Specific occupations at highest risk of exposure include welders, auto mechanics, tile setters, boilermakers, U S.Navy personnel, shipyard workers, merchant marines, sheet metal workers, bricklayers, building inspectors, carpenters, roofers, plumbers, plasterers, refinery workers, pipefitters, painters, demolition workers, drywall workers, electricians, floor covering workers, furnace workers, glaziers, millwrights, insulators, ironworkers, laborers, Libby vermiculite exfoliation plant workers, longshoremen, maintenance workers.