5. Safety/risk assessment USEPA RfD and USFDA ADI

• EPA Reference dose and FDA Acceptable Daily Intake based on Burek et al 1980 finding of sciatic nerve degeneration (electron microscopic)

  • 90 day study in rats
  • Lowest observed effect level 1000 mcg/kg
  • No observed effect level 200 mcg/kg
    • Only 3 animals examined at EM level per dose group
  • Recovery seen at 144 days for LOAEL dose

• 1000 fold uncertainty factor

• Routine EPA re-evaluation of RfD underway