There is increasing concern both in the United States and globally about whether a "pollinator crisis" has been occurring in recent decades. Reports worldwide indicate that populations of managed honey bees, wild bees, and native bees have been declining, with colony losses in some cases described as severe or unusual. Other reports indicate that many insect pollinator species may be becoming rarer, which some say may be a sign of an overall global biodiversity decline. Many reasons are cited for bee population declines, including bee pests and diseases, diet and nutrition, genetics, habitat loss, agricultural pesticides, and beekeeping management. Because pesticides have been the focus of concerns in Europe and in the United States, this CRS report briefly describes recent scientific research and analysis regarding the potential role of pesticides among the factors affecting the health and well-being of bees. The report concludes with a summary of recent regulatory activity regarding neonicotinoids, a type of pesticide, and also provides the statutory authority and regulatory activities related to pesticide use at the U.S. Environmental Protection Agency (EPA), the federal agency charged with assessing risks and regulating U.S. sale and use of pesticides. The focus of this report on bee exposure to pesticides is not intended to imply that pesticides are any more or less important in influencing the health and wellness of bees than any of the other identified factors influencing bee health. In the United States, honey bee colony losses due to bee pests, parasites, pathogens, and disease are not uncommon. However, in late 2006, concerns about honey bees gained heightened attention when commercial beekeepers along the East Coast began reporting sharp declines in their bee colonies. Because of the severity and unusual circumstances of these colony declines, scientists named this phenomenon colony collapse disorder (CCD). This issue was legislatively active in the 110 th Congress and resulted in increased funding for honey bee research, among other types of farm program support to protect pollinators, as part of the 2008 farm bill (Food, Conservation, and Energy Act of 2008, P.L. 110-246 ). The 2014 farm bill ( P.L. 113-79 ) reauthorized and expanded upon many of these provisions. The U.S. Department of Agriculture (USDA) reports that U.S. beekeepers continue to lose colonies each year. Since 2006, USDA estimates that overwinter bee colony losses have averaged nearly 30% annually. However, USDA reports that in 2012/2013, "there were more colonies that dwindled away" rather than suffering from CCD, which is characterized by a sudden loss in bee colony populations and the absence of dead bees. USDA also claims that "beekeepers did not report CCD as a major cause of colony loss" for overwinter losses reported in its 2012-2013 and 2011-2012 surveys. These data are tracked for managed honey bees only. Comparable data and information is not collected available for native or wild bee species. Such data collection is complicated by sheer number and solitary nature of native and wild bee species. To date, the precise reasons for honey bee colony losses are still unknown. USDA and most scientists working on the subject seem to agree that none of the research conclusively points to one single cause for the large-scale number of honey bee deaths. This general conclusion was reconfirmed in a May 2013 report by USDA and the U.S. Environmental Protection Agency (EPA), National Stakeholders Conference on Honey Bee Health (commonly referred to as the "USDA-EPA joint report"). A 2007 study by the National Research Council (NRC) of the National Academy of Sciences, Status of Pollinators in North America (referred to here as the 2007 NRC study), also provides a detailed scientific context for bee health. A series of other reports documenting the findings of USDA's ongoing research also describes the many factors affecting honey bees. See Figure 1 . Reasons cited for bee population declines include a wide range of possible factors. Potential identified causes include bee pests and diseases, diet and nutrition, genetics, habitat loss and other environmental stressors, agricultural pesticides, and beekeeping management issues, as well as the possibility that bees are being harmed by cumulative, multiple exposures and/or the interactive effects of each of these factors. One issue widely reported in the media is the potential role that pesticides—in particular, neonicotinoid pesticides—might play in overall bee health. As one of the potential causes of honey bee colony declines, this report addresses what role, if any, pesticides play in influencing the health and wellness of bees. Regarding honey bee health, the current state of knowledge of pesticides was summarized in a 2013 report by USDA and EPA: There is broad consensus among all stakeholders that pesticide use should not affect honey bees in such a way that (1) honey production is reduced or (2) pollination services provided by bees are threatened.... However, it is not clear, based on current research, whether