Threshold limit values.
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Biomedical subjects
Publications and source records attributed to L W Rampy.
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The effect of inhaled benzene on embryonal and fetal development was assessed in mice and rabbits. CF-1 mice and New Zealand white rabbits were exposed to 0 or 500 ppm of benzene for 7 hr per day from days 6 through 15 (mice) and 6 through 18 (rabbits) of gestation. Little evidence of maternal toxicity was seen in either species. Although some signs of embryonal toxicity were observed in both mice and rabbits, a teratogenic effect was not discerned in either species inhaling 500 ppm of benzene.
Rats and hamsters were exposed to the dust of pulverized asbestos pipe covering at an average concentration of 85 mg/m(3) for 6 h/d, 5 d/wk, for 7 mo, followed by a lifetime observation period. In rats, the pulmonary responses were alveolar adenomatous proliferation, nonprogressive fibrosis, squamous metaplasia, and a substantial incidence of pulmonary carcinoma formation. A smaller group of hamsters exposed under these conditions experienced an earlier onset of mortality than control hamsters, which were not subjected to the exposure regimen. Although this prevented conclusive evaluation of the pulmonary response in this species, no pulmonary neoplasms were noted in the surviving hamsters.
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Male and female Sprague-Dawley rats were exposed to vinylidene chloride (VDC) orally or by inhalation in 2-year toxicological studies. Interim results are included in this report. VDC was given in the drinking water at mean +/- S.D. concentrations of 0, 68 +/- 13, 106 +/- 22, and 220 +/- 35 ppm which produced mean +/- S.D. dosage levels of 0, 5.9 +/- 0.6, 10.0 +/- 1.2, and 19.3 +/- 2.7 mg/kg for male rats and 0, 7.5 +/- 0.4, 12.6 +/- 1.1, and 25.6 +/- 2.4 mg/kg for female rats. Forty-eight rats/sex/VDC level and 80 rats/sex in the control group were used in the 2-year study with an interim kill of an additional 10 rats/sex/level at 90 days. In the inhalation study, rats were exposed to 0, 10, or 40 ppm of VDC vapor 6 hr/day, 5 days/week for 5 weeks, after which the exposure levels were changed to 0, 25, and 75 ppm of VDC. Exposure continued for a total of 18 months and the rats held for observation an additional 6 months. Interim kills occurred at 1, 6 and 12 months. A separate 90-day study using 20 rats/sex/level was conducted at 0, 25, and 75 ppm of VDC vapor. There were 86 rats/sex/level in the 2-year portion of the study. The parameters monitored were: body weight, food and water consumption (drinking water study only), hematology, clinical chemistries, cytogentics of bone marrow cells (inhalation study only), mortality, terminal organ weights, and gross and histopathology. Based on interim kills and gross pathologic observations, the main conclusions are: increased cytoplasmic vacuolation of hepatocytes was seen in the livers of rats given 200 ppm VDC in drinking water or 25 or 75 ppm VDC vapor by inhalation; based on gross tumor count, tumor incidence in VDC-exposed rats was not greater than controls.