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PubMed1992

Regulation of existing chemicals under TSCA: information disclosure as the route to reducing risk and increasing available data.

The Toxic Substances Control Act (TSCA) empowers the Environmental Protection Agency (EPA) to regulate risk associated with the use of existing chemicals and the introduction of new chemicals into commerce. Due to a number of concerns, however, the authority to regulate existing chemicals under TSCA has enjoyed limited success. A more generic and flexible approach is needed to achieve significant risk reduction for existing chemicals. This paper presents a frame-work for a generic approach to the regulation of existing chemicals. Under this framework, EPA would officially recognize that the distribution of chemical substances without evaluating and communicating to the user how to avoid operationally undesirable exposures represents an unreasonable risk to health or the environment. Acting under the authority of TSCA, EPA would then generically require suppliers to communicate acceptable exposure levels and information regarding safe use. This framework is consistent with the express policy of TSCA, which states that development of data with respect to the effects of chemical substances and mixtures on health and the environment should be the responsibility of manufacturers and processors of chemicals. The approach outlined here is consistent with and complements initiatives of the Office of Toxic Substances (OTS) and would enable OTS to accomplish some of the fundamental goals of TSCA.

Chemical Industry↗

PubMed1997

Approaches to characterizing human health risks of exposure to fibers.

Naturally occurring and man-made (synthetic) fibers of respirable sizes are substances that have been identified by the U.S. Environmental Protection Agency (U.S. EPA) as priority substances for risk reduction and pollution prevention under the Toxic Substances Control Act (TSCA). The health concern for respirable fibers is based on the link of occupational asbestos exposure and environmental erionite fiber exposure to the development of chronic respiratory diseases, including interstitial lung fibrosis, lung cancer, and mesothelioma in humans. There is also considerable laboratory evidence indicating that a variety of fibers of varying physical and chemical characteristics can elicit fibrogenic and carcinogenic effects in animals under certain exposure conditions. This paper discusses key scientific issues and major default assumptions and uncertainties pertaining to the risk assessment of inhaled fibers. This is followed by a description of the types of assessment performed by the U.S. EPA to support risk management actions of new fibers and existing fibers under TSCA. The scope and depth of these risk assessments, however, vary greatly depending on whether the substance under review is an existing or a new fiber, the purpose of the assessment, the availability of data, time, and resources, and the intended nature of regulatory action. In general, these risk assessments are of considerable uncertainty because health hazard and human exposure information is often incomplete for most fibers. Furthermore, how fibers cause diseases and what specific determinants are critical to fiber-induced toxicity and carcinogenicity are still not completely understood. Further research to improve our knowledge base in fiber toxicology and additional toxicity and exposure data gathering are needed to more accurately characterize the health risks of inhaled fibers.

Air Pollution↗

PubMed1979

Problems associated with the application of short-term tests for mutagenicity in mass-screening programs.

The application of short-term tests for toxicological evaluation of environmental chemicals is certainly a reality in the near future as a result of the Toxic Substances Control Act, as well as other regulations under development [de Serres, 1977]. Many of the problems associated with this testing in the area of genetic toxicology are under study at the National Institute of Environmental Health Sciences in our National Toxicology Program and at the Environmental Protection Agency in their Gene-Tox Program. The other problems that I have discussed in connection with standardization of protocols, protocol review and modification, and training of personnel are not being pursued aggressively. Perhaps with their definition and acceptance as meaningful problems, mechanisms will be established for their resolution. It is in these latter areas that I hope that this society can provide the forceful leadership that will result in their resolution in the near future.

Animals↗

PubMed1993

Documenting temporal trends of polychlorinated biphenyls in the environment.

In the 15 years since the regulation of polychlorinated biphenyls (PCBs) in the United States, numerous studies have been undertaken to assess PCB levels in the environment. This report reviews the available data from published literature and government agency reports on temporal trends of PCB levels in various environmental compartments. Adequate data were identified to discuss PCB trends in foods for human consumption, human adipose tissue, human blood sera, various fish species, and shellfish. The review found that PCB levels in the human diet currently are less than 1% of the levels detected in the early 1970s as measured by the nationwide Total Diet Study of the FDA. Similarly, EPA data indicate a decrease in the percentage of persons with over 1 ppm of PCBs in adipose tissue from 62% in 1972 to 2% in 1984 when the study was terminated. Studies by the National Oceanic and Atmospheric Administration (NOAA) and other groups have shown a 2- to 10-fold decline in PCB contamination in fish and shellfish from the early 1970s to the late 1980s. The most dramatic declines across all environmental compartments appear in the late 1970s to the mid-1980s which corresponds to the time frame when regulatory controls were imposed by the Toxic Substances Control Act (TSCA). These declines are expected to continue but at slower rates.

Animals↗

PubMed1991

Impact of present and future regulations on bioremediation.

