Wetenschap - 9 oktober 2014

Toxicologist fought to replace animal test for 30 years

Rob Ramaker

Since the 1960s, rabbits have been used to test whether new personal care products and household cleaners, for instance, cause irritation to eyes. When opposition to animal testing started to grow in the early 1980s, this ‘Draize test’ be­came the preeminent example used by opponents of animal experiments.

Photo: Menk Prinsen

Menk Prinsen and his colleague Herman Koëter, who both worked at TNO at the time, were worried about this and started looking for an alternative. Prinsen gives an account of the difficult process that followed in his doctoral thesis, which he defended on 4 October. 

The start was promising. Prinsen and Koëter soon showed that you could also test substances using loose ‘dead’ rabbit eyes. At least that way the animals don’t suffer during the test. Later they switched to chicken eyes to avoid experimental animals altogether. They fetched the heads from the abattoir and then detached and prepared the eyes. After applying droplets of a substance to such a loose eye, you can see whether the cornea remains intact using a special eye microscope. 

According to Prinsen, the test not only avoids the use of experimental animals, it also produces better results. ‘It is much closer to reality,’ says Prinsen. The tests on living rabbits cause all kinds of problems, he says. For instance, the result can be seriously affected by animals scratching their eyes after the test. The microscopic examination of an eye also turns out to be more reliable than the subjective assessment of the rabbit’s eye irritation by a researcher.

You mainly feel frustrated, you’ve got a good test but you just can’t get it accepted
Menk Prinsen

But at the time, Prinsen was hardly able to convince the regulatory authorities at all. Regulators continued to demand equally ‘good’ scores from his alternative as from the Draize test. He was not able to achieve that. A major international validation study by the European Commission in the 1990s ended in ‘a huge disappointment,’ says Prinsen. All the alternative tests, including his, had inadequate scores. ‘You mainly feel frustrated,’ says Prinsen, ‘You’ve got a good test but you just can’t get it accepted.’ He decided to keep using the test in order to no longer have to test serious irritants on animals, but he stopped putting an effort into lobbying.

However, a turning point was reached in the years that followed. The European industry for household and personal care products eventually embraced the alternative test. The OECD also included the test in its guidelines in 2009. In 2010, Prinsen was awarded the Hugo van Poelgeest prize for alternatives to animal tests. That felt like ‘a fantastic accolade’. Indeed, Prinsen does not feel frustrated now and he expects the Draize test to disappear completely in the future. He personally intends never to perform it again.