improve vs pollute

improve

verb
  • To make (something) better; to increase the value or productivity (of something). 

  • To become better. 

pollute

verb
  • To make something harmful, especially by the addition of some unwanted product. 

  • To violate sexually; to debauch; to dishonour. 

  • To make something or somewhere less suitable for some activity, especially by the introduction of some unnatural factor. 

  • To corrupt or profane 

adj
  • Polluted; defiled. 

How often have the words improve and pollute occurred in a corpus of books? (source: Google Ngram Viewer )