He says the us has spent about 160 million dollars clearing contaminated land over the last 20 years.
他说，在过去20年里，美国已经花费了大约1。6亿美元清理污染土地。
英语百科
Contaminated land
Land that is contaminated contains substances in or under the land that are actually or potentially hazardous to health or the environment. Areas with a long history of industrial production will have many sites which may be affected by their former uses such as mining, industry, chemical and oil spills and waste disposal. These sites are known as Brownfield Land.