Sentence:  A particular problem is the disposal of small quantities of unwanted, surplus, or <WSD>unused</WSD> pesticides. Considerable attention has been given recently to the detoxification, prior to disposal, of sizable amounts of pesticides such as the herbicides returned from Vietnam. Some attention has also been given to the smaller amounts of <WSD>unused</WSD> pesticides at the consumer level, and in a few communities, specific pesticides such as DDT have been collected by authorities and safely disposed of by proven procedures. 
Meaning of the word marked with <WSD> tags:  Not used.