How many food additives are rodent carcinogens?

Adsorption of hydraulic fracturing fluid components 2-butoxyethanol and furfural onto granular activated carbon and shale rock

The objective of this study was to understand the adsorption ability of a surfactant and a non-surfactant chemical additive used in hydraulic fracturing onto shale and GAC. Experiments were performed at varying temperatures and sodium chloride concentrations to establish these impacts on the adsorption of the furfural (a non-surfactant) and 2-Butoxyethanol (2-BE) (a surfactant). Experiments were carried out in continuously mixed batch experiments with Langmuir and Freundlich isotherm modeling. The results of the experiments showed that adsorption of these compounds onto shale does not occur, which may allow these compounds to return to the surface in flowback and produced waters. The adsorption potential for these chemicals onto GAC follows the assumptions of the Langmuir model more strongly than those of the Freundlich model. The results show uptake of furfural and 2-BE occurs within 23 h in the presence of DI water, 0.1 mol L^-1 sodium chloride, and in lab synthesized hydraulic fracturing brine. Based on the data, 83% of the furfural and 62% of the 2-BE was adsorbed using GAC.

Evaluation of the toxicity of mastic gum with 13 weeks dietary administration to F344 rats

Dietary toxicity of mastic gum, a natural food additive, was studied in male and female F344 rats fed 0%, 0.22%, 0.67% and 2% levels mixed into powdered basal diet for 13 weeks. No mortality or obvious clinical signs were observed in any of the animals throughout the experimental period. Body weights were significantly reduced in the high dose-treated group from week 2 to the end of the experiment in males, and at weeks 8 and 13 in females. There were increased absolute and relative liver weights in a dose-related manner or limited to the high dose group males or females, along with changes in hematological parameters, including increased WBC and platelet in high dose males. Altered serum biochemistry parameters included increases of total proteins, albumin, and total cholesterol in both sexes, and gamma-GTP in females only. However, macroscopic examination at necropsy revealed no gross lesions, and microscopic examination also revealed no treatment-related findings in any organs examined. As dietary treatment of mastic gum for 13 weeks in the present study caused decreased body weights at the high dose, especially in males, and increased liver weights in a dose-related manner in both genders without any morphological findings, it is concluded that the administration of it has a no observed adverse effect level (NOAEL) of 0.67% in the diet.

Implications of the lack of accuracy of the lifetime rodent bioassay for predicting human carcinogenicity

The NTP lifetime rodent bioassay (LRB) is the "gold standard" for predicting human carcinogenicity. Unfortunately, little attempt has been made to validate it against human carcinogenicity. Here we show that the extremely limited data available do not support either of the two common interpretations of LRB results. If a risk-avoidance interpretation is used where any positive result in a sex/species combination is considered positive, 9 of the 10 known human carcinogens tested are positive, but an implausible 22% of all chemicals are positive. If a less risk averse interpretation is used where only chemicals positive in both rats and mice are considered positive, only 3 of the 6 known human carcinogens tested are positive. In either interpretation, some known human carcinogens are not positive in the LRB, potentially allowing widespread human exposure to misidentified chemicals. Improving the predictive accuracy of the LRB and other tests for human carcinogenicity requires that test results be validated against the known human carcinogenicity of chemicals. This will require redirecting available resources from screening chemicals to validating carcinogenicity tests as well as a substantial investment in epidemiology to identify more known human carcinogens and presumed human non-carcinogens.

How many high production chemicals are rodent carcinogens? Why should we care? What do we need to do about it?

High production volume (HPV) chemicals are produced in or imported to the US in amounts greater than 1 million pounds per chemical per year. The EPA has identified thousands of HPVs. Due to their abundance, such chemicals bring a substantial risk for human exposure, and as a result some level of adverse consequences to health are to be expected. In order to examine the potential for cancer risk associated with HPVs, this paper examines HPVs that have been tested in the National Toxicology Program's rodent cancer bioassay. The chemicals tested in the bioassay represent a small sample of the universe of environmental chemicals to which people are exposed. Unexpectedly, 60% of the 128 HPVs evaluated in the bioassay proved to be rodent carcinogens. This value compares to a predicted prevalence of only 16.5% carcinogens in a previous study. The previous study concluded that HPVs were less likely to be toxic by a variety of other test criteria as well. However, the approach involved identifying putative carcinogens using quantitative chemical structure-activity relationships (QSAR) in contrast to the direct tabulation of bioassay test results performed here. Detailed examination of bioassay results reveals that test outcomes depend heavily on route of administration as well as on dose level, sex, strain, and species used. Since most of these factors have little or no apparent relationship to chemical structure, results of this study suggest that QSAR, as well as virtually all other alternative methods, may not generally provide accurate predictions of carcinogenic potential. As we wait for efficient and effective methods for predicting carcinogens to be developed, people continue to be exposed to environmental carcinogens. Progress on regulating environmental carcinogens as well as on developing more effective test methods has been minimal since "war on cancer" began approximately 30 years ago. The present study questions whether the current strategy for dealing with environmental carcinogens will ever be successful. Close examination of rodent cancer test results seems to suggest that almost all chemicals may have carcinogenic potential in some genotypes under some exposure circumstances. If this hypothesis is correct, it would explain the general lack of progress in developing methods to differentiate carcinogens from noncarcinogens. A completely new strategy for dealing with cancer caused by exposures to environmental chemicals seems to be needed.