1,4-Dioxane exposure

No reproductive effects of 1,4-dioxane exposure of rats have been reported. 

Dioxan develops appreciable quantities of peroxides upon exposure to air or upon keeping. These can be eliminated by refluxing over anhydrous stannous chloride (compare Section VI, 12) or by filtration through a column of activated alumina. 

The nature of the initiation step, which may occur in a variety of ways, is not known in all cases. Commonly used ethers such as ethyl ether, isopropyl ether, tetrahydrofuran, and i)-dioxane are particulady prone to form explosive peroxides on prolonged storage and exposure to air and light (see Peroxides AND PEROXY COMPOUNDS, ORGANIC), and should contain antioxidants (qv) to prevent their build-up. One of the exceptions to the peroxide forming tendency of ethers is methyl fert-alkyl ethers such as methyl fert-butyl ether [1634-04-4] (MTBE) and fert-amyl methyl ether [994-05-8] (TAME). Both have shown htde tendency if any to form peroxides (2,8). 

Many ethers, either of open chain (diethyl or diisopropyl ether) or cyclic type (tetrahydrofuran, dioxane), are readily autoxidised on exposure to air or oxygen in presence of light. The hydroperoxides formed are less volatile than the parent ether and may be concentrated to a dangerous extent if distillation of peroxidised material is attempted. 

Toxicology. Dioxane is an irritant of the eyes and mucous membranes on prolonged exposure it is toxic to the liver and kidneys. It is carcinogenic in experimental animals. 

National Institute for Occupational Safety and Health Criteria for a Recommended Standard. .. Occupational Exposure to Dioxane. DHEW (NIOSH) Pub No 77-226. Washington, DC, US Government Printing Office, 1977... 

Once again photolysis experiments carried out with thin films or solutions of poly (p-formyloxystyrene) (IV) in dioxane or acetonitrile give essentially the same results. IR monitoring of the exposure (Figure 3) shows a... 

The American Conference of Govermnental Industrial Hygienists (ACGIH) (1997) has recommended 90 nig/in as the threshold limit value (TLV) for occupational exposures to 1,4-dioxane in the workplace air. Until 1981, the ACGIH TLV was 180 nig/ni (American Conference of Governmental Industrial Hygienists, 1991). Similar values have been used as standards or guidelines in many countries (International Labour Office, 1991). 

Young et al. (1977) exposed four volunteers to 50 ppm [180 mg/m ] 1,4-dioxane vapour for 6 h. It was rapidly taken up, with plasma levels reaching a plateau after 3 h. The major metabolite, P-hydroxyethoxyacetic acid (HEAA), was detected during the exposure period. At the end of the exposure, plasma levels of 1,4-dioxane fell with a half-life of 59 min. HEAA plasma levels reached their peak 1 h after the end of the exposure and fell thereafter with a half-life of 48 min. The absorption rate of 1,4-dioxane under these conditions was 76.1 mg/h and the total dose was 5.4 mg/kg. The dominant route of elimination was oxidation to HEAA, which is rapidly cleared in the urine 47% of the dose was excreted as HEAA during exposure and excretion was complete within 8 h of the end. The excretion half-life of HEAA was 2.7 h and its renal clearance was 121 mL/min, which indicates clearance by glomerular filtration, as creatinine clearance in these subjects was 124 mL/min. Renal clearance of 1,4-dioxane was 0.34 mL/min, compared with its metabolic clearance of 75 mL/min. 

In a cohort of workers exposed to various concentrations of 1,4-dioxane at the workplace (0.02-47.8 mg/m3), Thiess et al. (1976) observed no clinical effects or changes in mortality related to the exposure. 

Exposure to 1,4-dioxane may occur during its manufacture and its use as a solvent in a wide range of organic products. It has been detected in ambient air. 

The presence of oxygen in this solution as in all dioxane-based scintillators adversely affects the efficiency and background. Also, light excitation produces phosphorescence. Therefore, it is necessary to use high purity compounds and avoid contact with air and exposure to light. 

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