Scientists Link Silica, Not Coal, to Black Lung Disease

Tiny specks of sparkly rock, and not billowing black coal dust, are responsible for suffocating black lung disease, which saps the life from thousands of miners annually, a researcher says.

“When you think about it, there’s really no reason for coal to be toxic,” said Knox Van Dyke, a professor of pharmacology and toxicology at West Virginia University who has studied the issue for 15 years.

“Coal is carbon. Humans are made up mostly of carbon and water. When you get poisoned, they make you swallow charcoal. It just doesn’t make any sense,” Van Dyke said.

Using a machine that measures light given off by inflamed cells, Van Dyke said he and colleague Jaime Guitierrez determined that particles of silica bind with calcium in the lung cells, killing or inflaming them.

Researchers have known for decades that silica causes lung problems. Van Dyke said his research explains how the process works and demonstrates that inhaled coal dust poses little risk compared to silica breathed during mining.

“Any kind of dust can cause mild inflammation, but only silica dust has this kind of long-lasting toxic effects,” Van Dyke said.

Van Dyke said roof bolters who drill into hard rock above coal seams, miners who work near the rails where coal is hauled and those who work near continuous mining machinery risk exposure to silica, which is finely ground sand or quartz.

Van Dyke said his research also solves the mystery of how as many as 700 men died of silicosis, a debilitating lung disease similar to black lung, and complications during and after the digging of West Virginia’s Hawk’s Nest Tunnel six decades ago. The tunnel, blasted through the solid silica of Gauley Mountain, was built by Union Carbide Corp. to divert the New River to a power station.

Van Dyke said tiny specks of silica chemically bind with calcium in the body to set off enzymes within cells that destroy the cell’s DNA.

The researcher presented his findings earlier in Hershey, Pa., at a recent meeting of the Generic Respirable Dust Center. The center is jointly based at West Virginia University and Penn State.

The dust center’s goal is to come up with causes and ways to prevent respirable dust disease in mineral mines. Much of its research has centered on coal mines.

Van Dyke said his findings were buttressed by research on silica at Penn State.

Vincent Castranova, a researcher at the federal Appalachian Laboratory for Occupational Safety and Health in Morgantown, said coal dust can’t be ruled out as the cause of black lung.

Dr. Greg Wagner, director of the division of respiratory disease studies at the National Institute for Occupational Safety and Health, said he couldn’t comment on the study until it is published.

“There is a substantial amount of literature that indicates that silica is an extremely toxic substance and that silica needs to be controlled,” Wagner said. “There’s also a substantial amount of literature that coal dust, even without silica, is toxic and causes lung disease.”

Coal miners’ pneumoconiosis, emphysema and bronchitis are generally lumped into the general category of black lung disease, Wagner said. The diseases are chronic and generally require an extended exposure to dust in mines.