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Survey of chemical substances in dandruff shampoo 4 Exposure4.1 Human exposure In order to compare the following toxicity values to actual use, it is necessary to make assumptions as to how much dandruff shampoo is applied per hair wash, the frequency of use, and to make estimates as to the size of the area exposed. Other complications are involved in developing a realistic scenario of environmental exposure, including primary aquatic concentrations etc., because this requires knowledge about the overall consumption of dandruff shampoo, as well as about the concentrations of the relevant substances before and after water treatment etc. at water treatment plants. Such data is most easily collected via direct measurements, which have not been possible in this project. In the considerations below concerning human exposure, dermal area has been established on the basis of the values stated in the US EPA Exposure Factors Handbook (United States Environmental Protection Agency, 1997). Quantities and frequencies of use have been established partly on the basis of exposure scenario for use of shampoo in the risk assessment for 1,4-dioxane (Risk Assessment Report, 1999), and partly on the basis of data from the EU Technical Guidance Document TGD 2000) for use of rinse-off (nonpermanent) cosmetic products. 4.1 Human exposureIt is assumed a typical exposure scenario includes one hair-wash per day, for men and for women. Consumption per hair-wash is an estimated 12 grams of shampoo. The exposed dermal area during hair-washing assumedly includes the palm of both hands: that is, half of the area of both hands (840 cm²/2 = 420 cm², and all of the scalp (1200 cm²), which gives a total area of 1620 cm². A component comprising X % w/w of a product will therefore be present on: Hands: 12 g * (X/100) / 420 cm² = 0.29 * X mg/cm²dermal surface/event Scalp: 12 g * (X/100) / 1200 cm² = 0.1 * X mg/cm²dermal surface/event EU's Scientific Committee on Cosmetic Products and Non-food Products intended for Consumers (SCCNFP) has prepared guidelines for testing cosmetic ingredients in safety evaluation. These guidelines include the following exposure scenario: One hair-wash requires 8 grams of shampoo. It is assumed the hair is washed daily. Since the shampoo is applied to wet hair and skin, it is assumed that approximately 1 per cent of the shampoo applied will be absorbed. This means that with a content of X (calculated in weight percentage) exposure is: 8 gram/day * 0.01 * X = X * 0.08 g/day 4.2 Environmental exposureNaturally, it is expected that a rinse-off shampoo is discharged approximately 100 per cent to the aquatic environment either directly or via a wastewater treatment plant. For a total quantitative assessment of the discharge, it is essential we know how much dandruff shampoo is consumed per time unit per household. Moreover, it is equally important that we know which type of wastewater treatment plant the water passes through before ending up in the aquatic environment.
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