Many workers in Iowa’s two tallest skyscrapers are nervous. Archie Brooks, property manager for the Ruan Building in downtown Des Moines, says tenants in his building are letting workers go home if they’re spooked.Brooks was stunned by the collapse of the World Trade Center. He says there are five thousand people in the building and it’s scary.Iowa’s tallest building — 8-0-1 Grand in Des Moines — rises 41 stories. It’s owned by the Principal Financial Group. Rhonda Clark, a spokeswoman for the insurance company, read from a prepared statement, saying they continue to monitor the situation and have increased security while they continue business operations. Clark says workers can go home if they want.