You鈥檝e seen the headlines. Of the 80,000 or so synthetic chemicals in the market place only a few thousand have been adequately tested. Activist groups constantly scream about inadequate testing and how we have become a population of guinea pigs. Inflammatory rhetoric that riles up and scares many people. But the fact is that testing is a very complex, time-consuming and unfortunately often unreliable process and the expectation that thorough testing will ensure that only completely safe substances make it to the marketplace is scientifically na茂ve. For obvious reasons, testing chemicals on humans is not an option. That leaves us with two methodologies. We can test in animals and we can test on living cells in the laboratory. Both of these are wrought with problems. The human is not a giant rat, dog or chimp. There are plenty of examples of substances that have appeared to be safe in animals and turned out to be toxic to humans, and vice versa. It wasn鈥檛 long ago that six volunteers in London ended up in hospital, some suffering permanent organ damage after being injected with tiny doses of an experimental drug designed to dampen the immune system. The hope was that it would be effective in the treatment of rheumatoid arthritis, leukemia and multiple sclerosis. Mice, rats, rabbits and monkeys had shown no ill effects at all. But the men certainly did. As one of the volunteers who luckily had been given a placebo described: 鈥淭he men went down like dominoes. They began tearing their shirts off complaining of fever, then some screamed that their heads were going to explode. After that they started fainting, vomiting and writhing around their beds.鈥� And this from a drug that had been shown to be safe in animals.
There are also numerous cases of substances that cause problems in animals but not in humans. For example, when Viagra was tested in beagles, it caused severe stiffness. Not where it counted, but in the neck. Researchers referred to this as 鈥渂eagle pain syndrome.鈥� They also found that Viagra constipated mice and caused the livers of rats to swell. These problems were judged not to be severe enough to preclude human testing, and indeed it turned out that these side effects were not seen in men who took the drug. These are not unusual case. A survey of some 150 compounds that were produced by various pharmaceutical companies as prospective drugs that showed some sort of toxic effect on people revealed that only 43% of these caused similar problems in rodents and only 63% did so in other animals. Obviously better models of testing are needed. And eventually this could come from testing chemicals on human cells in the laboratory. Of course cells don鈥檛 represent the whole organism, so there are still many issues here, but there is optimism. Techniques are being developed whereby liver or skin cells can be placed in thousand of tiny wells on a single dish and different doses of chemicals be systematically applied and the effects on the cells noted. Researchers are working on correlating results from such experiments with animal and human data and within a few years we may in fact be able to test those thousands of chemicals to which we are exposed in a more reliable fashion. The next canary in a coal mine may very well be an isolated liver cell in a pinhole in a laboratory dish.聽
