<<Stakeholder Meetings

SESSION 1 - June 2, 1998
8:30- 12:00

Silica Stakeholders Meeting Summary

The format of the stakeholder sessions followed the questions in a stakeholder document that is also available on the Web page.There were four general areas of discussion: scope, controlling exspoures to crystalline silica, monitoring and sampling, and screening and surveillance.

SESSION 1 - JUNE 2, 1999
8:30 - 12:00

ISSUE 1: Scope

In which operations do silica exposures occur?

Operations in precast concrete plants where silica exposures occur include:

  • Batching/Mixing
  • Blasting
  • Cutting, drilling, and sawing
  • Sweeping
  • Air blowing
  • Mobile equipment (yard dust)
  • Grinding

Precast concrete exposures on construction sites include:
  • Saw-cutting joints
  • Drilling and cutting block and brick

Typically construction site exposures occur for 45 minutes; 8-hour exposures are rare. One stakeholder expressed concern that silica might be banned by OSHA. OSHA question: With respect to silica exposures, what differences exist between renovation and and new construction? Stakeholder answers: Except for demolition activities, new construction causes more exposure than renovation. A separate standard for silica in construction is needed. Typical construction operations where exposure to silica occurs include:
  • Crushing
  • Drilling
  • Mobile equipment (fugitive dust)

Wet cutting and water spraying are used to control dust

OSHA question: Does the percent of silica differ in different types of rocks?

Stakeholder answer:  Yes - different types of rocks lead to different exposures.

Granite quarry operations are using water to suppress dust. The standard needs to allow the use of objective data for construction sites.

Operations in bentonite (clay from volcanic glass produced in Wyoming, Montana, Alabama, Mississippi, and Texas) manufacturing with the potential for exposure to silica include:
  • Packaging dust exposure - currently meeting PEL, dust is 2 - 4 percent total silica
  • Dryers
  • Outside loading

Respirable silica content in bentonite is below 0.1 percent. Bentonite is an encapsulated silica in which the silica particles are encased in clay. Bentonite is used in many foundries, where silica exposures are limited to the grinding and cleaning operations but do not occur in mulling or shake out areas.

Typical operations in foundries where exposures to silica occur include:
  • Core making
  • Molding
  • Shake out
  • Casting, cleaning
  • Blasting
  • Grinding
  • Reconditioning (sand)
  • Housekeeping
  • All sand handling operations

But the sources and respirable fraction of silica (usually quartz) in sand used in foundries vary:
  • Lake sand is 90 percent crystalline silica but only 5 percent respirable silica.
  • Bentonite.
  • Highest levels occur in cleaning (28 percent free silica in respirable dust).
  • Core washing (over 20 percent respirable silica at times).
  • When using reconditioned sand, the respirable silica is reduced to 7 percent.

Silica exposures in sorbent manufacturing include:
  • Minimal exposures during drying, screening and bagging.
  • Silica content is typically 1- 10, percent which is mostly non-respirable size.
  • The silica in sorbent production is mostly encapsulated in clay.
  • Most manufacturers are in compliance with the current PEL.
  • Exposures during the use of sorbent products are often well below the current PEL.

Silica exposures during graphite manufacturing occur in:
  • Grinding (the only significant problem area: exposures range from 0.1 to 0.3 mg/M3)
  • Material transfer (handling)
  • Generally only a small portion of graphite operations involve silica exposures.

Real-time exposures over the current PEL occur in granite quarries in the following operations:
  • Dry cutting 0.05 - 23.77 mg/M3
  • Drilling 0.32 - 0.80 mg/M3
  • Core cutting 14.2 mg/M3
  • Sand blasting 0.52 - 1.80 mg/M3

EPA consent order testing was performed for a synthetic vitreous fiber manufacturer; it showed that vitreous fibers remain vitreous during their entire life cycle. Most exposures in manufacturing are less than the lower detectable limit (LOD) for the analytical method. Exposures in the removal of refractory material from an industrial furnace also remained low, but the LOD for the method varied due to high particulate loading. The stakeholder from this industry submitted a journal article documenting these findings.

A stakeholder from the bentonite clay industry submitted a journal article showing that bentonite clay and fuller's earth are very much the same and that no conversion of bentonite clay to crystalline silica occurs in foundry operations.

A stakeholder from the foundry industry stated that his industry had been battling silica for years and had made significant progress, but compliance with the current PEL had not been achieved in every foundry operation or area. The areas where exposure continued to be a problem were:
  • Cleaning
  • Shake out
  • Grinding (The use of air supplied hoods with full face shields reduces silica exposure and eliminated eye injuries during grinding. Such hoods would be used to eliminate the eye injuries in any case.)

OSHA question: Has the percentage of respirable silica increased over the years?

Yes, the respirable portion (quartz) has increased from 10 to 20 percent due to increased automation of processes, which tends to "beat sand up."

