Human cell tests have shown their superiority over animal tests.

Dr. Bjorn Ekwall and colleagues in the " Multicenter Evaluation of In-Vitro Cotoxicity (MEIC) trial based in Upsala, Sweden, recently released final data from 29 independent labbratories. The results showed that while rat and mouse tests have been about 65 percent accurate in predicting human risk, a combination of three human cell tests predicted the toxicity of chemicals with 77 percent precision. Further improvements can be made by statistical adjustments, based on a "test chemical's ability" to pass through the blood-brain barrier.

Human cell tests may also provide information for judging ecotoxicity. The most accurate human cell tests were developed in Belgium, Japan, and Mexico.

The MEf trial tested 61 different in-vitro assays for fheir correlations with human lethal blood concentrations, comparing the results with lethal dose (LD50) tests on rats and mice.

They tested 50 chemicals which varied widely in thelr chemlcal properties.

While the rodent tests showed varying degrees of accuracy for the 5 test chemicals, they were wildly inaccurate in predictimg human lethal doses for 9 chemicals. For one of these, dioxin, the problem was clear: rodents have less Na/K ATPase enzyme activity compared to humans, rendering rodent tests useless.

In fact, rat LD50s are not particularly good predictors of mouse LD50s. The MEIC review found that rat tests grossly underpredicted results of mouse tests for several chemicals. An animal LD50 test could exonerate a chemical or make it appear safer than it is. Human cell tests are far