# 

# 

**Final Number range CHAPTERSite Visit Report:**

**Beryllium Site 3**

**Submitted to:**

**Office of Regulatory Analysis**

**Directorate for Evaluation and Analysis**

**Occupational Safety and Health Administration**

**Submitted as partial fulfillment of**

**requirements for Task Order 41**

**Contract No. J-9-F-9-0010**

**Submitted by:**

**Eastern Research Group, Inc.**

**110 Hartwell Ave.**

**Lexington, MA 02421**

# TABLE OF CONTENTS

[TABLE OF CONTENTS 1](#table-of-contents)

[Introduction 2](#introduction)

[Facility and Process Description 3](#facility-and-process-description)

[Exposure Assessment 6](#exposure-assessment)

[Exposure Controls in Place 7](#exposure-controls-in-place)

[Discussion 9](#discussion)

[Specific Recommendations 11](#specific-recommendations)

[General Recommendations 11](#general-recommendations)

[References 14](#references)

#  

# Introduction

On January 16 and 17, 2003, a beryllium oxide (BeO, beryllia) ceramics
fabrication facility was visited. During this visit measurements were
made to characterize worker exposure to airborne and surface levels of
beryllium and gather data to assist in the development of some industry
guidance criteria.

Beryllia has unique characteristics that make it a superior material for
certain specialized applications. Beryllia ceramics provide thermal
conductivity only second to diamond among electrically insulating
materials, dissipating nearly 300 W/mK at room temperature.
Distinguished by excellent high heat and thermal conductivity, it
retains dielectric constant, loss factor and dielectric strength in the
range of most electrical insulators. Along with good mechanical strength
and stiffness to weight ratios, this unique combination of properties
provides a material that can reduce the size of heat generating
circuitry while retaining essential high power capability and improved
thermal stability. Typical applications include heat sinks in high power
electronics and semiconductors, and use as a heat dissipation medium in
a wide range of miniaturized circuitry applications in the defense,
aerospace and commercial markets.

However, exposure to beryllium compounds is associated with a chronic
debilitating lung disease\--chronic beryllium disease (CBD)\--that is
the result of a beryllium-specific, T lymphocyte-mediated
hypersensitivity. Symptoms of the disease are exertional dyspnea and
cough, followed by weight loss, chest pain, arthralgias, and fatigue.
Progression of the disease may lead to heart failure as a result of
chronic respiratory insufficiency.

# Objectives

The objective of this work is to develop guidance material that would
help business to reduce worker exposure during the processing of
beryllium from the best practices currently found in industry. These
practices are for all users of beryllium regardless of the form the
beryllium is in; metal, oxide or alloy.

The amount or length of exposure to beryllium necessary to cause a
specific individual to develop CBD is not known, but recent information
suggests that even short exposures to levels of beryllium below OSHA's
Permissible Exposure Limit (PEL) of 2 µg/m^3^ averaged over an 8-hour
day may lead to CBD in some workers. CBD may develop within months after
initial exposure to beryllium or may have a very slow onset and not
develop for 25 years or more and may even develop after exposure has
ceased. The prevalence of CBD among beryllium-exposed workers has been
reported to range from an average of about 2% to a high of approximately
15% for workers involved in machining operations in the manufacturing of
beryllium products.

Measurement of exposure to total airborne beryllium dust may not be the
best predictor of CBD. Particle size, surface area, number of particles,
solubility, and the chemical form of beryllium involved may all be
relevant to the development of disease. It has also been suggested that
beryllium can enter through either intact skin or breaks in the skin to
initiate sensitization. Recent studies have shown that particles less
than 1 μm in diameter can penetrate intact skin that has been flexed.
Therefore, it is essential that all possible pathways of exposure be
considered when assessing a work site for potential exposure to
beryllium.

# Facility and Process Description

The company, located in Northern New Jersey, was originally founded in
1956 as a beryllium oxide manufacturer. The company was a pioneer in the
research and development of high purity oxide ceramics. In the early
1960s and developed the technology to press, extrude and fire BeO in
both standard and custom shapes to suit a wide variety of applications.
In the late 1960s and early 1970s, precision ceramic grinding machinery
was installed along with the technology and equipment needed for
drilling, metallizing, lapping, polishing and dicing operations. During
time of peak production the company operated a three 8-hour shift
schedule and employed over 500 workers.

