1. Environmental Hazard Assessment
2. Environmental Exposure Assesment
3. Risk Characterisation
4. Other Relevant Material on Environmental Risk Assessment
Click here to see the Summary Table of Available Tools for Risk Assessment
List of Available Exposure Models (coming soon)
The process of environmental risk assessment includes four steps: hazard identification, hazard characterisation, exposure assessment, and risk characterization and the first two steps are regarded as the process of hazard assessment. The explanation of each step, together with available OECD documents is shown below.
The way in which the tools included here might be used in real situations is illustrated in a number of examples. These examples are not full risk assessments; rather they provide a roadmap of the process, showing the steps involved in each case and the tools which were used. They show only the steps and the results, not the detailed work required to carry out the steps. The work involved may be significant for both hazard characterisation and exposure assessment. Tools included in the summary table provide more detail on these areas. Examples of actual assessments can be found through eChemPortal. The examples also do not include any discussion of uncertainty in the assessment. How to consider this is discussed in a number of the tools included in the summary table and may be demonstrated in actual assessments available through eChemPortal.
NOTE: This web site does not provide extensive guidance for all aspects of Risk Assessment or specific substances such as Persistent, Bioaccumulative and Toxic (PBT) substances, but focuses on products and tools developed in the OECD Environment, Health and Safety Programme, and if relevant in OECD member countries.
1. Environmental Hazard Assessment
Identifying and characterising the inherent properties of chemical substances is basically the first step of environmental risk assessment. Environmental hazard assessment (hazard identification and hazard characterisation) involves gathering or generating and evaluating data of chemical substances and concluding on their inherent eco-toxicological effects and environmental fate. It does not mean that generating data for every kind of such data is always necessary in the first step of environmental risk assessment. For example, in some cases the exposure potential of target chemical can determine the extent to which hazard information is collected. Furthermore, the tools and strategies for assessing chemical hazards and how they will fit into environmental risk assessment are evolving rapidly. OECD has contributed in this field through numerous projects.
(1) Gathering existing information
Initial hazard assessments for many chemicals have been elaborated in the OECD Co-operative Chemicals Assessment Programme, an international cooperation among OECD member countries and chemical industry to investigate chemicals of high production volume (HPV). Information is provided on toxicological and eco-toxicological properties as well as environmental fate. The status of each chemical in the programme as well as access to the published assessments is provided via the Existing Chemical Database.
In general, hazard information on chemicals gathered by member countries, either in the form of databases or full hazard assessments is accessible through eChemPortal, a Global Portal to Information on Chemical Substances.
The OECD Manual for the Assessment of Chemicals (espically chapter 2) provides useful guidance for gathering existing information.
(2) Evaluating the existing information
The gathered information needs to be evaluated as to its reliability and relevance for the assessment. The OECD Manual for the Assessment of Chemicals provides guidance for this evaluation process (see section 3.1 for evaluating the quality of data).
(3) Generating new data
If hazard information is not available for all relevant endpoints, data gaps can be filled through testing or non-testing methods. It is important to note that a data gap is not always a data need, e.g. if a target chemical is insoluble in water, fish toxicity testing may be inappropriate and thus not required (see for example section 2.3.1 of chapter 2 of The OECD Manual for the Assessment of Chemicals).
Internationally harmonised Test Guidelines for hazard identification of chemicals are developed by OECD. More than 130 Test Guidelines covering physical-chemical properties, ecotoxicity, environmental fate and human health effects are used by government, industry and laboratories to assess the safety of industrial chemicals, pesticides and other chemical products. By performing tests according to OECD Test Guidelines and the Principles of Good Laboratory Practice, the test results for required data are accepted in all countries having adhered to the programme of Mutual Acceptance of Data (MAD). The MAD is a system for avoiding duplication of testing. Before performing any testing, it is recommended to contact the relevant authorities about the appropriateness of the proposed testing.
Data gaps can also be filled by non-testing methods. The OECD (Quantitative) Structure Activity Relationship Project provides guidance and tools for different non-testing approaches. The non-testing methods such as QSAR could contribute to reduce time, monetary cost and animal testing.
(4) Concluding on the inherent properties
Once reliable and relevant information is available for all the endpoints needed, conclusions need to be derived for the different endpoints. Chapter 4 of the Manual for the Assessment of Chemicals provides guidance on assessing the hazards of chemical substances to man and the environment and Chapter 5 provides guidance on elaborating a hazard assessment report.
Besides those materials described above, OECD has published various guidance documents and reports related to assessment of several inherent effects such as inhalation, chronic toxicity, carcinogenicity and reproductive toxicity in the Series of Testing and Assessment.
2. Environmental Exposure Assessment
Another important step of the environmental risk assessment is to estimate or predict the extent of exposure of chemicals to the target species and/or the environment through its production, use and disposal. Again please note that hazard assessment and exposure assessment are in many cases performed iteratively in a tiered approach.
