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C C Travis

Publications and source records attributed to C C Travis.

51 records · Page 3Linked to original sources
PubMed1988

Interspecific scaling of toxicity data.

This paper reexamines the scaling approaches used in cancer risk assessment and proposes a more precise body weight scaling factor. Two approaches are conventionally used in scaling exposure and dose from experimental animals to man: body weight scaling (used by FDA) and surface area scaling (BW0.67--used by EPA). This paper reanalyzes the Freireich et al. (1966) study of the maximum tolerated dose (MTD) of 14 anticancer agents in mice, rats, dogs, monkeys, and humans, the dataset most commonly cited as justification for surface area extrapolation. This examination was augmented with an analysis of a similar dataset by Schein et al. (1970) of the MTD of 13 additional chemotherapy agents. The reanalysis shows that BW0.75 is a more appropriate scaling factor for the 27 direct-acting compounds in this dataset.

Animals↗
PubMed1987

Interspecies extrapolations in risk analysis.

Quantitative risk assessment for carcinogenic chemicals is usually based on data obtained in animal studies conducted at very high levels of exposure. A key issue in using such data is the extrapolation of results from animals to man. Recently, physiological pharmacokinetic models can also be used to aid in extrapolating extrapolations. The models can also be used to aid in extrapolating between routes of administration. Model results for inhalation and ingestion of tetrachloroethylene will be presented and compared to experimental data for rats and humans.

Administration, Inhalation↗
PubMed1984

Metabolism of organically bound tritium in man.

The classic methodology for estimating dose to man from environmental tritium assumes that all tritium, whether organically bound or free, enters directly into man's free body water compartment and is uniformly distributed as tritiated water. This methodology ignores the fact that organically bound tritium in foodstuffs may be directly assimilated in the bound compartment of tissues without previous oxidation. A four-compartment model consisting of a free body water compartment, two organic compartments, and a small, rapidly metabolizing compartment is proposed. The utility of this model lies in the ability to input organically bound tritium directly into organic compartments representing tissue solids. The model will be used to illustrate the potential importance of organically bound tritium to cumulative dose estimates. It is found that organically bound tritium in foodstuffs can increase cumulative total body dose by a factor of 1.7-4.5 times the free body water dose alone, depending on the bound-to-loose ratio of tritium in the diet.

Animals↗
PubMed1984

Validation of a metabolic model for tritium.

The purpose of this paper is to validate a metabolic model describing the kinetics of tritium in man. The validation is based on measurements of background levels of loose and bound tritium in Italian subjects and their diets. Model predictions are compared with empirical measurements of tritium in human urine and tissue samples, and appear to be in close agreement.

Diet↗
PubMedDate not supplied

Pentachlorophenol: environmental partitioning and human exposure.

This paper uses a six compartment environmental partitioning model to explore the transport and accumulation of pentachlorophenol (PCP) within and between various environmental media. Environmental concentrations were then used to estimate the amount of PCP entering the food chain and the long-term, average daily intake of PCP by the general population of the U.S. Results show that PCP partitions mainly into soil (96.5%) and that the food chain, especially fruits, vegetables, and grains, accounts for 99.9% of human exposure to PCP. The long-term, average daily intake of PCP is estimated to be 16 micrograms/day, which agrees well with a previous estimate of 19 micrograms/day (Geyer et al. 1987).

Chlorophenols↗
PubMedDate not supplied

Validation of a terrestrial food chain model.

An increasingly important topic in risk assessment is the estimation of human exposure to environmental pollutants through pathways other than inhalation. The Environmental Protection Agency (EPA) has recently developed a computerized methodology (EPA, 1990) to estimate indirect exposure to toxic pollutants from Municipal Waste Combuster emissions. This methodology estimates health risks from exposure to toxic pollutants from the terrestrial food chain (TFC), soil ingestion, drinking water ingestion, fish ingestion, and dermal absorption via soil and water. Of these, one of the most difficult to estimate is exposure through the food chain. This paper estimates the accuracy of the EPA methodology for estimating food chain contamination. To our knowledge, no data exist on measured concentrations of pollutants in food grown around Municipal Waste Incinerators, and few field-scale studies have been performed on the uptake of pollutants in the food chain. Therefore, to evaluate the EPA methodology, we compare actual measurements of background contaminant levels in food with estimates made using EPA's computerized methodology. Background levels of contaminants in air, water, and soil were used as input to the EPA food chain model to predict background levels of contaminants in food. These predicted values were then compared with the measured background contaminant levels. Comparisons were performed for dioxin, pentachlorophenol, polychlorinated biphenyls, benzene, benzo(a)pyrene, mercury, and lead.

Air Pollutants↗