title: The toxicity data landscape for environmental chemicals.
abstract: OBJECTIVE
  Thousands of chemicals are in common use, but only a portion of them have undergone significant toxicologic evaluation, leading to the need to prioritize the remainder for targeted testing. To address this issue, the U.S. Environmental Protection Agency (EPA) and other organizations are developing chemical screening and prioritization programs. As part of these efforts, it is important to catalog, from widely dispersed sources, the toxicology information that is available. The main objective of this analysis is to define a list of environmental chemicals that are candidates for the U.S. EPA screening and prioritization process, and to catalog the available toxicology information.
  
  
  METHODS
  We are developing ACToR (Aggregated Computational Toxicology Resource), which combines information for hundreds of thousands of chemicals from > 200 public sources, including the U.S. EPA, National Institutes of Health, Food and Drug Administration, corresponding agencies in Canada, Europe, and Japan, and academic sources.
  
  
  METHODS
  ACToR contains chemical structure information; physical-chemical properties; in vitro assay data; tabular in vivo data; summary toxicology calls (e.g., a statement that a chemical is considered to be a human carcinogen); and links to online toxicology summaries. Here, we use data from ACToR to assess the toxicity data landscape for environmental chemicals.
  
  
  RESULTS
  We show results for a set of 9,912 environmental chemicals being considered for analysis as part of the U.S. EPA ToxCast screening and prioritization program. These include high-and medium-production-volume chemicals, pesticide active and inert ingredients, and drinking water contaminants.
  
  
  CONCLUSIONS
  Approximately two-thirds of these chemicals have at least limited toxicity summaries available. About one-quarter have been assessed in at least one highly curated toxicology evaluation database such as the U.S. EPA Toxicology Reference Database, U.S. EPA Integrated Risk Information System, and the National Toxicology Program.
authors.affiliation: National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA. judson.richard@epa.gov
authors.forename: Richard
authors.initials: R
authors.lastname: Judson
authors.forename: Ann
authors.initials: A
authors.lastname: Richard
authors.forename: David J
authors.initials: DJ
authors.lastname: Dix
authors.forename: Keith
authors.initials: K
authors.lastname: Houck
authors.forename: Matthew
authors.initials: M
authors.lastname: Martin
authors.forename: Robert
authors.initials: R
authors.lastname: Kavlock
authors.forename: Vicki
authors.initials: V
authors.lastname: Dellarco
authors.forename: Tala
authors.initials: T
authors.lastname: Henry
authors.forename: Todd
authors.initials: T
authors.lastname: Holderman
authors.forename: Philip
authors.initials: P
authors.lastname: Sayre
authors.forename: Shirlee
authors.initials: S
authors.lastname: Tan
authors.forename: Thomas
authors.initials: T
authors.lastname: Carpenter
authors.forename: Edwin
authors.initials: E
authors.lastname: Smith
mesh_terms: D016208:Databases, Factual; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis*; D006801:Humans; D014481:United States; D014484:United States Environmental Protection Agency; D037041:United States Government Agencies
chemical_list: D004785:Environmental Pollutants