Hassett-Sipple, B; Swartout, J; Mahaffey, KR; Rice, GE; Schoeny, R
Section 112(n)(1)(B) of the Clean Air Act (CAA), as amended in 1990, directs the U.S. Environmental Protection Agency (U.S. EPA) to submit to Congress a comprehensive study on atmospheric emissions of mercury. This document, which covers the human health effects of mercury and mercury compounds, is one volume of U.S. EPA's eight-volume Report in response to this directive. Mercury is a naturally occurring element that is found in air, water and soil. It exists in any of three valence states: Hg0 (elemental mercury), Hg2(2+) (mercurous mercury), or Hg2+ (mercuric mercury). Most of the population of the earth have some exposure to mercury as a result of normal daily activities. The general population may be exposed to mercury through inhalation of ambient air, consumption of contaminated food, water, or soil; and/or dermal exposure to substances containing mercury. In addition, some quantity of mercury is released from dental amalgam. The health effects literature contains many investigations of populations with potentially high exposure to mercury, including industrial workers, people living near point sources of mercury emissions, people who consume large amounts of fish, and dental professionals. There also are numerous studies of populations unintentionally exposed to high levels of mercury, such as the Minamata poisoning episode in Japan. Volume IV (An Assessment Exposure to Mercury in the United States) presents measured and predicted mercury exposure for various U.S. populations. The purpose of this volume, Volume V, is to summarize the available health effects information for mercury and mercury compounds and to present U.S. EPA's analysis for two critical pieces of the risk assessment paradigm described by the National Academy of Sciences in 1983. Specifically, this volume contains the hazard identification and dose-response assessments for three forms of mercury: elemental mercury, mercuric chloride (inorganic mercury), and methylmercury (organic mercury). In order to characterize risk for any populations, the evaluations presented in this volume must be combined with the assessment of exposure presented in Volume IV. Volume V is not intended to be an exhaustive survey of the voluminous health effects literature available for mercury. Rather, the purpose is to present a brief survey of the studies relevant for assessing potential human health effects and to present more detailed information on those studies which form the basis for U.S. EPA's hazard identification and dose-response assessments. The three forms of mercury which are emphasized in this volume were selected based on data indicating that these are the predominant forms of mercury to which humans are exposed. In addition, examination of the published literature indicates that most health data are on these forms. It is acknowledged that certain populations can be exposed to many types of organic mercurials, such as antiseptics and pesticides. Volume V, however, deals with methylmercury except in cases where information on another organic is presented for illustrative purposes.