Elimination

Over 95% of absorbed xylene is metabolised. Approximately 5% is eliminated unchanged from the lungs (Sedivec and Flek, 1976; Astrand et al., 1978; Riihimaki et al., 1979). After cessation of exposure the concentration in expired air initially falls rapidly (half-life in the range 0.5-1.0 hours) and then the rate of decline decreases. The last phase of elimination has a half-life of approximately 20-30 hours (Riihimaki et al., 1979; Riihimaki and Savolainen, 1980). Trace quantities of xylene may be detected in expired air 48 hours after cessation of exposure (Sedivec and Flek, 1976).

Xylene can be detected in the urine within two hours of exposure. However, only trace amounts of xylene are excreted by this route (Sedivec and Flek, 1976). Excretion of the xylenol metabolites appears to be slower than that of the methylhippuric acids (Sedivec and Flek, 1976; Riihimaki et al., 1979). The methylhippuric acid metabolites can be detected in the urine within two hours of exposure (Sedivec and Flek, 1976). The concentration has been reported to peak in the last two hours of exposure (Senczuk and Orlowski, 1978) and two hours after cessation of exposure (Sedivec and Flek, 1976). Trace quantities can still be detected 4-5 days after cessation of exposure (Sedivec and Flek, 1976). The urinary metabolites in a volunteer study (m-xylene 150 ppm for four hours) were found in the following concentrations: m-methylhippuric acid 97.4%, 2,4-dimethylphenol 2.5%, 3-methylbenzylalcohol 0.05% (Engström et al., 1984). Most absorbed xylene is excreted as methylhippuric acids (Lauwerys et al., 1978) and only 1-2% as the xylenol metabolites (Sedivec and Flek, 1976; Riihimäki et al., 1979; Riihimäki and Hänninen, 1987).

Elimination of xylene from adipose tissue is slow with an average elimination half-life of 58 hours with a range of 25-128 hours (Engström and Riihimäki, 1979; Riihimäki et al., 1979).

Metabolism and excretion of xylene is efficient and rapid, consequently the effects following a short exposure are expected to resolve rapidly. However, following prolonged or repeated exposure, elimination will be governed by the rate of release from adipose tissues (Riihimäki and Hänninen, 1987).

Peripheral Neuropathy Natural Treatment Options

Peripheral Neuropathy Natural Treatment Options

This guide will help millions of people understand this condition so that they can take control of their lives and make informed decisions. The ebook covers information on a vast number of different types of neuropathy. In addition, it will be a useful resource for their families, caregivers, and health care providers.

Get My Free Ebook


Post a comment