Today, the newly-named and operated company has over 35,000 square feet
of manufacturing space (see Figure 1). It currently operates a single
8-hour shift and has 14 workers employed. During the time of this visit
the company was operating at an estimated 10% of capacity.

## ![](media/image1.jpeg){width="5.993055555555555in" height="4.340277777777778in"} 

## Job Descriptions

Company offers a wide range of manufacturing capabilities and services
designed to meet virtually any application need involving BeO. These
capabilities encompass a variety of material preparation (forming),
firing and finishing methods to suite exact customer requirements. The
following operations were available for observation and sampling during
this evaluation.

*Material Preparation Operator (Subject 1)*

Material preparation involves a series of operations that prepare raw
beryllium oxide powder supplied from an outside vendor into powder
having the necessary size and chemistry configurations to meet specific
product and customer specifications. The material preparation tasks
observed during this visit were not all inclusive as only relatively
small batch lots of material are necessary for current demand,
therefore, only certain tasks are performed at any given time. During
the visit the material preparation tasks observed were powder transfer
from vendor container into intermediate milling containers and loading
powder into the rotational BeO powdering mill. All powder transfer tasks
are performed in a negative pressure ventilation hood or containerized
in a seal tight enclosure. Highly disciplined and careful work practices
were observed to clean all potentially contaminated surfaces
(containers, bags, gloves, hands, skin) are cleaned with running water
and sponge, prior to removal from the exhaust ventilation hoods. Most
hoods have clean running water and drainage capability to facilitate and
encourage cleaning practices. The operator also performed a number of
physical and chemical analyses and general housekeeping tasks during the
sampling period.

*Dry Pressing Operator (Subject 2)*

Dry pressing involves compacting of ceramic powder to a particular shape
or form in a carbide-lined steel die. A plastic bag of BeO powder is
stored inside the press negative pressure enclosure; as necessary the
operator pours powder from the bag into the press reservoir container.
The powder is feed to a simple, shaped punch or a compound, multi-stage
die, and pressure is applied to consolidate the part. Parts are ejected
onto a holding tray. The parts are weighed, visually inspected and
stored for firing.

The pressing operator also operated a dry abrasive cut-off saw for
separate line of parts. The saw was positioned inside an exhaust
ventilation enclosure and in addition, a local exhaust ventilation
pick-up was positioned close the point of operation. Parts are removed
from a holding tray, placed in position to be cut, the machine is cycled
and the parts are loaded onto another storage tray and stored for
firing.

The worker frequently uses a wet sponge to clean potentially
contaminated surfaces, hands and skin before removing anything from the
exhaust ventilation enclosure. This operator was observed to wash his
hands at least 16 different times during the shift.

*Iso-Pressing Operator (Subject 4)*

Isostatic pressing involves placing prepared ceramic powder in a
liquid-tight rubber mold under a negative pressure exhaust ventilation
hood. This hood is approximately 10 feet in length and has running water
and both a back and down draft air flow design. The mold subsequently
immersed in a non-compressible fluid such as oil or water contained in a
pressure vessel. When the fluid is pressurized, all surfaces of the mold
receive equal pressure resulting in a uniform density. The molds are
removed from the Isopress, positioned inside the hood, the mold is
disassembled and the part is cleaned and stored in a covered container
outside the exhaust ventilation hood.

The operator observed disciplined and careful work practices to clean
all potentially contaminated surfaces (containers, bags, hands, finger
nails and skin) with running water, sponge and small bristled brush,
prior to removal from the exhaust ventilation hood. The worker would
traverse the 10-foot length of the hood, being careful not to remove her
contaminated hands prior to cleaning them under water, sponge and
scrubbing under fingernails.

*Precision Grinding Operator (Subject 3)*

Both manual and automatic grinding techniques are used to achieve
precise physical dimensions. Other available methods in the shop include
centerless, cylindrical, surface and inside diameter grinding using
diamond wheels. The precision grinding operator was running a surface
grinder on the day of this visit. The surface grinder is fully enclosed
and under exhaust ventilation; the cutting action is performed under a
flood of coolant. The worker positions part in grinder enclosure; cycles
the machine to cut part (cycle time approximately 3 min); he removes the
part, rinses it in a tray of water, wipes it off with a sponge and
places it in a part tray.

