The federal agencies we reviewed undertake distinct chemical toxicity assessment activities that differ in type and purpose and are driven largely by agency needs derived from statutory requirements, while officials in the 10 states we reviewed told us that they largely rely on federal agencies’ chemical toxicity assessment activities. Officials in the federal agencies we reviewed told us their toxicity assessments activities include evaluating hazards at contaminated sites, identifying potential health risks to workers, and providing information about potential toxic chemicals to regulators. Officials in 6 of the 10 states we reviewed told us they do not conduct their own toxicity assessments and rely instead on existing sources of information primarily supplied by federal agencies, while officials from the remaining 4 states told us they sometimes produce their own assessments but more often rely on federal sources. The toxicity assessment activities that these five federal agencies conducted are driven primarily by agency needs derived from the statutory authorities that created the programs. For example, several programs are designed to provide quantitative values that can be used to regulate chemicals, while others provide a qualitative conclusion about the nature of a chemical that can be shared with regulatory agencies and the public. The scope of some assessments is limited to whether the chemical causes cancer, while other assessments look beyond cancer at neurological, respiratory, and reproductive effects (see fig. 3). ATSDR, a federal public health agency of the U.S. Department of Health and Human Services, prepares toxicity assessments—called toxicological profiles—in response to statutory requirements under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). These profiles provide interpretations of data that can be useful for officials evaluating the chemical hazards at hazardous waste sites. During the development of toxicological profiles, if the agency determines that reliable and sufficient data exist to identify the specific health effects that result from exposure to a hazardous substance, the agency will derive Minimal Risk Levels (MRL). MRLs estimate safe levels of human exposure, are quantitative in nature, and are not based on a consideration of cancer effects. To address cancer, the agency issues separate assessments that include qualitative conclusions regarding cancer effects from human exposure to chemicals. Although ATSDR is not a regulatory agency, CERCLA requires it to prepare a list, in priority order, of chemicals that are most commonly found at hazardous waste sites on the National Priorities List and which are determined to pose the most significant potential threat to human health. ATSDR then must prepare toxicological profiles on substances on that list. ATSDR’s toxicological profiles typically evaluate the effects of exposures to hazardous chemicals for three possible durations: acute (14 days or less), intermediate (15-364 days), and chronic (365 days or more). According to ATSDR, these profiles generally take 18 to 24 months to complete. In recent years, ATSDR has typically completed six or seven toxicological profiles each year; a total of 319 new and updated toxicological profiles have been published or are under development. ATSDR’s MRLs are an estimate of daily human exposure to a hazardous substance at or below which that substance will likely not pose a measurable risk of adverse noncancerous effects—such as neurological, respiratory, and reproductive effects—over a specified time period. MRLs are quantitative in nature, and, according to ATSDR’s website, are used as screening values to allow ATSDR health assessors and others to identify contaminants at hazardous waste sites and determine whether further investigation is needed to protect communities from exposure. Although MRLs do not consider possible cancer effects, the agency endorses the use of a narrative statement that conveys the agency’s qualitative conclusions regarding cancer effects. In this regard, ATSDR adopts the findings for chemicals addressed by the Department of Health and Human Services’ most recent biennial Report on Carcinogens, as coordinated by the National Toxicology Program, to the extent available. These are described in ATSDR’s Cancer Policy Framework, which defines what the agency has identified as scientifically credible, internally consistent policy positions to guide ATSDR’s activities that address the public health implications of exposure to carcinogens. EPA toxicity assessments are generally used to determine the levels of chemical pollutants in the air, land, and water that would not present a significant adverse risk to the public and environment. EPA’s ability to effectively implement its mission of protecting public health and the environment is critically dependent on credible and timely assessments of the risks posed by chemicals. Such assessments are the cornerstone of scientifically sound environmental decisions, policies, and regulations under a variety of statutes, such as the Toxic Substances Control Act (TSCA), Safe Drinking Water Act, and the Clean Air Act. EPA activities are also authorized by CERCLA, the Resource Conservation and Recovery Act, the Clean Water Act, and the Federal Insecticide, Fungicide, and Rodenticide Act. EPA offices provide a variety of toxicity assessments, including both quantitative and qualitative conclusions about cancer and noncancer effects. According to EPA officials, three EPA program offices and two EPA regional offices develop a variety of chemical toxicity assessments