ABSTRACT
Generally S should be assigned for substances with a low dermal LD50 (less than 2000 mg/kg). However, the present use of S does not refl ect this proposal (Table 4.2) as only few countries assigned the S to all such chemicals on their OEL lists (4). ACGIH’s criteria were never clear, so that for many of the compounds with the S the documentation did not refer to published data (2,3). These inconsistencies could be attributed to different factors, namely, lack of systematic dermal absorption studies on chemicals of occupational interest, confl icting information on dermal absorption obtained with different experimental systems, dependence of the absorption rate on exposure conditions, and lack of criteria to defi ne the importance of skin penetration in occupational exposure to chemicals. Additionally, the lack of a warning for substances that were extremely corrosive or irritating to the skin itself sometimes resulted in S being inappropriately assigned to these hazards. Moreover, S represents a rigid criterion to distinguish between compounds that can defi nitely cause systemic effects due to limited skin contact and nonhazardous compounds. In other words, S is a qualitative hazard indicator while workplace exposures should be evaluated in quantitative terms. This concept seems very limiting as the cases of acute intoxication are relatively unusual today. Furthermore, S does not take into account a number of situations in which most of the workplaces are involved, such as dermal exposure to mixtures, increased percutaneous penetration in certain dermatologic diseases and skin contamination with percutaneous penetration enhancers. To this we must add the lack of consensus on quantitative dermal risk assessment that at the moment prevents the use of dermal occupational exposure limits (DOEL) mainly due to (5):
● lack of validated and standardized techniques of dermal exposure measurements (there is no general agreement on how to measure skin contamination);
At the 28th International Congress on Occupational Health (Milan, Italy, 2006) a Satellite Workshop on “Dermal Risk Assessment at Workplace” was organized by the Scientifi c Committee on Occupational and Environmental Dermatoses of the International Commission on Occupational Health (ICOH SC OED) with the aim of exploring the actions needed to improve the S system in an international harmonized perspective. A position paper was published focusing the following ‘aspects (6):
● At the time S was the only example of a regulatory tool for dermal risk communication. Various international agencies and individual author groups proposed new strategies for development of S that differed from each other in a number of ways, but generally suggesting that S should be based on human/animal evidence when available, or otherwise supported by experimental evidence based on internationally accepted methods [e.g., derived following existing guidelines of the Organization for Economic Co-operation and Development (OECD)] or on mathematical/probabilistic models, such as [quantitative] structure-activity relationships ([Q]SARs). Unfortunately, human in vivo evidence (i.e., credible evidence indicating the incidence of systemic effects among workers as a result of chemical exposure) is diffi cult to obtain and decisions are mostly likely to be based on in vitro experimental evidence, models, or animal data that relate the absorbed dermal dose to the calculated dose from inhalation.
