The useful properties of thousands of chemicals provide a wide range of benefits to American consumers and bolster the U.S. economy. However, experiences with certain chemicals—for example, DDT, leaded gasoline, and asbestos—have shown that adverse effects sometimes occur when there is insufficient information about potential toxicity and widespread human or wildlife exposure. Various statutes have been enacted to gather information about chemicals produced, sold, and used in the United States and to control associated risks. This report focuses on the Toxic Substances Control Act of 1976 (TSCA). Recent legal, scientific, and technological developments are prompting legislators to reexamine TSCA; it has been the subject of a hearing and several legislative proposals in the 111 th Congress. This is a change from the situation that prevailed in most of the previous 30 years since it was enacted; during that time, most legislators demonstrated little interest in amending the law, despite the long-standing concerns of a few Members. The basic TSCA Title I provisions concerning chemical regulation have never been amended. Companion bills in the 110 th Congress, H.R. 6100 and S. 3040 , would have amended TSCA to significantly reshape U.S. chemical assessment and management. This report provides an overview of basic TSCA provisions, briefly examines the history of TSCA implementation by the U.S. Environmental Protection Agency (EPA), and describes the legal, scientific, and technological developments that are being used to provide support to calls for TSCA reform. Federal legislation to regulate U.S. commerce in chemical substances was originally proposed in 1971 by the President's Council on Environmental Quality (CEQ). Its report, "Toxic Substances," defined a need for comprehensive legislation to identify and control chemicals whose manufacture, processing, distribution, use, and/or disposal was potentially dangerous, and not adequately regulated under other environmental statutes. The House and Senate each passed bills in both the 92 nd and 93 rd Congresses (in 1972 and 1973, respectively), but controversies over the scope of chemical screening prior to commercial production and distribution, level of costs, and the relationship to other regulatory laws stalled final action. Episodes of environmental contamination—including contamination of the Hudson River and other waterways by polychlorinated biphenyls (PCBs), the threat of stratospheric ozone depletion from chlorofluorocarbon (CFC) emissions, and contamination of agricultural produce by polybrominated biphenyls (PBBs) in the state of Michigan—together with more exact estimates of the costs of imposing toxic substances controls, opened the way for final passage of the legislation. President Ford signed TSCA into law on October 11, 1976. Title I contains the original, general provisions of TSCA, which are the subject of this report. TSCA established three general federal policies with respect to chemical substances and mixtures in U.S. commerce, "... that— •    [A]dequate data should be developed with respect to the effect of chemical substances and mixtures on health and the environment and that the development of such data should be the responsibility of those who manufacture and those who process such chemical substances and mixtures; •    [A]dequate authority should exist to regulate chemical substances and mixtures which present an unreasonable risk of injury to health or the environment, and to take action with respect to chemical substances and mixtures which are imminent hazards; and •    [A]uthority over chemical substances and mixtures should be exercised in such a manner as not to impede unduly or create unnecessary economic barriers to technological innovation while fulfilling the primary purpose of this act to assure that such innovation and commerce in such chemical substances and mixtures do not present an unreasonable risk of injury to health or the environment." In addition, Congress expressed its intent in TSCA, Section2(c): It is the intent of Congress that the Administrator shall carry out this Act in a reasonable and prudent manner, and that the Administrator shall consider the environmental, economic, and social impact of any action the Administrator takes or proposes to take under this Act. The scope of TSCA is very broad, covering all "chemical substances," as defined in Section 3(2). ... the term "chemical substance" means any organic or inorganic substance of a particular molecular identity, including— (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature, and (ii) any element or uncombined radical. The law excludes from this definition substances that are otherwise regulated, such as mixtures, pesticides, tobacco, nuclear material, substances subject to certain taxes (e.g., alcohol), and food, drugs, cosmetics, and devices regulated under the Federal Food, Drug, and Cosmetic Act. To attain these policy goals, TSCA Section 4 directs EPA to require chemical manufacturers and processors to conduct tests for existing chemicals if: (1) the manufacture, distribution, processing, use, or disposal of the chemical "may present an unreasonable risk" of injury to health or the environment; or (2) the chemical is produced in very large volume and there is a potential for a substantial quantity to be released into the environment or for substantial or significant human exposure. Under either condition, EPA must issue a rule requiring tests (known as a test rule) if: (a) existing data are insufficient, and (b) testing is necessary to develop the data. Because there were roughly 61,000 chemicals covered by TSCA and in U.S. commerce at the time EPA was to begin developing test rules, Congress established a special interagency committee to help EPA determine which chemicals should be considered first, and to coordinate testing needs and efforts among government agencies. At least every six months the Interagency Testing Committee (ITC) must consider candidate chemicals for inclusion on a list of substances that the ITC recommends to EPA for development and promulgation of test rules. TSCA directs the ITC to "designate" a subset of chemicals for EPA action within 12 months. In response to a new listing on this Priority Testing List of chemicals designated for testing, EPA is required to publish a Federal Register notice within 12 months either to propose a test rule, or to provide reasons for not doing so. The Priority Testing List can contain no more than 50 designated chemicals at any time. EPA also is authorized under TSCA Section 8 to collect existing information about chemicals to help evaluate the potential risks of exposure. Section 8(a) allows EPA to issue rules requiring record keeping and reports by manufacturers and importers for specified chemicals. Required elements of such reports may include the chemical identity, molecular structure, and names; categories of use; amount manufactured or processed and expected to be manufactured or processed; description of any byproducts; existing environmental and health effect data; number of individuals exposed occupationally and duration of exposure; and the manner of its disposal. TSCA Section 8(c) requires chemical manufacturers, processors, and distributors to maintain records of "significant adverse reactions to health or the environment ... alleged to have been caused by the substance or mixture." All records must be maintained for five years, and records of employee allegations must be kept for 30 years. Under Section 8(d), EPA must require that manufacturers submit lists of unpublished health and safety studies known to have been conducted, and copies of such studies. Finally, Section 8(e) requires that any commercial chemical manufacturer, processor, or distributor who has information that "reasonably supports the conclusion that such substance or mixture presents a substantial risk of injury to health or the environment" must immediately inform EPA. Other data may be collected through federal research programs. TSCA Section 10 directs EPA to conduct and coordinate among federal agencies research, development, and monitoring that is necessary to the purposes of the act. In addition, TSCA Section 27 authorizes research and development of test methods for chemicals by the Public Health Service in cooperation with EPA. EPA is required to prevent future risks through pre-manufacture screening and regulatory tracking of new chemical products. Section 5 of TSCA requires manufacturers, importers, and processors to notify EPA at least 90 days prior to producing or otherwise introducing a new chemical product into the United States. At the same time, those submitting a Pre-Manufacture Notice (PMN) also must submit any information or test data that are known to, reasonably ascertainable by, or in possession of the notifier, and that might be useful to EPA in evaluating the chemical's potential adverse effects on human health or the environment. Exemptions from these requirements are provided or allowed upon application under certain circumstances. For existing chemicals, a similar notification procedure may be required, if the Administrator has determined by rule that new uses of a particular chemical may produce significant changes in human and environmental exposures and therefore require notification. The 90-day notice required by a Significant New Use Rule (SNUR) provides EPA with the opportunity to evaluate the chemical use and, if necessary, to prohibit or limit such activity before it occurs, to prevent unreasonable risk of injury to human health or the environment. EPA has 90 days after notification (or up to 180 days if it extends the period for good cause) to evaluate the potential risk posed by the chemical that is the subject of a PMN or SNUR. If EPA determines that there is a reasonable basis to conclude that the substance presents or will present an unreasonable risk, the Administrator must promulgate requirements to protect adequately against such risk. EPA may determine that the proposed activity related to a chemical may present an unreasonable risk based on the available scientific evidence with respect to potential for exposure and adverse effects, or, when no data exist to document such effects, on what is known about the effects of chemicals with similar chemical structures. The latter method, known as structure-activity relationship analysis, often is used to screen new chemicals.