During the week of August 7, 2000, an industrial hygiene evaluation was conducted at Dinosaur National Monument by researchers

During the week of August 7, 2000, an industrial hygiene evaluation was conducted at Dinosaur National Monument by researchers from the National Institute for Occupational Safety and Health. This evaluation centered on the exposure of the 2 National Park Service paleontologists to silica and respirable dust, but also included assessments of the workplace ventilation, exposure to ionizing radiation, the personal protective equipment program and ergonomic factors. An in-depth report on that evaluation is being prepared, but the relevant results are presented here in summary form.

A. Silica and respirable dust exposures

Six personal and one area sample were collected during normal laboratory and quarry activities to measure airborne concentrations of respirable crystalline silica and dust. Results of those samples are presented in Table 1. This table indicates airborne particulate concentrations below detectable levels in the lab but above recommended levels in the quarry. The recommended maximum exposure for respirable dust is 3 mg/M³ if the crystalline silica (quartz) content is less than 1%. The recommended maximum exposure for quartz is 0.05 mg/M³.[1]

Real-time dust measurements (previously provided as part of an exposure monitoring video) indicate peak measurements as high as 30 mg/M³. The paleontologist working in the quarry during those peak measurements was wearing personal protective equipment, including an air-purifying respirator, during these short peak exposure intervals.

Four bulk samples of dust collected from the lab and quarry were analyzed for crystalline silica and found to range from 26% to 31% quartz (see Table 2).

B. Local exhaust ventilation

The lab hood and flexible duct system were evaluated and judged to be working properly. Evaluation of both was conducted by visual observation of smoke to determine air flow patterns and by measurements of air velocity at the hood face or duct inlet with a thermo-anemometer.

Smoke released in front of the hood showed good air movement into the hood with the sash open 12 and 18 inches, although with the sash open 4 inches or fully opened there was visible air flow moving to the left of the hood. Air velocity measurements with the hood open approximately 18 inches, a normal working position, showed a mean air flow rate of 115 feet per minute, which is within the range of 60 – 150 fpm recommended by the ACGIH.[2]

Smoke released during the dematrix operation at the working piece near the flexible duct indicated appreciable air flow into the duct. There is no specific ACGIH ventilation illustration guide recommending a minimum velocity for this process. However, VS909 (granite cutting and finishing) is similar and recommends an air flow of 4000 cfm and a velocity of 3500 fpm. While the system at DNM was below that, measuring 400 cfm at 2000 fpm through a 6 in diameter duct, the lack of measurable airborne particulate (see Table 1) indicates that it is effective in removing dust from the work area. The low duct velocity could produce problems with particulate settling in horizontal segments of the system and reducing system effectiveness over time.

C. Ionizing radiation

The potential for exposure to ionizing radiation from uranium bearing materials in the fossils or matrix prompted measurements of ionizing radiation in the work area. A Ludlum survey meter was used to measure levels of radiation near various specimens as well as in the general laboratory workspace. Readings ranged generally from 20 to 60 mR/hr, with peaks to 150. These are considered NORM exposures (Naturally Occurring Radioactive Materials) and as such are not federally regulated. Most of the radiation emanated from the fossil itself rather than from the matrix around the bone. This data was reviewed by NIOSH health physicists who concluded that the levels emitted by most of the specimen at DNM were above the background of 5 - 10 mR/hr. They recommended quarterly radon measurements be made in the DNM lab and that new specimen be measured (the GM meter currently available to DNM paleontologists is acceptable) to screen and segregate hot items. A similar study along with some of the recommendations, conducted as a NIOSH Health Hazard Evaluation, will be included by reference in the In-Depth report.[3]

D. Personal Protective Equipment

The use of various personal protective devices was documented during the time on site. Eye and hearing protection was used both in the lab and in the quarry when grinding operations were taking place. A Wilson Model 6100S half-mask respirator with P100 filter was used in the quarry during periods of high dust generation. Use of all PPE was at the discretion of the worker, respirator fit testing had not been conducted, and no respirator protection program was in place.

