Some 1.85 million construction workers are at risk from exposure to silica. Press Association via AP Images

The U.S. government is planning stricter controls on exposure to silica, a carcinogen found in workplaces ranging from dentist's offices to granite quarries, according to a new report.

Silica occurs most commonly as quartz and is found in stone, brick, concrete and other common construction materials. Working with those materials can create dust containing silica particles so small, they can be inhaled deep into the lungs. That has long been known to cause silicosis, and evidence now confirms that silica exposure can cause lung cancer as well, Kyle Steenland of Emory University in Atlanta, a co-author of the new report, published in CA: A Cancer Journal for Clinicians, told Reuters Health.

The Occupational Safety and Health Administration (OSHA) estimates that 2.2 million people in the U.S. are exposed to silica at work, including 1.85 million construction workers. Other occupations with a risk of silica exposure include sandblasting, mining, stone grinding and ceramic and glass manufacturing. Dental assistants may be exposed if they grind silica-containing casts and porcelains.

Silicosis causes varying degrees of breathing difficulty, and there is no cure or treatment. Recent research has also shown that nonsmokers can get lung cancer from silica exposure and that people who develop silica-related lung cancer don't always have silicosis, Steenland and his colleague Elizabeth Ward of the American Cancer Society note.

OSHA is planning to lower permissible levels of silica exposure from 0.1 milligrams per cubic meter of air to 0.05 milligrams per cubic meter — which, the agency estimates, would save 700 lives and prevent 1,700 cases of silicosis annually. The current standard dates back to 1971.

The preferred approach to reducing silica exposure is to use less hazardous materials, ventilate work areas where silica dust is produced and use water-based methods so dust can't escape into the air, Steenland said.

"Respirators may be useful for workers in short-term high-exposure situations but are generally not recommended as the primary means of exposure control, due to worker discomfort, difficulties in communicating with others, lack of compliance and enforcement and the fitting and maintenance requirements," Steenland and Ward write in their report.

Anyone who has been exposed to silica and smokes should quit, Steenland said in an interview. Smoking aggravates the carcinogenic effects of silica, and smokers with high silica exposure can cut their risk of lung cancer up to fivefold by quitting, according to the new report.

People with a history of silica exposure may qualify to undergo screening for lung cancer using CT scanning, the investigators say.

OSHA recently extended the public comment period for the proposed silica exposure rule to Jan. 27.

While there is always a balance between worker protection and employers' interests, "I'm fairly confident that this standard will be put into place," Steenland said.

Reuters