of Laboratory Aquatic Toxicity Data to the Real Environment, OECD Environment Monographs No. 59, Organisation for Economic Co-operation and Development, Paris.

OECD 1995, Guidance Document for Aquatic Effects Assessment, OECD Environment Monographs No. 92 (Series on Testing and Assessment: Ecotoxicity Testing No. 3), Organisation for Economic Co-operation and Development, Paris.

Warne, MStJ, Batley, GE, van Dam, RA, Chapman, JC, Fox, DR, Hickey, CW & Stauber, JL 2018, Revised Method for Deriving Australian and New Zealand Water Quality Guideline Values for Toxicants, Australian Government Department of Agriculture and Water Resources, Canberra.