Don't trust animals

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THIS week's column is based on 'Why Animal Tests?'. in Science for People No. 52.* Most animal experiments in Britain are carried out to test the safety of various chemicals le.g. drugs, cosmetics) to humans. The fundamental assumption then is that the results actually apply to humans. Unfortunately, there is little evidence that this is so.

Let us look more closely at how chemicals are tested in animals.

Chemicals intended for human 'consumption' must be tested to see if they cause cancers and/or if they have toxic effects on living tissue (including the unborn).

Tests for cancer-causing compounds involve giving the chemical to animals such as mice or guineapigs over a period of time, often in doses relatively Socialist Organiser Science Group Interested in science and intereste in socialism?

Contact: SO science group, c/o Les Hearn, 28 Middle Lane, London N8. much higher than humans would take.

The most common animal test is the LD50 test (Lethal Dose 50%) which attempts to identify poisonous chemicals by seeing how large a dose will kill 50% of animals given it. The test lasts for 2 weeks, or until death (whichever is sooner) and no pain relief is given. Common signs of toxicity of chemicals tested are 'tears, 'unusual vocalisation' (I assume this is a euphemism for cries of pain or distress), diarrhoea, discharge and bleeding from the conjunctiva (outer membrane of the eye) or mouth, (and) convulsions.' Now, though at a very basic level, living organisms are remarkably similar le.g. our DNA operates on the same code as the humblest bacterium) at the level where most chemical reactions go on in our cells, we are remarkably dissimilar from even quite close relatives: So what is poisonous to us may not be poisonous to other species - and vice versa! E.g. Eraldin (ICI's latest disaster) caused blindness only in humans, while aspirin causes birth defects in rats, but not humans _ luckily, as it was never tested on animals! Also introduced before animal testing came in were anaesthetic! in fox-gloves, "laughing gas' (the dental (the poison used to stimulate weak hearts, and cinchona bark (natural source of the anti-malarial drug, quinine).

As well as being an unreliable indicator of risk to humans, the LD50 test is frequently unreliable even with the same species, with different labs reporting wildly different results! As well as being cruel, LD50 cannot even be justified in terms of its value to human health.

Testing chemicals on unborn animals is even less reliable as the differences in embryo development between humans and other animals are even greater than the differences in cell chemistry.

Cancer testing is also quite unreliable. Firstly, too high doses in experimental animals may result simply in the killing of sensitive cells which might, with lower doses, become cancerous.. Secondly, a chemical causing cancer in one species may be converted in the body of another species to a harmless chemical.

Why, then, are these misleading tests used? One answer came from Geoffrey Finsberg MP of the DHSS in 1981.

'LD50 results ed by drug regulatory authorities in countries to which we export, contributing to a net favourable balance of trade in pharmaceuticals of over £500 million"

Another answer came from R.W.Smithells, Protessor of Paediatrics at Leeds University and former member of the government watchdog Committee on the Safety of Medicines, who said that tests on animal embryos were "more in the nature of a public relations exercise than a serious contribution to drug safety"

As a result both of protests by animal welfare campaigners and of a realisation by researchers that animal tests are unreliable, alternative test systems which are both more humane and more reliable are being developed (see SO 92 for testing antiepilepsy drugs on moong beans).

Influential

The most influential development in this field was the Ames test, introduced about a decade ago. The theory behind this was that, because all cancers involve some alteration of the cell's DNA, testers could give the suspect chemical to bacteria and look for mutations in their DNA. These could be spotted very easily, in a short time, often in a day *Possibly more reliable still are tests using human cells - either cancer cell lines such as the Hela line (which came from a cancer victim who died in the 1930s), or cells from specific human tissues, such as glands, liver, gut cells etc, 0389 HODIG which might be particularly susceptible to certain types of damage. An individual person's reaction to certain anti-cancer drugs (which can be unique) can perhaps be most reliably found out A a de a o HiN

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IAN SWINDALE looks at ITV's new series Organiser no.100 September