Chronic Toxicity Study

• To determine the life-long "safe" dose of non-carcinogenic chemicals, NOEL = No Observable Effect Level.
• Usually 2 years in length for rodent studies.
• Doses usually set at the MTD, 1/4 MTD, and 1/8 MTD.
  50 rats/sex/group
• Used for setting safety factors such as ADI (Allowable Daily Intake)
  ADI = NOEL/100
  10-fold for species difference
  10-fold for individual variation