Occupational Dermal Exposure Assessment

AbstractThe skin is generally considered to be a good barrier to the systemic absorption of chemicals. However, many chemicals can partially or fully breach the skin where they may be metabolized, and interact with dermal macromolecules or components of the skin immune system, and then be systemically absorbed and distributed. Thus, dermal exposure to chemical substances can contribute significantly to the total systemic dose as well as result in acute or chronic skin toxicity and disease.Skin diseases related to occupational exposure are the second most prevalent type of occupational disease. From 1983 to 1994, occupational skin diseases increased by 26%. In 1994, approximately 66,000 cases were reported, which accounted for 13% of all occupational related disease. Since occupational skin diseases are believed to be severely under‐reported, the actual rate may be much higher. Total costs (including lost productivity) have been estimated at $1 billion annually. Given such widespread prevalence of skin diseases, we need better measures for predicting, quantifying, and preventing dermal exposure to hazardous agents.Dermal exposure to hazardous chemicals in the workplace has become an important occupational hygiene issue and a growing field of interest to health professionals in occupational hygiene and dermatology. Dermal exposure has been indicated as the primary source for the systemic exposure from chlorophenols, polychlorinated biphenyls, polycyclic aromatic hydrocarbons (PAH), glycol ethers, chlorpyrifos, acrylamide, cyclophosphamide, and 4,4’‐methylene dianiline. Exposure to chemicals, which may interact with endogenous nucleophilic sites in the skin directly (e.g., electrophilic isocyanates) or following metabolism to reactive metabolites (e.g., benzo[a]pyrene diolepoxide), has not been systematically investigated and is poorly understood. The deposition, absorption, and uptake of chemicals into and through the epidermis, and the biological consequences of dermal penetration are also difficult to measure. Thus, the significance of adverse health effects associated with dermal exposure is difficult to evaluate.A major limitation to our understanding and development of this area of research has been the absence of a reliable noninvasive method to determine chemical‐specific skin deposition and to investigate mechanisms of dermal toxicity. Thus, the threshold dose required to induce an adverse effect and toxicity from occupational and environmental exposure conditions cannot be determined accurately.Methods to assess the significance of dermal exposure are limited in number and scope. The current methods available for measuring dermal exposure, e.g., removal tecniques, surrogate techniques, fluorescence techniques, all suffer from fundamental problems and have not been adequately documented and validated. This chapter reviews and summarizes our current knowledge on dermal exposure assessment, and reviews and evaluates the current sampling methods.