Nashville, Tenn. ? When an accumulation of sugar dust ignited and blew up the Imperial Sugar plant in Port Wentworth, Ga., in 2008, killing 14 and injuring dozens, the state responded by issuing emergency regulations on combustible dust. No Georgia workers have been killed by exploding dust since.

For most of the nation, however, tighter regulations are still years away even though federal safety officials have been closely studying the threat posed by dust at industrial sites since 2003. Federal figures show that deadly explosions from finely powdered food, wood, metals and chemical happen each year in the U.S., killing and maiming multiple workers.

Combustible dust has been linked to at least six deaths at industrial sites this year, five of them in separate accidents at a Tennessee plant that makes metal powders for automotive and industrial uses. Between those two accidents, another worker was seriously injured by a fireball that investigators blame on an accumulation of iron dust at the same Hoeganaes Corp. plant in Gallatin, Tenn.

These industrial sites are regulated separately from grain handling facilities like the one that exploded last month in Kansas, also killing six. While that tragedy served as a reminder of the dangers for grain industry workers, experts say there are even fewer protections for their 2.5 million counterparts around the country in other industries susceptible to dust explosions.

“The science of explosion control is pretty simple. It’s not rocket science,” said retired University of Michigan professor of aeronautical engineering Bill Kauffman. “If you can see your footprint or can write your name on the wall, it’s going to explode.”

In an inspection before the deadly explosions at the Tennessee plant, dust hazards weren’t checked. Hoeganaes was fined days before the second fatal blast but not for breaking rules meant to prevent dust explosions — because there are none. The plant continues to operate.

That frustrates Mitchel Corley, whose little brother died from injuries caused by one of the explosions.

“Yes. I’m mad. Absolutely. They knew for certain that dust was flammable,” he said of the company.

Figures compiled by the U.S. Chemical Safety Board illustrate the scope of the problem. A 2006 study reported there were at least 281 dust explosions in the U.S. between 1980 and 2005 that killed 119 workers and injured 718. In 2007, it recommended that the Occupational Health and Safety Administration create workplace rules to control dust and cut down on explosions. The CSB is charged with investigating industrial accidents, but it must rely on regulatory agencies like OSHA to effect change from its findings.

“Despite the seriousness of the combustible dust problem in industry, OSHA lacks a comprehensive standard to require employers in general industry to implement the dust explosion prevention and mitigation measures,” the CSB wrote in its 2007 report.

OSHA decided instead to initiate a National Emphasis Program that stepped up education and inspections at plants in key industries. While the aim is to reduce dust explosions, inspectors have had to use regulations related to worker training and housekeeping because dust-specific rules are still being developed. The Chemical Safety Board says the rules currently being used are insufficient for preventing dust explosions.