塑料的前世今生，来自Teens的好文章

Lego bricks (乐高积木) can stay in the ocean for about 1,300 years. Plastic (塑料) causes problems for the environment (环境). We use many things made from plastic. But we have to solve the plastic pollution (污染) problem. How much do you know about plastic?

Birth of plastic

Before the invention of plastic, people used natural materials (自然材料) such as wood, metal (金属), stone and bone. But they were not enough. Over 100 years ago, an American man named John Wesley Hyatt made a new material from cotton fiber (棉纤维). It was strong, long-lasting (耐用的) and light. Water and heat could not damage (毁坏) it. It could be turned into different shapes. This was the world’s first plastic. Today, most plastic is made from petroleum (石油). 

They changed the way we live

Plastic is cheap. It can replace many expensive things. For example, toothbrushes used to be made of animal bones. They were expensive. Not many people could buy them. But then, plastic toothbrushes came out. They were cheap. They could be used for a long time. So many people began to brush their teeth. Thanks to plastic, today we can have healthy teeth. 

Plastic saved wild elephants  

The invention of plastic saved many wild animals, such as elephants. In 1860s, billiards (台球) were popular around the world. At that time, billiard balls were made of elephant ivory (象牙). One tusk (象牙) could only be made into five balls. So people killed thousands of elephants for their tusks. Afte