Hydrolysis, absorption and metabolism of di(2-ethylhexyl) terephthalate in the rat.

1. The hydrolysis of di(2-ethylhexyl) terephthalate (DEHT) and di(2-ethylhexyl) phthalate (DEHP) were studied using rat gut homogenate fractions in vitro. Both isomers were hydrolysed by the intestinal fraction; however, DEHP was hydrolysed to 2-ethylhexanol (2-EH) and mono(2-ethylhexyl) phthalate (MEHP) in about equal proportions, whereas DEHT was hydrolysed to 2-EH and terephthalic acid (TPA). The half-lives for disappearance of the diesters were determined to be 12.6 min for DEHP and 53.3 min for DEHT. 2. The absorption and metabolism of DEHT were studied by administering [hexyl-2-14C]DEHT (in corn oil) by oral gavage at a dose level of 100 mg/kg to 10 adult male Sprague-Dawley rats. Urine, faeces and expired air were collected for 144 h and analysed for the presence of radioactivity, and faeces and urine were analysed for unlabelled metabolites. 3. Radioactivity was eliminated in faeces (56.5 +/- 12.1% of dose) primarily as unchanged DEHT, small amounts of MEHT and polar metabolites; excreted in urine (31.9 +/- 10.9% of dose) principally as MEHT and metabolic products of 2-EH; and expired as 14CO2 (3.6 +/- 0.9% of dose). Less than 2% of the administered radioactivity was found in the carcass. Small amounts of 14C were found in the tissues with the highest amounts found in liver and fat. 4. Metabolites identified in urine included terephthalic acid (equivalent to 51% of dose), oxidized metabolites of 2-EH and MEHT, and glucuronic and sulphuric acid conjugates (equivalent to about 10% of dose).(ABSTRACT TRUNCATED AT 250 WORDS)

Biologic monitoring of workers exposed to silver.

The smelting and refining of silver and the preparation of silver salts for use in photosensitized products can lead to occupational exposures to silver. Our objectives in this study were to determine the absorption and elimination of silver by workers exposed to different species of silver, to estimate the body burden of silver and to relate these findings to the potential development of argyria. Workers potentially exposed to silver (n = 37) and a similar number of controls (n = 35) participated in this study. Blood, urine, feces and hair samples were collected and were analyzed for total silver content by atomic absorption spectroscopy. The mean concentration of silver in the blood, urine and feces of silver workers was 0.011 microgram/ml, less than 0.005 microgram/g and 15 microgram/g, respectively; and of controls was less than 0.005 microgram/ml, less than 0.005 microgram/g and 1.5 microgram/g, respectively. The concentration of silver in hair was markedly higher for the silver workers than for controls (130 +/- 160 vs 0.57 +/- 0.56 microgram/g, respectively). The importance of these latter findings was questionable since airborne particles of silver can bind to hair and lead to apparent high values. Since silver is eliminated predominantly in the feces, fecal measurements were used as an index of exposure and as a means of calculating body burdens. Human exposure to metallic silver at the TLV (0.1 mg/m3) is expected to lead to a fecal excretion of about 1 mg of silver per day.(ABSTRACT TRUNCATED AT 250 WORDS)