Innovative treatment technologies are in increasing demand to clean up the nation's existing environmental contamination. There also are mounting pressures for industry to minimize the production or generation of hazardous pollutants. Bioremediation is a viable, cost-effective treatment option for both field remediation and treatment in enclosed systems. The use of innovative treatment technologies is largely regulatory driven. Over the last two decades, at least a dozen Federal environmental statutes have been enacted and hundreds of regulations implemented to control releases of pollutants into the air, water and on land. These statutes not only have created markets for the use of treatment technologies, they also may regulate some aspect of the application of that technology. Regarding bioremediation, four statutes should be reviewed to determine if compliance is necessary before employing microorganisms in the field or in enclosed systems. This paper summarizes the Federal statutes (i.e., the Toxic Substances Control Act (TSCA); the Resource Conservation and Recovery Act (RCRA); the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA); and the Federal Plant Pest Act (FPPA], and regulations that may impact the bioremediation industry; outlines potential markets for bioremediation that are being driven by regulations; and highlights, within the regulatory framework, promising applications for the bioremediation of hazardous wastes.

Biotechnology↗

PubMed1985

Heavy metal toxicity to microbe-mediated ecologic processes: a review and potential application to regulatory policies.

Microorganisms are sensitive to heavy metal pollution as are other components of the biota. However, most studies on the interactions between microbes and heavy metals have been conducted in synthetic media or in altered (e.g., sterilized) environmental samples and usually have used only single species. Few studies have evaluated the effects of heavy metals on the activities of natural heterogeneous microbial populations, both autotrophic and heterotrophic, in terrestrial and aquatic environments. These latter studies have shown that heavy metals inhibit primary productivity, nitrogen fixation, the mineralization of carbon, nitrogen, sulfur, and phosphorus, litter decomposition, and enzyme synthesis and activity in soils, sediments, and surface waters. The potential adverse effects of heavy metals on such microbe-mediated ecologic processes need to be incorporated into the methodologies used by regulatory agencies, such as the U.S. Environmental Protection Agency, to prepare environmental risk assessments which, in turn, are used to formulate environmental criteria, such as the Water Quality Criteria, and to evaluate the safety to the environment of exposure to "new chemical substances," as mandated by the U.S. Toxic Substances Control Act of 1976. To provide appropriate data that can be assimilated into regulatory policy, it is essential that microbial ecotoxicity tests be standardized, are neither costly nor difficult to train personnel to conduct, and produce data that can be quantitated.

Bacteria↗

PubMed1989

Expert systems survey on biodegradation of xenobiotic chemicals.

To determine the feasibility of developing an expert system for biodegradability assessment, a survey was conducted in which biodegradation experts were asked to estimate rates and products of degradation for 50 chemicals. These chemicals, which varied widely in structure, were considered representative of the spectrum of premanufacture notice chemicals subject to EPA review under the Toxic Substances Control Act. There was substantial agreement among the 22 experts on both sites of initial attack and rates of degradation. The approximate order in which various groups were viewed as contributing to aerobic biodegradability is as follows: ester, amide, anhydride greater than hydroxyl greater than carboxyl, epoxide, site of unsaturation greater than benzene ring, methyl, methylene. Hydrolyzable groups, azo bonds, halogens, and nitro groups were preferred sites of anaerobic attack. Among the negative influences on aerobic biodegradability were molecular mass, branching, halogenation, and nitrogen heterocycles. Results also indicate that estimates of removal by biodegradation in aerobic wastewater treatment and time for aerobic ultimate and primary degradation were well correlated, and that the predictive value of such correlations could be improved using correction factors for certain classes of chemicals. The results lend support to existing rules of thumb, but also offer additional insight that will prove useful in designing a prototype system.

Biodegradation, Environmental↗

PubMed1991

Performance of on-line chemical property estimation methods with TSCA premanufacture notice chemicals.

CHEMEST is an interactive on-line system for estimating chemical properties important in environmental fate assessment. In 1988 we described an extensive validation study of CHEMEST. That study showed that for existing chemicals, most properties could be estimated with accuracy sufficient for screening-level assessment. Reported here are the results of a study of system performance with "new" chemicals, for which Premanufacture Notices (PMNs) must be submitted under the Toxic Substances Control Act. Measured values of key properties were retrieved for more than 300 PMN chemicals having discrete structures, which represented the majority of notices with submitted data that were received by the U.S. Environmental Protection Agency during the period 1979-1990. The measured values were compared to estimates from AUTOCHEM, an automated version of CHEMEST. Errors were generally greater than those for existing chemicals, as expected. Water solubility and the octanol/water partition coefficient (Kow) were estimated with acceptable accuracy, but the results for melting point and boiling point indicate that additional effort is needed to improve the estimation methods.

Chemical Industry↗

PubMed1983

Thresholds for carcinogenesis and their significance to medical practice.

