ISSN:0030-2414    

DOI:10.1159/000225101

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:0030-2414    

DOI:10.1159/000225102

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

A short review on environmental carcinogenesis by chemicals is given. Problems related with the determination of carcinogenicity of chemicals are mentioned. Some critical factors in the monitoring of environmental carcinogens are discussed in relation to a quantification of human exposure to such compounds. An attempt at risk evaluation is made for polycyclic aromatic hydrocarbons, vinyl chloride, N-nitroso compounds and aflatoxins. It is concluded that there is a “threshold dose” for individual carcinogens that does not lead to tumor induction within the normal life span. The probability of multifactorial cause of human cancer by environmental carcinogens, however, does not allow the definition of “safe” levels of such compounds in view of syncarcinogenic and other enhancing and/or modifying

ISSN:0030-2414    

DOI:10.1159/000225103

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The problem of the presence of carcinogens in the environment has become of considerable concern to the public, as it has been to the biomedical community for some time. The burden of identifying carcinogenic agents and determining threshold levels, if they exist, falls upon the scientific community. Particular care must be exercised in the design, conduct and analysis of experiments directed toward the identification of carcinogens. The data generated from such tests provides the basis for regulatory decisions by governmental authorities. The advice provided by scientists must be based on sound data. There have been instances, however, and there will be others, in which biological variability and the limits of sensitivity of our tests will give equivocal results. It is the duty of scientists to bring such uncertainties to the attention of the public while working towards the development of more sensitive and precise techniques.

ISSN:0030-2414    

DOI:10.1159/000225104

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:0030-2414    

DOI:10.1159/000225105

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Many of the previously proposed theories of carcinogenesis which relate the exposure level of a carcinogen to expected tumor response, are summarized and it is pointed out that these theories assume the existence of no threshold level. A modification of the one-hit carcinogenic model which would incorporate a threshold, is proposed along with a generalization to variable thresholds over the population at risk. The statistical problems of discriminating between threshold and non-threshold models from experimental bioassay data are discussed and an example is given.

ISSN:0030-2414    

DOI:10.1159/000225106

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Three studies of Druckrey and his group, on diethylnitrosamine and 4-dimethylaminostiIbene, are described. In a recent experiment, urethane was given chronically to rats and mice, at doses between 100 and 12,500 μg/kg/day. The results in rats were evaluated with the Mantel-Bryan procedure; risk estimates greatly differed, depending on the slope used for calculation

ISSN:0030-2414    

DOI:10.1159/000225107

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:0030-2414    

DOI:10.1159/000225108

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Most of the malignant tumors of man are not caused by only one specific carcinogen, but have to be attributed to additive effects of various carcinogenic factors, predominantly from the environment. Experimental studies in rats and mice showed syncarcinogenic effects of small doses of different carcinogens with the same organotropy, given either simultaneously or consecutively. These effects were proved in both local and systemic carcinogens. Extensive studies carried out in some thousand rats showed that the action of pre-or postnatally applied chemical carcinogens is not influenced by immunostimulating or immunodepressive measures. In view of the topicality of combination effects of chemical carcinogens and lacking influences by regulative mechanisms of the host organism, it is recommended to eliminate chemical carcinogens as far as possible from the human environment.

ISSN:0030-2414    

DOI:10.1159/000225109

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

In order to understand variations in thresholds to chemical carcinogens, it is important to appreciate, besides the genetic determinants, those many environmental factors which are at play, at all times, modifying the thresholds for chemical carcinogenesis. An understanding of the mechanisms of action of these factors may make it possible to tackle the difficult problem of determining human threshold levels.

ISSN:0030-2414    

DOI:10.1159/000225110

出版商:S. Karger AG    

年代:1976

数据来源: Karger