Water Quality and Health - Antimony

Guideline

The interim maximum acceptable concentration (IMAC) for antimony in drinking water is 0.006 mg/L (6 µg/L).

Identity, Use and Sources in the Environment

Elemental antimony (Sb) is a silvery white, brittle solid that, along with arsenic and bismuth, belongs to group VA of the periodic table. It is classified as both a metal and a metalloid. Its principal oxidation states are +3 and +5.

Antimony is present in the Earth's crust at a concentration of about 0.2-0.5 mg/kg. It is seldom found in the environment as a pure element, but it is often found as trivalent and pentavalent sulphides and chlorides. A major source of antimony in Canada is its recovery as a by-product from lead smelting operations in British Columbia and New Brunswick. Antimony is also recycled in lead bullion recovered during the recycling of lead-acid batteries in Toronto and Montreal. ¹Canadian production of antimony was 652 000 kg in 1997, with a total estimated value of approximately $2 million. ²

Antimony, as a pure metal, is used for the production of semiconductors, infrared detectors and diodes. Alloys of antimony are used in the manufacture of batteries, cable sheathing, printing type, plumbing solder and antifriction materials; non-metal antimony products are used in flame retardant materials, paint pigments, ceramic enamels, plastics, glass and pottery, ammunition primers and fireworks. ³Potassium antimony tartrate is widely used in the pharmaceutical industry.

Antimony may enter the aquatic environment by way of natural weathering of rocks, runoff from soils, effluents from mining and manufacturing operations, and industrial and municipal leachate discharges.^{4, 5}Household piping and possibly non-leaded solders are sources of antimony in tap water, as soft water may leach antimony from the pipes. The potential for antimony to leach from copper pipes with solder joints made from 95% tin/5% antimony into high-purity, tap and well water samples has been investigated. ⁶The high-purity water had a pH of 6.8; the pH, alkalinity and chloride values of the tap water were 7.8, 30 mg/L (as CaCO₃) and 4 mg/L, respectively, whereas the corresponding values for the well water were 8.1, 155 mg/L and 19 mg/L. There was no detectable leaching (detection limit 1.2 µg/L) of antimony into the high-purity water or the well water; however, leaching occurred into tap water, but only after 7 days of contact. After 7, 28 and 90 days' contact time, the amount of antimony leached into tap water resulted in final concentrations of 2.0, 3.7 and 7.3 µg/L, respectively. It is noted that no tests were conducted with acidic (below pH 6) waters.

Antimony is released into the air as stack dust from industrial sources, such as coal-fired power plants, inorganic chemical plants and metal smelters. ⁷

Antimony is not degradable per se. The two main factors that influence the behaviour of antimony are its solubility and complexation. Antimony compounds range in solubility from insoluble to fully soluble. Most inorganic antimony compounds are insoluble, whereas compounds that become attached to organic ligands are soluble. ⁸Some antimony salts, such as the trichloride, sulphate, potassium tartrate and pentachloride, are soluble in water, whereas the oxides tend to precipitate. ⁹Sorption may also be a key environmental process, but the available information is incomplete. Antimony does not bioaccumulate.

The fate of antimony in the aquatic environment is determined by several factors, including pH, oxidation-reduction potential, sorptive interactions and biologically mediated methylation. In the aquatic environment, antimony can be present as an ion or a soluble complex. Most of the dissolved antimony (in the +5 oxidation state) ¹⁰that might be discharged to natural water would soon precipitate as antimony trioxide or antimony pentoxide and be removed by sedimentation.⁹