Ecosystems and Human Health—Toxicology and Environmental Hazards, Third Edition

"1 1 Principles of Pharmacology and Toxicology The right dose differentiates a poison and a remedy. Paracelsus, 1493-1541 Introduction The past century has seen a tremendous expansion in the number of synthetic chemicals employed by humankind as materials, drugs, preservatives for foods and other products, pesticides, cleaning agents, and even weapons of war. The American Chemical Society maintains a chemical registry. Since 1907 it has recorded 33 million organic and inorganic substances and 58 million sequences as of 2008. About 4000 new chemicals are added each day. A study by the Danish Environmental Protection Agency calculated that 13.4% of them possess acute toxicity, 2.5% reproductive toxicity, 3.9% are mutagens, 1.8% carcinogens, and 3.5% are dangerous to the aquatic environment. Four thousand chemicals are used as medicinals and at least 1200 more as household products. Add to this the numerous natural substances, both inorganic and organic, that possess toxic potential, and it is little wonderthat the public expresses concern and even, sometimes, panic about the harmful effects these agents may exert on their health and on the environment. Tens of thousands of these agents have never been subjected to a thorough toxicity testing. According tothe Danish study, thousands of chemicals are potential carcinogens but the number that has been confirmed to be human carcinogens is much smaller. About 500 chemicals have been evaluated for carcinogenic potential. Some 44 have been designated as possible human carcinogens on the basis of evidence, either limited or conclusive, obtained from human studies. "--

Richard Philp, D.V.M., Ph.D., is an emeritus professor and former chair of the Department of Pharmacology and Toxicology at The University of Western Ontario. He conducted research in the physiology of deep sea diving, investigations into arterial thrombosis, and, for the last 15 years of his 40-year career, taught a course on environmental toxicology. He also authored two textbooks on the subject. Professor Philp has conducted studies on heavy metal pollution of the waters of the Gulf of Mexico and was a member of the Thames-Sydenham Regional Source-water Protection Committee. He has served as a consultant in environmental toxicology to citizens’ groups and to Santa Cruz County, California. He has also published more than 100 papers in peer-reviewed journals and 6 books, mostly on environment-related subjects.