Thresholds and risks - tensions between policies and biological effects
Mikael Hildén
Finnish Environment Institute, SYKE
Abstract
Many EU policies emphasise unified limits, goals and measures,which can be monitored by the Commission. Uniform limits seem to conform to the idea of harmonisation. It is therefore tempting to think that one could use thresholds related to sudden changes in biological and ecological systems as a basis for unambiguous risk assessments and policies. In health risk management of chemicals, one can find references to thresholds in standards/guidelines that have been based either on threshold models from toxicology or linear models for many carcinogens. Wider ecological considerations and thereby new types of thresholds have gained importance, for example in the Dangerous Substances Directive (1976),the directive on integrated pollution prevention and control, the Marine Strategy and the Water Framework Directive (WFD).
A quality standard is a way toexpress a threshold or an assumed threshold in legal terms. The relationship between standards and thresholds are, however, complicated, because ecological thresholds are not constant entities, whereas standards have to be constant in some bureaucratic /political time & space domain. Further economic, social and political factors affect the design of standards including the degree of precaution adopted. Finally the implementation of legally binding quality standards requires that they can be applied in specific places and cases unambiguously.
In EU policy uniform standards have been used for dioxins, and more generally in directives related directly to chemicals and health. An alternative approach does not fix the standards as such, but fixes instead the Uniform procedures through which place and time specific standards are expected to emerge in the member states. These include the requirement for programmes or plans maintaining/achieving desired states as in the Water Framework Directive, procedural rules for permits protecting (local) state of the environment (IPPC) and to a certain extent procedures for setting Environmental Quality Criteria / Objectives (EQCs).
Implementation problems arise because setting standards usually implies a narrow ”discretisation” of great variety and the aggregation of dimensions into a specific typology as in the WFD. The risks and uncertainties with respect to thresholds are further difficult to formalise; e.g., the repeated safety factors in derivation of standards; and the selection of cut-off points in risk distributions introduce uncertainties that are non-transparent and potentially problematic in specific cases. The specification and application of multiple standards for multiple but non-separable risk agents, such as mixtures, require a large number of combinations to be considered and the recognition of a large number of different conditions. This also means that economic, social and technical considerations cause tensions in the use of standards across EU.
On the basis of present experiences one can conclude that major challenges with respect to the use of thresholds as reference points for standards in risk assessments include the following:
- Avoiding unjustified cementing of thresholds into EU-wide or regional legal norms through standards or rigid procedures;
- Development of procedures for providing information on and dealing with uncertainties concerning thresholds: finding reliable early signals – verification/falsification of the risks;
- Adaptive management and policy learning for developing appropriate use of thresholds, in particular in the case of multiple risks, which require a non-normative presentation of thresholds contrary to the idea of uniformity.