One stakeholder from a high production/high automation foundry noted that his firm had enclosed operations to reduce exposures. For example, knock off and hooker (moves casting) were automated. This stakeholder stated that his firm has spent $30-40 million in process automation, which was designed to reduce exposures to silica and ergonomic hazards as well as to increase productivity.

A stakeholder from the foundry industry noted that during repair of furnaces silica exposures occur during chipping of the refractory and that there is a cloud of dust during off-loading.

In the graphite industry, as well, exposures occur when moving material among containers. Crane operators and ground personnel are also exposed when trains unload. Maintenance and repair personnel also have exposures.

The stakeholder from the a state regulatory agency has data on exposures from general industry, construction, and agriculture from the following operations:

  • Cleaning
  • Concrete cutting
  • Finishing repair
  • Masonry
  • Grinding
  • Repair of older buildings.
  • Finishing Granite Counter Tops
  • Seed Cleaning (agriculture)

A stakeholder from the construction industry noted that wet methods were generally adequate for achieving compliance in the construction industry, but that secondary exposures after the water dries can be a problem. Clean up is essential to control such exposures.

One stakeholder noted that silica sand is essential for architectural finishes on precast concrete. Some substitutes have been tried but they are unacceptable because they leave a color on the concrete and may have toxicity problems of their own. Also, substitutes do nothing to prevent exposure to silica generated from the concrete being blasted.

The NIOSH participant noted that NIOSH research shows that the clay coating remains intact in vitro and that the clay coating remains for some period. Eventually, the clay coating is removed in the body but the remaining particle is very different from an uncoated crystalline silica particle.

One stakeholder cautioned OSHA that the use of data from the SEP or OSHA's IMIS could lead to an inaccurate characterization of exposures in the affected industries. Bias in the data was cited as a reason for this cautionary note.

ISSUE 2: Controlling Exposures

A stakeholder from the precast concrete industry noted that sandblasting enclosures are being used because of EPA rules, but that this control method has increased exposures for sandblast operators. Water blasting is a problem with architectural finishes because it leaves a "mud" on the surface that obscures the desired finish. (Although this stakeholder noted that some contractors had used it successfully.) Wet blasting is performed with respiratory protection. Grinding and cutting of concrete is usually performed using face masks. Many times area samples are taken to ensure that bystanders are not exposed. Regulated areas are established to control bystander exposure. Dust suppressants can be effective in reducing exposure during pre-cast concrete blasting. All sand blast workers are trained and given physical examinations annually. Also some written materials describing silicosis are provided to each employee.

One stakeholder addressed controlling exposures on construction sites as follows:

  • Housekeeping is critical to controlling exposures.
  • Vacuums equipped with HEPA filters are used.
  • Clean-up throughout the day is essential
  • Cleaning-up contaminated water before it dries is also essential
  • Isolation is difficult on construction sites. Silica is not handled like asbestos or lead where plastic enclosures are used to isolate work areas.
  • Ventilation is used only in limited areas.
  • Training for silica is non-existent on most construction sites. The stakeholder suggested that training on silica-related hazards could be incorporated in the respirator training (provided during fit testing).

Silica could be included in HAZCOM training but HAZCOM training is also not typically performed on construction sites.

Controlling silica exposures in foundries is accomplished by the following:

  • Enclosing materials handling equipment; however, enclosing conveyors is difficult to accomplish.
  • Substituting lower silica content core wash materials.
  • Cleaning furnace inserts outside the shop.
  • Vacuum systems (a culture change is needed that encourages vacuuming rather than air blowing to clean work area).
  • Ventilation (Push-Pull) has been used extensively and effectively.

Wet methods do not work well in foundries because of the heat in the environment or process. Electrostatic dust collectors also do not work well. In foundries, controlling exposures during maintenance is difficult.

One stakeholder noted that studies of household dust using x-ray diffraction showed prominent quartz peaks. TEM (Transmission Electron Microscope) analysis showed quartz, felspar, and mica from local soils.

A stakeholder from the graphite manufacturing industry noted that silica was a natural impurity in graphite, which can be reduced by (1) thermally purifying or (2) density separation.

A stakeholder from the precast concrete industry requested that OSHA not adopt the ANSI 9.4 standard which prohibits the use of silica for abrasive blasting because feasible alternatives (substitutes) are not available for this industry.

The stakeholder from the a state regulatory program noted that there are a number of tools available for controlling exposures during concrete operations on construction sites. These include local exhaust on concrete cutting equipment (however, filters on collection equipment clog up quickly). He also stated that a separate section on respirators for abrasive blasting should be included in the standard.

