DictationListen to the passage. For questions 21—25, fill in the blanks with th

Dictation
Listen to the passage. For questions 21—25, fill in the blanks with the exact words or phrases you hear.
Chemicals are added to a huge variety of products to give them certain properties. Many of these common chemicals are toxic to mammals and other animals. For example, one class of chemicals , called alkylphenols, can interfere with hormone systems and growth. Alkylphenols are often found in shampoo. Not only are these chemicals toxic, but they do not readily biodegrade. In other words, they will be on our planet for a very, very long time. Chemicals with a combination of these properties are commonly known as "Persistent Organic Pollutants," or POPs. The combined effect of POPs on our health and on the environment is increasingly being studied and recognized. Some work has been done to control the use of POPs, but only a handful of chemicals fall under current government controls. Additionally, companies don’t label their products with their chemical components, so consumers must do extensive research to learn about them. Contrary to popular belief, POPs don’t stay locked away inside of the materials where they are used. These chemicals can escape and enter the soil during manufacture and disposal. In fact, it now seems that no part of the planet is free of chemicals.