*Other Operations*

Additional operations not running during the time of this evaluation
include Spray Drying, Hot Pressing, Extrusion, Sintering, Green
Machining, Lapping and Polishing, Dicing, and Metalizing.

# Exposure Assessment

Sampling was conducted to determine the beryllium air and surface
contamination to which workers are potentially exposed and to derive
some simple measure of dose for these workers. The first day of the site
visit was spent meeting with company personnel (company management and
employees) to arrange sampling on the subsequent day, and to walk
through the plant to begin the industrial hygiene assessment of exposure
and control technology. Employees with the highest potential beryllium
exposures in each process area or operation were the major focus of the
sampling. Workers selected for sampling were briefed on the sampling
procedures to be conducted. Because the goal of this study is to assess
the effects of engineering controls and work practices on beryllium
exposures, samplers were placed outside of any respiratory protective
equipment worn by the worker. Two days of sampling were then conducted
on the only three employees present who worked with beryllium alloy.

## [Sampling Methods]{.underline}

Beryllium-related disease is assumed to be related to the number of
deposited beryllium particles and perhaps the available surface area of
those particles in the lung. Thus, parameters of interest include
surface contamination, skin exposure, airborne particle number
concentration (for particles of a size that deposits in lung), and the
surface area distribution of the beryllium particles, in addition to the
total gravimetric concentration of beryllium in air. The methods used to
assess these parameters are listed below and briefly described in this
section.

+------------------------+---------------------------------------------+
| **Parameter**          | **Sampling Method \[unit of measure\]**     |
+------------------------+---------------------------------------------+
| Surface contamination  | NIOSH Method 9100, surface wipe samples     |
|                        | \[μg/100 cm^2^\]                            |
+------------------------+---------------------------------------------+
| Skin exposure          | Hand wipe samples \[μg/100 cm^2^\]          |
+------------------------+---------------------------------------------+
| Total airborne         | Traditional air sampling for total dust     |
| beryllium              | \[μg/m^3^\]                                 |
| concentration          |                                             |
+------------------------+---------------------------------------------+
| Airborne deposited     | Condensation particle counter (CPC)         |
| particle number        | measuring airborne concentration of         |
| concentration          | particles proportional to that which would  |
|                        | deposit in the lung \[number of particles   |
|                        | between 0.01 and 1 μm per cm^3^ of air\]    |
+------------------------+---------------------------------------------+
|                        |                                             |
+------------------------+---------------------------------------------+
|                        | # Laboratory Analysis                       |
+------------------------+---------------------------------------------+
| Total mass             | Gravimetric analysis \[μg/sample\]          |
+------------------------+---------------------------------------------+
| Beryllium mass (in     | NIOSH Method 7102, graphite furnace atomic  |
| wipe and air samples)  | absorption \[μg beryllium/sample\]          |
+------------------------+---------------------------------------------+

### 

### Surface Samples

Surface contamination evaluation followed the well-established protocol
for lead surface contamination measurements, as did skin sampling.
Surface sampling was done by marking off a 100 cm^2^ area using a
plastic template, with a square hole 10 cm on a side, which was placed
on the surface and the corners marked with the moistened towelette. The
template was then removed and the perimeter lined out with the same
moistened towel. The inside of the square was then wiped according to
NIOSH Method 9100 and the towel placed in a screw-top glass vial for
analysis. The template was cleaned before reuse.

### Skin Samples

Hand wipe samples were obtained by asking study participants to wipe
their hands before the end of their shift or during the shift, at least
two hours after their last hand washing. They were instructed to lift a
fresh wet-wipe from its opened container and to thoroughly wipe both
hands (including the front and back, up to the wrists, and each finger),
removing as much visible dirt as possible. The wipe was then placed in a
labeled screw-top glass vial. The hand wiping exercise was supervised
and timed for 30 seconds by the investigators to ensure consistency from
subject to subject. A tracing of both hands of each participant was
taken to estimate the total surface area of the participants' hands. The
concentration of beryllium on the workers' hands is reported in
micrograms of beryllium per 100 cm^2^.

