Antimony is a metalloid found in nature in over 100 mineral species; it can exist in four oxidation states, −3, 0, +3, and +5, of which the Sb(III) (trivalent) and Sb(V) (pentavalent) forms are the most common in nature. Elemental antimony is a silver-white metal used primarily to make alloys. The trivalent compound antimony(III) trioxide is the most commercially significant form of processed antimony, used primarily as a synergist for halogenated flame retardants in plastics, rubber, and textiles.

The objective of this monograph is to conduct a cancer hazard evaluation of antimony(III) trioxide for possible listing in the Report on Carcinogens (RoC). Antimony species can be interconverted in the environment and in vivo. The monograph evaluation focuses on antimony(III) trioxide and also provides scientific and exposure information on elemental antimony and other antimony compounds, because (1) people can be exposed to antimony(III) trioxide resulting from transformation from other forms of antimony, and (2) studies of biological effects and other relevant information may inform understanding of antimony(III) trioxide’s mechanistic basis for potential carcinogenicity. Table 1 summarizes the evidence streams, exposures of interest, and outcomes. This is somewhat analogous to a “population, exposure, comparator, outcome” statement (Whaley et al. 2016) except that population has been replaced by evidence stream (e.g., humans, experimental animals, in vitro studies). The comparator (no or low exposure to antimony compounds) is the same for all outcomes.

Table 1

Summary of Evidence Streams, Exposures of Interest, and Outcomes.

The monograph also assesses exposure information (summarized in Table 2) to determine whether a significant number of people residing in the United States are currently exposed or were exposed in the past to antimony(III) trioxide.

Table 2

Summary of Exposure Information.