Exposure to 1,4-dioxane from the atmosphere around the high-emission plants and from consumer products used in daily life that contain the substance may have adverse health effects: however, its emission into the atmosphere is not regulated. In this document, the health risk posed by 1,4-dioxane is assessed to investigate whether countermeasures should be undertaken to reduce exposure to 1,4-dioxane.
The notion of the margin of exposure (MOE), given by the ratio of no observed adverse effect level (NOAEL) to estimated exposure level, is used to assess risk.
In exposure assessment, two types of exposure channel are considered: (a) the use of consumer products that contain 1,4-dioxane and (b) the inhalation of air around high-emission plants. To estimate exposure via channel (a), we measured the concentration of 1,4-dioxane in consumer products and estimated the individual variability of exposure by Monte Carlo simulation that reflects the measured data. To estimate exposure via channel (b), we employed a local-level atmospheric dispersion model to estimate the concentration of 1,4-dioxane immediately around high-emission plants.
For hazard assessment, we derived the inhalatory and oral NOAELs for liver adenomas and carcinomas and the uncertainty factor.
The results suggest that measures are not needed to reduce exposure to 1,4-dioxane from consumer products. As for inhalation exposure around high-emission plants, some residents may be exposed to health risks if certain conservative analytical conditions are assumed. Even in this case, we conclude that it is not necessary for Plant A to stop the use of 1,4-dioxane immediately and that medium- to long-term emission reduction measures should be sufficient.
1,4-dioxane Risk Assessment Document was produced under the Comprehensive Chemical Substance Assessment and Management Program funded by the New Energy and Industrial Technology Development Organization (NEDO).
The full text of 1,4-dioxane Risk Assessment Document (in Japanese) was published by Maruzen Co., Ltd. in Feb 2005.