# *Personal Air Sampling* (Airborne deposited particle number concentration and Total airborne beryllium)

Each full-shift air-sampling subject wore a backpack containing a
condensation particle counter (CPC) \[make, model, calibration date\]
and two personal air-sampling pumps \[make, model\].One of the air
sampling pumps \[nominal air flow rate\] was attached to an Anderson
personal impactor \[model, 8^th^ and final stages only\] clipped outside
the backpack at the worker's lapel. While stage 8 of the impactor
screened larger particles, a triple layer of polycarbonate filters in
the impactor base captured particles 0.01 to 1.0 μm, the size range that
would deposit in the lung. A battery-operated valve allowed the CPC to
alternately measure the concentration of particles in two air
streams: 1) air drawn through the polycarbonate filters and 2) ambient
air from a tube also attached at the workers lapel. By comparing the
particle concentration values recorded by the CPC for the filtered and
unfiltered air-streams, it was possible to estimate the concentration of
particles removed by the layered polycarbonate filters, which represents
the deposited submicrometer particle concentration (DSP).

The second personal air-sampling pump in the worker's backpack was used
for collecting the "total" airborne beryllium sample. This pump was
connected to a 37 mm cassette containing pre-weighed PVC filters,
clipped outside the backpack at the worker's lapel.

When short-term samples were collected during specific tasks, the second
personal air-sampling pump was eliminated and instead a high-flow pump
(Gast, Model, 25 LPM) was connected to the 37 mm cassette assembly on
the workers lapel. The higher flow rate was required to ensure an
adequate volume of air was collected during the shorter sampling period.
A member of the investigative team held the pump and followed the worker
around to assure the tether did not interfere with the worker's
activities. The sampling pumps were calibrated both before and after the
shift using a Bios Dry-Cal meter. Pumps were set within one percent of
the target flow rate.

The PVC filters were analyzed to obtain the total mass and beryllium
mass, from which the fractional beryllium content (% beryllium) was
determined. This percentage was applied to the DSP number concentration
obtained from CPC results, to estimate the percent of that concentration
that was beryllium (Be DSP). This final value, Be DSP, represents the
airborne concentration of beryllium particles that are of a size that
would deposit in the lung and is reported as particles per cubic
centimeter of air (p/cc).

# *[Laboratory Analysis]{.underline}*

OSHA's Salt Lake City Laboratory performed the laboratory analysis.
Gravimetric results were reported to the nearest microgram. Beryllium
mass was determined for surface wipes, hand wipes, and air samples using
NIOSH Method 7102, graphite furnace atomic absorption spectrophotometry.
Field blanks made up 10 percent of the samples analyzed and another five
percent were media blanks.

