contaminate

Concise Oxford English Dictionary © 2008 Oxford University Press:
contaminate/kənˈtamɪneɪt/

▶verb make (something) impure by exposure to or addition of a poisonous or polluting substance.

– derivatives
contaminant noun,
contamination noun,
contaminator noun.

– origin ME: from L. contaminat-, contaminare ‘make impure’, from contamen ‘contact, pollution’, from con- ‘together with’ + the base of tangere ‘to touch’.