Diet, Nutrition, and Cancer (1982) / Chapter Skim
Currently Skimming:
18 Assessment of Risk to Human Health
18 Assessment of Risk to Human Health
Pages 430-446
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 430... ...
In contrast to compounds that act as initiators, many other compounds may modify either the initiating events per se, or the subsequent multistaged events responsible for the progression of the initiated cell to the fully developed neoplastic cell (Slaga, 1980~. A wide variety of chemicals can modify later stages of carcinogenesis.
|
From page 431... ...
This procedure was modified by the Safe Drinking Water Committee to estimate acceptable daily intake for contaminants in drinking water because of the paucity of data for these compounds (National Academy of Sciences, 1977~. To establish an ADI, the highest experimental dose that produces no observable effects is decreased by an "uncertainty factor" or "safety factor" (ranging from 18-2
|
From page 432... ...
This approach is comprised of two quantitative estimations: first, interpolation from responses obtained at high doses to estimate the response at low doses within the test species and, second, extrapolation of the data from the test species to estimate the response in humans. Several mathematical models have been proposed to interpolate from high to low doses within the test species (Scientific Committee of the Food Safety Council, 1978; National Academy of Sciences, 1980a)
|
From page 433... ...
This "gamma hit model" was found to fit dose-response data for various types of toxic responses better than did some of the simpler models (Scientific Committee of the Food Safety Council, 1978~. There is little support for and use of other models that mathematically describe a tolerance distribution, because they do not take into consideration the multistep nature of chemical carcinogenesis (Finney, 1952~.
|
From page 434... ...
Not only is there great uncertainty in the mathematical modeling procedures, but also there is no sound biological basis for any of them (Scientific Committee of the Food Safety Council, 1978~. The Safe Drinking Water Committee concluded that the most suitable model may be the multistage model because of the multistep nature of carcinogenesis and because of the model's relatively conservative estimate of risk (National Academy of Sciences, 1980a)
|
From page 435... ...
The Safe Drinking Water Committee concluded that conventional risk extrapolation methodology accompanied by sufficient data and reasonable models would predict risk to humans from studies in animals using low doses with a precision varying from 1 to 2 orders of magnitude (National Academy of Sciences, 1980a)
|
From page 436... ...
Incidence can be accumulated over a lifetime in a population to measure cumulative incidence, which is approximately equivalent to the lifetime risk of disease (Day, 1976~. In cohort studies, the incidence of disease is measured directly: the ratio of incidence in exposed and unexposed cohorts provides a measure of the relative risk.
|
From page 437... ...
Another example is the risk for lung cancer, which has been increasing with successive cohorts, especially among males, so that cross-sectional incidence curves show maximum risk at middle ages and declining risk at older ages. For cervical cancer, there have been complex birth cohort effects.
|
From page 438... ...
provides ranges of intake for three vitamins and six minerals, the upper limits being defined as "safe" on the basis of available information. But, it is clear that epidemiological studies will be needed to confirm or deny whatever risk estimates for nutrient intake may be obtained from experiments in animals.
|
From page 439... ...
Hence, diets may contain increasing amounts of vegetable products, some of which may be protective against cancer. However, if it is decided that changes have to be instigated, we should consider reducing exposure of the population to total dietary fat and increasing exposure to protective substances such as those found in fruits and vegetables, while ensuring the maintenance of an ideal body weight for height and well-balanced but varied nutrition.
|
From page 440... ...
Both of these estimates are probably too low, because artifacts in the diet tend to lead to low estimates of relative risk (Marshall _ al., 1981~. This is particularly true for breast cancer, since estimated effects of dietary factors based on current intake are likely to be substantially below the true effect for a factor that is operational earlier in life, possibly during adolescence.
|
From page 441... ...
Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. Campbell, T
|
From page 442... ...
1978. Low dose extrapolation of animal carcinogenicity data.
|
From page 443... ...
A report prepared by the Safe Drinking Water Committee. National Academy of Sciences, Washington, D.C.
|
From page 444... ...
Scientific Committee, Food Safety Council.
|
From page 445... ...
Sixteenth Report of the Joint FAD/WHO Expert Committee on Food Additives.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.