## Sampling Results

*Surface Samples*

**Table I. Results of Surface Samples**

+-----------------------------------+-------+-----------+--------------+
| **Material Preparation**          | **    | **Surface | **Be         |
|                                   | Total | Area      | Con          |
|                                   | Be**  | (cm2)**   | centration** |
|                                   |       |           |              |
|                                   | **(   |           | **(ug/100    |
|                                   | ug)** |           | cm2)**       |
+-----------------------------------+-------+-----------+--------------+
| Metal work table 20ft from hood   | 1     | 100       | 133.40       |
|                                   | 33.40 |           |              |
+-----------------------------------+-------+-----------+--------------+
| Window btw hood and blending mill | 1.30  | 100       | 1.30         |
+-----------------------------------+-------+-----------+--------------+
| Sliding hood window               | 3.40  | 100       | 3.40         |
+-----------------------------------+-------+-----------+--------------+
| Top of balance                    | 1.90  | 100       | 1.90         |
+-----------------------------------+-------+-----------+--------------+
| Top of product barrel             | 1.10  | 100       | 1.10         |
+-----------------------------------+-------+-----------+--------------+
|                                   |       |           |              |
+-----------------------------------+-------+-----------+--------------+
| **Dry Pressing**                  | **    | **Surface | **Be         |
|                                   | Total | Area      | Con          |
|                                   | Be**  | (cm2)**   | centration** |
|                                   |       |           |              |
|                                   | **(   |           | **(ug/100    |
|                                   | ug)** |           | cm2)**       |
+-----------------------------------+-------+-----------+--------------+
| Operator work table               | 1     | 100       | 109.90       |
|                                   | 09.90 |           |              |
+-----------------------------------+-------+-----------+--------------+
| Weight scale bench top            | 277.7 | 100       | 277.7        |
+-----------------------------------+-------+-----------+--------------+
| Floor in front of cut-off saw     | 51.80 | 100       | 51.80        |
+-----------------------------------+-------+-----------+--------------+
| Counter by sink                   | 50.00 | 100       | 50.00        |
+-----------------------------------+-------+-----------+--------------+
|                                   |       |           |              |
+-----------------------------------+-------+-----------+--------------+
| **Iso-Pressing**                  | **    | **Surface | **Be         |
|                                   | Total | Area      | Con          |
|                                   | Be**  | (cm2)**   | centration** |
|                                   |       |           |              |
|                                   | **(   |           | **(ug/100    |
|                                   | ug)** |           | cm2)**       |
+-----------------------------------+-------+-----------+--------------+
| Iso-Press table top               | 2     | 100       | 286.00       |
|                                   | 86.00 |           |              |
+-----------------------------------+-------+-----------+--------------+
| Laser bore storage container lid  | 37.00 | 100       | 37.00        |
+-----------------------------------+-------+-----------+--------------+
| Floor in front of hood            | 15.00 | 100       | 15.00        |
+-----------------------------------+-------+-----------+--------------+
|                                   |       |           |              |
+-----------------------------------+-------+-----------+--------------+
| **Precision Grinding**            | **    | **Surface | **Be         |
|                                   | Total | Area      | Con          |
|                                   | Be**  | (cm2)**   | centration** |
|                                   |       |           |              |
|                                   | **(   |           | **(ug/100    |
|                                   | ug)** |           | cm2)**       |
+-----------------------------------+-------+-----------+--------------+
| Work bench by micrometer          | 95.00 | 100       | 95.00        |
+-----------------------------------+-------+-----------+--------------+
| Work bench by radio               | 20.10 | 100       | 20.10        |
+-----------------------------------+-------+-----------+--------------+
| Floor in front of bench           | 4.00  | 100       | 4.00         |
+-----------------------------------+-------+-----------+--------------+
|                                   |       |           |              |
+-----------------------------------+-------+-----------+--------------+
| **Administration Areas 2^nd^      | **    | **Surface | **Be         |
| Floor**                           | Total | Area      | Con          |
|                                   | Be**  | (cm2)**   | centration** |
|                                   |       |           |              |
|                                   | **(   |           | **(ug/100    |
|                                   | ug)** |           | cm2)**       |
+-----------------------------------+-------+-----------+--------------+
| Floor at manufacturing entrance   | 1.80  | 100       | 1.80         |
| stairs                            |       |           |              |
+-----------------------------------+-------+-----------+--------------+
| Electrical panel door             | 0.29  | 100       | 0.29         |
+-----------------------------------+-------+-----------+--------------+
| Mail box drawer                   | 0.21  | 100       | 0.21         |
+-----------------------------------+-------+-----------+--------------+
| Top of microwave in production    | 0.38  | 100       | 0.38         |
| office                            |       |           |              |
+-----------------------------------+-------+-----------+--------------+
| Top of bookcase in production     | 0.12  | 100       | 0.12         |
| office                            |       |           |              |
+-----------------------------------+-------+-----------+--------------+
| Display case in conference room   | 0.11  | 100       | 0.11         |
+-----------------------------------+-------+-----------+--------------+
| Top of paper shredder             | 0.80  | 100       | 0.80         |
+-----------------------------------+-------+-----------+--------------+
|                                   |       |           |              |
+-----------------------------------+-------+-----------+--------------+

It is apparent that beryllium is being transferred from work processes
and materials to adjacent production area walking and working surfaces.
This was true of all production areas sampled. Beryllium is also being
transferred out of the production area and into the adjacent
administrative office and support areas. While not as high, on average,
as the production areas all of the support areas had detectable levels
of beryllium on the surfaces that were sampled.