pesticide exposure is a major factor associated with U.S. honey bee health declines in general, or specifically affects production of honey or delivery of pollination services. It is clear, however, that in some instances honey bee colonies can be severely harmed by exposure to high doses of insecticides when these compounds are used on crops, or via drift onto flowers in areas adjacent to crops that are attractive to bees. This report examines in greater detail the role of pesticides, providing a summary of selected scientific literature. The relative importance of pesticides in U.S. or global bee health is a subject of numerous research projects, some of which are discussed in this report. Some groups have expressed concern about the assessment of most experts that the causes of pollinator health concerns are multifaceted and may involve the interaction of multiple factors, since this may deflect attention from the potential role of exposure to pesticides. On the other hand, some groups appear unwilling to acknowledge that pesticide exposure may play an important role in pollinator health concerns, especially if this acknowledgment leads to restrictions or reductions in the use of certain pesticides or related crop pest controls. This report provides information regarding the potential role of pesticides in the health of bee colonies, and also the importance of pesticides relative to other influences on bee health. The report provides general information about the nature of pesticides, pesticide uses, and pesticide regulation in the United States, as well as more specific information about the registration status of a class of pesticides known as neonicotinoids, which have been implicated in some studies concerning honey bee colony declines. This report also describes a range of options to address pesticide exposure by bees, including implementing crop- and/or product-specific best management practices (BMPs) regarding pesticide use and applications. Some U.S. cities as well as some other countries, including Canada and those in Europe, have opted to institute restrictions on the use of certain pesticides. Congress has introduced similar legislation, but has also considered alternative policy options to address this issue. Pesticides are broadly defined in U.S. law as chemicals and other products used to kill, repel, or control pests. Familiar examples include pesticides used to kill insects (insecticides) and weeds (herbicides) that can reduce the yield, and sometimes harm the quality, of agricultural crops, ornamental plants, forests, and pastures, or wooden structures (e.g., through termite damage). But the broad legal definition of "pesticide" also applies to products with less familiar "pesticidal uses." For example, substances are pesticides when used to control mites, mold, mildew, and other nuisance growths in hives or on equipment. The term also applies to disinfectants and sterilizing agents, animal repellents, rat poison, and many other substances. An estimated 18,000 pesticide products are currently in use in the United States. Pesticides vary greatly in toxicity, persistence in the environment, and ability to bioaccumulate up the food chain, as well as in the range of plants and animals that are likely to be affected in the event of exposure. Some are nearly nontoxic to some species but exquisitely toxic to other species. All pesticides are regulated by EPA under the authority of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and approximately 5,800 pesticide products used in food production also are regulated under the Federal Food, Drug, and Cosmetic Act (FFDCA). FIFRA requires EPA to regulate the sale and use of pesticides in the United States through product registration and labeling so as to prevent unreasonable adverse effects on people and the environment, taking into account the costs and benefits of various pesticide uses. FIFRA prohibits the sale of any pesticide in the United States unless it is registered (licensed) and labeled to indicate approved uses and restrictions. It is a violation of the law to use a pesticide in a manner that is inconsistent with the label instructions. EPA registers each pesticide product for each approved use. For example, a product may be registered for use on bee hives to control mites or as a seed treatment for corn. In addition, FIFRA requires EPA to reregister pesticides first registered prior to 1984 and to review all registered pesticides periodically on a 15-year cycle, based on new data that meet current regulatory and scientific standards. For the 600 or more active ingredients in pesticide products that are registered for use in food production, Section 408 of the FFDCA authorizes EPA to establish maximum allowable residue levels (also known as "tolerances") to ensure that human exposure to the pesticide ingredients in food and animal feed will be "safe." A "safe" tolerance is defined in the law as a level at which there is "a reasonable certainty of no harm" from the exposure, even when considering total cumulative and aggregate pesticide exposure of children.