Non-specificity of clinical signs and symptoms caused by environmental chemicals

1. A review of the scientific literature revealed that 220 environmental chemicals had caused documented systemic toxicity in humans. This number is relatively small compared to the large number of industrial chemicals in the environment. 2. A total of 149 of these chemicals were verified as neurotoxins, thus emphasizing the sensitivity of this target organ. Despite the exclusion of chemicals that cause airway irritation only, 99 chemicals caused adverse effects on the respiratory system. Toxicity to the liver, kidneys and blood forming organs was less frequent. 3. Most of the individual clinical effects had a very low specificity in cases of human intoxication. Of 80 major signs and symptoms, 17 had only a single documented chemical aetiology. However, the combination of two or more signs or symptoms was found to provide an improved guidance to aetiological diagnosis. The paucity of specific signs and symptoms is probably one of the reasons that only 220 environmental chemicals have been documented as causes of human disease.