(1) General guidance on exposure assessment
The OECD published an overview of the approaches that were used in the late 1990s by OECD member countries for exposure assessment (Environmental Exposure Assessment Strategies for Existing Industrial Chemicals in OECD Member Countries). Although somewhat dated, many of the approaches described remain relevant today.
In addition, Chapter 6 of the OECD Manual for the Assessment of Chemicals (Guidance Document on Reporting Chemical Exposure) provides some guidance on initial exposure assessment and reporting exposure information.
Several national guidelines developed by OECD member countries could also be useful. For example, the US Environmental Protection Agency (USEPA) has published materials that have been developed so far at its website including Guidelines for Exposure Assessment and general guidance on models and tools.
(2) Measuring or estimating releases to the environment
OECD has published a series of Emission Scenarios Documents (ESDs) which describe the sources, production processes, pathways and use patterns with the aim of quantifying the emissions (or releases) of a chemical in specific industry and use categories. While estimating releases to the environment, existing control measures and/or possible impacts of additional control measures need to be taken into consideration.
The Pollutant Release and Transfer Registers (PRTRs) which have been introduced mainly in OECD countries provide useful data related to emission of various substances to the environment. The OECD developed the Global Portal to PRTR Information (PRTR net) which provides free access to PRTR information from countries and organizations around the world, including the Resource Centre for PRTR Release Estimation Techniques and the Centre for PRTR Data.
(3) Environmental fate and pathways
The OECD Co-operative Chemicals Assessment Programme provides information on environmental fate. The status of each chemical in the programme as well as access to the published assessments is provided via the Existing Chemicals database.
Properties relating to environmental fate and pathways such as degradation or accumulation can be experimentally determined using OECD Test Guidelines, or can be estimated by non-testing methods such as (Q)SARs. (See also 1.(3) above)
Concerning environmental fate and pathways, partitioning between compartments is also important. Partitioning is also essential for modelling to estimate concentrations. The OECD developed a model called Pov and LRTP Screening Tool, which is useful to estimate the overall Persistency (Pov) and long-range transport potential (LRTP) of POPs/PBTs at a screening level. The Guidance Document on the Use of Multimedia Models for Estimating Overall Environmental Persistence and Long-range Transport is also available.
Other models developed by OECD countries such as the US-EPA's EPISuiteTM are also useful for estimating environmental fate of chemical substances.
(4) Measuring or estimating concentrations in the environment
Estimated or measured concentrations are compartment-specific so that they are directly relevant for particular target species for which effects data are available. Results from monitoring of concentrations of chemicals in the environment are often used in the environmental exposure assessment. The report from the OECD workshop on improving the use of monitoring data provides criteria for quality and representativeness of monitoring data.
OECD collects information on various tools and models developed and used in OECD member countries. A summary table of available tools and models are available.
3. Risk Characterisation
Risk characterisation, the last step in the environmental risk assessment, is the qualitative and, wherever possible, quantitative determination of the probability of occurrence of the adverse effects of chemicals to the environment under predicted exposure conditions. This process is based on outcomes of the previous steps, i.e. environmental hazard and environmental exposure assessment. In many regulatory frameworks environmental risks are often expressed by ratios between PEC (Predicted Environmental Concentration, derived from environmental exposure assessment) and PNEC (Predicted No Effect Concentrations for target ecosystems, an outcome of environmental hazard assessment, see section 4.2 of the OECD Manual for the Assessment of Chemicals).
4. Other Relevant Material on Environmental Risk Assessment
OECD conducted a comparison of risk assessments for new chemicals, which outlines similarities and differences in the risk assessment processes used by the various jurisdictions. The Report from the Policy Dialogue on Exposure Assessment also provides comparison of approaches to exposure assessment in OECD member countries.
As for risk assessment of specific types of chemicals e.g. pesticides and biocides, useful tools are available at the dedicated webpages for Pesticide Testing and Assessment and Biocides.
Example of how to use the toolkit: a textile dye
This example briefly outlines risk assessment of textile dye planned to be newly introduced to a company.
Example of how to use the toolkit: a pesticide
This example briefly outlines risk assessment by using the toolkit to identify information of pesticide available in other countries.
Example of how to use the toolkit: setting an Environmental Quality Standard
This example briefly outlines risk assessment of a substance possibly released into watercourses by using the toolkit to investigate whether setting an EQS would be protective of short-term exposures.
Click here to go back to the OECD Environmental Risk Assessment Toolkit (Flow Chart).
Summary Table of Available Tools for Risk Assessment
The OECD Environmental Risk Assessment Toolkit: Steps in Environmental Risk Management and Available OECD Products
The OECD Environmental Risk Assessment Toolkit: Tools for Environmental Risk Assessment and Management
Manual for the Assessment of Chemicals