Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:10:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 10 (pt 2/4)
Character Range: 2572721–2575637

Plant Uptake
Limited data is available on the potential for plant uptake of toxaphene. ATSDR (1996) notes that toxaphene is not expected to be available to humans via ingestion of plants unless they have been recently treated with the mixture.

Toxaphene has a high Koc value (log Koc = 2.45) and very low solubility in water (ATSDR 1996), suggesting that the compound is largely bound to soil particulates and is immobile in soil. For plant uptake to be significant, the chemicals must be able to partition to soil water.

With respect to toxaphene bound to the soil, the potential for partitioning to soil water is considered to be low and hence plant uptake is considered to be negligible.

10.3.5     Intakes from Other Sources – Background
No data is available regarding background concentrations of toxaphene in Australia. Given the chemical's persistence in the environment and that it is no longer used in Australia, dietary intakes of residues are expected to be of most significance for the general population. Toxaphene was not included in the Australian Total Diet Surveys. Limited data reported from the US (ATSDR 1996) suggests intakes from dietary sources (based on data from 19861991) are approximately 0.007 µg/kg/day for adults and 0.0224 µg/kg/day for children aged 2 years. These intakes are less than 10% of the recommended threshold TRV and, given that the compound is not used in Australia (and has not been used in 1987), potential background intakes are expected to be lower than estimated in the US. As no Australian data is available to confirm this assumption, a conservative approach has been adopted where background intakes have been assumed to comprise 10% of the adopted TRV.

10.4          Identification of Toxicity Reference Values

10.4.1     Classification
The International Agency for Research on Cancer (IARC 2001) has classified toxaphene as Group 2B—possibly carcinogenic to humans.

It is noted that US EPA has classified toxaphene as Group B2—probable human carcinogen. The evaluation is based on increased hepatocellular adenomas and carcinomas in mice and increased thyroid tumours in rats.

10.4.2     Review of Available Values/Information
Toxaphene induces hepatocellular adenomas and carcinomas in mice, thyroid follicular-cell adenomas and carcinomas in both sexes of rats, and pituitary adenomas in female rats. However, the available human data did not indicate a significant increase in cancer risk associated with exposure to toxaphene (IARC 2001). The mechanism underlying the carcinogenic effect is at present unclear. IARC (2001) notes that some in vitro tests for genotoxicity were positive, however due to limitations in the available database it cannot be concluded if toxaphene has genotoxic potential in vivo or not. Review by ATSDR (1996) suggests that toxaphene may be genotoxic. Review by ATSDR (1996) suggests that while organochlorines in general