Preemption raises complex issues of law, policy, and federalism. Under the Supremacy Clause of the U.S. Constitution, state law and policy (or law and policy of local subdivisions of states, acting under state law) that conflicts with federal law must yield to the exercise of Congress's powers. Whether a certain state action is preempted by federal law is a question of congressional intent. When it acts, Congress can preempt state action within a field entirely, allow for states to act freely, or permit state action to any intermediate degree. Federal statutes relating to protection of the environment and public health have taken a diverse range of approaches to preemption ranging between these two extremes of field preemption and no preemption. The Toxic Substances Control Act (TSCA), which defines the authority of the Environmental Protection Agency (EPA) to assess and regulate chemical substances in U.S. commerce, takes an intermediate approach. An overview of TSCA as a whole is necessary to place TSCA's preemption provisions in context. For more information, see CRS Report RL31905, The Toxic Substances Control Act (TSCA): A Summary of the Act and Its Major Requirements , by [author name scrubbed]. TSCA establishes a chemical regulatory program allowing EPA to review new chemical substances before they enter U.S. commerce, as well as significant new uses of chemical substances as designated by EPA (§5); to regulate chemicals in commerce that EPA determines to present unreasonable risks of injury to human health or the environment, using the least burdensome requirements that adequately protect against such risks (§6); and to require testing on chemicals that may present an unreasonable risk, or that merit testing by virtue of certain high production volume or high exposure potential criteria (§4). TSCA also authorizes and mandates that EPA require reporting of certain information on chemicals by manufacturers (including importers), processors, and sometimes distributors, and to maintain an inventory of chemicals and substances that have commenced non-exempt manufacture or import in the United States (§8). In addition, among other provisions, TSCA requires EPA to maintain confidentiality of trade secrets and privileged or confidential business information in a particular manner (§14), coordinate with other federal agencies and EPA offices (§9), and respond to citizens' petitions (§21). TSCA's core provisions (Title I) have not been significantly amended since the law's enactment in 1976. It is also important to note that TSCA applies to "chemical substances" (defined in §3). To avoid overlapping with other federal statutes, TSCA defines this term to exclude certain categories of materials and substances from its scope. Substances when used in pesticides, foods (including ingredients and additives), food contact substances (such as containers), personal care products, tobacco, nuclear materials, firearms, and shells and cartridges are not within the scope of TSCA—or consequently, within the scope of TSCA preemption. TSCA's preemption provisions (§18) base preemption on certain actions taken by EPA under a handful of specified statutory provisions. So long as EPA has not specifically addressed a chemical under TSCA, there is no preemption of state regulation of that same chemical. When EPA does take certain actions regarding a chemical, TSCA provides for preemption of duplicative testing requirements and of non-identical state regulations, other than total bans or disposal regulations, unless the state regulations are adopted under other federal laws or an exemption is granted. Specifically, TSCA Section 18(a) provides the following: If EPA promulgates a rule under TSCA Section 4 requiring manufacturers or processors of a chemical substance to conduct testing on that substance to develop data on its health and environmental effects, then a state or political subdivision cannot establish or continue its own testing requirement rule for that chemical substance "for purposes similar to those for which testing is required" by EPA. EPA has issued testing rules for several hundred chemicals under Section 4. These would preempt similar testing requirements by states, but research has uncovered no cases finding preemption of state testing requirements by EPA testing rules. If EPA prescribes a rule or order under TSCA Section 5 (new chemicals) or Section 6 (existing chemicals), which is designed to protect against a risk of injury to health or the environment associated with a chemical substance, then a state or political subdivision cannot establish or continue any non-identical requirement applicable to the same chemical substance (or article containing such chemical substance) that is designed to protect against the same risk. Since 1976, EPA has promulgated rules imposing restrictions to protect against risk of injury to health or the environment from six existing chemicals under Section 6 of TSCA and four new chemicals under Section 5(f). These few EPA rules have not preempted many state or local requirements. Because these are the only bases for preemption, EPA information-gathering rules under Section 8, or actions under any other section of TSCA, do not preempt state or local actions. Pursuant to exceptions, any preemption by EPA rules or orders under Sections 5 or 6 would not extend to the following: State regulations on the manner or method of disposal of chemicals; an EPA rule pertaining to disposal has no preemptive effect. State requirements that are identical to federal requirements, enabling states to provide additional enforcement (co-enforcement) of those requirements. State requirements that are adopted under the authority of any other federal law. Complete prohibitions on the use of particular chemicals within a state's jurisdiction. However, a state cannot prohibit the chemical's use in manufacturing or processing of other substances. TSCA Section 18(b) allows a state