Assessment of chemicals

Example of how to use the toolkit: setting an Environmental Quality Standard



The purpose of this example if to demonstrate how the OECD Environmental Risk Assessment Toolkit can be used to guide a review of the scientific factors that may need to be taken into account when developing an Environmental Quality Standard (EQS) or similar standards. The example is based on a fictional substance and considers only the development of a standard for protection of the environment. For standards for human health, please refer to the WHO Human Health Risk Assessment Toolkit project conducted by WHO/IPCS. As noted in the main toolkit description, this is an example of the steps involved in this type of assessment, not an actual assessment. It does not show in detail how the assessment was carried out, only in the steps and the results and the tools used at each stage.


As this is a fictional case study, it should be born in mind that the setting of an EQS itself could be seen as a risk management measure resulting from a risk assessment. Therefore, in many cases much of the information that would need to be used in the development of an EQS may already be available from the original risk assessment. Further, the setting of an EQS doed not itself necessarily require any further assessment of exposure nor a further risk characterisation step. However it is possible that an existing EQS could be built into a risk assessment process by, for example, comparison of the available monitoring data (or estimated exposure concentrations) with the EQS.



The country in question was concerned about the possible widespread release of Substance X into watercourses and wished to investigate setting an EQS that would be protective of short-term exposures. The country dedcided to use the OECD risk assessment toolkit for this purpose. A summary of the overall process is given in Figure 1.


Environmental Hazard Assessment

Gathering existing information

As a starting point the country carried out a search to see if an EQS or similar standard had been set for Substance X in any other country or region. The following sources were consulted.

As no existing EQS was located the country decided that they should develop their own. The country used the Existing Chemicals Database in the OECD toolkit to identify that there was an OECD hazard assessment report available for Substance X. The country decided that EQS should be based on the data in this report.


Figure 1 Summary roadmap for the EQS case study


Evaluating the existing information

As the data in the OECD hazard assessment report had already been agreed using Chapter 3 of the OECD Manual for Investigation of HPV Chemicals from the OECD toolkit the country considered that no further evaluation of the data was necessary. As part of the evaluation process, the country also considered whether sufficient hazard data were available with which to set an EQS. The information gathering phase of the work had already identified a number of possible methods for setting EQSs and similar standards.


A review of these methodologies showed that sufficient data were available for setting an EQS and it was decided to use one of these methods directly.


The following data were considered to be the key data for development of the EQS.




 Octanol-water partition coefficient (log value)



 Inherently biodegradable

 Acute toxicity to fish

 96h-LC50 = 0.15 mg/l

 Acute toxicity to aquatic invertebrates

 48h-EC50 = 0.22 mg/l

 Acute toxicity to algae

 72h-EC50 = 43 mg/l

 72h-NOEC = 17 mg/l

Generating new data

It was considered that sufficient data had been identified during the information gathering and evaluation phases and so it was not necessary to generate any new data.


Conclusion on the inherent properties

The data gathering and evaluation process identified suitable data (and an existing method) for deriving the environmental quality standard.


Environmental Exposure Assessment

As the current objective was to determine an environmental quality standard it was not necessary to carry out a full environmental exposure assessment. However the exposure-related considerations were taken into account during the development of the EQS.


Measuring or estimating releases to the environment

The country was concerned about release of the substance into water courses and had decided previously that an EQS to protect aquatic ecosystems was needed. As part of this process the country had taken into account the sources of release into the aquatic environment and the duration of release episodes amongst other factors. The country concluded that the EQS shoud be protective of short term releases from point sources.


Environmental fate and pathways

The country considered the available environmental fate fata in relation to the behaviour in water courses and concluded that once released to the environment the substances would not absorb significantly to sediment of bioaccumulate in biota. The country concluded that the EQS would be best set in terms of a concentration in water.


Measuring or estimating concentrations in the environment

As part of the process, the country considered a number of aspects related to the implementation of any EQS recommended. These included the following.

  • The availability of suitable analytical methods with a sufficiently low limit of quantification and adequate precision.
  • Identification of suitable monitoring points taking into account appropriate mixing zones.
  • The number of samples to be collected and the duration of sampling periods.
  • Appropriate quality control and assurance procedures.


Risk Characterisation

As the current objective was to determine an environmental quality standard it was not necessary to carry out risk characterisation. The work carried out under the steps above was documented fully in a report.



The OECD risk assessment toolkit was used to identify suitable data that could be used in the setting of an EQS.




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