Chemicals and Risk > Background Information

Environmental risk assessment (ERA) is a requirement of most regulatory schemes including new(1) and existing(2) chemicals, biocides(3), plant protection products(4) and more recently medicinal products for human(5) and veterinary(6) use. Although the detailed requirements of each scheme may vary, the principles on which the assessments are based, the data required to complete the assessment, and the models used, have much in common.

ERA will play an increasingly important role under the REACH Regulation as Chemical Safety Assessments will be developed for many more substances that are judged to have hazardous properties. Additionally, the responsibility for preparing the assessment (which be known as a chemical safety assessment or CSA) is with industry rather than the regulatory authority. The downstream industry is also required to contribute, either by collaborating with their suppliers or by preparing their own CSA.

The characterisation of risk under REACH will concentrate on the highest priority endpoints, and therefore be less demanding than those assessments produced under the Existing Substances Regulation.

Human health safety assessment is needed for hazardous substances where there is risk of exposure for workers, consumers and humans that have contact via the environment. The human health assessment covers both toxicological endpoints and hazardous physicochemical properties (e.g. explosivity).

Standard models and methods

Standard guidance exists for risk assessment of all types of substance.

In an environmental exposure assessment(7), information on the life cycle of a substance is used to estimate releases to the environment via air, water and soil. Physicochemical and degradation property data (obtained for example from notification tests or from literature) are used to assess the fate and behaviour of any released substance in the environment and the wastewater treatment plant (relevant for emissions to municipal sewer or an industrial biological treatment plant). Standard models use these details to determine Predicted Environmental Concentrations (PECs) in the different environmental compartments (air, surface water, sediment, soil and biota).

The environmental hazard assessment uses the results of ecotoxicity tests on aquatic or terrestrial organisms, with appropriate assessment factors (to account for uncertainty and possible variation in sensitivity between species) to determine a Predicted No Effect Concentration (PNEC).

A risk characterisation ratio (RCR) is defined as PEC/PNEC. For a substance to be deemed of no immediate concern for the environment PEC/PNEC should be below 1. Different criteria and conclusions apply under different regulatory schemes, but in general if PEC/PNEC is greater than 1, further refinement of the risk assessment may be achieved. This is approached either by obtaining more accurate emission data (e.g. monitoring effluent concentrations), or by further testing such as additional degradation studies, or chronic ecotoxicity testing.

A high priority requirement of environmental risk assessment is to consider the properties of Persistence, Bioaccumulation and Toxicity (PBT). PBT substances are a priority concern of regulatory authorities and those confirmed to have PBT properties are likely to be subject to future restrictions or bans.

Environmental risk assessment can be straightforward or can be extremely complex, depending on the nature and properties of the substance, and the level of complexity of its life cycle.

Under REACH, a similar approach is taken for human health risk assessment. Toxicological data for the substance are used to determine 'Derived No Effect Levels' (DNELs) using appropriate assessment factors, which are selected on the basis of the type of data available and the exposed population (i.e. workers or the general public). Exposure assessment is carried out using standard models based on the substance properties and the tasks carried out, resulting in estimates of daily exposure to the substance. A risk characterisation ratio (RCR) is determined by comparing the exposure level to the DNEL, and an RCR below 1 indicates 'safe use' of the substance.

Peter Fisk Associates has extensive experience in the field of environmental risk assessment. We are also able to advise on human health assessments. Click here for details of some of the services we offer or contact us for further information.

Images:
Ole Jrrgen Bratland & Gisele Jaquenod
Department APS, University of Sheffield