Ames test limitations

The inhalation toxicity of NF on animals has been studied extensively (37—40). These studies provide the basis of emergency exposure limits (EEL) that have been proposed for NE. The NAS—NRC Committee on Toxicology recommends that the EEL for NE be 10 min at 2250 ppm, 30 min at 750 ppm, and 60 min at 375 ppm. Gaseous NE is considered to be innocuous to the skin and a minor irritant to the eyes and mucous membranes. NE does give a weakly positive metabotically activated Ames test but only at concentrations greater than 2% or 10 times the 10 minute EEL. 

Succinic anhydride is extremely irritating to the eyes. It causes skin, mucous membranes, and respiratory tract irritation. It may be a sensiti2er. There is no evidence of carcinogenic activity in male or female tats given 50 or 100 mg/kg succinic anhydride (186) the Ames test is negative (187). LD q in rat 1510 mg/kg. There ate no estabflshed exposure limits for ACGIH TLV or TWA. 

In order to expedite the launch of a new chemical and allow further time to complete the toxicological package for full registration, a "limited announcement" is normally used. This requkes only parts of the full toxicological packages, usually acute toxicity and Ames test. Consequentiy, it is less expensive ( 20,000) and quicker (90 days) than full registration. However, only 1 t or less of the chemical per year is allowed to be sold in the EEC. 

A variety of methods are available to test a chemical for mutagenicity, i.e., its effect on the genetic material. The Ames Test has gained most recognition as a shortterm test [23],This is a bacterial test which allows fast performance and requires limited expense. Its correlation with the mutagenicity of mammals or even with a carcinogenic effect on mammals or humans has repeatedly been tested [24], but remains controversial. 

The use of yeast cells as a eukaryotic complement to the Ames test led to the development of several protocols for the detection of mutation, gene conversion and recombination. The formal introduction of methods [23] followed by much development work from Zimmermarm s laboratory led to large systematic studies [24, 25] and OECD guidelines for the test battery (OECD 480, 481). However the assays are now rarely used, at least in part because of concerns over low sensitivity, thought to reflect limited permeability of the cell wall. 

I think those would be the logical mutagens to pursue on a name-by-name basis. Then go to Ames testing for toxicological assessment, setting limits, whether they are industrial outfalls or whatever then, having removed them from the problem, you can look at the other category that I described, for example, the question of chlorination byproducts in the absence of those industrial compounds. 

The initial limit based arbitrarily upon a known carcinogen could be relaxed upon submission of favorable short-term testing data for carcinogenicity and mutagenicity (Ames test, cell transformation, DNA repair, chromosome damage. Drosophila etc.,) The test compound could be compared to a known carcinogen (and mutagen). The new limit for the test substance would be decreased in proportion to its potency as related to the standard (e.g., bis-chloromethyl ether). 

Several preservatives have been scrutinized for being possible carcinogens, and their use regulated (e.g., chloroform and formaldehyde). Another possibility is that the preservative interacts with amines or amides to form carcinogenic nitrosamines. Published data on the mutagenicity of preservatives is limited as tests such as the Ames test can only be carried out at concentrations far less than those employed. 

Substances not on the Inventory or are not otherwise excluded or exempt are considered new and are subject to a premanufacture notice (PMN). Examples of exclusions would include mixtures, substances subject to another statute, impurities, by-products and nonisolated intermediates. Additional exemptions also include test marketing products, low volume products, polymer exemptions, LoREX (low release and exposure exemption), and R D substances. By statute, chemical manufacturers must notify the Agency at least 90 days before manufacturing a chemical substance that is not listed on the TSCA Chemical Substance Inventory. However, TSCA does not empower the US EPA to require routine testing of new chemicals to permit a valid evaluation of the potential risks. This has been a limitation in the overall effectiveness of the PMN process. Erequently, very little data accompanies the PMN (50% of submissions present no safety data and 90% have only an LD50 and an Ames test) however, the EPA must decide within 90 days if the submitted chemical will pose a health or environmental hazard. 

Manipulation of cell environment Technically easy and rapid Often trial and error often limited improvements The Ames test binary cell cultures sandwich techniques... 

Styrene tested positive in an EPA mutagenicity study. It tested positive in a histidine reversion-Ames test, Saccharomyces cerevisiae gene conversion, in vitro human lymphocyte micronuclens, and Drosophila melanogaster sex-linked lethal tests (NIOSH 1986). Carcinogenicity of styrene in humans is not known. There is limited evidence of carcinogenicity in animals for both the monomer and the polymer. 

Hillebrecht, A., Muster, W., Brigo, A., Kansy, M., Weiser, T., Singer, T. (2011). Comparative evaluation of in silico systems for ames test mutagenicity prediction scope and limitations. Chemical Research in Toxicology, 24, 843-854. 

In general, short-term tests have limitations. They do not include variables that animal studies do. It becomes difficult to use mathematical models to extrapolate test results to humans. For example, one of the notable short-term tests for carcinogens is the Ames test. The procedure uses Salmonella and the results involve dose, but not time or duration of exposure. Some people criticize the Ames test for a lack of reliability. The Ames test demonstrates high correlations between certain known carcinogens and human experience. For other carcinogens there are low correlations between test results and human experience. 

Ames test, chromosomes aberration, cytogenetic test negative Occupational exposure limit 6mg/m. ... 

Trade name Companies Modification method Fire retardant agents Tenacity (cN/dtex) Elongation (%) Melting tempe- rature (°C) Density (g/cm ) Limiting oxygen index (%) Ames test... 

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