By Chris Marsh
If your company works with materials that generate silica dust, you should actually be concerned on several different levels. The first of these is the potential for health problems that can be caused by silica dust, which can lead to a disease called silicosis.
Another reason to take an interest is that OSHA’s eye is upon you. In 1997, OSHA began a special emphasis program that is now part of its Strategic Plan. This means that there is official interest from OSHA to make sure companies follow the standards for silica.
A third reason to worry about silica and the health problems associated with it is the long-term expense your company could experience under your workers’ compensation policy. Silicosis is an expensive disease to treat and can be fatal, and there is no cure. This can increase your liability for many years.
As an employer, how can you eliminate – or at least minimize – these hazards? This article discusses the levels of illness and some of the protections you can give your employees.
Why is OSHA so keen on crystalline silica exposure? First, its toxicity is well-documented. Also, exposures can be controlled. Plus, there is wide-spread worker overexposure that is not being controlled.
Some examples of crystalline silica are sand, granite and other hard rocks. Quartz is the most common, while cristobalite and tridymite are less common but more toxic than quartz.
Potential exposures come from foundries, the ceramics industry, abrasive blasting, mining and construction. Some of the construction targets are jack hammering, concrete mixing, and brick and concrete block or slab cutting.
Silicosis is one of the world’s oldest known occupational diseases with reports dating back to ancient Greece. Since the 1800s, the silicotic health problems associated with crystalline silica dust exposure have been referenced under a variety of names such as mason’s disease, sewer disease, potter’s rot and grinder’s asthma. Silicosis was considered the most serious occupational hazard during the 1930s and is still present today.
OSHA originally targeted industry to focus on particular businesses where overexposure to crystalline silica is known or most likely to occur. This was determined by a records review of workers’ compensation claims that reflected a variety of diagnoses, including pneumoconiosis, fibrosis, respiratory disease and congenital heart failure.
There are three classes of silicosis: acute silicosis (the highest exposure) which comes from the highest exposure with latency of just weeks to five years; accelerated silicosis (high exposure) with latency of five to 15 years; and chronic silicosis (moderate exposure) with latency of more than 15 years. (Latency is the time it takes for the disease to be diagnosed or symptoms to show up.)
Acute silicosis is caused by intense crystalline silica exposure. It produces inflammation in the gas exchange
area of the lung and fibrosis.
Accelerated silicosis may result in smaller fibrotic nodules, massive fibrosis in the mid-zones of the lungs, shortness of breath, fever, and bluish skin at the ear lobes and/or lips. (The bluish skin means the lungs are not providing enough oxygen to distant body parts.)
Chronic silicosis results from 20 to 45 years of exposure to crystalline silica. (Chronic diseases are long-term, such as diabetes, and are most often incurable.) It results in nodular lesions in the upper lobes of the lungs, shortness of breath with exertion, cough and expectoration, fatigue, loss of appetite and chest pain from airway obstruction.
Silicosis can be diagnosed only by chest X-ray, which must be read by a qualified “B-reader.” Silica nodules found in the lungs are nonreversible. Since silicosis is not a curable disease, prevention in the workplace through safe work practices is critical to the health of employees. In the medical field of prevention, it is recommended that there should be a baseline X-ray prior to exposure and a history of any prior exposure. If a worker has less than 20 years exposure, it is recommended that a chest X-ray be given every five years. For those with more than 20 years exposure, the X-ray should be done every two years.
In the early stages of the disease, the problem will most likely go unnoticed unless a medical exam is performed. Continued exposure can result in shortness of breath, possible fever, bluish skin and susceptibility to infectious lung diseases such as tuberculosis (TB). The disease progresses from fatigue to extreme shortness of breath, followed by loss of appetite and pain in the chest, and finally to respiratory failure resulting in death.
How prevalent is silica exposure? While there are no known published studies of precast plants, a survey was conducted in Georgia at both ready-mix and concrete block plants at the request of the Georgia Concrete Products Association. There were 10 site visits with about 50 air samples taken. In the concrete block plants, 26 samples were taken and average silica exposure was 51 percent of OSHA’s Permitted Exposure Limit (PEL). One sample was 128 percent of the PEL and was associated with short-term cleanup work. The jobs surveyed were block machines, cubers, front-end loaders and maintenance. In the ready-mix plants, the average exposure was 47 percent PEL. The jobs surveyed were batch processors, front-end loaders and general laborers.
In addition to the medical surveillance program recommended by OSHA, other methods can be used to prevent silicosis. The employer should provide dust control, training on crystalline silica, a respiratory protection program, and an area to wash and change clothes. The employer should also provide an air monitoring program and promote good housekeeping.
OSHA has a recordkeeping requirement that is mandatory for companies with more than 10 employees and companies that have been asked specifically to keep the 300 and 301 logs by a government agency. This should be used to record illnesses and help you work toward preventing them.
Employers can install various engineering controls to reduce the risk of exposure. One form of engineering controls is the use of wet methods. This provides water suppression of dust and is very effective, but it requires a water supply and provisions for cleanup.
A second method of control is ventilation, including dust exhaust for portable tools such as surface grinders, disc grinders, crack chasers, scarifiers and power chipping tools. You can also retrofit dust hoods. A third method of engineering controls is the use of substitute abrasives. These may include coal slag or black beauty, steel grit and shot, aluminum oxide, sodium bicarbonate (baking soda), dust-suppressed sand, frozen CO2, or agriculture products such as walnut shells or corn cobs. A blast and recovery system permits multiple cycles of abrasives, reduces costs, especially when using more expensive abrasives, and reduces fugitive emissions into the environment.
Some other alternate abrasive methods are wet blasting, water jetting and sponge jet blasting. Wet blasting is similar to air blasting in that water is injected into air/abrasive stream. Water jetting is the use of high-pressure water to remove most paint, rust mill scale and chemical contaminants. Ultra high pressure – more than 25,000 psi – removes all coatings. Sponge jet blasting is used primarily in light-duty abrasion leading to less aggressive cleaning and the elimination of the hazards associated with high-pressure blasting.
Working with concrete can cause problems with silica in several different ways. OSHA’s mandate is to assure that every working man or woman in the United States is working in a safe environment. It is up to the employer to ensure problems are minimized.
Chris E. Marsh of Ogeechee Training Service in Statesboro, Ga., helps businesses come into compliance with OSHA regulations and also helps them with employee risk problems.