*Hand Samples*

**Table II. Wipe Samples Obtained from Both Hands Together**

+----------------------------------+-------+--------------+------------+
| **Bare-Hand Samples**            | **    | **Surface    | **Be       |
|                                  | Total | Area (cm2)** | Conce      |
|                                  | Be**  |              | ntration** |
|                                  |       |              |            |
|                                  | **(   |              | **(ug/100  |
|                                  | ug)** |              | cm2)**     |
+----------------------------------+-------+--------------+------------+
| Material Prep Op. (01/17/03 @    | 43.4  | 652          | 6.66       |
| 10:03)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Material Prep Op. (01/17/03 @    | 25.3  | 652          | 3.88       |
| 10:05)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Material Prep Op. (01/17/03 @    | 73.1  | 652          | 11.21      |
| 13:30)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Dry Pressing Op. (01/17/03 @     | 276.2 | 816          | 33.85      |
| 10:01)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Dry Pressing Op. (01/17/03 @     | 179.1 | 816          | 21.95      |
| 12:01)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Dry Pressing Op. (01/17/03 @     | 232.3 | 816          | 28.47      |
| 14:58)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Iso-Pressing Op. (01/16/03 @     | 221.5 | 624          | 35.50      |
| 11:56)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Iso-Pressing Op. (01/16/03 @     | 179.7 | 624          | 28.80      |
| 11:58)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Iso-Pressing Op. (01/16/03 @     | 426.4 | 624          | 68.33      |
| 14:25)                           |       |              |            |
+----------------------------------+-------+--------------+------------+
| Precision Grinding Op. (01/16/03 | 346.3 | 812          | 42.65      |
| @ 12:03)                         |       |              |            |
+----------------------------------+-------+--------------+------------+
| Precision Grinding Op. (01/16/03 | 128.3 | 812          | 15.80      |
| @ 12:05)                         |       |              |            |
+----------------------------------+-------+--------------+------------+
| Precision Grinding Op. (01/16/03 | 336.7 | 812          | 41.47      |
| @ 16:30)                         |       |              |            |
+----------------------------------+-------+--------------+------------+
| Admin -- Production Mgr.         | 29.5  | 736          | 4.01       |
| (01/16/03 @ 13:10)               |       |              |            |
+----------------------------------+-------+--------------+------------+
| Admin -- Production Dir.         | 5.3   | 776          | 0.68       |
| (01/16/03 @ 13:30)               |       |              |            |
+----------------------------------+-------+--------------+------------+

The hand wipes results follow a similar type trend as those described
for the surface wipes, only in this case representing a measured
exposure to the skin. The levels are generally higher than those
observed in other studies. Finding beryllium on the hands of
administrative personnel who spend time in the production area should be
considered a sign that beryllium contamination could be leaving the
plant and is definitely migrating from the production areas.

*Air Samples*

Table III. Personal Samples -- Total Beryllium

  ---------- ------------- ----------- --------------- ----------- ------------ ------------- ------------- ------------- -----------------
  **Sample   **Subject**   **Date**    **Sample        **Flow      **Sample     **Mass        **Beryllium   **Beryllium   **Beryllium
  Number**                             Duration**      Rate**      Volume**     Collected**   Collected**   Fraction**    Concentration**

                                       **(minutes)**   **(lpm)**   **(m^3^)**   **(μg)**      **(μg)**      **(%)**       **(μg/m^3^)**

  2853       1             1/17/2003   435             1.99        0.87         25            \< 0.02       \<0.08        \<0.02

  2858       2             1/17/2003   455             1.99        0.91         48            0.09          0.188         0.1

  2847       4             1/16/2003   368             2.04        0.75         ND            \<0.02        ND            \<0.03

  2746       3             1/16/2003   365             2.02        0.74         41            0.07          0.171         0.1
  ---------- ------------- ----------- --------------- ----------- ------------ ------------- ------------- ------------- -----------------

