Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p2
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 2/5)
Character Range: 2616361–2619252

not been considered in the derivation of HIL A.

Note that the phytotoxic effects of these compounds may need to be addressed on a site-specific basis if detected in soil.

3.3.5         Intakes from Other Sources – Background
Limited data is available for the assessment of background intakes of MCPA, MCPB and mecoprop. These compounds are currently registered for use in Australia (while some areas are only allowed controlled use of MCPA) and they are generally not considered persistent in the environment. The compounds are not included in the Australian Total Diet Surveys (FSANZ 2003; FSANZ 2011) and there is no data regarding concentrations in drinking water or air in Australia. Away from areas where these herbicides are used, exposure by the general public is expected to be low. In the USA, MCPA was detected up to 0.54 µg/L in surface waters and up to 5.5 µg/L in groundwater (WHO 2011). Background intakes may be similar to those considered for 2,4-D, which is essentially negligible (where these products are not used).

3.4              Identification of Toxicity Reference Values

3.4.1         Classification
The International Agency for Research on Cancer (IARC 1987) has classified chlorophenoxy herbicides as Group 2B—possibly carcinogenic to humans. Information provided in the IARC evaluation relates more specifically to MCPA and mecoprop. No evaluation is available for MCPB.

US EPA has not classified MCPA, MCPB or mecoprop.

3.4.2         Review of Available Values/Information
There is limited information on the assessment of carcinogenicity and genotoxicity for these compounds. WHO (2011) notes that recent studies on rats and mice do not indicate that MCPA was carcinogenic and there is only limited and inconclusive data on the genotoxicity of MCPA. Limited studies available on MCPB and mecoprop were negative with respect to genotoxicity. On the basis of the available information, it is considered appropriate that a threshold doseresponse approach be adopted for these herbicides. The following are available from Level 1 Australian and International sources:

3.4.2.1         MCPA
Source              Value                    Basis/Comments
Australian
ADWG (NHMRC 2011)   TDI = 0.011 mg/kg/day    MCPA has been assessed with a health-based guideline of 0.04 mg/L based on a TDI of 0.011 mg/kg/day based on a NOEL of 1.1 mg/kg/day from a 2-year study in rats, and an uncertainty factor of 100
OCS (2012)          ADI = 0.01 mg/kg/day     The ADI is noted to have been set in April 1994 and is based on a NOEL of 1.1 mg/kg/day (as considered in the ADWG (NHMRC 2011)).
International
WHO (2011)          TDI = 0.0005 mg/kg/day   The TDI was derived on the basis of a NOAEL of 0.15 mg/kg/day associated with renal and liver toxicity observed in a 1-year feeding study in dogs, and an uncertainty factor of 300. It is noted that the current guideline has