Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1:p12
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1 (pt 12/14)
Character Range: 2721345–2724460

of 0.29 mg/kg/day associated with neurobehavioral effects in mice, and an uncertainty factor of 3000.
                                                                     Hexa‑BDE RfD established (in 2008) for BDE‑153 on the basis of a NOAEL of 0.45 mg/kg/day associated with neurobehavioral effects in mice, and an uncertainty factor of 3000.
                      RfD = 0.0002 mg/kg/day for hexa‑BDE (BDE‑153)  Tetra‑BDE RfD established (in 2008) for BDE‑47 on the basis of a benchmark dose approach and a BMDL1SD of 0.35 mg/kg/day associated with neurobehavioral effects in mice, and an uncertainty factor of 3000.
                                                                     Octa‑BDE RfD (established in 1986) for octa‑BDE based on a NOAEL of 2.51 mg/kg/day associated with liver effects in rats, and an uncertainty factor of 1000.
                      RfD = 0.0001 mg/kg/day for tetra‑BDE (BDE‑47)
                                                                     Note the US EPA (2008) review established an RfD = 0.007 mg/kg/day for deca‑BDE (BDE‑209), based on a NOAEL of 2.22 mg/kg/day associated with neurobehavioral effects in mice, and application of a 300‑fold uncertainty factor. While not part of the lower‑BDEs evaluated for the derivation of the soil HIL, this evaluation indicates that deca‑BDE is less toxic than the lower BDEs.
                      RfD = 0.003 mg/kg/day for octa‑BDE

Limited quantitative data is available for the characterisation of chronic exposures to lower BDEs. The more recent evaluations by US EPA (IRIS 2012) for individual congeners BDE‑99, BDE‑153 and BDE‑47 have considered threshold values (BMDLs or NOAELs) that are consistent with those identified in reviews by NICNAS (2007), JECFA (2006) and Health Canada (2006), that are associated with the more sensitive end point of neurobehavioral/developmental effects. These end points are more sensitive than those considered by ATSDR in the derivation of intermediate duration MRLs and considered in older reviews by US EPA for penta‑BDE and octa‑BDE. The uncertainty factor applied by US EPA to the individual congeners considered, 3000, includes an additional 10‑fold factor to address database deficiencies.

There is no evaluation of a chronic threshold value that would be applicable to all lower BDEs as a group, hence application of the US EPA values requires an assumption that the congeners studied are an appropriate indicator for total lower BDEs. This is likely to be conservative but no more detailed evaluations are available. The individual congener studies by US EPA are noted by NICNAS (2007) to be those within commercial penta‑BDE that are of most importance in biomonitoring and environmental sampling.

The lower RfD of 0.0001 mg/kg/day derived by US EPA for BDE‑99 and BDE‑47, similar to that derived for BDE‑153, is recommended for use in the derivation of a soil HIL for lower BDEs. As noted in most other reviews, the available database is poor and limited with respect to identification of a threshold associated with chronic exposures to the group of congeners. Hence, the use