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| CATEGORY | QUALITY | THRESHOLD | OCCURENCE | REFERENCE |
|---|---|---|---|---|
| smell | sweet organic, chemical | water | details | |
| smell | chemical | water | details |
| Toxicity Summary |
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| Link to the Distributed Structure-Searchable Toxicity (DSSTox) Database |
| IDENTIFICATION AND USE: 4-Xylene (p-xylene) is a colorless liquid (Note: A solid below 56 degrees F). It is used for synthesis of terephthalic acid for polyester resins and fibers; pharmaceutical synthesis; insecticides. p-Xylene is also frequently used for paints or in the printing trade. HUMAN EXPOSURE AND TOXICITY: Three women exposed to p-xylene at 100 ppm for 1 to 7.5 hours/day, for 5 days, showed no effects on electroencephalograms, evoked potentials, or cognitive performance, but frequently reported headache and dizziness as a result of exposure. In contrast, four men exposed at concentrations of up to 150 ppm p-xylene under the same exposure conditions reported no increase in headaches or dizziness. Slight impairment of vestibular and visual function and reaction time was noted at exposure levels from 200 to 300 ppm. There was adaption to the impairment over five successive daily exposures. Human data indicate that acute inhalation exposures to 460 ppm mixed xylene and 100 ppm p-xylene vapors produce mild and transient eye irritation. p-Xylene is possibly ototoxic at concentrations that are relevant to the occupational setting. Levels of blood xylenes reflect recent exposure. The m-and p-xylene isomers usually are measured together and reported as m/p-xylene. ANIMAL STUDIES: Increased hepatic cytochrome p450 concentrations and reduced nicotinamide adenine dinucleotide cytochrome C reductase activity occurred in rats exposed 3 days to 2000 ppm of p-xylene. In lung microsomes, cytochrome p450 content was decreased. Marked activation and tremor were observed at concentrations between 400 and 1500 ppm p-xylene in rats. The CNS depressant threshold was 1940 ppm. In a study of levels of noradrenaline and dopamine in the forebrain and hypothalamus, rats (six males/group) were exposed to 0 or 2000 ppm p-xylene 6 hr/day for 3 days. The animals were killed 16-18 hr after the last exposure. In exposed animals there was a significant increase in catecholamine levels and turnover in various parts of the hypothalamus. There was no effect on dopamine levels or turnover in the forebrain. Histological damage to the outer hair cells of the organ of Corti provided evidence of ototoxicity in rats exposed by oral gavage to p-xylene, but not m- or o-xylene, at a dose of 900 mg/kg/day, 5 days/week for 2 weeks. The losses of hair cells occurred in the area of the cochlea responsive to medium frequencies (10-25 kHz). Mice were exposed to p-xylene at 150, 1500, or 3000 mg/cu m, 24 hr/day from days 7-14 of gestation. Toxic effects were decr weight of fetuses, increased incidence of skeletal retardation, and decrease in activity of enzymes, succinic dehydrogenase, alkaline, acid phosphatase, glucose 6-phosphatase and changed characteristic features of functional maturity of the nephron, retardation of fetus was dose related. In other experiment, increased incidence of malformations mostly cleft palates, were observed only with m- or p-xylene. Malformations (ie cleft palate) associated with mixed or individual isomers were primarily reported at maternally toxic doses. Each xylene isomer was administered to male rats intraperitoneally in 2 similar doses, 24 hours apart over a range of concentrations from 0, 0.12-0.75 mL/kg (105-650 mg/kg) and evaluated femoral bone marrow 30 hours after the first injection. No increase in micronucleated polychromatic erythrocytes was observed for any xylene isomer. p-Xylene was nonmutagenic using the Ames assay. It did not revert Salmonella typhimurium strains TA1535, TA1537, TA1538, TA98, & TA100 either with or without metabolic activation. ECOTOXICITY STUDIES: The xylene isomers have a similar degree of toxicity as mixed xylenes to estuarine/marine invertebrates. For m-xylene and p-xylene, the respective 48-hour LC50 values are 19.3 and 24.5 mg/L in brine shrimp, suggesting that the m-xylene and p-xylene isomers are slightly toxic to estuarine/marine invertebrates on an acute basis. |
| Source: DrugBank or Hazardous Substances Data Bank (HSDB) |
| Spectrum Type | Spectrum View | Description | Polarity |
|---|---|---|---|
| Experimental GCMS | view | GCMS | positive |