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Dermal absorption of vaporous and liquid 2-methoxyethanol and 2-ethoxyethanol in volunteers
S Kezić1, K Mahieu, A C Monster
1Coronel Laboratorium, Vakgroep Gezondheidkunde, Academisch Medisch Centrum, Amsterdam, The Netherlands.
Objectives:
To estimate dermal absorption of vaporous and liquid 2-methoxyethanol (ME) and 2-ethoxyethanol (EE) in volunteers.
Methods:
Five volunteers (two men and three women) were dermally exposed to vaporised and liquid ME and EE. Dermal exposure on an area of about 1000 cm2 (forearm and hand) to vapours of ME and EE (4000 mg/m3 ME and 3700 mg/m3 EE) lasted for 45 minutes. Duration of exposure to liquid ME and EE on an area of 27 cm2 (forearm) was 15 minutes. Dermal uptake was assessed by measurement of the main metabolites in urinary methoxyacetic acid (MAA) and ethoxyacetic acid (EAA). For each volunteer, excretion of metabolites was compared with a reference inhalatory exposure.
Results:
Mean (SD) absorption rates of ME and EE vapour were 36 (11) and 19 (6) cm/h respectively. The mean (SD) absorption rates of the liquid ME and EE amounted to 2.9 (2.0) and 0.7 (0.3) mg/cm2.h.
Conclusions:
Vaporised and liquid ME and EE are readily absorbed through the skin. In the combined inhalatory and dermal exposure when whole body surface is exposed to vapour, the uptake through the skin is estimated to be 55% of the total uptake of ME and 42% of EE. Dermal uptake resulting from skin contact of both hands and forearms (about 2000 cm2) with liquid ME and EE for 60 minutes would exceed inhalatory uptake of the eight hour occupational exposure limit by 100 times at 16 mg/m3 of ME and 20 times at 19 mg/m3 of EE. The substantial skin uptake of ME and EE indicates that in assessing the health risks biological monitoring and use of biological exposure indices are preferable to environmental monitoring.