A stakeholder from the minerals mining/processing industry noted that the silica content in sand plants is typically greater the 90 percent. Also, the ventilation systems in many of the smaller plans that his compnay has acquired were poorly maintained and not well understood. The abrasive nature of silica reduces the life of ventilation equipment and dust collection systems to 1 to 2 years. He further noted that control can be a technical challenge, especially for small establishments.

One stakeholder responded that information on silica controls can be transferred through trade associations such as the National Industrial Sand Association, as well as from MSHA or the Bureau of Mines.

One stakeholder noted that training is one good method to help control exposure and bring about the needed culture change.

ISSUE 3: Monitoring

A stakeholder from the precast concrete industry stated:

  • Yearly monitoring is typical in precast concrete establishments.
  • Area monitoring is used to reduce bystander exposure.
  • Monitoring data, over time, has allowed them to remove some employees from the monitoring program.
  • In some states the monitoring is performed for free.
  • Consultants are also used frequently (labs are typically selected by the consultant).
  • Annual monitoring cost is between $1,000-$2,000 per year.

A stakeholder from the refractory manufacturing industry suggested that exposure monitoring be conducted using homogeneous exposure groups, statistical analysis, and random selection. A stakeholder from the construction industry noted that:
  • Consultants are often used to monitor for silica.
  • When monitoring data from one site indicate compliance, these data are applied to other sites which are then presumed to be safe.(Some guidance on when re-sampling should take place was requested.)

Another stakeholder from the construction industry stated that his firm performed silica sampling in-house. This firm collects approximately 125 samples per year.An employee or job is eliminated from the monitoring program when two sets of samples indicate compliance. A stakeholder from the foundry industry stated:
  • It is meaningless to sample individual employees because they move around too much; job-specific monitoring is critical.
  • Foundries typically use consultants for monitoring.
  • The cost of monitoring by a consultant is typically $200.00 per sample plus the sample analytical cost.
  • Labs should be AIHA accredited and PAT proficient and must use particle size correction.
  • The fact that the PAT results show that there is + 50 percent variability among labs is a difficult problem.

Several stakeholders noted that the SAE (standard analytical error), the detection limit and laboratory qualifications will be critical to effective monitoring.

A stakeholder from the industrial sand industry who has an active monitoring program (over 700 samples last year) noted that approximately 6 percent of the monitoring data showed exposures above the current PEL, even using state-of-the-art control technology. OSHA citations for silica exposure in this firm were reduced from 47 in 1989 to 1 citation each in 1997 and 1998.

ISSUE 4: Medical Surveillance

A stakeholder from the foundry industry noted that:

  • Employee x-rays and pulmonary function tests are performed.
  • The use of pulmonary function testing has been reduced because the results are "interesting but not useful."
  • He was concerned that x-rays might be misread.
  • Employee wellness programs make medical removal protection (MRP) unnecessary because employees are not hesitant to come forward under the wellness system.
  • MRP may be misued because employees may choose to claim MRP when overtime is common and they would be better off financially than on regular pay.

A stakeholder from the precast concrete industry stated:
  • "Smoking should be prohibited."
  • Annual physicals in this industry include chest x-ray, tuberculosis test, pulmonary function test.
  • High turnover in the industry is a problem.Employers do not follow employees that leave the firm and have few contract employees.
  • There is a need for government regulation to ensure that all employers provide the same medical surveillance.
  • Medical information is shared with the employees
  • "There is no silicosis problem in the precast concrete industry."

A stakeholder from the construction industry stated that medical surveillance in the construction industry was nearly non-existent due to high employee turnover.

A stakeholder from the industrial sand manufacturing industry stated:

  • Only 8 of 800 employees (1 percent) have x-ray tests of ILO 1/0 or higher.
  • Pulmonary function tests are not useful because they can represent a variety of causes (especially smoking).
  • Employees have chest x-rays every two years (don't find new cases - the 1 percent having ILO 1/0 or higher represents cases resulting from pre-existing exposures.)
  • Medical surveillance is essential for effective program evaluation.
  • Silica panel supports standard with sampling, surveillance, etc.


Stakeholders raised the following additional issues:

  • Laboratories are typically not competent to tell the difference between cristobalite and opaline silica.
  • There are analytical problems - "there is no way to do it fast."
  • If OSHA changes the PEL, the assigned protection factor (APF) should be required to be printed on respirators or filters.
  • Silicosis prevention is an important management task and should receive management support. Management bonuses should be keyed to reduction in silica exposure.
  • Some exposures remain above the NIOSH REL and the current PEL even in those companies that have state-of-the-art controls.
  • Health effects (benefits) of reducing PEL from 0.1 to 0.05 are not significant.
  • Epidemiology studies have very questionable data.
  • OSHA should keep the current PEL and adopt ancillary provisions.
  • There are concerns about the effect of the standard on export prices.
  • Ninety-five percent of foundries are small businesses. The SBREFA process is critical.
  • Don't use a one-size fits all approach - need different provisions for large/small firms.