Setting OELs

The next topic to address is the process of setting OELs. The rationale for setting OELs has no basis in absolute information, and the procedure to be followed may differ from country to country and from substance to substance. Scientific criteria for health protection should be used in combination with considerations of their technical and economic feasibility in a dynamic process in which the development of scientific knowledge underlies rapid changes entailing the need to periodically review the data. 

Scientific information for the process of establishing OELs may come from human or animal data obtained using different methods, from studies of acute, subacute, and chronic toxicity through various routes of entry. Human data, which is usually the best source, is not easily available, and frequently it is incomplete or inadequate due to poor characterization of exposure and clear dose-response relationships. Human data falls into one of the following categories  

The crucial objective is to identify what effects can be produced by exposure to chemical agents and to select which effects should be considered 

In this scheme, OELs should be a dose somewhere between compensatory effects, in which the organism is able to detoxify, metabolize, or excrete the substance, and early impairment. Although there may be profound differences of opinion as to what constitutes this dose, this approach leads to the conclusion that available scientific data permits identification of a clear threshold dose below which exposure to the substance in question is not expected to lead to adverse effects. 

However, for some type of adverse effects, such as genotoxicity, carcinogenicity, and respiratory sensitization, it may not be possible from present knowledge to define this threshold of activity, so we may conclude that any level of exposure might carry some finite risk. In this case, OELs should be established at levels sufficiently low to avoid risks these are called pragmatic OELs. 

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Another difficulty comes from the consideration of the route of entry (sf the contaminant, as chemicals can enter the body by various routes and the human body responds to the action of a toxic agent primarily on the basis of the rate and route of exposure. Without any doubt, the most important route of exposure at the workplace is inhalation, and this should be the route used to set OELs. However, if there is a threat of significant exposure by other routes, such as cutaneously (including mucous membranes and the eyes), either by contact with vapors or by direct skin contact w ith the substance, additional recommendations may be necessary. 

Similar to the OEB setting, there is not a specific method to setting OELs that is used by everyone. However, there are some recognized and peer-reviewed models2 that many organizations use or modify. Although the type of data that is used in... 

Approaches in the past. The objective of setting OELs in the European Union (EU) was introduced into EU legislation by Council Directive 80/1107/EEC, as amended by Directive 88/642/EEC. Under this Directive, two types of OELs were defined, binding limit values and indicative limit values (ILVs). Member States were asked to take the ILVs into account when establishing national OELs, but there was no legal obligation to do so. 

Table 33 Summary of procedures for setting OELs in EU 15 countries...

The OELs are the products of a compromise reached after considering health, administrative, political and economic issues. There is a two tier system in place to set OELs, comprising a scientific advisory committee and a second level in the form of the National Council for Health and Safety at Work (SYAE) in which stakeholder interests are able to take account of these issues. Negotiations take place within SYAE. SYAE deliberates on all matters pertaining to occupational health and safety and is effectively an institutionalised forum for national consultation 17 bodies are represented on the Council. 

Although many of these caveats concerning the limits of toxicological imderstanding in relation to NOAELs and LOAELs and their application to OEL setting are familiar from previous approaches to setting OELs, the generally... 

National structure and institutions involved with setting OELs, Until recently there was no national committee/advisory board or other regulatory body established doling exclusively with the establishment of OELs. The only (historical) example of such a body existed in 1975, when the former ENPI Ente Nazionale Prevenzione Infortuni -National Agency for Prevention of Accidents at Work) issued a provisional list of recommended OELs, which was never approved at national level. ENPI was shut down in 1979, after the National Health Service was installed in 1978. 

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