The Delaney Amendment covering the addition of carcinogens to foods, the Toxic Substances Control Act governing the release of carcinogens into water, and other regulations are based on a "no-threshold" concept. That is, they assume that any level above zero will induce cancer in an exposed population. The threshold concept holds that zero risk occurs at or below some finite exposure which is greater than zero. This paper shows that thresholds for carcinogenesis are in accord with common medical experience, and discusses the medical implications of thresholds.

Adult↗

PubMed1995

Development of structure-activity relationship rules for predicting carcinogenic potential of chemicals.

Since the inception of Section 5 (Premanufacturing/Premarketing Notification, PMN) of the Toxic Substances Control Act (TSCA), structure-activity relationship (SAR) analysis has been effectively used by U.S. Environmental Protection Agency's (EPA) Structure Activity Team (SAT) in the assessment of potential carcinogenic hazard of new chemicals for which test data are not available. To capture, systematize and codify the Agency's predictive expertise in order to make it more widely available to assessors outside the TSCA program, a cooperative project was initiated to develop a knowledge rule-based expert system to mimic the thinking and reasoning of the SAT. In this communication, we describe the overall structure of this expert system, discuss the scientific bases and principles of SAR analysis of chemical carcinogens used in the development of SAR knowledge rules, and delineate the major factors/rules useful for assessing the carcinogenic potential of fibers, polymers, metals/metalloids and several major classes of organic chemicals. An integrative approach using available short-term predictive tests and non-cancer toxicological data to supplement SAR analysis has also been described.

Animals↗

PubMed1981

Development of a format for abstracting dose-response information from published studies for use in quantitative structure-activity relationships (QSARs).

The Toxic Substances Control Act subjects some 70 000 chemicals to regulatory action. However, empirical testing of the biological activities of this number of compounds is not feasible. An attractive alternative is the development of predictive methodology which can be used to estimate the potency of an untested compound toward a specific biological receptor. Prerequisite to such an enterprise is the highly systematic compilation of dose-response information for a wide range of biological end points and for a wide variety of molecular species. A format is described for abstracting relevant information from published studies. The format outlines the test system, experimental conditions, response analysis, exposure protocol, and results and presents the original data, all in an organized form. Regression analysis is used to estimate thresholds and potencies in the various test systems. The data may then be used to develop a predictive methodology.

Computers↗

PubMed1981

Evaluation of an information retrieval system for assessment of toxicological effects of chemicals on fish, wildlife, and ecosystem components.

A user-oriented information retrieval system is needed for assessment of materials hazardous to fish, wildlife, food chain organisms, and other organisms essential to the maintenance to ecosystem processes and functions. Critical evaluation of data also requires rigorous documentation of test conditions, precision of methods used, and the sensitivity of the test organism. Particular emphasis of the evaluation was in developing practical criteria that aid in the use and interpretation of data with respect to need for further testing in a scoring exercise performed for the Toxic Substances Control Act Interagency Testing Committee. Recommendations are made for the integration of information on physical and chemical properties, health effects, ecotoxicology, and environmental concentration or exposure level.

Animal Population Groups↗

PubMed1985

Method for estimating the human and environmental exposure potential of chemicals having designated uses.

This paper describes a methodology that was designed to assist the Environmental Protection Agency in setting priorities for regulating chemicals in accordance with requirements of the Toxic Substances Control Act by indicating the extent of exposure potentially associated with a particular use of a chemical. Development and application of the methodology to actual chemical uses proceeded in four stages: (1) development of an exposure classification scheme, (2) development of a chemical use list, (3) assignment of exposure category scores to chemical uses, and (4) merging of exposure scores into ranked groups, creating the Index of Exposure. The purpose of the Index was to identify those chemical uses having the greatest potential for human and environmental exposure. Theoretically, the objectivity of the scoring methodology is such that, given the same data for a chemical use, different scorers will be able to arrive at the same exposure score for that use.

Environmental Exposure↗

PubMed1999

Correlative and mechanistic QSAR models in toxicology.

An outline is provided on the development and use of correlative and mechanistic approaches to predictive toxicology, with particular emphasis on the experience at the U.S. EPA as applied to assessing the potential hazard posed by new industrial chemicals for which little or no test data are provided under the Toxic Substances Control Act. This information is presented with a historical perspective.

Animals↗

PubMed1980

Design of a computerized chemical information file in response to the initial inventory requirements of TSCA.

A computerized file of chemical information, "CHEMFO", was developed at BASF Wyandotte Corporation to help comply with the initial reporting requirements of the Toxic Substances Control Act. This organization and approach allowed collecting the required information on all the manufactured and imported chemicals, editing and entry of the data, structuring of the computer file and interactive capabilities, and selecting the final program and subsequent printout. Besides using this system to meet the TSCA initial inventory reporting requirements, the file also has the capacity to be updated and revised as needed, which further expands its potential benefits. Some of the other information that can be derived from this system are: identification of chemical substances, quantities, and each site; tie-in to the medical/occupational health data bank; foundation for recording the industrial hygiene monitoring data; supplement for toxicology and environmental data base; and index for generating compilation of site specific material on health and environmental information.

