Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p4
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 4/6)
Character Range: 2657967–2660959

Review of dietary intakes by APVMA (2009), based on a conservative estimate of chemical residues in food, indicated that intakes may comprise up to 55% of the TRV, similar to the estimate presented on the basis of the above.

As chlorpyrifos remains in use in Australia it is reasonable, based on the above, to consider background intakes to be more than negligible. Based on the estimates, intakes derived from dietary and atmospheric sources have been estimated to be approximately 1.6 µg/kg/day (50% of the TRV) and have been considered in the derivation of soil HILs.

6.4              Identification of Toxicity Reference Values

6.4.1         Classification
The International Agency for Research on Cancer (IARC) has not classified chlorpyrifos as to carcinogenicity and US EPA has classified it as Group D—not classified for carcinogenicity

6.4.2         Review of Available Values/Information
Limited data is available on the carcinogenicity of chlorpyrifos. However, chlorpyrifos has not been identified as carcinogenic in long-term animal studies, and was not genotoxic in a wide range of assays (NRAAVC 2000; APVMA 2009). On this basis, the assessment of exposures to chlorpyrifos on the basis of a threshold approach is appropriate.

The following are available from Level 1 Australian and International sources:

Source                            Value                       Basis/Comments
Australian
ADWG (NHMRC 2011)                 ADI = 0.003 mg/kg/day       Current ADWG (NHMRC 2011, established in 1998) of 0.01 mg/L based on a NOEL of 0.03 mg/kg/day for plasma cholinesterase inhibition from a 28-day volunteer study in humans, and an uncertainty factor of 10.
OCS (2012)                        ADI = 0.003 mg/kg/day       The ADI of 0.003 mg/kg/day (set in December 1998) is based on the same approach as noted in the ADWG above.
NRAAVC (2000) and APVMA (2009)    ADI = 0.003 mg/kg/day       The APVMA (2009) review provided an updated toxicology assessment for chlorpyrifos. The review considered the range of threshold values derived by different countries with respect to the selection of relevant end points and other factors (including sensitive sub-populations such as children). The review did not identify any new studies that would result in changes to the toxicological end points selected for either public or occupational health assessments. The end points used in the NRA (2000) review were considered to be valid. No toxicological effects were observed at doses lower than those that resulted in inhibition of plasma cholinesterase activity in a human volunteer study. On the basis of this effect in humans at a dose of 0.1 mg/kg/day, with no effects seen at 0.03 mg/kg/day, the ADI at 0.003 mg/kg/day was established, with a 10-fold safety factor used to account for inter-individual variability.
International
WHO (2011) and JMPR (1983, 2000)  ADI = 0.01 mg/kg/day        ADI adopted in derivation of the current WHO DWG and JMPR (1983, 2000) is based on