NIOSH issues warning on dust, firefighting hazards

National safety officials have issued a special warning that might apply to first responders in various industrial settings, and occupational health professionals may want to share that warning.

The warning comes after the Cincinnati-based National Institute for Occupational Safety and Health (NIOSH) investigated the deaths of two volunteer fire fighters responding to an 18,000-gallon bulk propane tank fire. The fire started after unprotected external piping from the tank was struck by an all-terrain vehicle, and the propane vapors were ignited by a pilot flame from a nearby vaporizer. Upon arrival at the fire scene, the firefighters watered down the buildings adjacent to the propane tank and allowed the tank to burn itself out, since the tank was venting. About eight minutes after the fire fighters arrived, the tank exploded, separated into four parts, and flew in four directions.

The two firefighters (who were approximately 105 feet from the tank) were struck by a piece of the exploding tank and killed instantly. Six other firefighters and a deputy sheriff were injured as a result of the explosion. Such explosions may occur whenever flames contact propane tanks, NIOSH warns.

During propane tank fires, the potential always exists for an explosion known as boiling liquid expanding vapor explosion (BLEVE), the NIOSH warning states. To reduce this risk, fire departments, firefighters, and propane tank owners and users should follow recommendations based on emergency response procedures in the 1996 North American Emergency Response Guidebook (NAERG96), which were developed jointly by Transport Canada, the U.S. Department of Trans-portation, and the Secretariat of Communications and Transportation of Mexico.

NIOSH says firefighters should follow these rules:

- Fight fire from the maximum distance possible or use unmanned hose holders or monitor nozzles.

- Cool containers by flooding them with large quantities of water until well after fire is out.

- Do not direct water at the source of leak or at safety devices; icing may occur.

- Leave the area immediately if you hear a rising sound from venting safety devices or see discoloration of the tank.

- For massive fires, use unmanned hose holders or monitor nozzles; if this is impossible, leave the area and let the fire burn.

- Be aware that when a BLEVE occurs, sections of the tank can fly in any direction. Just avoiding the ends of the tank should not be considered a safe operating procedure.

Fire departments should follow the OSHA regulations [29 CFR*1910.120 (q) emergency response to hazardous substance releases]. These regulations should be incorporated into fire department standard operating procedures, which should be strictly enforced, the agency says.

NIOSH also urges occupational health providers to train first responders to be aware of the hazards associated with propane tank fires, including BLEVE. Safety officials also should ensure that fire department code enforcement personnel adhere to the guidelines specified by the National Fire Protection Association and NAERG96 for the evaluation and certification of propane tanks.

Another warning recently issued from NIOSH relates to the control of drywall sanding dust exposures. NIOSH warns that construction workers who sand drywall joint compound often are exposed to high concentrations of dusts and, in some cases, respirable silica.

Drywall joint compounds are made from many ingredients, including talc, calcite, mica, gypsum, and silica. Some of these have been associated with varying degrees of eye, nose, throat, and respiratory tract irritation, NIOSH says. Over time, breathing the dust from drywall joint compounds may cause persistent throat and airway irritation, coughing, phlegm production, and breathing difficulties similar to asthma. Smokers or workers with sinus or respiratory conditions may risk even worse health problems. When silica is present, workers may also face an increased risk of silicosis and lung cancer.

A recent NIOSH Health Hazard Evaluation (HHE) found that drywall sanders were exposed to as much as 10 times the permissible exposure limit (PEL) of 15 mg/m3 for total dust set by the Occupational Safety and Health Administration (OSHA). The OSHA PEL for respirable dust (5 mg/m3), the very small particles that can go deep into the lungs, also was exceeded.

Drywall joint compound manufacturers recognize that workers might be exposed to too much dust during drywall sanding. NIOSH studied five manufacturers material safety data sheets (MSDSs), which warned workers to avoid generating dust and to use respiratory protection when dry sanding. Four of the MSDSs told construction workers to use wet sanding whenever possible, and the fifth said to cut dust exposures by ventilation. However, these guidelines are seldom followed in actual work practice. Wet sanding is generally avoided because of concerns about drying time and finish texture. Wet sanding is used to protect equipment or furnishings rather than to reduce work exposures. NIOSH says that when respiratory protection is worn, it often is used incorrectly with little thought to training, proper selection, or fit.

Several light-weight sanding systems are available to control drywall workers sanding exposures. These systems use portable vacuums to capture and remove the dust before the worker is exposed to it. In 1994, NIOSH studied several of these sanding systems at the International Brotherhood of Painters and Allied Trades (IBPAT) Apprenticeship Training Facility in Seattle. NIOSH engineers compared the dust exposures from three pole-sanding and two hand-sanding vacuum control systems with the exposures from traditional, nonventilated sanding methods. The five commercially available vacuum sanding controls successfully reduced dust exposures by 80% to 97%. Four of the five sanding controls cut exposures by nearly 95%. If engineering controls had reduced total dust exposures by 90% in the HHE case report described earlier, the construction workers exposures would have remained below the OSHA PEL.

Since the 1994 NIOSH study, more manufacturers are now making drywall sanding controls to cut dust exposures. Although NIOSH has not tested these controls, researchers expect them to perform well.

In addition to lower exposures, vacuum sanding systems can help the sander, subcontractor, general contractor, and building owner in other ways. The dramatic reduction in airborne dust exposures results in a much cleaner work area during and after sanding. For workers, the clean working environment is more comfortable; less irritating to eyes, nose, and throat; and less likely to require respiratory protection. For the subcontractor, a comfortable worker is likely to be more productive, be absent less often, and require fewer breaks for fresh air. The savings and reduced regulatory liability given by lower respiratory protection requirements will be passed from the subcontractor to the building owner. Other cost savings will result from a cleaner environment that reduces dirt, cleanup time, and repair or repainting of stained floors and carpets.

NIOSH study results also suggest that the construction workers exposures to dust might be cut simply by switching from hand sanding to pole sanding. This change is even more important when working overhead. The pole increases the space between the worker and the sanding surface, which in turn reduces the amount of dust close to the worker’s nose and mouth.