contamination       
noun [ U ] uk/kənˌtæm.ɪˈneɪ.ʃən/ us/kənˌtæm.əˈneɪ.ʃən/
 弄脏,污染;玷污
the process of making something dirty or poisonous, or the state of containing unwanted or dangerous substances 
  The water supply is being tested for contamination . 供水系统正在接受污染测试。 
 The police immediately sealed off the crime scene to prevent contamination of evidence. 警方立即封锁了犯罪现场,以免污染证据。 
 See: contaminate
 - More examples
 - The cause of the contamination was never discovered.
 - The contamination has spread to tap water in Tokyo.
 - The company is investigating the extent of soil and groundwater contamination and plans to clean it up.