Human activities constantly affect the natural environment, causing changes in environmental quality, and then affecting human normal life and health. Production activities are relatively simple and small in scale, so human activities have little impact on the environment. The industrial revolution promoted the development of human social productive forces, and also affected and destroyed the human environment, especially the ecosystem.
Since the 20th century, with the rapid development of coal, steel, petroleum, chemical industry and transportation, new cities and industrial and mining areas have appeared constantly, and the urban population has increased dramatically. Therefore, waste water, waste gas, waste residue, pesticides and other organic synthetic substances, radioactive substances and noise seriously pollute the environment and form public hazards.
Major public hazards such as London smog, Los Angeles photochemical smog, Minamata disease in Japan, pain, four-day asthma and rice bran oil incident (polychlorinated biphenyl poisoning) claimed thousands of lives. In addition, the increase in the incidence and mortality of cancer and nonspecific diseases, which seriously threaten human life, has also aroused widespread concern and become an important research topic in contemporary medicine.