Toxicity Testing Strategies to Determine Needs and Priorities (1984) / Chapter Skim
Currently Skimming:
2. SAMPLE SELECTION
2. SAMPLE SELECTION
Pages 33-50
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 33... ...
The committees' decision was based on a desire to include to the fullest feasible extent the substances of possible interest to NTP; to avoid the unnecessary inclusion of substances not of interest to NTP; to choose a select universe that, through analysis, most completely reflects true toxicity-testing needs; and to take advantage of chemical-name lists that were computerized, are associated with CAS Registry numbers, and permit retrieval for sampling purposes. In consideration of these factors, the committees established the select universe by identifying five classes of chemicals: (1)
|
From page 34... ...
The sizes, contents, and formats of the lists varied. The lists of pesticides and inert ingredients in pesticide formulations, cosmetic ingredients, drugs and excipients used in drug formulations, and food additives had characteristics, such as use functions, that were more consistent internally than the characteristics of the TSCA Inventory of chemicals in commerce.
|
From page 35... ...
us :~ o In In i as c)
|
From page 37... ...
to the randomized chemicals in each category of the sample, in sequential order of randomization , On the basis of the screen, select a subsample of predetermined size from each category consisting of substances with minimal toxicity information that appear first in the randomized sample (see Table 1) FIGURE 1 Process used to draw sample and subsample from select universe 37
|
From page 38... ...
The list of registered inert ingredients contains 1,132 ingredients that are present in pesticide formulations, but have no claim of pesticidal action (not necessarily implying that they might not have adverse ef feats on human health) ; because of the potential for human exposure to pesticide-formulation ingredients, the inert ingredients were included in the select universe.
|
From page 39... ...
Furthermore, other lists of international scope may have different sizes and contents, because different criteria were used in placing substances on them. FOOD ADDITIVES The FDA Bureau of Foods chemical dictionary was used.
|
From page 40... ...
13 codes were animal-drug additives, food additives, biologics, cosmetic-label ingredients, cosmetic substances, indirect food additives (temporary file) , drugs for human use, industrial chemicals, pesticide chemicals, and trade names for food additives, human drugs, pesticides, and veterinary drugs.
|
From page 41... ...
Although, on the basis of reported production volumes, gasoline is the leading substance and most of the next 10 high-volume substances are also petroleum products, some agents that are major fractions of mixtures are not reported as individual chemicals, but rather as parts of mixtures (e.g., benzene in gasoline)
|
From page 42... ...
The Committee on Sampling Strategies believes that the sampling plan it adopted satisfies the competing demands and constraints efficiently. However, two issues required additional discussion: o The partition of the sample among the various lists and sublists.
|
From page 43... ...
The Committee further decided that a 10:10:20 split of the 40 substances from the TSCA Inventory would allow at least minimal inferences regarding specific subcategories, roughly in proportion to the expected need for information on their toxicity. These samples are probably at the lower limit of sample sizes that are usable for the present purposes; making some groups larger at the expense of other groups would have eliminated the latter from separate consideration, although they would still have contributed to inferences regarding the whole select universe.
|
From page 44... ...
All 675 entities in the sample were screened to identify substances on which there was minimal toxicity information. The 675 substances were distributed among the seven categories of the select universe in a proportion of 50:100:50:100:125:125:125, representing pesticides {active ingredients and registered inert ingredients of pesticide formulations)
|
From page 45... ...
However, the Committee on Sampling Strategies paid special attention to this aspect of the sampling method and concluded that the effect of the systematic sampling was negligible and that, for variance purposes, the sample was obtained by a simple random process within seven strata. SCREENING THE SABLE FOR MINIMAL TOXICITY INFORMATION After the selection of substances for the sample, each entry in each category was assigned a random number.
|
From page 46... ...
me criteria for minimal toxicity information presented in Table 3 were delineated by the Committee on Toxicity Data Elements. That committee recommended that a combination of toxicity assays as described in the table -- acute, chronic, subchronic, genetic, and reproductive or developmental, each including human and animal studies -- be considered to constitute minimal toxicity information.
|
From page 49... ...
offer toxicity data extracted from published research findings. TOXLINE houses 11 subfiles, including those generated for chemical-biologic activities, air pollution and industrial hygiene, toxicity bibliography abstracts on health effects of environmental pollutants, pharmaceutical abstracts, pesticide abstracts, Environmental Mutagen Information Center and Environmental Teratology Information Center files, and the toxicology section of Chemical Abstracts.
|
From page 50... ...
-- If the requirement still was not met after all preceding parts of the search strategy, the books and other resources of TIC were used -- at least two appropriate toxicology reference books in each case. In this manner, 100 substances constituting a subsample with minimal toxicity information as defined by the Committee on Toxicity Data Elements were selected from a larger, randomly ordered, stratified sample of 675, which was itself a product of a large select universe of 65,725 listings.
|
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.