Chemical carcinogens. A review and analysis of the literature of selected chemicals and the establishment of the Gene-Tox Carcinogen Data Base. A report of the U.S. Environmental Protection Agency Gene-Tox Program

The literature on 506 selected chemicals has been evaluated for evidence that these chemicals induce tumors in experimental animals and this assessment comprises the Gene-Tox Carcinogen Data Base. Three major sources of information were used to create this evaluated data base: all 185 chemicals determined by the International Agency for Research on Cancer to have Sufficient evidence of carcinogenic activity in experimental animals, 28 selected chemicals bioassayed for carcinogenic activity by the National Toxicology Program/National Cancer Institute and found to induce tumors in mice and rats, and 293 selected chemicals which had been evaluated in genetic toxicology and related bioassays as determined from previous Gene-Tox reports. The literature data on the 239 chemicals were analyzed by the Gene-Tox Carcinogenesis Panel in an organized, rational and consistent manner. Criteria were established to assess individual studies employing single chemicals and 4 categories of response were developed: Positive, Negative, Inconclusive (Equivocal) and Inconclusive. After evaluating each of the individual studies on the 293 chemicals, the Panel placed each of the 506 chemicals in an overall classification category based on the strength of the evidence indicating the presence or absence of carcinogenic effects. An 8-category decision scheme was established using a modified version of the International Agency for Research on Cancer approach. This scheme included two categories of Positive (Sufficient and Limited), two categories of Negative (Sufficient and Limited), a category of Equivocal (the evidence of carcinogenicity from well-conducted and well-reported lifetime studies had uncertain significance and was neither clearly positive nor negative), and three categories of Inadequate (the evidence of carcinogenicity was insufficient to make a decision, however, the data suggested a positive or negative indication). Of the 506 chemicals in the Gene-Tox Carcinogen Data Base, 252 were evaluated as Sufficient Positive, 99 as Limited Positive, 40 as Sufficient Negative, 21 as Limited Negative, 1 as Equivocal, 13 as Inadequate with the data suggesting a positive indication, 32 as Inadequate with the data suggesting a negative indication, and 48 Inadequate with the data not suggesting any indication of activity. This data base was analyzed and examined according to chemical class, using a 29 chemical class scheme.(ABSTRACT TRUNCATED AT 400 WORDS)

Mutant allele frequencies in domestic cats of Taiwan

Preliminary data for Taiwanese cats generally agree with previous findings in far eastern populations, especially Vladivostok. However, surveys are still too few in number to achieve any detailed perspective for this vast region.

An analysis of lung cancer risk from exposure to hexavalent chromium

Lung cancer risk in relation to airborne levels of hexavalent chromium was analyzed for chromium chemical production workers studied by Hayes, Lilienfeld, and Snell. Hayes et al [18] had observed statistically significant increases in lung cancer mortality among chromium chemical production workers hired during 1945-1959 and followed to mid-1977. A dose-response was observed by Hayes et al. in that long-term workers had a higher lung cancer risk than short-term workers. Concurrent exposure data for the study plant were abstracted from the records of a local health department. The usual air concentration of hexavalent chromium was estimated as 413 micrograms per cubic meter (micrograms/m3) during 1945-1949. Cumulative exposure estimates for individual workers could not be developed with available information. Instead, cumulative exposures in terms of micrograms/m3-years were estimated for groups of short-term workers and long-term workers (cumulative exposure = usual exposure level in micrograms/m3 X average length of exposure). For workers hired during 1945-1949, cumulative exposures were estimated as 670 and 3,647 micrograms/m3-years for short-term and long-term workers, respectively. Like most estimates based on historical data, these exposure estimates are subject to uncertainty. Nevertheless, these results suggest a potential excess risk of death from lung cancer among U.S. workers exposed to the current permissible exposure limit (PEL) for hexavalent chromium of 52 micrograms/m3 because such workers could accumulate exposures (micrograms/m3-years) similar to those associated with excess risk in Hayes et al's cohort. Moreover, many current workers are estimated to be exposed to levels above the PEL. Further exploration of the dose-response relationship for chromium carcinogenesis is indicated.

The association between dietary sucrose consumption and microbial population shifts at six oral sites in man

Sucrose-related microbial population shifts were evaluated at 6 oral sites in 22 volunteers, who consumed high-sucrose diets for 21 days followed by low-sucrose diets for 21 days. Culturing was performed at 0, 12, 21, 33 and 42 days of the 6-week experiment. Over 50,000 microbial isolates were characterized and analysed. Analysis of initial cultures showed the following site-specific microbial characteristics of the 6 sites evaluated: (1) molar fissures harboured higher levels of Neisseria species and showed the highest facultative-to-anaerobic ratio; (2) molar fissures and cervical buccal sites showed high Streptococcus sanguis levels and total Gram-positive cocci and fewer Gram-negative bacilli; (3) the tongue and saliva gave high concentrations of Streptococcus salivarius and Veillonella sp. Sucrose intake was positively related to concentrations of yeasts and Streptococcus mutans in the molar fissures; Actinomyces viscosus in the mandibular approximal site; Strep. mutans, Veillonella sp. and Lactobacillus sp. in the maxillary approximal site and Strep. salivarius on the tongue and in saliva. Sucrose intake was negatively related to concentrations of Neisseria sp. on the tongue and total Gram-positive bacilli in saliva. A definite ecological effect of sucrose on the oral microflora was confirmed. The high inter-subject and site variations of target bacteria and the generally low magnitude of shifts, however, discourage implementation of microbiological criteria in dietary assessments.

Determination of x-ray spectral distribution from transmission measurements using K-edge filters

Accurate high-resolution x-ray spectral distributions can be obtained with an intrinsic germanium crystal. This technique is difficult to implement since it requires expensive, complicated, and bulky equipment. If energy resolution requirements are relaxed, then the above drawbacks can be overcome and an x-ray spectrometer that is small, inexpensive could be built. A technique that meets these requirements is described here. X-ray spectra with about 7-keV resolution can be achieved by obtaining transmission measurements through a number of different K-edge filters. Using these measurements, a system of equations is set up and solved giving the required spectral distribution. The technique has been tested using 80, 100, and 120-kVcp x-ray beams with total filtrations of 3.78, 5.78, 9.06 mm A1, and 3.78 mm A1 + 0.137 mm Ho. The results show that the calculated spectra closely resemble tabulated spectra. The errors ranged from 3% to 13%. The half-value layers (HVL) were also calculated and compared to the HVL obtained from tabulated spectra and were found to differ by about 7%.

In vitro information system for collection and analysis of experimental data

The In Vitro information System (IVIS) provides for the collection, maintenance, analysis and reporting of mutagenesis data for the In Vitro Carcinogenesis Program of the Carcinogenesis Testing Program in the National Cancer Institute. Initial development or IVIS focused on the microbial mutagenicity assays conducted in a collaborative study in four laboratories. Information is collected about contract management, chemicals, microorganisms strain checks, preparation of activation enzymes, test results, and confirmation of mutation. IVIS provides for editing and maintenance of the information on computers at the National Institutes of Health. Analysis and reporting features were designed to assist both laboratory investigators and NCI staff in evaluating the mutagenic activity of test compounds. The analysis has focused on two principal goals: using the computer to examine the results of each test to determine if the test was adequate for a further statistical analysis; and secondly, if the plate counts are adequate, developing statistics that indicate whether there is a positive or negative trend. Reports have been developed for tabular displays of test results, frequency distributions, dose response graphs and statistical computations.