Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 3/5)
Character Range: 2619033–2621914

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 remained unchanged since first derived in 1993. MCPA is included in the rolling revisions to the WHO DWG (2011) with no significant revisions issued to date.
ATSDR               No evaluation available
US EPA (IRIS 2012)  RfD = 0.0005 mg/kg/day   The RfD (last reviewed in 1987) is derived based on the same study and evaluation provided in the WHO DWG (2011).

3.4.2.2         MCPB
Source              Value                            Basis/Comments
Australian
ADWG (NHMRC 2011)   No evaluation available
OCS (2012)          ADI = 0.01 mg/kg/day             The ADI is noted to have been set in May 1994 and is based on a NOEL of 1.1 mg/kg/day.
International
WHO (2011)          No quantitative value available  Insufficient data was available to establish a guideline value for MCPB in drinking water.
ATSDR               No evaluation available
US EPA (IRIS 2012)  RfD = 0.01 mg/kg/day             The RfD (last reviewed in 1991) is derived based on a NOEL of 12 mg/kg/day associated with reproductive effects in a 13-week feeding study with dogs, and an uncertainty factor of 1000.

3.4.2.3         Mecoprop (MCPP)
Source              Value                    Basis/Comments
Australian
ADWG (NHMRC 2011)   No evaluation available
OCS (2012)          ADI = 0.01 mg/kg/day     The ADI is noted to have been set in July 1998 and is based on a NOEL of 1 mg/kg/day, and an uncertainty factor of 100.
International
WHO (2011)          TDI = 0.0033 mg/kg/day   The TDI was derived on the basis of a NOAEL of 1 mg/kg/day associated with kidney effects in 1- and 2-year studies in rats, and an uncertainty factor of 300. It is noted that the current guideline has remained unchanged since first published in 1996. Mecoprop is included in the rolling revisions to the WHO DWG (2011) with no significant revisions issued to date.
ATSDR               No evaluation available
US EPA (IRIS 2012)  RfD = 0.001 mg/kg/day    The RfD (last reviewed in 1990) is derived based on a NOEL of 3 mg/kg/day associated with kidney effects in a 90-day rat feeding study, and an uncertainty factor of 3000.

The available evaluations in relation to MCPA, MCPB and mecoprop are all dated (none more recent than 1996) and are based on limited databases of studies. In relation to MCPB, the evaluations available from OCS (2012) and US EPA are consistent. In relation to MCPA and mecoprop, the critical studies identified for the determination of the point of departure differ between the OCS and WHO/US EPA evaluations. The subsequent application of uncertainty factors (with WHO/US EPA more conservative) also differs. Insufficient data is available to support any one evaluation,