to assist the agency in fulfilling these statutory requirements. These offices include the following: Office of Research and Development. The Office of Research and Development produces two types of toxicity assessments, which are developed through its National Center for Environmental Assessment (NCEA). These toxicity assessments provide fundamental information for EPA’s risk management decisions, such as whether EPA should establish air emissions standards and water quality standards to protect the public from exposure to particular toxic chemicals. These two types of assessments are as follows: NCEA’s IRIS is a human health assessment program that evaluates scientific information on human health effects that may result from exposure to chemicals in the environment. These assessments are used by other EPA offices, as well as federal, state, and local environmental agencies, and some international regulatory bodies. IRIS assessments, which currently include information on about 550 chemicals, undergo extensive internal and external peer review and are developed using a process that allows for public input. According to EPA, the importance of the IRIS Program has increased as its program and regional offices have increasingly relied on IRIS toxicity assessments in making environmental protection and risk management decisions. NCEA’s Provisional Peer Reviewed Toxicity Values (PPRTV) provide information to support cleanup decisions at Superfund sites. NCEA prepares PPRTVs for EPA’s Office of Solid Waste and Emergency Response when IRIS toxicity assessments are not available. PPRTVs receive internal review by a panel of NCEA scientists and external peer review by independent scientific experts, but they differ from IRIS values in that they do not undergo as extensive a process of internal and external peer review and public participation as IRIS assessments and are generally completed more quickly. Office of Chemical Safety and Pollution Prevention. Two offices within the Office of Chemical Safety and Pollution Prevention—the Office of Pollution Prevention and Toxics and the Office of Pesticide Programs—also conduct toxicity assessments as follows: The Office of Pollution Prevention and Toxics is responsible for implementing TSCA, which gives EPA the authority to obtain more information on chemicals and to regulate those chemicals that the agency determines pose unreasonable risks to human health or the environment. The office sometimes uses the hazard and dose response information described in an IRIS toxicity assessment for a particular chemical to develop its own subsequent toxicity assessments. We reported in March 2013 that officials from the Office of Pollution Prevention and Toxics told us that IRIS assessments are generally used to estimate risks associated with continuous exposures to a pollutant in the air or water rather than the intermittent exposures that workers and consumers are subject to from chemicals contained in products. The Office of Pesticide Programs, along with state agriculture offices, registers or licenses pesticides for sale and distribution in the United States under the authority of the Federal Insecticide, Fungicide, and Rodenticide Act. States may also have pesticide licensing programs. Because pesticides must be registered by EPA, the office reviews scientific information on pesticides submitted by pesticide registrants and comprehensive laboratory- based data on multiple routes of exposure. The office uses this information to conduct comprehensive risk assessments for pesticide active ingredients, among other things. Office of Water. EPA’s Office of Water develops a limited number of toxicity assessments to implement the Clean Water Act and Safe Drinking Water Act. According to Office of Water officials, because the IRIS Program can only select and develop a limited number of IRIS assessments at one time, the Office of Water develops its own assessments for chemicals that have less controversy surrounding them and take less time and staff to complete in order to address some of its programmatic needs. Regional offices. EPA regional offices, which are responsible for the execution of EPA programs within their respective states and territories; EPA officials told us that two EPA regional offices develop chemical toxicity assessments in support of their work. For example, officials in EPA’s Region 2 told us that they rely primarily on IRIS toxicity values. They will also use PPRTVs, values from other federal agencies such as ATSDR, and state toxicity values where available. When officials needed toxicity information for a chemical for which none was available, regional officials worked with others at EPA, NTP, and with officials from a potential responsible party to gather toxicity information that led to the development of a PPRTV for that chemical. Similarly, officials in Region 9 told us that they conducted toxicity assessment activities with ATSDR and NCEA that helped identify a previously unknown effect of a chemical commonly found in waterways throughout the country. NTP is an interagency program established in 1978 to coordinate chemical toxicity assessment activities across the Department of Health and Human Services. NTP officials told us the program was created to coordinate toxicity testing, strengthen the science base in toxicology, develop and validate improved testing methods, and to provide information about potentially toxic chemicals to health-related regulatory and research agencies, scientific and medical communities, and the public. NTP toxicity assessment activities include these four activities.