Construction health hazard: silica dust
How to limit your exposure to this lung-damaging material.
As a plumbing or mechanical contractor, you might think the Occupational Safety and Health Administration’s proposed silica standard has nothing to do with you. But are you sure? Have you ever had to cut through concrete or tile to install pipe — or drill holes in concrete to hang ductwork? Everyone who works in the construction industry needs to be aware of potential exposure to airborne crystalline silica.
Silica is found in many materials common on construction sites, including concrete, masonry, brick, block and stone. The dust created by cutting, grinding, drilling or otherwise disturbing these materials can contain respirable crystalline silica. Inhaling this dust can result in serious illnesses, which are sometimes fatal. These illnesses include silicosis, lung cancer and other respiratory diseases. It only takes a small amount of airborne silica dust to create a health hazard.
Recognizing that very small, respirable silica particles are hazardous, OSHA’s regulation 29 CFR 1926.55(a) requires construction employers to keep worker exposures at or below a Permissible Exposure Level of 250 micrograms per cubic meter of air (ug/m3). The National Institute for Occupational Safety and Health has a lower Recommended Exposure Level of 50 ug/m3.
Yet every year, hundreds continue to die of health conditions related to silica exposure. That’s why OSHA has proposed to lower its PEL to the level recommended by the scientists at NIOSH, a move the agency estimates will save nearly 700 workers per year from deaths related to silica exposure on the job.
Silica and lung disease
At least 1.7 million U.S. workers are exposed to silica. A worker’s chance of becoming ill from exposure to silica dust depends on the tasks performed, the amount of dust he is exposed to and the frequency of the exposures. Each exposure to silica adds into the total load of silica in the lungs. In other words, each exposure adds to the lung damage.
Health professionals express the total silica dose one person accumulates over time as mg/m3 years, usually calculated as an average exposure each year in mg/m3 multiplied by the number of years with that exposure or by an estimated average for each year. As the total dose increases, so does the likelihood, or the risk, for developing silicosis, lung cancer or chronic obstructive pulmonary disease.
Repeated exposures to silica add up to a total dose that can cause serious lung disease. Some workers become ill after many years of low exposure levels, while other workers who perform less frequent but high-exposure tasks can become ill with a lower cumulative exposure. Why? Because a high exposure to silica dust overwhelms the lungs’ defenses; most of the dust settles deep into the lungs where it does the most damage.
Silica exposure can cause silicosis, an irreversible disease that can be disabling and lead to death. When workers inhale crystalline silica, the lung tissue reacts by developing fibrotic nodules and scarring around the trapped silica particles. If the scarring becomes too extensive, breathing becomes difficult. People with silicosis also are at a higher risk of developing tuberculosis.
The three types of silicosis are:
- Chronic silicosis. Usually occurs after 10 or more years of exposure to crystalline silica at relatively low concentrations;
- Accelerated silicosis. This results from exposure to high concentrations of crystalline silica and develops five to 10 years after the initial exposure; and
- Acute silicosis. Occurs where exposure concentrations are the highest and can cause symptoms to develop within a few weeks or four to five years after the initial exposure.
Silica and other dusts also cause COPD, which includes chronic bronchitis, emphysema, bronchiectasis and chronic airway obstruction. In 1999, COPD ranked as the fourth-leading cause of death, with more than 124,000 deaths. COPD is projected to become the third-most common cause of death worldwide by 2020.
Symptoms from both silicosis and COPD may not be obvious and can initially include shortness of breath, chest pain or a persistent cough. Silicosis and COPD can be severe enough to cause respiratory failure, which may eventually lead to death.
In 1996, the World Health Organization’s International Agency on Cancer Research classified silica as a known human carcinogen, and in 2009 it reaffirmed its position. Study after study has confirmed that silica exposure does indeed cause lung cancer in humans.
Silicosis has no cure but it is 100% preventable. A growing number of tools and technologies are available to protect workers from exposure to airborne crystalline silica. Keeping your employees safe is probably easier than you think.
The Center for Construction Research and Training (CPWR), a nonprofit construction safety/health research and training institute, has stepped up to help. Relying on decades of research experience on the silica hazard, as well as input from contractors, workers, researchers and other stakeholders, CPWR created a one-stop online resource on the silica hazard.
Plumbing and mechanical contractors can use the information and planning tool available on the Work Safely with Silica website (www.silica-safe.org) to assess their risk and take action to prevent exposures and related illnesses.
The Work Safely with Silica website features a unique online planning tool that enables contractors to determine if silica exposure is a potential hazard on the jobsite. If so, they can design a site-specific plan for controlling exposure in just three steps:
- Users identify the construction materials they will be using that contain silica and the activities they will perform on the job.
- Based on those selections, a list of equipment and control options is generated for each material-task combination, along with an option to learn more by simply clicking on the prompt, such as “Click here for examples of commercially available equipment and controls.” Examples include manufacturer information and videos (if available), and impartial third-party information on the different types of equipment and controls. Contractors also can manually enter equipment and controls of their own; space is provided to describe how the material(s) and equipment is to be used on the job.
- The program provides prompts and space to fill in other details of the job and elements of a comprehensive silica control plan for a project. Click “Continue” to generate a site-specific plan, which can be printed, emailed or saved as a PDF.
Within each step are prompts and links to additional information if users are not sure if a material contains silica, what type of control to use and what additional information should be included in the jobsite plan. A recently added feature allows plumbing and mechanical contractors to set up a password-protected account and confidentially save their plans so they can be retrieved and edited for use on future jobs.
We have known the facts about this deadly dust for decades. We now have the knowledge and the technology to keep workers safe — if we all do our part.
About the author: Pete Stafford is executive director of The Center for Construction Research and Training. Research for this article was made possible by a cooperative agreement with the National Institute for Occupational Safety and Health(OH009762). The contents are solely the responsibility of the authors and do not necessarily represent the official views of NIOSH.