How to perform application specific Environmental Risk Assessment (ERA)
 

1. Finding the routes of release
Try to find information on how the chemical or product containing the chemical is used and handled and in which quantities. Also try to find information on the geography and lay-out of the site, process or application.
Make a picture or map of the site, process or application and find the flows of the chemical in this picture.

By looking at this picture or map and considering how the chemical is handled; how and where can the chemical reach the environment and in which quantities or concentrations?
– By air or water?
– To water treatment plant?
– Continuous, intermittent or single release?

Result: a schematic picture or map that includes all of the flows of the chemical with quantities and all of the possible releases to the surrounding environment. An example is presented here.

2. Gather environmental information
Once the chemical has reached the environment, how does it spread?
Based on how and where the chemical can reach the environment, information on the site specific environmental conditions at these release points is needed. The information can include temperatures, soil type(s) and their hydrological conductivity, water flows and temperatures. Distances between the points of release and species or other things of interest to protect, e.g. a river, a water protection area or the ground water are also needed.

Try also to find all information about the physico-chemical properties of the chemical. Especially the octanol-water partition coefficient (Kow), volatility, molecular weight and degradability (biodegradation, photolysis and hydrolysis) are important parameters for modeling the chemical in the environment.

Search in the European chemical Substances Information System (ESIS) for any Risk Assessment made for the chemical or similar chemicals. The risk assessments found in ESIS can also provide information about how other people have modeled chemicals in the environment.

Result: a list of all of the available environmental information about the points of release and the physico-chemical properties. An example is presented here.

3. Modeling the exposure

Work out a model of how the chemical spreads and how it is distributed between air, water, soil and sediment (whichever is relevant at the different release points) based on information about the environmental conditions and the physico-chemical properties. The Technical Guidance Document (TGD) can give guidance on how to model chemicals in the environment. EUSES (European Union System for the Evaluation of Substances) is a software tool that also can be used to model the exposure of a chemical, but it needs to be set with site specific environmental conditions, otherwise it will use default parameters that represent the EU.

Use site specific information on the needed parameters, e.g. hydrological conductivity or depth to ground water. If no site specific information is available, try to find more general information about the area such as temperatures, precipitation or type of soil normally found in the area. As a last resort average data for the EU can be used (which is included in the EUSES model).

Use chemical specific data on physico-chemical properties. If no chemical specific data is available, the TGD has guidance on how to calculate certain parameters from the structure of the molecule using so called (Q)SAR (Quantity Structure Activity Relationships). A simple QSAR computer program that has been developed by the US EPA, called EPISuite, can be found on the internet and downloaded here for free.
There are also commercial software models that can be used for modeling a chemical release in a river, such as CORMIX or Visual Plumes.

Air releases can be dealt with by using the EUSES model, but generally the air releases are spread out over such a large area that the concentrations become very low and do therefore not constitute a risk to the environment. Chemicals that are toxic, bioaccumulating and persistent can however accumulate in the environment and reach toxic concentrations in the environment as well as in species higher up in the food chain.

Result: Predicted Environmental Concentrations (PECs) for the compartments water, sediment and soil, for each of the different release points.

4. Determining the effect level
Try to find as much information on the eco-toxicity of the chemical as possible. Start by finding the Safety Data Sheet (SDS) for the chemical and if needed there are databases for information on chemicals available on the internet, e.g. TOXNET or ESIS. Depending on the importance of the result, different levels of data quality may be needed. Try to find test results from labs certified with Good Laboratory Practices (GLP) and double check these results with other data from a couple of other sources in order to be sure that the results are consistent with these other data.

Safety factors, called assessment factors, are applied to the lowest of the available toxicity data and these factors depend on the availability of toxicity data. The value of the assessment factors that should be applied can be found in the TGD.

If no toxicity data can be found for species in sediment, the equilibrium partitioning method can be used to find the Predicted No-Effect Concentration (PNEC) for sediment, as described in the TGD. If the equilibrium partitioning method has been used to find the PNEC for sediment an additional factor of 10 has to be applied to the assessment factor.

Result: Predicted No Effect Concentrations (PNECs) for the chemical in water, sediment, soil and water treatment plant (whichever is applicable).

5. Determining the risk characterization ratios (RCR)
The RCRs are calculated as the ratio between the PEC and the PNEC for each of the environmental compartments

Result: a table with all of the RCR figures for the different compartments and release points.

If any of these RCR figures are higher than 1, further development of the model, more site specific measurements or a reduction in the released amount may be needed.

Experiences