Two-generation reproduction and cross-foster studies of perfluorooctanesulfonate (PFOS) in rats.

Perfluorooctanesulfonate (PFOS) is a persistent acid found widely distributed in wildlife and humans. To understand the potential reproductive and developmental effects of PFOS, a two-generation reproduction study was conducted in rats. Male and female rats were dosed via oral gavage at dose levels of 0, 0.1, 0.4, 1.6, and 3.2 mg/(kg day) for 6 weeks prior to mating, during mating, and, for females, through gestation and lactation, across two generations. Due to substantial F1 neonatal toxicity observed in the 1.6 and 3.2 mg/(kg day) groups, continuation into the second generation was limited to F1 pups from the 0, 0.1, and 0.4 mg/(kg day) groups. No adverse effects were observed in F0 females or their fetuses upon caesarean sectioning at gestation day 10. Statistically significant reductions in body-weight gain and feed consumption were observed in F0 generation males and females at dose levels of 0.4 mg/(kg day) and higher, but not in F1 adults. PFOS did not affect reproductive performance (mating, estrous cycling, and fertility); however, reproductive outcome, as demonstrated by decreased length of gestation, number of implantation sites, and increased numbers of dams with stillborn pups or with all pups dying on lactation days 1-4, was affected at 3.2 mg/(kg day) in F0 dams. These effects were not observed in F1 dams at the highest dose tested, 0.4 mg/(kg day). Neonatal toxicity in F1 pups, as demonstrated by reduced survival and body-weight gain through the end of lactation, occurred at a maternal dose of 1.6 mg/(kg day) and higher while not at dose levels of 0.1 or 0.4 mg/(kg day) or in F2 pups at the 0.1 or 0.4 mg/(kg day) dose levels tested. In addition to these adverse effects, slight yet statistically significant developmental delays occurred at 0.4 (eye opening) and 1.6 mg/(kg day) (eye opening, air righting, surface righting, and pinna unfolding) in F1 pups. Based on these data, the NOAELs were as follows: reproductive function: F0> or =3.2 and F1> or =0.4 mg/(kg day); reproductive outcome: F0=1.6 and F1> or =0.4 mg/(kg day); overall parental effects: F0=0.1 and F1> or =0.4 mg/(kg day); offspring effects: F0=0.4 and F1> or =0.4 mg/(kg day). To distinguish between maternal and pup influences contributing to the perinatal mortality observed in the two-generation study, a follow-up cross-foster study was performed. Results of this study indicated that in utero exposure to PFOS causally contributed to post-natal pup mortality, and that pre-natal and post-natal exposure to PFOS was additive with respect to the toxic effects observed in pups.

Subchronic toxicity studies on perfluorooctanesulfonate potassium salt in cynomolgus monkeys.

This study was conducted to determine the earliest measurable response of primates to low-level perfluorooctanesulfonate (PFOS) exposure and to provide information to reduce uncertainty in human health risk assessment. Groups of male and female monkeys received 0, 0.03, 0.15, or 0.75 mg/kg/day potassium PFOS orally for 182 days. Recovery animals from each group, except the 0.03 mg/kg/day dose group, were monitored for one year after treatment. Significant adverse effects occurred only in the 0.75 mg/kg/day dose group and included compound-related mortality in 2 of 6 male monkeys, decreased body weights, increased liver weights, lowered serum total cholesterol, lowered triiodothyronine concentrations (without evidence of hypothyroidism), and lowered estradiol levels. Decreased serum total cholesterol occurred in the 0.75 mg/kg/day dose group at serum PFOS levels > 100 ppm. Hepatocellular hypertrophy and lipid vacuolation were present at term in the 0.75 mg/kg/day dose group. No peroxisomal (palmitoyl CoA oxidase) or cell proliferation (proliferating cell nuclear antigen immunohistochemistry) was detected. Complete reversal of clinical and hepatic effects and significant decreases in serum and liver PFOS occurred within 211 days posttreatment. Liver-to-serum PFOS ratios were comparable in all dose groups, with a range of 1:1 to 2:1. Serum concentrations associated with no adverse effects (0.15 mg/kg/day) were 82.6 +/- 25.2 ppm for males and 66.8 +/- 10.8 ppm for females. Comparison of serum PFOS concentrations associated with no adverse effect in this study to those reported in human blood samples (0.028 +/- 0.014 ppm) indicated an adequate margin of safety.

The north american control animal database: a resource based on standardized nomenclature and diagnostic criteria.

Historical control data have been shown to be valuable in the interpretation and evaluation of results from rodent carcinogenicity studies. Standardization of terminology and histopathology procedures is a prerequisite for meaningful comparison of control data across studies and analysis of potential carcinogenic effects. Standardization is particularly critical for the construction of a database that includes incidence data from different studies evaluated by pathologists in different laboratories. Standardized nomenclature and diagnostic criteria have been established for neoplasms and proliferative lesions. Efforts of the National Toxicology Program, the Society of Toxicologic Pathology (STP), and the Registry of Industrial Toxicology Animal-data (RITA) have led to a harmonized pathology nomenclature for the rat and the mouse. This nomenclature with detailed descriptions of lesions is available in publications by the STP and International Agency for Research on Cancer (IARC). A listing of these terms is available on the World Wide Web. Utilizing the model established by RITA and working with the International Life Sciences Institute (ILSI), companies with laboratories in North America formed a working group in 1994 to establish and maintain a database of neoplastic and proliferative lesions from control animals in carcinogenicity studies. The rationale for development of the North American Control Animal Database (NACAD), the factors that influence tumor incidence, operation of the database, and the benefits to be realized by using a standardized approach are discussed.