Chemical Industry↗

PubMed1982

What industrial hygienists should know about TSCA.

Direct participation of industrial hygiene personnel in planning and implementing compliance with several pertinent sections of the Toxic Substances Control Act (TSCA) is warranted. TSCA is administered by the Environmental Protection Agency and there is a variety of areas in which industrial hygiene input is and will be required. Major sections of TSCA which require industrial hygiene participation include Testing, Premanufacture Notices (PMNs), Regulation of Hazardous Chemicals, and Reporting and Recordkeeping. The industrial hygiene input requires interaction with other groups such as Toxicology, Environmental, Government Regulations, Legal, Medical, Research and Development, Marketing and Manufacturing in order to provide a comprehensive response to and compliance with current and anticipated TSCA rules.

Chemical Industry↗

PubMed1994

Evaluation of chemical releases and worker exposures from filter press operations.

The exposures (inhalation and dermal) and releases (air, water, solids, and process streams) associated with the filtration of industrial wastewater sludge from an electronics manufacturing plant were characterized. Chemical releases and worker exposures for a target chemical (total copper) were measured over four operational cycles. Various aspects of the filtration operation believed to influence the measurement values were documented. Worker exposures associated with the discreet stages of the filter operation were measured. Ventilation patterns around the filter press were also monitored. The workers' time-weighted average exposures to total copper during the 113-minute operational cycle ranged from 3.1 to 25 micrograms/m3 (2.2 geometric standard deviation, 6.4 micrograms/m3 geometric mean concentration). The manual removal of filter cake comprised only 15% of the time in an average filtration cycle, but produced 72% of the workers' inhalation exposure. During this cake-removal stage, inhalation exposures ranged from 11 micrograms/m3 to 130 micrograms/m3 (2.5 geometric standard deviation, 30 micrograms/m3 geometric mean concentration). Differences in worker technique may account for the large range of inhalation exposures during the cake-removal stage. Exposures and releases were successfully determined for a single unit operation, as well as for the discreet stages of operation. The data generated will enable EPA to more accurately estimate worker exposures and chemical releases for new chemicals as required by the Toxic Substances Control Act. The approach utilized will benefit industrial hygienists in providing estimates of worker exposures and aid in the targeting of survey sampling.

Air Pollution↗

PubMed2006

Nature of the binding interaction for 50 structurally diverse chemicals with rat estrogen receptors.

This study was conducted to characterize the estrogen receptor (ER)-binding affinities of 50 chemicals selected from among the high production volume chemicals under the U.S. EPA's (U.S. Environmental Protection Agency's) Toxic Substances Control Act inventory. The chemicals were evaluated using the rat uterine cytosolic (RUC) ER-competitive binding assay, with secondary analysis using Lineweaver-Burk plots and slope replots to confirm true competitive inhibition and to determine an experimental K(i). Data from these ER-competitive binding assays represent the types of competitive binding curves that can be obtained when screening chemicals with broad structural diversity. True competitive inhibition was observed in 17 of 50 chemicals. Binding affinities were much lower than that of estradiol (E(2)) with K(i) concentrations ranging from 0.6 to 373 microM as compared with that of E(2) (0.77 nM). Other chemicals that appeared to displace radiolabeled E(2) binding to ER were, in fact, found not to be competitive inhibitors in the secondary K(i) experiments. These seven chemicals likely altered the stability of the assay by changing the buffer pH, denaturing ER, or disrupting the ER-binding kinetics. Thus, several conditions that may confound interpretation of RUC ER-binding assay data are illustrated. For another group of eight chemicals, neither an IC(50) nor K(i) could be determined due to solubility constraints. These chemicals exhibited slight (20-40%) inhibition at concentrations of 10-100 microM, suggesting that they could be competitors at very high concentrations, yet K(i) experiments were not possible as the limit of chemical solubility in the aqueous assay buffer was well above the IC(50). An additional 18 of the 50 chemicals were classified as nonbinders because in concentrations up to 100 microM they produced essentially no displacement of radiolabeled E(2). These results show that although the ER-competitive binding assay is a valuable tool for screening chemicals, secondary tests such as a double reciprocal Lineweaver-Burk experiment with slope replot should be used to confirm true competitive inhibition. This information will be useful for the ongoing validation of the RUC ER-competitive binding assay under the U.S. EPA's Endocrine Disruptor Screening Program, as well as to support research efforts to develop computational models designed to identify chemicals with the ability to bind to ER.

Animals↗