The long-term or chronic toxic character of environmental agents is rarely obvious. Scientific research is almost always required in order to detect the harm that such materials can cause to human health. Some of the most dangerous substances were thought not so very long ago to be harmless or even beneficial. These include cigarette smoke, radiation, asbestos, and lead. In some cases the first reports of a linkage between these agents and health problems were greeted with skepticism and fierce denials from the relevant industries and interest groups. Scientific research has helped to define the chemicals that cause disease and has been trying to understand the mechanisms by which these diseases are caused.
A good deal of this research is supported by the National Institute of Environmental Health Sciences, one of the many National Institutes of Health (NIH). Scientists are also trying to find ways to avoid human illness and misery caused by exposure to toxic chemicals. As an example of how different fields of science all contributed to the elimination of a specific chemical threat, we can look at the case of a chemical called bischloromethyl ether or BCME.
The chloromethyl ethers such as BCME are chemicals that were once used in many industrial processes. The identification of these compounds as human carcinogens made use of several scientific approaches, all of which were followed at roughly the same time. In a factory that produced BCME, an epidemiological study found that chemical workers showed an increased risk of lung cancer. The longer and higher the exposure to BCME, the greater was the risk. Meanwhile, several animal studies also showed that BCME was carcinogenic when applied to the skin of mice or when rats or hamsters breathed in the chemical. The data from both the animal experimental studies and the human epidemiological studies led IARC to its decision that these compounds are clearly human carcinogens.
A regulatory decision banning the use of BCME in most industrial applications and thereby preventing any further exposure of workers to these carcinogens led to industry-wide changes in plants and factories in order to eliminate all human exposure to BCME. Because it has now been decades since anyone has been exposed to this compound, the number of cancer cases in workers from the affected plants is now the same as that of the control unexposed population. We know that the lives of many potentially exposed workers were saved due to the work of several scientific disciplines followed by strong regulatory action.
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