OSHA plans to slash silica workplace exposure limits

A worker helps his colleague to lift a bucket of limestone as they work in a stone crushing factory at Burimari in Lalmonirhat district. According to a report by the Bangladesh Institute of Labor Studies, those working in the industry run the risk of contracting silicosis, an incurable lung disease caused by inhalation of silica dust. (REUTERS/Andrew Biraj)

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 is powdered quartz, in particles so small they can be inhaled deep into the lungs. 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 carrying a risk of silica exposure include sandblasting, mining, stone grinding, as well as ceramic and glass manufacturing. Dental assistants may be exposed if they grind silica-containing casts and porcelains.

Silica 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, told Reuters Health.

Silicosis causes varying degrees of breathing difficulty, and there is no cure or treatment. Recent research has also shown that non-smokers 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 mg/m3, which the agency estimates will save 700 lives per year, and prevent 1,700 cases of silicosis annually. The current standard dates back to 1971.

The preferred approach to reducing silicon exposure is to use less hazardous materials, ventilate work areas where silicon 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, published in CA: A Cancer Journal for Clinicians

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 five-fold by quitting, according to the new report.

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

OSHA recently extended the public comment period for the proposed silica exposure rule to January 27, 2014.

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.