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(2) Approach to chemical exposure via farm and laboratory
environment
In view of concern over the exposure of experimental animals to
chemicals in the farm and laboratory environment, animal feeds,
feed water, litter and ambient air were analyzed in order to
check the reliability of animal experiments related to endocrine
disruptors.
The fact that bisphenol A, phthalic acid esters and nonylphenol
were found in feeds and litter indicates that the animals are
actually exposed to chemical substances including them via the
farm and laboratory environment.
Animal experiments concerning the currently hot issue of
low-dose effects should, therefore, take the contamination level
into account by determining beforehand the relevant compounds in
the feeds and litter to be used.
Contaminant-free farm and laboratory conditions are evidently
ideal but unrealistic. It is recommended, as a practical
approach, to specify the lot numbers and relevant analytical
data of the feeds and litter used in farming the experimental
animals and, if necessary, to analyze the feeds and litter to
obtain accurate information on the baseline exposure of the
animals and report the results.
Use of feeds and litter contaminated beyond a certain level is
obviously unadvisable.
While exposure via litter, air or cage is usually difficult to
estimate, that via feeds and feed water can be calculated from
the concentrations of relevant chemicals contained and daily
intake. The estimated exposure should be taken into account when
interpreting experimental results.
Also acting as nutrients, phytoestrogens in feeds can have
considerable effects on animal experiments in which estrogen
activity is observed. It is desirable to check the composition
and phytoestrogen content of the feed before experiment.
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