PROPOSAL FOR THE ASSESSMENT OF QUANTITATIVE DERMAL EXPOSURE LIMITS INOCCUPATIONAL ENVIRONMENTS - PART 1 - DEVELOPMENT OF A CONCEPT TO DERIVE A QUANTITATIVE DERMAL OCCUPATIONAL EXPOSURE LIMIT

Dermal uptake of chemicals at the workplace may contribute considerabl y to the total internal exposure and so needs to be regulated. At pres ent only qualitative warning signs-the ''skin notations''-are availabl e as instruments. An attempt was made to develop a quantitative dermal occupational exposure Limit (DOEL) complementary to respiratory occup ational exposure Limits (OELs). The DOEL refers to the total dose depo sited on the skin during a working shift. Based on available data and experience a theoretical procedure for the assessment of a DOEL was de veloped. A DOEL was derived for cyclophosphamide and 4,4-methylene dia niline (MDA) according to this procedure, The DOEL for MDA was tested for applicability in an actual occupational exposure scenario. An inte grated approach is recommended for situations in which both dermal and respiratory exposures contribute considerably to the internal exposur e of the worker. The starting point should be an internal health based occupational exposure limit-that is, the maximum dose to be absorbed without leading to adverse systemic effects. The proposed assessment o f an external DOEL is then either based on absorption rate or absorpti on percentage. The estimation of skin penetration seems to be of cruci al importance in this concept. If for a specific substance a maximal a bsorption rate can be estimated a maximal skin surface area to be expo sed can be assessed which may then serve the purpose of a DOEL. As lon g as the actual skin surface exposed is smaller than this maximal skin surface area the internal OEL will not be exceeded, and therefore, no systemic health problems would be expected, independent of the dermal dose/unit area. If not, the DOEL may be interpreted as the product of dermal dose/unit area (mg/cm(2)) and exposed skin surface area (cm(2) ). The proposed concept for a DOEL is relevant and can be made applica ble for health surveillance in the occupational situation where dermal exposure contributes notably to the systemic exposure. Further resear ch should show whether this concept is more generally applicable.