one explosion, also in 2003, at west pharmaceutical industries in kinston, north carolina, showed just problem can be. because it was a drug company, the factory floor was immaculate. but plastic dust was hidden above the workers' heads. >> we know that as much as 2 inches of dust had accumulated in the ceiling, probably about a ton of material. that makes for a powerful explosion. >> hours after the blast, employees were still trapped inside. seven died, and scores were injured. carolyn merritt's investigation concluded that osha, the government agency created to safeguard workplaces, had no effective regulation on its books to deal with explosive dust. and she found that osha inspectors routinely overlook the hazard. did osha inspect that work site before the explosion? >> yes, osha had been in that facility. >> what did they find? >> they didn't find any dust issues. >> even when the dust was in plain sight, osha inspectors missed it. as they did at c.t.a., a plant that made soundproofing in corbin, kentucky, where the workplace had been covered in plastic dust. that factory explode