In one of Bill Watterson’s “Calvin and Hobbes” cartoon strips, six-year-old Calvin asks his dad how they calculate the maximum weight allowances for bridges.
His father explains that they drive heavier and heavier trucks across the span until the bridge collapses; note the weight; then rebuild the whole thing.
We’re amused as much by the father never lost for an answer, as by the absurdity of the methodology he invents.
And yet a similar philosophy was applied to developing a test of chemical toxicity known as lethal dose 50, or LD50. The LD50 test establishes the dose of a substance that will prove fatal to half the test animals exposed to it. It does this by killing them.
Attitudes to animal welfare have changed since LD50 was introduced in the 1920s. The severe suffering of a substantial number of animals in LD50 was becoming unacceptable to an increasing number of people in OECD countries, but at the same time the test provided important information. Experts from the UK, Germany and the USA took the lead in developing three alternative tests.
In November 2001, the OECD agreed that the three different methods could provide sufficient information to replace LD50 (or OECD Guideline 401 for the Testing of Chemical as it was known).
The number of animals needed was drastically reduced by the new protocols, and would normally be well below one-third of those used for LD50. Moreover, one of the alternatives (Guideline 420) does not require the death of any animals at all, whereas in Guidelines 423 and 425 the expected number of deaths is typically not more than 3 compared with at least 10 in LD50.
Guideline 401 was deleted in 2002 and a number of countries now ban LD50 tests.
Animal welfare benefits from another OECD procedure too. In 1981, the OECD Council adopted a legally-binding Decision stating that data generated in a Member country in accordance with OECD Test Guidelines and Principles of Good Laboratory Practice shall be accepted in other Member countries for assessment purposes and other uses relating to the protection of human health and the environment.
In other words, with Mutual Acceptance of Data (MAD) there is no need to duplicate tests in each country before approving or banning a substance. Of course humans benefit too, and not just from safer products. Governments and industry save over 150 million euros a year from MAD for pesticides and industrial chemicals alone.
In line with the internationalisation of research, the scheme is expanding beyond OECD countries. Today, India became the third key emerging economy to sign up to MAD, after Singapore and South Africa, while Argentina, Brazil, Malaysia and Thailand are provisional adherents to the system.
That’ll keep a lot of bunnies happy.