Absorption of vapors through skin has been largely ignored in occupational health, although for ethylene glycol ethers this route of exposure could be more important than inhalation. We used an automated concentration and humidity controlled system to measure real-time percutaneous absorption of 2-methoxy ethanol (ME) vapor in seven volunteers. The exposure concentration (300 ± 10 ppm or 25 ± 0.5 ppm), humidity (80 ± 2%), and temperature (27.5 ± 0.5°C) were controlled throughout the experiments. Uptakes during 4-hour single-arm exposure at 25 ppm and 300 ppm were 7.0 mg and 65.3 ± 25.0 mg, respectively, with corresponding uptake rates of 1.36 μg/cm2/hr and 13.2 ± 5.0 μg/cm2/hr. Percutaneous absorption was consistent and unsaturated during exposure. Because the permeability constant of ME vapor (14.0 ± 5.3 cm/hr) was much higher than that of many widely used organic chemicals, we concluded that vapor absorption through skin is a significant contributor to overall ME exposure.
From the Institute of Occupational Safety and Health, Council of Labor Affairs, Taipei (Dr Shih, Dr Chen); the Graduate Institute of Environmental Engineering, National Central University, Chun-Li, (Dr Wang); the Institute of Pharmaceutical Laboratory, National Defense Medical Center, Taipei (Dr Hu); Taiwan, Republic of China; and the Occupational Health Program, Harvard School of Public Health, Boston, Mass. (Dr Smith).
Address correspondence to: Tung-Sheng Shih, ScD, Director, Division of Method Development and Analysis, Institute of Occupational Safety and Health, Council of Labor Affairs, 4th Floor, 132, Min-Sheng E. Rd, Section 3, Taipei, Taiwan, Republic of China; e-mail: firstname.lastname@example.org.