ThemostwidelyknownacutetoxicitytestistheLD50.LD50
stands for “lethal dose 50 percent”: the amount of the
substance
thatwillkillhalfoftheanimalsinthestudy.Tofindthatdose
level, sample groups of animals are poisoned. Normally,
beforethepoint atwhich halfof themdieis reached, the
animalsareallveryillandinobviousdistress.Inthecaseof
fairly harmless substances it is still considered good
procedureto findtheconcentration thatwillmakehalfthe
animals die; consequently enormous quantities have to be
force-fedtotheanimals,anddeathmaybecausedmerelyby
thelargevolumeorhighconcentrationgiventotheanimals.
Thishasnorelevancetothecircumstancesinwhichhumans
will use the product. Since the very point of these
experimentsistomeasure howmuchofthesubstancewill
poisonhalftheanimalstodeath,dyinganimalsarenotputout
oftheirmiseryforfearofproducinginaccurateresults.The
U.S. Congress Office of Technology Assessment has
estimatedthat“severalmillion”animalsareusedeachyear
for toxicological testing in the United States. No more
specific estimates for the LD50 test are available.^50
Cosmeticsandothersubstances aretestedinanimals’eyes.
TheDraizeeyeirritancytestswere firstusedinthe1940s,
when J. H. Draize, working for the U.S. Food and Drug
Administration,developedascaleforassessinghowirritating
asubstanceiswhenplacedinrabbits’eyes.Theanimalsare
usuallyplacedinholdingdevicesfromwhichonlytheirheads
protrude.Thispreventsthemscratchingorrubbingtheireyes.
Atestsubstance(suchasbleach, shampoo, orink) isthen
placedinoneeyeofeachrabbit.Themethodusedistopull
outthelowereyelidand placethesubstanceintothesmall
“cup”thusformed.Theeyeisthenheldclosed.Sometimes