For the worsening water pollution problem, the way the water plant adopts is to add a large amount of chlorine (bleaching powder) that exceeds the standard to disinfect and sterilize. Although chlorine can kill all kinds of bacteria in water, once it is combined with organic matter in water, it will produce a large amount of organic chloride (such as chloroform and dibromochloromethane) due to residual chlorine or bleaching powder, which is harmful to human health. . Organic chloride has been identified as a carcinogen in animal system tests. Most people think that just boiling the tap water will kill the bacteria, but in fact the water must be boiled for 20 minutes to remove harmful bacteria or viruses. During the boiling process, the chlorine gas in the water will be combined with organic matter, which will generate a large amount of carcinogens such as trihalomethane, especially at 100 ℃. To remove the chlorine gas, it needs to be boiled for more than 30 minutes, and the lid must be opened to let the chlorine gas volatilize with the steam. Otherwise, the trihalomethanes synthesized by chlorine gas will still remain in the water, chronically endangering health.