Assessment of chemicals

Example of how to use the toolkit: a pesticide



The purpose of this fictional example is to outline how the OECD Environmental Risk Assessment Toolkit  an be used to guide a review of the factors that may need to be taken into account when using a risk assessment conducted in one country as the basis for regulatory decision-making in a second country. The example is based on a fictional pesticide but could equally be applied to other types of substances. The example considers only the risk to the environment. For risk assessment 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 the steps and the results and the tools used at each stage.



The relevant authorities in Country X had noted an increasing use of Pesticide Y as a fungicide on cereal crops and had decided that there was a need to assess whether or not the use presented a risk to the environment.


If a pesticide registration process or pesticide registry exists in the country in question this could provide the primary source of information on the environmental hazard of the substances for use in such a risk assessment. However for the purposes of this fictional case study it is assumed that such a process or registry does not exist in Country X and so the country decided to consider information from other countries in order to evaluate the risk to the environment. A summary of the overall process is given in Figure 1.


Environmental Hazard Assessment

Gathering existing information

As, for the fictional case study, it is assumed that no pesticide registration process or pesticide registry exists in Country X, the country decided to use the OECD toolkit to identify sources of infomration from outside of the country. The toolkit listed a number of sources of existing information on chemical substances and the OECD pesticide web pages gave links to various national and international pesticide registration bodies. Using these sources the following information was found on Pesticide Y and/or formulations containing Pesticide  Y as the active ingredient.

  •  A peer reviewed risk assessment of Pesticide Y that included the relevant environmental fate and effects data. The outcome of the peer review was available as a European Food Safety Authority (EFSA) Scientific Report published in the EFSA Journal. This Scientific Report summarises the key data and conclusions of the risk assessment. The underlying full risk assessment was also available.
  • pesticide fact sheet produced by the United States Environmental Protection Agency along with a docket folder containing supporting information.


The country decided to use these reports as sources of existing information for the environmental hazard assessment.


Figure 1 Summary roadmap for the pesticide example


Evaluating the existing information

An initial evaluation of the available reports revealed that one of the documents identified focussed more on human exposure than environmental exposure. The Scientific Report included a detailed assessment of the risks to the environment and so it was decided that this document would form the basis of the environmental hazard assessment.


As the Scientific Report had undergone an expert peer review the country decided that an extensive evaluation of the underlying environmental fate and effects data was not necessary. However the country thoguht it was important to consider the relevance of the data, and hence the conclusions of the assessment, to the specific conditions in Country X.


The most important findings from the EFSA Scientific Report are summarised below.

  • The substance is persistent in soil.
  • The potential for leaching from soil is low.
  • Absorption to sediment occurs rapidly and the estimated degradation half-time in sediment-water systems is beween 70 and 170 days.
  • The half-life for degradation in the atmosphere is 1.8 days and the substance has a very low volatilisation rate from soil and plant surfaces.
  • The potential for bioaccumulation was low (BCF = 65).
  • The most sensitive species tested in acute aquatic toxicity tests were algae (Pseudokirchneriella subcapitata) with a 72 hour EbC50 of 0.9 mg l-1 and aquatic plants (Lemna gibba) with a 7 day EbC50 of 0.002 mg l-1.
  • In longer-term studies a NOEC of 0.01 mg l-1 was determined for effects on growth from a 28-day study and a full lifecycle study with fish (Oncorhynchus mykiss).
  • For sediment organisms a NOEC of 0.045 mg kg-1 dry weight was determined in a 28 day study with Chironomus riparius.


Based on these data the report identified that a potential risk to aquatic organisms, in particular aquatic plants and sediment-dwelling organisms, may exist, and that further refinement of the assessment and/or risk mitigation such as use of no-spray buffer zones was necessary.


The country's evaluation of the available risk assessment concluded that some of the key species used in the existing risk assessment were not relevant to their situation and so the relevance of these conclusions was uncertain. It was therefore decided that, in order to reduce some of the uncertainty in the assessment, further test with additional, more relevant, sediment species would be undertaken.


Generating new data

Toxicity testing was carried out in line with the OECD Test Guidelines on a further two species of sediment organisms. The specied used were chosen to be representative of the local situation. These tests showed that both species had a similar, but slightly lower, sensitivity to the pesticide as the existing sediment data, with a NOEC of 0.050  mg kg-1 dry weight being determined for one of the species.


Conclusion on the inherent properties

The country's assessment of the inherent properties concluded that the data used in the European Food Safety Authority Scientific Report were appropriate for use in their own risk assessment. The existing dataset had been supplemented with further toxicity information on sediment species in order to reduce the uncertainty in the property database.


Environmental Exposure Assessment

Measuring or estimating releases to the environment

The existing risk assessment considered several environmental release scenarios based on a representative formulation containing 125 g l-1 of Pesticide Y. The scenarios were reviewed by Country X and, taking into account how the pesticide was used, it was decided that four of the scenarios were relevant to their situation but that the concentration of Pesticide Y in a formulation representative of use in their country would be higher at 150 g/l.


Environmental fate and pathways

The main pathway of concern identified in the review of the existing risk assessment was from overspray into nearby water courses. This was considered to be a relevant pathway in the country of concern.


Measuring or estimating concentrations in the environment

The concentrations in the environment were estimated for the four relevant scenarios using the same methodology as in the existing risk assessment report but using a Pesticide Y concentration of 150 g/l in the representative formulation.


Risk Characterisation

A risk characterisation was carried out and a report prepared comparing the concentrations estimated in the environment with the new toxicity data generated for sediment organisms. This indicated that there was a potential risk from overspray into nearby water courses in some situations and it was concluded that there was a need to consider further risk management, for example the implementation of buffer zones in these situations, in order to mitigate risk.



Country X used the OECD risk assessment toolkit to identify information available in other countries on the hazards and risks from use of Pesticide Y as a fungicide on cereal crops. Guided by the toolkit, Country X extrapolated the existing information and risk assessment to their current situation. This included both consideration of the need for further testing in order to reduce uncertainty in the underlying data set and the extrapolation of the existing exposure assessment to better represent the conditions of use in Country X. The outcome of the risk assessment was that there was a need to consider future risk management measures.








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