Triclosan is a broad-spectrum antimicrobial agent to which humans are widely exposed. Very limited data are available regarding the dermal toxicity and the carcinogenic potential of triclosan. In this study, groups of 48 male and 48 female B6C3F1/N mice were untreated or were dermally administered 0 (vehicle), 1.25, 2.7, 5.8, or 12.5 mg triclosan/kg body weight/day (mg/kg/day) in 95% ethanol, 7 days per week for 2 years. Vehicle control animals received 95% ethanol only; untreated, naive control mice were not dosed. There were no significant differences in survival among the groups. The highest dose of triclosan decreased the body weights of mice in both sexes, but the decrease was ≤8%. (Abstract Abridged).
Black cohosh (Actaea racemose L.) is widely used as a botanical dietary supplement to alleviate female gynecological symptoms, such as premenstrual syndrome and changes associated with menopause, and to stimulate labor. Despite its popularity, limited data are available on the long-term safety of black cohosh products. To address this knowledge gap, 2-year National Toxicology Program (NTP) carcinogenicity studies were conducted in Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice. To emulate a potential human exposure scenario in which a woman might use black cohosh throughout pregnancy and lactation, perinatal exposure was included for the rat study. (Abstract Abridged).
Tris(chloropropyl) phosphate (TCPP) is used as a flame retardant in textiles, furniture foam, and other related products. In addition, it is manufactured for use in construction materials, electronic products, paints, coatings, and adhesives. Several flame retardants, including structurally similar organohalogen compounds, have been removed from products in commerce due to toxicity concerns, and TCPP has been proposed as a replacement flame retardant for use in these products. An anticipated increase in use of TCPP has generated concerns for increased human exposure through oral, dermal, and inhalation routes; however, publicly available toxicity data are scarce. The U.S. Consumer Product Safety Commission therefore requested that the National Toxicology Program (NTP) form a research program on TCPP to conduct subchronic and chronic exposure studies in rats and mice for hazard identification and characterization information. Because TCPP is commercially available as an isomeric mixture, the NTP studies tested a commercial TCPP product containing four isomers commonly found in other commercial mixtures of TCPP: tris(1-chloro-2-propyl) phosphate (TCIPP; CASRN 13674-84-5), bis(2-chloro-1-methylethyl) 2-chloropropyl phosphate (CASRN 76025-08-6), bis(2-chloropropyl) 2-chloroisopropyl phosphate (CASRN 76649-15-5), and tris(2-chloropropyl) phosphate (CASRN 6145-73-9). Following procurement of TCPP, the percent purity of the four isomers was determined prior to conducting hazard characterization studies. (Abstract Abridged).
Di(2-ethylhexyl) phthalate (DEHP) is a member of the phthalate ester chemical class that occurs commonly in the environment and to which humans are widely exposed. Lifetime exposure to DEHP is likely to occur, including during the in utero and early postnatal windows of development. To date, no carcinogenicity assessments of DEHP have used a lifetime exposure paradigm that includes the perinatal period (gestation and lactation). The National Toxicology Program (NTP) tested the hypothesis that exposure during the perinatal period would alter the DEHP carcinogenic response quantitatively (more neoplasms) or qualitatively (different neoplasm types). Two chronic carcinogenicity assessments of DEHP were conducted in which Sprague Dawley (Hsd:Sprague Dawley SD) rats were exposed to dosed feed containing 0, 300, 1,000, 3,000, or 10,000 ppm DEHP for 2 years using different exposure paradigms. In Study 1, groups of 45 F0 time-mated females were provided dosed feed beginning on gestation day (GD) 6 through lactation. On postnatal day (PND) 21, groups of 50 F1 rats per sex continued on the study and were provided dosed feed containing the same DEHP concentration as their respective dam for 2 years. In Study 2, groups of 50 rats per sex, aged 6 to 7 weeks at study start, were provided dosed feed containing DEHP for 2 years. (Abstract Abridged).
Di-n-butyl phthalate (DBP) is a phthalate used in the manufacture of consumer products such as plastics and personal care products. Widespread exposure in the population occurs throughout life, including during pregnancy and lactation. Because limited data are available in both animals and humans to evaluate DBP as a human carcinogen, the National Toxicology Program conducted 2-year studies of DBP in rats and mice. Time-mated female Sprague Dawley (Hsd:Sprague Dawley SD) rats were exposed to 0, 300, 1,000, 3,000, or 10,000 ppm DBP in feed during gestation and lactation. Postweaning, F1 offspring consumed diets with the same exposure concentrations as the dam for 2 years (n = 50/sex/exposure group). Male and female adult B6C3F1/N mice were exposed to 0, 1,000, 3,000, or 10,000 ppm DBP in feed for 2 years (n = 50/sex/exposure group). Estimated average chronic chemical consumption was 16-17, 54-57, 152-169, and 510-600 mg DBP/kg body weight/day (mg/kg/day) in rats in the 300, 1,000, 3,000, and 10,000 ppm groups, respectively, and 105-112, 329-347, and 1,306-1,393 mg/kg/day in mice in the 1,000, 3,000, and 10,000 ppm groups, respectively. (Abstract Abridged).
