For many agents, the toxic effects following a single exposure are quite different from those produced by repeated exposure.
For example, the primary acute toxic manifestation of benzene is central nervous system depression, but repeated exposures
can result in leukemia. Acute exposure to agents that are rapidly absorbed is likely to produce immediate toxic eggects, but
acute exposure can also produce delayed toxicity that may or may not be similar to the toxic effects of chronic exposure.
Conversely, chronic exposure to a toxic agent may produce some immediate (acute) effects after each administration, in
addition to the long-term, low-level, or chronic effects of the agent. In characterizing the toxicity of a specific chemical agent, it
is evident that information is needed not only for the single dose (acute) and long term (chronic) effects, but also for exposures
of intermediate duration.