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: 1031908–1035268

4                                                                                                                                                                                                                                          Probably not carcinogenic to humans
1 — IARC defines an agent as 'specific chemical groups, groups of related chemicals, complex mixtures, occupational or environmental exposures, cultural or behavioural practices, biological organisms and physical agents (IARC 2006).

There may also be circumstances where the data relating to the classification of a substance as a carcinogen is not relevant to soil contamination. This would apply, for example, where the cancer classification was based on an occupational study where inhalation of metal fumes had been found to cause cancer. Since the metal in soil would not be capable of causing fumes, this hazard would be inapplicable and could be reasonably discounted.

Hazard identification for carcinogens should detail the following:
    * the IARC classification
    * whether the chemical is considered genotoxic or non-genotoxic
    * whether a threshold or non-threshold approach is to be used, and the reasons for the choice
    * what kinds of cancer might result, and what kind of studies this conclusion is based on
    * differences in effects between oral, dermal or inhalation exposure
    * whether there may be any specific susceptible groups in the population
    * the reliability of the available information.

5.3              Doseresponse assessment

    5.3.1          Overview
The doseresponse assessment looks at establishing a quantitative relationship between the exposure to a chemical and the effect realised. For the purposes of contaminated land health risk assessment, doseresponse assessment comprises selection of suitable reference values from the authoritative data sources listed in this Schedule.

The term toxicity reference value (TRV) refers to measures of tolerable dose that are derived by expert panels on behalf of government or international bodies responsible for public health guidelines or standards. The TRVs recommended have been developed for use in risk assessment or in setting public health guidelines or standards. They incorporate allowances for uncertainty in the studies upon which they are based and generally also accommodate (where possible) safety factors to provide for particularly sensitive groups in the population. The information provided to support the TRVs invariably provides a description of the process followed.

It is recognised that these approaches have a number of limitations and that a more unified approach would be sensible. Concern has also been expressed in the international risk assessment community that the current approach both underemphasises non-cancer effects, and provides an unrealistic 'bright line' divide between possible harm and safety (NRC 2008). Future developments in doseresponse assessment are likely to move towards a unified approach covering all chemicals and perhaps a single mechanism to express risk.

Currently, the threshold and non-threshold approaches still dominate risk assessment practice, and the TRVs associated with each are described below.

    5.3.2          Threshold toxicity reference values
The US EPA's IRIS database describes the toxicity criteria