uAny animal may have a positive, negative or neutral non-response to any given dose of any toxin at any time depending on the habituating vs. sensitizing nature of the magnitude, frequency, duration and route of all their prior exposures
uThese parameters are
studied in exposure assessment models but not integrated into exposure standards based on dose response models that focus on time weighted averages or total cumulative doses.
uToxicological
studies need to assess different exposure patterns: naïve (no prior exposure), habituated (aka addiction), and sensitized (post addiction).