to apply to EPA for an exemption to allow a more stringent state chemical risk management regulation that would otherwise be preempted. EPA may, by rule, grant such an exemption so long as compliance with the state requirement would not cause a violation of the federal requirements for the chemical; would provide a significantly higher degree of protection from risk; and would not "unduly burden interstate commerce." It appears that no exemption rule has ever been issued. Section 18 of TSCA does not expressly preempt or affect lawsuits regarding chemical exposures under common law. Nonetheless, courts would generally interpret preempted "requirements" to include state common law. Thus, it is possible, for example, that a defendant's compliance with TSCA could provide a viable preemption defense to a lawsuit, if the common law or statutory requirement forming the basis for the lawsuit were designed to protect against the same risk as an EPA rule or order under TSCA Sections 5 or 6. The division of federal and state authority over chemicals is also affected by the lack of express authority, in Section 18 or elsewhere, for EPA to share with states any trade secret information that it collects that is confidential under TSCA Section 14. Legislative efforts to revise TSCA's chemical regulatory framework date back at least to 2005. The legislative proposals that have been discussed over this time generally would preserve the basic organization of TSCA Title I; for example, provisions related to testing would remain in Section 4, new chemicals and new uses in Section 5, regulation of existing chemicals in Section 6, and preemption in Section 18. They would also generally continue TSCA's exclusion of specified categories of substances regulated under other laws. Yet the proposals would make significant changes to the operation of TSCA. The proposals differ in various respects from one another, however, including with respect to preemption. In the 114 th Congress, S. 697 , the Frank R. Lautenberg Chemical Safety for the 21 st Century Act, was introduced on March 10, 2015. A hearing on the bill was held before the Senate Environment and Public Works Committee on March 18, 2015. Following a markup, an amended version of S. 697 was ordered to be reported out of the committee on April 28, 2015, on a 15-5 vote with bipartisan support. S. 697 was reported with an amendment in the nature of a substitute on June 17, 2015, and placed on the Senate legislative calendar. An alternate proposal, S. 725 , the Alan Reinstein and Trevor Schaefer Toxic Chemical Protection Act, has not been ordered to be reported out of committee. S. 725 would eliminate express preemption from TSCA entirely, and is not included in this report's comparison. In the House of Representatives, a discussion draft entitled the TSCA Modernization Act of 2015 was released in early April, and a hearing was held in the Subcommittee on Environment and the Economy of the Committee on Energy and Commerce on April 14, 2015. After some revisions, the House discussion draft was approved by the subcommittee on May 14, 2015, on a 21-0 voice vote, also on a bipartisan basis. The TSCA Modernization Act of 2015 was formally introduced, with some amendments, on May 26, 2015, as H.R. 2576 and referred to the full committee on Energy and Commerce. The committee ordered the bill to be reported on June 3, 2015, on a 47-0 vote, with one abstaining, and the bill was reported on June 23, 2015. The bill, as amended, was debated on the House floor and passed the House on June 23, 2015, on a 398-1 vote. S. 697 and H.R. 2576 address many of the same topics and provisions of TSCA, with important similarities and differences in their approaches. For additional discussion of select issues addressed by the bills, see CRS Report R44434, Proposed Amendments to the Toxic Substances Control Act (TSCA) in the 114th Congress: H.R. 2576 Compared with the Senate Substitute Amendment , by [author name scrubbed] and [author name scrubbed]. S. 697 generally takes a more comprehensive and detailed approach to amending TSCA. It would add, among other new definitions, a definition of the term "safety standard" to mean a standard that ensures, without taking into consideration cost or other nonrisk factors, that no unreasonable risk of injury to health or the environment, including to any relevant "potentially exposed or susceptible population," will result from exposure to a chemical substance under the conditions of use. EPA would be required to establish a risk-based screening process to identify chemicals as high or low priorities for assessment, and then to conduct assessments on the high priority chemicals, with at least 25 assessments initiated by five years after enactment (along with other deadlines). Chemicals found not to meet the safety standard would have to be regulated; EPA would not be limited to the "least burdensome requirements" as under current TSCA, although it would have to take into account costs, benefits, and alternatives. S. 697 would make changes to the new chemical provisions, including imposing new duties on EPA to review such chemicals against the safety standard. New provisions on policies and guidance, including pertaining to use of science, would also impose duties on EPA. Based on amended reporting requirements, EPA would be required to identify chemicals that have not recently been in U.S. commerce as "inactive." H.R. 2576 would make fewer changes to TSCA. Unlike S. 697 , it would not change TSCA's new chemical provisions. Nor would it add a detailed new prioritization scheme for evaluating chemicals (although EPA could likely continue its existing prioritization efforts, the TSCA Work Plan for Chemical Assessments). Similar to S. 697 , H.R. 2576 would prohibit EPA from taking into account information on cost and other factors not directly related to health or the environment in conducting risk evaluations, give EPA a mandate and framework to