Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:6:p5
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 6 (pt 5/6)
Character Range: 2660705–2664121

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 a NOAEL of 0.1 mg/kg/day based on effects of chlorpyrifos on brain acetylcholinesterase activity in animal studies, and erythrocyte acetylcholinesterase inhibition in human subjects, and an uncertainty factor of 10. Review of this data by APVMA (2009) noted that both of these measures of toxicity are less sensitive than the inhibition of plasma cholinesterase activity, and hence the JMPR ADI is higher (i.e. less conservative) than that set by the OCS.
ATSDR (1997)                      Oral MRL = 0.001 mg/kg/day  Chronic oral MRL based on a NOAEL for acetylcholinesterase inhibition in rats exposed to 0.1 mg/kg/day of chlorpyrifos in feed for 2 years, and an uncertainty factor of 100.
US EPA (IRIS 2012)                Not available               The previous evaluation (oral RfD of 0.003 mg/kg/day) was withdrawn by the US EPA in 2011. No new evaluation is available.

The ADI of 0.003 mg/kg/day identified and considered current in the most recent review by APVMA (2009) and NRA (2000) is consistent with that considered in the derivation of the ADWG (NHMRC 2011) and listed in the ADI List (OCS 2012). The value is considered relevant for the derivation of a soil HIL in Australia.

No dermal or inhalation-specific studies or data are available. For the presence of chlorpyrifos in soil, it is considered appropriate to consider use of the available ADI for all pathways of exposures.

6.4.3         Recommendation
On the basis of the discussion above, the following toxicity reference values (TRVs) have been adopted for chlorpyrifos in the derivation of HILs:

6.5              Calculated HILs
On the basis of the above, the following HILs have been derived for chlorpyrifos (refer to Appendix B for equations used to calculate the HILs and Appendix C for calculations):
HIL Scenario            HIL (mg/kg)                      Percentage Contribution from Exposure Pathways
Ingestion of Soil/Dust  Ingestion of Home-grown Produce  Dermal Absorption of Soil/Dust                  Inhalation (dust)
Residential A           160                              72                                              --                 28  <1
Residential B           340                              38                                              --                 62  <1
Recreational C          250                              55                                              --                 45  <1
Commercial D            2000                             31                                              --                 69  <1

-- Pathway not included in derivation of HIL

6.6              References
APVMA 2009, Chlorpyrifos, Preliminary Review Findings Report on Additional Residues Data, a reconsideration of the active constituent approvals of chlorpyrifos, the registration of products containing chlorpyrifos and their associated labels, APVMA, August 2009.
ATSDR 1997, Toxicological profile for Chlorpyrifos, Agency for Toxic Substances and Disease Registry (ATSDR), September 1997.
Baskaran, S, Kookana, RS, & Naidu, R 1999, 'Degradation of bifenthrin, chlorpyrifos and imidacloprid in soil and bedding materials at termiticidal application