Abstract  The distribution of 1,4-dioxane in the waters from 27 sites in 12 rivers including the Shinano River, the longest river in Japan, was investigated in 2002. 1,4-Dioxane was detected in concentrations ranging from 0.02 to 0.49 microg/L. The monthly variations in the 1,4-dioxane concentrations at 6 sites along the Shinano River showed mutually different patterns, and the concentrations did not correlate with the concentrations of the biochemical oxygen demand and the suspended substances. The annual mean concentrations were from 0.02 microg/L at sites located in the middle reaches to 0.11 microg/L at the river mouth. The 1,4-dioxane concentration in the Shinano River has shown a downward trend from 1989 to 2003.

Abstract  The disposal of organic chemicals in trenches at a waste disposal site near Ottawa, Ontario, Canada, has resulted in the contamination of the underlying aquifer. The organic residues measured in groundwater samples are reported and the mechanisms of contaminant transport in the aquifer discussed. Groundwater samples from monitoring wells and multilevel samplers were analyzed by gas chromatography-mass spectrometry. Ultratrace quantities of chlorinated dibenzodioxins and furans were found in groundwaters directly beneath the trenches. A wide variety of compounds were identified and quantitated in samples from the aquifer. The compound of greatest concern was 1,4-doixane, because of its toxicity and mobility, while that present in greatest concentration was a Freon, F113, which appeared to be very persistent, although three transformation products were identified.

Abstract  1,4-Dioxane has been classified by the US Environmental Protection Agency and the International Agency for Research on Cancer as a compound that may be carcinogenic in humans. Although there are several reports of 1,4-dioxane being detected in the environment, such as in tap water, there have been few reports on the content of 1,4-dioxane in food. We therefore studied the intake of 1,4-dioxane in food based on the average intake of food in the Kanto area of Japan as reported by the Ministry of Health, Labor and Welfare. The food was cooked in the normal manner and then homogenized in a mixer. A 20 g of sample of the homogenate was added to a solution of the purified water with 0.2 μg of 1,4-dioxane-d_8 as a surrogate and the 200 ml azeotropic solution was recovered using the steam distillation method. This solution was applied to a pair of active carbon solid-phase cartridges and the analyte was eluted from each cartridge with dichloromethane. The eluted solution was prepared for gas chromatographic/mass spectrometric analysis by reduction to a volume of 1 ml under a gentle stream of nitrogen. The detection limit of the analysis was 2 μg/kg. We found that the 1,4-dioxane content of 12 food groups ranged between 2 μg/kg and 15 μg/kg. From these results, the total daily intake of 1,4-dioxane was calculated to be 0.440 μg. An intake of this magnitude corresponds to 0.055% of the calculated total daily intake (TDI) (16 μg/kg body weight/day). This study indicates that the amount of 1,4-dioxane intake contributed by food is very low and that this value does not represent a potential problem as it does not raise the risk of carcinogenesis.

Abstract  1,4-Dioxane impurity in nonionic surfactants and cosmetics were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Experimental results show that there is no significant difference using SPME-GC and SPME-GC-MS for analysis of 1,4-dioxane in three types of nonionic surfactants at the 95% confidence level. The relative standard deviation (R.S.D.) values of each analytical method were smaller than 3%. The amount of 1,4-dioxane was found to vary from 11.6 +/- 0.3 ppm to 73.5 +/- 0.5 ppm in 30% of nonionic surfactants from manufacturers in Taiwan. These methods were linear over the studied range of 3-150 ppm with correlation coefficients higher than 0.995. The recoveries of 1,4-dioxane for these nonionic surfactants following SPME were all higher than 96 +/- 1% (n = 3). The detection limits of 1,4-dioxane for these nonionic surfactants following SPME were from 0.06 ppm to 0.51 ppm. The experimentally determined level of 1,4-dioxane in cosmetics from manufacturers in Taiwan varied from 4.2 +/- 0.1 ppm to 41.1 +/- 0.6 ppm in 22% of daily used cosmetics following SPME coupled with GC and GC-MS. Conventional solvent extraction takes around 1 h for extraction and reconcentration but SPME takes only around 10 min. SPME provides better analyses of 1,4-dioxane in nonionic surfactants and cosmetics than conventional solvent extraction and head space pretreatments in term of simplicity, speed, precision, detection limit, and solvent consumption.

Abstract  Soluble di-iron monooxygenases (SDIMOs), especially group-5 SDIMOs (i.e., tetrahydrofuran and propane monooxygenases), are of significant interest due to their potential role in the initiation of 1,4-dioxane (dioxane) degradation. Functional gene array (i.e., GeoChip) analysis of Arctic groundwater exposed to dioxane since 1980s revealed that various dioxane-degrading SDIMO genes were widespread, and PCR-DGGE analysis showed that group-5 SDIMOs were present in every tested sample, including background groundwater with no known dioxane exposure history. A group-5 thmA-like gene was enriched (2.4-fold over background, p < 0.05) in source-zone samples with higher dioxane concentrations, suggesting selective pressure by dioxane. Microcosm assays with (14)C-labeled dioxane showed that the highest mineralization capacity (6.4 ± 0.1% (14)CO2 recovery during 15 days, representing over 60% of the amount degraded) corresponded to the source area, which was presumably more acclimated and contained a higher abundance of SDIMO genes. Dioxane mineralization ceased after 7 days and was resumed by adding acetate (0.24 mM) as an auxiliary substrate to replenish NADH, a key coenzyme for the functioning of monoxygenases. Acetylene inactivation tests further corroborated the vital role of monooxygenases in dioxane degradation. This is the first report of the prevalence of oxygenase genes that are likely involved in dioxane degradation and suggests their usefulness as biomarkers of dioxane natural attenuation.