conduct such risk evaluations, and remove the "least burdensome requirements" language from TSCA's risk management provisions for chemicals found to present an unreasonable risk. H.R. 2576 would instead require that chemical rules be cost-effective, unless EPA determines that additional or different requirements are necessary to protect against the identified risk. EPA would have to initiate at least 10 risk evaluations per year, subject to the availability of appropriations. While doing so in different ways, both bills would also generally expand EPA's testing authority; impose certain requirements pertaining to scientific standards; modify TSCA's confidentiality provisions; expand TSCA's fee provisions; and make certain other changes and additions to other sections of the law—although as noted above, S. 697 would make substantially more changes and additions. Table 1 below provides a side-by-side comparison of the preemption provisions and other provisions related to the state-federal relationship in these two bills. Table 1 first describes limits on the universe of state or local rules that would potentially be subject to preemption by EPA actions by comparing the bills' overall preemption scope, exceptions, and savings clauses. These are broadly similar, with some differences at the margins; most notably, both would retain TSCA's chemical-by-chemical preemption approach. Table 1 then compares the scope and timing of preemption (subject to the exceptions) based on various EPA actions under each proposal. Here, there are somewhat larger structural differences between the bills: for example, S. 697 preempts new state restrictions while a chemical is undergoing assessment by EPA, while H.R. 2576 has somewhat broader preemption on the basis of EPA actions on new chemicals and significant new uses of chemicals. Both bills would preempt state requirements after EPA either imposed requirements on a chemical found to present an unreasonable risk, or after EPA determined that a chemical did not present an unreasonable risk. Table 1 then compares S. 697 's new waiver provisions with those of H.R. 2576 , which are retained from current TSCA. Finally, Table 1 notes several other provisions not pertaining to preemption that nonetheless relate to the federal-state relationship under TSCA.

Summary: The Toxic Substances Control Act (TSCA) was enacted in 1976 to govern the regulation of chemical substances in U.S. commerce. Its core provisions have not been significantly amended since that time. Under TSCA, the Environmental Protection Agency (EPA) has implemented a chemicals management program over the past four decades. EPA has issued a very limited number of risk management rules under TSCA to restrict chemicals it has found to present unreasonable risks of injury to human health or the environment. Meanwhile, states and, in a few cases, local subdivisions of states have enacted an increasing number of their own chemical programs and restrictions. The federal preemption doctrine derives from the Supremacy Clause of the U.S. Constitution, which provides that federal laws "shall be the supreme Law of the Land." Congress can expressly preempt state and local laws by statute, and the scope of preemption is determined by Congress's intent. Because TSCA preemption is based on EPA's issuance of certain types of rules and orders targeting particular chemicals (subject to exceptions), state and local chemical programs and restrictions—for the most part targeting chemicals not subject to EPA risk management rules—generally have not faced preemption under TSCA. As legislative proposals to amend TSCA have been discussed in recent years, one major topic of debate has been the extent to which the scope of TSCA's preemption of state chemical regulations should be preserved, expanded, or reduced. This report provides a brief background on preemption in current TSCA. The report then provides a side-by-side comparison of the preemption provisions of House and Senate bills in the 114th Congress to amend TSCA. S. 697, the Frank R. Lautenberg Chemical Safety for the 21st Century Act, was ordered to be reported out of the Senate Environment and Public Works Committee on April 28, 2015, on a 15-5 vote. It was reported, as amended, on June 17, 2015, and placed on the Senate Legislative Calendar. H.R. 2576, the TSCA Modernization Act of 2015, was first released as a discussion draft on April 7, 2015. It was introduced as H.R. 2576 on May 26, 2015, and passed the House as amended on June 23, 2015, on a 398-1 vote. Both bills would expand EPA's authority to regulate chemicals in a number of ways, similar in some respects, although S. 697 is a longer and more detailed bill that would make more changes to TSCA's language than H.R. 2576. The preemption provisions of the two bills have many similarities as well, including in their overall structure, which retains TSCA's approach of only preempting state and local laws on a chemical-by-chemical basis after EPA action on a chemical. Both bills would also exclude from preemption state and some local chemical requirements in effect as of August 1, 2015, and any state or local requirements arising from long-standing state chemical laws such as California's Proposition 65. However, the bills have a number of differences with respect to preemption. For example, S. 697 would preempt new restrictions on a chemical while EPA prepared a safety assessment on that chemical, a period of up to several years; H.R. 2576 may impose somewhat broader preemption on the basis of EPA actions for new chemicals and new uses than S. 697. Various other similarities and differences between the two bills regarding preemptive EPA actions, exceptions, exemptions, and waivers are also compared. A third proposal to amend TSCA, S. 725, the Alan Reinstein and Trevor Schaefer Toxic Chemical Protection Act, would eliminate express TSCA preemption entirely. S. 725 is not included in this report's comparison.