Biocides are products that are designed to kill or control unwanted organisms. They can therefore include products that potentially have effects on organisms other than those they are intended to control.
How do the substances behave in nature?
First, we look at how the substances behave in nature, i.e. the fate of the substances. Does the substance degrade slowly, whereby there can be problems with accumulation in the environment? Is it a substance that can seep down into the groundwater?
Effects on different organisms
We then look at the effects that the substance has on different organisms. The producer/applicant must submit tests which show how toxic the substance is with regard to a number of organisms (in accordance with the data requirements). In the short-term acute trials, an LC50 value is generally calculated. This is the concentration at which half the test animals die. In the long-term acute trials, a NOEC value is generally calculated. This is the highest concentration at which no effects on the animals used in the tests are seen.
Calculating the overall effect
We use what we know about the substance's physical/chemical properties and fate in nature, as well as the product's use, to calculate what quantities will end up in the aquatic environment, the ground, the air and, for example, waste water treatment works.
The calculated concentration of the substance in nature is compared with the highest dose that did not produce any harmful effects in the tests. In order to take account of the uncertainty associated with differences between the laboratory environment and nature as well as differences between different species, for example, there must be a factor of 10-1000 between the concentration in nature and the LC50 or NOEC value determined in the laboratory, depending on the quantity and quality of the data available.
More information
Biocides are evaluated in accordance with the principles for risk assessment in the 2003 "Technical Guidance Document on Risk Assessment", popularly known as the TGD. Read the TGD here.
Common EU guidelines for the evaluation of biocides and cut-off criteria can be found in Annex VI to the Biocidal Products Directive. Read the Directive here .
Calculations of concentrations in the environment are performed using the "Emissions Scenario Documents" (ESDs), which have been prepared for each product-type. You can find the ESDs here
Under the direction of the EU, a programme has been developed which can perform the actual calculations in the risk assessment. This programme is called EUSES (European Union System for the Evaluation of Substances) and can be downloaded here on the European Commission Website.
Examples of EU environmental assessments can be found in the evaluation reports that are available on the European Commission's website and elsewhere. The reports can be found under the relevant product-types (PTs) and under the name of the active substance.