Five years ago, OSHA clamped down on jobsite silica levels. The fate of millions depends on how well that’s working.

Second of three parts.

Know Your Enemy

Airborne crystalline silica causes pulmonary disease among railroad workers and those in many other fields. But what is it, and how exactly does it hurt the lungs?

Through a microscope, which is the only way to see it, crystalline silica may look like shards of dark glass.

Silica is like broken glass in one other way, too: its capacity for ravaging human tissue. Though the damage silica can do to the human body is internal—if inhaled it can have a debilitating effect on the lungs, liver, or kidneys—the harm it does is irreversible and ultimately may amount to a death sentence. Years or decades after exposure to silica, usually on a jobsite, many workers develop lung cancer. One industry whose employees are at especially high risk of silica exposure is the railroad, whose tracks often have ballast made of granite, which has a relatively high silica content of 45 percent.

But what is silica, and how can something so small imperil so many? Though bigger than a virus, which must be viewed through an electron microscope, crystalline silica is 100 times smaller than a grain of sand and invisible to the human eye—about the size of dust, bacteria, and fumes. And yet, as those who have lung cancer from the even-smaller particulates of tobacco smoke can attest, it’s often the littlest intruders in the body that cause the greatest damage.

A serious threat

Though usually not airborne or respirable and therefore not hazardous, silica—a mineral found in natural materials such as sand, soil, stone, and ore—is all around us. The hard, colorless compound, which is most commonly found in quartz and is a component of most rocks, accounts for more than a quarter of the earth’s crust.

Silica is in many manmade things, too: concrete and brick, ceramic tiles and dental fillings, jewelry and tombstones. It’s also in sand, clay, mortar, pavers, cement sheeting, and the engineered stone slabs used in the manufacture of kitchen counters.

Respirable crystalline silica is released into the air as a result of certain construction and industrial processes, such as metal work, abrasive blasting, and hydraulic fracking. It’s released in the crushing, drilling, and jackhammering of rock or concrete, in masonry and concrete work on roads, in demolition projects, and in the cutting, sawing, or sweeping of silica-containing substances. It’s released in quarry work, mining, and tunneling, in the manufacture of marble, stucco, plaster, drywall, glasses, plates, cosmetics, bricks, tiles, joint sealants, cement roof tiles, and in welding and metal work. Railroad workers are at risk of inhaling crystalline silica when dumping or arranging granite track ballast.

Silica exposure is a serious threat to nearly 2 million U.S. workers, according to the Centers for Disease Control. In 2016, OSHA lowered the permissible exposure limit, of PEL, in workplaces in an effort to better protect workers from airborne silica, but exposure above that limit continues. According to AMI Environmental, the percentage of workers exposed to respirable crystalline silica who were exposed at a level above the new PEL is almost 50 percent in the concrete industry, 35 in foundries, 66.1 in oil and gas operations, 32 in railroads, 40 in pottery, 36 in jewelry, 45 in asphalt roofing materials, 73 in shipyards, and 3 in dental labs.

‘Like a coal miner’

Once inhaled, the dust enters the lungs. There, it’s small enough to travel to the bottom of the lungs, imperiling the alveolar sacs through which oxygen and carbon dioxide are exchanged with the blood stream.

Ironically, in damaging the lungs silica has help from the body’s immune system. The fractured surfaces of the crystalline silica dust have biologically active sites that interact with the water in human tissue. The particles also scratch the tissue. And the body responds. the lung tissue reacts by developing fibrotic nodules and scarring around the trapped silica particles. If the nodules grow too large, breathing becomes difficult. In an ill-begotten attempt to fight off the jagged little intruders, the immune system dispatches scavenger cells—primarily white blood cells—to engulf and destroy the crystalline silica in the lungs. But these scavenger cells release enzymes that cause the lung tissue to scar and eventually become compromised, impairing the person’s ability to breathe. Then disease takes hold.

Disease development typically takes over 10 years of dust exposure—about the same amount of time it takes, under normal circumstances, to develop a vaccine. Or save the world from climate change.

Kevin Howell of Ohio can attest to railroad work’s slow hand of fate. Though he never was supplied safety equipment to help protect him against dust and fumes until breathing protection was introduced in the 1990s, he often worked closely with diesel track equipment that would disturb the silica-containing ballast along the road beds. At the end of a work day, he says, he looked like a coal miner.

Now, retired and long free of that dust as well as the asbestos he breathed while working with switch boxes, he has cancer—and a $4.5 million verdict in his favor.


Next week:

Part three of Lives in the Balance: “Telltale Dust”