Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:4:p1
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 4 (pt 1/8)
Character Range: 2123932–2126912

4                   Cadmium

4.1              General
Several comprehensive reviews of cadmium in the environment and its toxicity to humans are available and should be consulted for more detailed information (ATSDR 2008; EA 2009a; WHO 2004). The following provides a summary of the key aspects of cadmium that are relevant to the derivation of a soil HIL.

Pure cadmium is a silver-white lustrous and malleable metal, is a solid at room temperature, is insoluble in water, and has a relatively low melting point and vapour pressure. The most common oxidation state of cadmium is 2+. Naturally occurring cadmium is commonly found in the Earth's crust associated with zinc, lead and copper ores. Whereas pure cadmium and cadmium oxides are insoluble in water, some cadmium salts including cadmium chloride, cadmium nitrate, cadmium sulfate and cadmium sulfide are soluble in water (ATSDR 2008).

Cadmium is found naturally in mineral forms (primarily sulfide minerals) in association with zinc ores, zinc-bearing lead ores, and complex copper-lead-zinc ores. Due to its corrosion-resistant properties, a wide range of commercial and industrial applications have been developed involving cadmium-containing compounds and alloys that are used in a wide range of materials and products including batteries, pigments, metal coatings and platings, stabilisers for plastics, nonferrous alloys and solar cell devices (ATSDR 2008).

Cadmium is toxic to a wide range of organs and tissues, and a variety of toxicological  end points (reproductive toxicity, neurotoxicity, carcinogenicity) have been observed in experimental animals and subsequently investigated in human populations (MfE 2011).

4.2              Previous HIL
The derivation of the previous HIL (HIL A = 20 mg/kg) for cadmium is presented by Langley (1991). In summary, the HIL was derived on the basis of the following:
    * Intakes of cadmium from other sources were estimated with dietary intakes considered most significant for the general population. Background intakes were considered in the derivation of the current HIL (Langley 1991), where intakes from other sources were estimated to be up to 80% of the adopted PTWI.
    * A provisional tolerable weekly intake (PTWI) of 7 µg/kg/week, referenced from WHO, was adopted as the toxicity reference value.
    * Ingestion of both soil and dust has been considered assuming 100% is bioavailable and is absorbed.
    * Dermal absorption has been considered to be low with a conservative assumption of 0.1% assumed.
    * Inhalation of cadmium in dust has been considered both outdoors and indoors.
    * The total absorption of cadmium, based on 20 mg/kg in soil, for a young child was calculated to be 0.32 µg/day, approximately 28% of the adopted toxicity reference value. This intake was considered to provide a significant buffer below the tolerable daily absorption.

4.3              Significance of Exposure Pathways
Ingestion of soil and dust is considered the