E. Heat stress and ergonomics

During the time of this study temperatures in the laboratory ranged from approximately 75 to 85^oF and relative humidity was approximately 30%. At the quarry the temperature ranged from 85 to 105^oF and humidity was generally less than 10%. Both paleontologists appeared to be knowledgeable with regard to proper heat stress procedures and did take appropriate precautions. The person working in the lab was doing so partially because he had recently returned from an extended field assignment in a much colder climate and was no longer acclimatized to the hot environment, and partially due to an injury (discussed below) which limited his work in the heavier tasks conducted at the quarry.

Both employees evaluated experienced traumatic injury of their right elbows diagnosed by their physicians as tendonitis, and both had been receiving steroid injections to treat those injuries.

Several instances where ergonomic improvements could be implemented were noted by the industrial hygienist on-site and by staff ergonomists upon review of photographs and video taped work practices. Suggestions regarding work at the quarry centered around problems with the rock saw. It is recommended that, until the current saw is replaced, vibration be damped with the addition of a handle wrap or vibration reducing gloves, particularly those gloves which meet ISO 10819. When the existing saw is replaced, consideration should be given to purchasing a low vibration saw, as small and light weight as possible, and with electronic ignition to reduce the problems in starting which plagued the current tool. Examples of such saws are given at www.dynatech-diamond.com (select “high speed gas saws”).*

Suggestions regarding work in the laboratory include positioning of the work piece, the worker and the tools. The substitution of an adjustable base for the sand table would enable the paleontologist to better position the work piece, allowing a better biomechanical positioning for the matrix removal operation. This, along with an adjustable stool or sit/stand, would reduce the likelihood for chronic injuries to the shoulder and lower back. Positioning of large work pieces (greater than approximately 10 to 20 pounds) is best at about chest level, while smaller objects can be best manipulated somewhat lower. The addition of a vibration reducing wrap or glove to the tool used in this operation is also recommended, as is the substitution of an ergonomically designed chipping or grinding tool, such as those manufactured by Atlas Copco or ATA Tools. This would reduce the flexion of the wrist during work, decreasing the likelihood of chronic injuries to the wrist, forearm, elbow and shoulder. Examples of adjustable tables, ergonomic stools, sit/stands, vibration wrap, gloves and tools can be seen in most ergonomic supply catalogs, such as from AliMed Ergonomics Division, 297 High St., Dedham, MA 02026, 800-225-2610, www.alimed.com.*

References:

Table 1

Respirable dust & silica samples from Dinosaur National Monument

Sampling Sample Job Resp.Dust Quartz

Date Duration Location Description conc.* conc.*

(minutes) (mg/M3) (mg/M3)

August 8, 2000 386 Area sample / laboratory Center of work area during de-matrix operation <0.02 <0.01

August 8, 2000 375 Paleontologist / laboratory De-matrix operation in lab; using standard small tools <0.02 <0.01

August 8, 2000 239 Paleontologist / quarry Quarry site DNM16, using rock saw, hammer & chisel 1.78 0.54

August 9, 2000 285 Paleontologist / laboratory De-matrix operation in lab; using standard small tools <0.02 <0.01

August 9, 2000 96 Paleontologist / quarry Quarry site DNM16, using rock saw, hammer & chisel 5.12 1.63

August 10, 2000 210 Paleontologist / laboratory De-matrix operation in lab; using standard small tools <0.02 <0.01

August 10, 2000 154 Paleontologist / quarry Quarry site DNM16, using rock saw, hammer & chisel 0.01 <0.01

*Concentrations reported as an 8 hour time weighted average

Table 2

Silica concentration in bulk samples

Sample Description Quartz*

(%)

Settled dust from 8/8/00 AM rock saw operation 26

Chips from lab, removed by Scott from workpiece 31

Chips & dust from 8/10/00 AM grinding in lab 29

*No cristobalite detected, LOD = 1%

* Mention of product or manufacturer does not constitute endorsement by NIOSH or CDC. Examples are given here for illustrative purposes only.