Is labor a proper noun

No, the noun labor (labour, British spelling) is a common noun, a Word for any labor of any kind.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• Ed Miliband MP, Leader of the Labour Party
• Labor Street, San Antonio, TX or Labour Street, Nassau, New Providence, The Bahamas
• Labor Day (holiday)
• "Labor Day", movie to be released 2013, with Kate Winslet, Josh Brolin
• "Labor Day Weekend: A Deal of Cold Business", a novel by Robert W. Witt