An investigation of the potential causes for the seasonal and annual variations in indoor radon concentrations.

Indoor radon concentrations exhibit strong variations on short and long timescales. Besides human influences, meteorological factors significantly affect the radon concentrations indoors as well as outdoors. In this article, long-term measurements showing strong annual variations are presented, which take a very similar course in different buildings located in largely separated regions in Switzerland. Also, seasonal variations can be very significant. In general, variations in indoor radon levels can primarily be attributed to human influences. On the other hand, specific weather conditions can have a significant impact on indoor radon levels. In order to further investigate the connection between indoor radon levels and meteorological factors, a measuring campaign has been started in two buildings located in two different regions in Switzerland exhibiting different climatic characteristics. Preliminary results of these investigations are presented, which provide evidence for correlations between indoor radon levels and in particular outdoor temperatures, contributing to seasonal and annual as well as short-term variations in indoor radon concentrations.

Adequacy of required regulatory hazard testing for the detection of potential hormonal activity of crop protection chemicals.

The capacity of some synthetic chemicals, the so-called "endocrine-disrupting chemical," to alter hormonal activity, as well as the adequacy of the testing of chemicals to evaluate this capacity, has been called into question. Among the chemicals indicted have been certain crop protection agents or pesticides. Crop protection chemicals rank among the most closely regulated and thoroughly tested chemicals in use in both the human health and environmental hazard areas. However, it has been proposed that in vitro and in vivo screening tests be used to identify potential endocrine-active chemicals and to supplement or replace required regulatory bioassays. In vitro tests, such as receptor binding, examine a single chemical event, do not measure toxicity, post-receptor-mediated biological response, or the absorption, distribution, metabolism, and elimination of a chemical. Therefore, data derived solely from such a limited testing technique should not be used as a basis for selection of chemicals for making regulatory decisions. In vivo screening tests, such as the uterotrophic assay, which promise to provide a rapid answer to a targeted question, do not capture the complexity of the biological response. As in the case with in vitro tests, results from a single in vivo test, such as a change in uterine weight, should not be used as a basis for regulatory decision making. Further, it has been suggested that such a screening battery should be put into place for ecotoxicity testing. Yet it is well recognized that endocrine-active chemicals that affect fish and wildlife in their natural habitat have been shown to cause similar adverse effects in laboratory test animals. Therefore, these screening tests do not add value to the current regulatory test battery. Evidence is presented that demonstrates that the regulatory safety assessment paradigm has a low likelihood of missing potential endocrine-active chemicals and has served society well.

Overview of animal test methods for skin irritation.

Determining the irritant effects of chemicals in experimental animals provides the public with information on and protection against possible hazards that may arise from exposure of the human skin. Furthermore, the data obtained are used for registration and classification purposes. This paper reviews the methods proposed in the most important guidelines (OECD, EEC and FIFRA guidelines) and points out the critical experimental points. It shows that the introduction of OECD Guideline No. 404 can lead to a reduction in the number of test animals used for skin irritation testing.

Distribution of eye irritation scores of industrial chemicals.

Eye irritation results obtained in tests on agricultural and industrial chemicals (raw materials, intermediates, formulation components and sales products) were classified on the basis of an arbitrary breakdown of the scores (which ranged from 0 (no irritation) to a maximum of 110) into six categories. This showed that of the materials (about 600) tested over a 2-year period, 18-31% caused no irritation at all, 42-51% caused minimal irritation (scores of 0.1-10.9), 9-17% were classed as slightly irritant (11.0-25.9) and 8-12% as moderately irritant (26.0-55.9), while 2-6 and 1-5% came into the categories of strong and extreme irritants, respectively (with scores of 56.0-84.0 and 84.1-110). Testing of the last two groups involves the test animals in discomfort, but because of the seriousness of eye damage to man this cannot always be avoided.

Advances in the design and reporting of conventional carcinogenicity tests.

It is generally acknowledged that animal experiments provide the most important and best reliable service of information for assessing the possible carcinogenic activity of chemicals. In the past, experimental procedure has mainly concentrated on the choice of species, improved animal husbandry, the modes of exposure, test conditions and pathological examination. Although experience gained thereby indicated the necessity for further scientific exploitation of bioassay models, the rather rigid stereotyped procedures--proposed for convenience--were generally accepted and adopted. Nevertheless, continuous improvements have been made in the design of carcinogenicity tests in rodents. Current developments in test design tend to be primarily concerned with the predictive significance of carcinogenicity studies. Modern protocols call for optimum facility operation as much as for computerized support of study monitoring and data evaluation. Of particular significance are the automated handling of autopsy and histopathological data and their proper statistical evaluation. By the economical use of modern technology, cost-saving protocols can be designed for the production of the data which are essential for the reliable assessment of risk.