Table IV. Personal Task Samples -- Total Beryllium

<table style="width:100%;">
<colgroup>
<col style="width: 9%" />
<col style="width: 7%" />
<col style="width: 11%" />
<col style="width: 9%" />
<col style="width: 5%" />
<col style="width: 7%" />
<col style="width: 9%" />
<col style="width: 11%" />
<col style="width: 11%" />
<col style="width: 13%" />
</colgroup>
<tbody>
<tr class="odd">
<td><strong>Sample Number</strong></td>
<td><strong>Subject</strong></td>
<td><strong>Date</strong></td>
<td><strong>Sample Duration</strong></td>
<td><strong>Flow Rate</strong></td>
<td><strong>Sample Volume</strong></td>
<td><strong>Mass Collected</strong></td>
<td><strong>Beryllium Collected</strong></td>
<td><strong>Beryllium Fraction</strong></td>
<td><strong>Beryllium Concentration</strong></td>
</tr>
<tr class="even">
<td> </td>
<td> </td>
<td> </td>
<td><strong>(minutes)</strong></td>
<td><strong>(lpm)</strong></td>
<td><strong>(m<sup>3</sup>)</strong></td>
<td><strong>(μg)</strong></td>
<td><strong>(μg)</strong></td>
<td><strong>(%)</strong></td>
<td><strong>(μg/m<sup>3</sup>)</strong></td>
</tr>
<tr class="odd">
<td>2728</td>
<td>1</td>
<td>1/17/2003</td>
<td>69</td>
<td>28.0</td>
<td>1.9</td>
<td>58</td>
<td>&lt;0.02</td>
<td>&lt;0.03</td>
<td>&lt;0.01</td>
</tr>
<tr class="even">
<td colspan="10"><blockquote>
<p>This task sample represents the Material Preparation operator’s
personal exposure while transferring BeO powder from the supplier
product drum, into intermediate plastic bags then into the product
mill.</p>
</blockquote></td>
</tr>
<tr class="odd">
<td>2743</td>
<td>4</td>
<td>1/17/2003</td>
<td>162</td>
<td>28.0</td>
<td>4.5</td>
<td>32</td>
<td>&lt;0.02</td>
<td>&lt;0.06</td>
<td>&lt;0.01</td>
</tr>
<tr class="even">
<td colspan="10"><blockquote>
<p>This task sample represents the Iso-Pressing operator’s personal
exposure while loading BeO powder into the laser bore isostatic press
die container.</p>
</blockquote></td>
</tr>
</tbody>
</table>

The beryllium concentrations were low for both personal full-shift and
task samples obtained during this survey. The fractional content of the
airborne beryllium was similar to that seen in other plants, generally
less than 1%.

The current OSHA Permissible Exposure Limit (PEL) for beryllium in air
is 2.0 μg/m^3^. OSHA considers this level to be insufficient to protect
all workers^1^ and new level has not been established. In the interim
OSHA advises that levels be maintained to the lowest level feasible.

+----------------------------+---+-------+---+------+------+---------+
| **MATERIAL PREP**          |   |       |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| ** **                      | * | ###   |   |      | ##   |         |
|                            | * | ## To |   |      | ## B |         |
|                            |   | tal D |   |      | e DS |         |
|                            | * | SP^1^ |   |      | P^2^ |         |
|                            | * |       |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **Average**                |   | 5     |   | p/cc | \<   | p/cc    |
|                            |   | 9,411 |   |      | 47   |         |
+----------------------------+---+-------+---+------+------+---------+
| **Median**                 |   | 4     |   | p/cc | \<   | p/cc    |
|                            |   | 3,264 |   |      | 35   |         |
+----------------------------+---+-------+---+------+------+---------+
| **standard deviation**     |   | 13    |   |      |      |         |
|                            |   | 1,615 |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **number of measurements** |   | 131   |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **%Beryllium**             | * | \     |   |      |      |         |
|                            | * | <0.08 |   |      |      |         |
|                            |   |       |   |      |      |         |
|                            | * |       |   |      |      |         |
|                            | * |       |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+

+---------------------------+---+------+---+------+--------+--------+
| **PRESSING OPERATOR**     |   |      |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| ** **                     | * | ##   |   |      | ##     |        |
|                           | * | ###  |   |      | ## Be  |        |
|                           |   | Tota |   |      | DSP^2^ |        |
|                           | * | l DS |   |      |        |        |
|                           | * | P^1^ |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| **Average**               |   | 7    |   | p/cc | 14     |        |
|                           |   | ,517 |   |      | p/cc   |        |
+---------------------------+---+------+---+------+--------+--------+
| **Median**                |   | 10   |   | p/cc | 20     |        |
|                           |   | ,431 |   |      | p/cc   |        |
+---------------------------+---+------+---+------+--------+--------+
| **standard deviation**    |   | 216  |   |      |        |        |
|                           |   | ,339 |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| **number of               |   | 361  |   |      |        |        |
| measurements**            |   |      |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| **%Beryllium**            | * | 0    |   |      |        |        |
|                           | * | .188 |   |      |        |        |
|                           |   |      |   |      |        |        |
|                           | * |      |   |      |        |        |
|                           | * |      |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+

