text: Toxicity of a substance can be affected by many different factors, such as the pathway of administration (whether the toxicant is applied to the skin, ingested, inhaled, injected), the time of exposure (a brief encounter or long term), the number of exposures (a single dose or multiple doses over time), the physical form of the toxicant (solid, liquid, gas), the concentration of the substance, and in the case of gases, the partial pressure (at high ambient pressure, partial pressure will increase for a given concentration as a gas fraction), the genetic makeup of an individual, an individual's overall health, and many others.  Several of the terms used to describe these factors have been included here.
  ; Acute exposure: A single exposure to a toxic substance which may result in severe biological harm or death; acute exposures are usually characterized as lasting no longer than a day.
  ; Chronic exposure: Continuous exposure to a toxicant over an extended period of time, often measured in months or years; it can cause irreversible side effects.