It is difficult, therefore, to find definite proof that a chemical can cause illness or death. However, the majority of scientists who conduct independent research into the effect of chemicals on the environment believe that complete certainty is not needed. According to them, if a connection is found between a chemical and serious health problems in test animals, we must stop the use of that chemical. It is better to ban a chemical which may be safe than to use a chemical which may cause serious illness or death. ‘