Types
Reference doses are chemical-specific, i.e. the EPA determines a unique reference dose for every substance it evaluates. Often separate acute and chronic RfDs are determined for the same substance. Reference doses are specific to dietary exposure. When assessing inhalation exposure, EPA uses "reference concentrations" (RfCs), instead of RfDs. Note that RfDs apply only to non-cancer effects. When evaluating carcinogenic effects, the EPA uses the Q1* method.
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—Saul Bellow (b. 1915)
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—Henry David Thoreau (1817–1862)