As chemical companies develop more pesticides, cleaners, and
other potentially toxic compounds, traditional methods of safety
testing can hardly keep up. Animal tests, which have been the gold
standard for decades, are slow and expensive, and these sorts of
tests are increasingly socially unacceptable, too. What's more, the
results of animal testing sometimes don't translate to humans, so
researchers are eager for better alternatives.
http://tech1207.blogspot.com/2008/02/improving-toxicity-tests.html