Lindsay Pasquale
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Dose Response Relationship
The dose response relationship describes the change in effects on
some sort of organism caused by different levels of exposure, or doses, to a
stressor, usually a chemical, after a certain exposure time. This could apply
to individuals or a population. Dose response helps determine safe and hazardous
levels and dosage. It generally depends on the exposure time and exposure
route. A dose response curve is used to relate the magnitude of the stressor
which includes, the concentration of the pollutant, amount of drug, temperature,
intensity of radiation, to the response of the receptor.
There are two types of dose response curves, one describes the
graded responses of an individual to varying doses of the chemical and one that
describes the distribution of responses to different doses in a population of
people. The dose is represented on the X-axis and the response is represented
on the y-axis. Threshold is an important aspect of dose response relationships.
The threshold is the magnitude or intensity of that must be exceeded for a
certain reaction, result, or condition to occur. The human body is able to take
some toxic insult and still remain healthy. It’s important to identify a level
of exposure to a chemical at which there is no effect to determine thresholds
when possible. It’s based on acute responses, such as death, which is more
easily determined. Chemicals that cause cancer or other chronic responses are more
difficult to determine. When the threshold is difficult to determine
toxicologists look at the slope of the dose response curve to give them
information about the toxicity of a chemical.
Exposure to poisons can be intentional or unintentional, the effects
of the exposure to poisons vary with the dose, or amount of exposure. The measurements
used for expressing levels of contamination in the environment are usually
parts per million (ppm), or parts per billion (ppb). Those are extremely small
quantities. Another commonly used measures of toxicity is the LD50, the lethal
dose for 50 percent of the animals tested of a poison, and is usually expressed
in milligrams of a chemical per kilogram of body weight (mg/kg). A chemical
with a large LD 50 is practically nontoxic, a chemical with a small LD50 is far
more dangerous. The danger or risk of adverse effect of chemicals is mostly
determined by how they are used, not by the toxicity of the chemical itself.
The more potent the poison is, the less it will take to kill, the
less potent the poison is, the more it takes to kill. The potency of a poison
is a measure of its strength compared to other poisons. It is often compared
using signal words such as danger, warning, or caution. It can also be
expressed in categories such as highly toxic, moderately toxic, slightly toxic,
or nontoxic.
The threshold limit value (TLV), is the airborne concentration of
the chemical expressed in ppm, that produces adverse effects in workers exposed
for five days per week, eight hours per day. The TLV is usually set to prevent
minor toxic effects (skin or eye irritations).
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