Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p6
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 6/8)
Character Range: 2793536–2796348

of the midpoint of RfCs derived from 2 studies. An RfC of 0.015 mg/m3 was derived from a LOAEL of 15 mg/m3 associated with colour confusion in an adult occupational study (Cavalleri et al. 1994), and application of a 100-fold uncertainty factor. An RfC of 0.056 mg/m3 was derived from a LOAEL of 56 mg/m3 associated with cognitive and reaction time effects in an adult occupational study (Echeverria et al. 1995), and application of a 100-fold uncertainty factor. The derived value is consistent with that derived for liver effects from the study by Mutti et al. (1993), and 1000-fold uncertainty factor. The 100-fold uncertainty factor applied to these key studies includes a 10-fold factor to address database deficiencies in relation to characterising the hazard and dose response in the human population.
                                                  The US EPA review also identified non-threshold values not considered relevant in this evaluation.

In relation to the identification of an appropriate inhalation TRV for use in the derivation of a soil vapour interim HIL, the following is noted from the above studies:
    * The point of departure (LOAELs in this case) from key studies by WHO (2006; 2010) and US EPA (2012) are similar, ranging from 0.02 to 0.056 mg/m3;
    * The key studies identified in the US EPA (2012) review were also considered in the WHO (2006 and 2010) reviews, with the WHO (2006) review determining that the study conducted by Cavalleri et al. (1994) (used by US EPA as the lower end of the range of two principal RfCs derived) provided results that were difficult to interpret and hence not suitable for the determination of a threshold criterion. The other principal study considered by US EPA was not used as a key study by WHO. Similarly, the key study adopted by WHO (2006), while initially identified by US EPA as an appropriate key study, was not considered due to concerns regarding discrepant results;
    * The key difference between the WHO and US EPA reviews and derived inhalation TRVs is the application of uncertainty factors. The WHO reviews have consistently applied an uncertainty factor of 100 to address intra-species variability and the use of a LOAEL. US EPA (2012) has applied an additional factor of 10-fold to address database deficiencies in relation to characterising the hazard and doseresponse in the human population (i.e. residents rather than workers). The WHO (2006) review considered the use of occupational studies to be conservative for the general population, as worker exposures are likely to include short duration peaks of higher concentrations. This approach (by WHO) is consistent with that adopted in the assessment of exposures by the general public, based on occupational studies, in Australia.
    * Based on the above, both