Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:12:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 12 (pt 1/7)
Character Range: 2292059–2295090

12             Selenium

12.1          General
Several comprehensive reviews of selenium in the environment and its toxicity to humans are available and should be consulted for more detailed information not presented in this summary (ATSDR 2003; WHO 1987; CCME 2007; NHMRC 2006; EA 2009a; EA 2009b). The following provides a summary of the key aspects of selenium that are relevant to the derivation of a soil HIL.

Selenium is a non-metal that is widely but unevenly distributed in the Earth's crust. In its elemental form selenium forms metallic grey to black crystals but in nature it primarily occurs as sulfide minerals or with silver, copper, lead, and nickel minerals. Selenium's physical and chemical properties are similar to those of sulfur (ATSDR 2003).

Selenium is manufactured as a by-product of copper refining. It is widely used in electronics and photography because of its semiconductor and photoelectric properties. A variety of selenides, selenates and selenium salts are used in pigments, some pharmaceutical products (sodium selenide in anti-dandruff shampoo) and in dietary supplements (ATSDR 2003).

Selenium is considered an essential element and is important for an extensive range of biochemical functions within the body. As such, adverse effects are associated with both deficiency and toxicity associated with excess intake.

12.2          Previous HIL
No previous HIL has been established for selenium in soil.

12.3          Significance of Exposure Pathways
Ingestion of soil and dust is considered the most significant pathway of exposure for inorganics in soil. The consideration of bioavailability and inclusion of other exposure pathways in the derivation of a soil HIL has been further reviewed, as noted below.

    12.3.1     Oral Bioavailability
Insufficient data is available to adequately define the bioavailability of selenium from soil. On this basis, a default approach of assuming 100% oral (and inhalation) bioavailability has been adopted in the derivation of an HIL. It is noted that a site-specific assessment of bioavailability can be undertaken where required.

    12.3.2     Dermal absorption
ATSDR (2003) notes that there is little or no information available on the dermal absorption of selenium sulfides, but selenium disulfides are not believed to be absorbed through intact skin. This is consistent with reviews provided by CCME (2007) and EA (2009a), where dermal absorption of selenium through intact skin has been considered negligible. Based on the limited data available, dermal absorption has been considered negligible in the derivation of soil HIL.

    12.3.3     Inhalation of Dust
Selenium is not volatile and inhalation exposures associated with particulates outdoors and indoors are expected to be of less significance than ingestion of soil. While likely to be negligible, potential inhalation exposures associated with dust have been considered in the HIL derived.

    12.3.4     Plant Uptake
A detailed review of the plant uptake of selenium is presented