Low correlation between health hazard categorisation (HHC) and OELs

An alarming low relationship between hazard rating and the Norwegian OELs has been shown. No significant improvement has been demonstrated in adopting the new CLP legislation.

The R- and S- phrases are used in several risk assessment tools as proxies for OELs. In Norway this control banding approach have been implemented in CHEMIRiSK – a Risk Assessment tool developed by Proactima. In 2010 we conducted a study to look at the relationship between the severity of the hazards expressed by R- and S- phrases and the Norwegian Occupational Exposure Limits (OEL). In this study we used the Health Hazard Categories applied in the NORSOK-002 (rev. 4) standard for Working Environment and the Norwegian OELs.


The results showed that the OELs in all HHC range from very low levels to moderate or high levels (Figure 1). For substances defined in HHC 1 there are no correlation between the hazard categorization and the range of the OEL, whereas for the other hazards categories there were a downward trend in OELs as expected. There were, however a substantial differ­ences between gases, solids and liquids as shown in Table 1.


This study shows that for chemicals characterized as having a low hazard according to official EU classification scheme, there was a low correlation between this classification and the Norwegian OELs.

The reason for this lack of relationship might come from the the fact that the two different hazard and risk char­acterisation regimes have origin from different sources. The Norwegian OELs was first defined by NLI in 1978 and was based mainly on ACGIH TLVs and Danish OELs. New chemicals have been added, and limits have been changed, but the list has not been subject to any systematic review. The chemical index list was defined by EU and introduced along with the EU chemical directive. One other aspect is that R- and S- phrases relates to the hazard whereas OEL relates more to the total risk of the substances. The same findings have been shown applying the new CLP legislation.

These finding should encourage legislators, organisations and risk tools providers to improve the quality of both the hazard categorisation and the OELs to ensure a sound basis for chemical health risk assessment. These and similar results call for a lager degree of harmonization of the hazard and exposure categorisation used in risk assessments.

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