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There are many types of chemical substances on earth. The CAS Registry of the Chemical Abstracts Service in the United States, a database of chemical substance information, listed more than 70 million different chemical substances as of June 2013. It is said that several tens of thousands of those substances are used in industrial fields, mainly as raw materials and additives.
In addition, a large number of new chemical substances are produced every year and the total number of chemical substances is increasing year by year. Chemical substances can increase the convenience of our daily lives. However, some of these substances may adversely affect human health and the environment because of their properties, toxicity, or usage status. Recently, environmental pollution caused by these hazardous chemical substances has become a major concern.