+----------------------------+---+-------+---+------+------+---------+
| **ISOPRESS**               |   |       |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| ** **                      | * | ###   |   |      | ##   |         |
|                            | * | ## To |   |      | ## B |         |
|                            |   | tal D |   |      | e DS |         |
|                            | * | SP^1^ |   |      | P^2^ |         |
|                            | * |       |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **Average**                |   | 2     |   | p/cc | ND   |         |
|                            |   | 4,323 |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **Median**                 |   | 1     |   | p/cc | ND   |         |
|                            |   | 6,786 |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **standard deviation**     |   | 8     |   |      |      |         |
|                            |   | 7,006 |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **number of measurements** |   | 299   |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+
| **%Beryllium**             | * | ND    |   |      |      |         |
|                            | * |       |   |      |      |         |
|                            |   |       |   |      |      |         |
|                            | * |       |   |      |      |         |
|                            | * |       |   |      |      |         |
+----------------------------+---+-------+---+------+------+---------+

+---------------------------+---+------+---+------+--------+--------+
| **PRECISION GRINDING**    |   |      |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| ** **                     | * | ##   |   |      | ##     |        |
|                           | * | ###  |   |      | ## Be  |        |
|                           |   | Tota |   |      | DSP^2^ |        |
|                           | * | l DS |   |      |        |        |
|                           | * | P^1^ |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| **Average**               |   | 42   |   | p/cc | 72     |        |
|                           |   | ,021 |   |      | p/cc   |        |
+---------------------------+---+------+---+------+--------+--------+
| **Median**                |   | 16   |   | p/cc | 29     |        |
|                           |   | ,787 |   |      | p/cc   |        |
+---------------------------+---+------+---+------+--------+--------+
| **standard deviation**    |   | 125  |   |      |        |        |
|                           |   | ,861 |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| **number of               |   | 318  |   |      |        |        |
| measurements**            |   |      |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+
| **%Beryllium**            | * | 0    |   |      |        |        |
|                           | * | .171 |   |      |        |        |
|                           |   |      |   |      |        |        |
|                           | * |      |   |      |        |        |
|                           | * |      |   |      |        |        |
+---------------------------+---+------+---+------+--------+--------+

+--------------------------+---+------+---+-----+----------+--------+
| **POWDER TRANSFER**      |   |      |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| ** **                    | * | ##   |   |     | #### B   |        |
|                          | * | ###  |   |     | e DSP^2^ |        |
|                          |   | Tota |   |     |          |        |
|                          | * | l DS |   |     |          |        |
|                          | * | P^1^ |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| **Average**              |   | 29   |   | p   | \< 9     |        |
|                          |   | ,929 |   | /cc | p/cc     |        |
+--------------------------+---+------+---+-----+----------+--------+
| **Median**               |   | 29   |   | p   | \< 9     |        |
|                          |   | ,675 |   | /cc | p/cc     |        |
+--------------------------+---+------+---+-----+----------+--------+
| **standard deviation**   |   | 2459 |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| **number of              |   | 68   |   |     |          |        |
| measurements**           |   |      |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| **%Beryllium**           | * | \<   |   |     |          |        |
|                          | * | 0.03 |   |     |          |        |
|                          |   |      |   |     |          |        |
|                          | * |      |   |     |          |        |
|                          | * |      |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+

+--------------------------+---+------+---+-----+----------+--------+
| **LOADING ISOPRESS DIE** |   |      |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| ** **                    | * | ##   |   |     | #### B   |        |
|                          | * | ###  |   |     | e DSP^2^ |        |
|                          |   | Tota |   |     |          |        |
|                          | * | l DS |   |     |          |        |
|                          | * | P^1^ |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| **Average**              |   | 16   |   | p   | \< 10    |        |
|                          |   | ,543 |   | /cc | p/cc     |        |
+--------------------------+---+------+---+-----+----------+--------+
| **Median**               |   | 15   |   | p   | \< 10    |        |
|                          |   | ,790 |   | /cc | p/cc     |        |
+--------------------------+---+------+---+-----+----------+--------+
| **standard deviation**   |   | 2665 |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| **number of              |   | 41   |   |     |          |        |
| measurements**           |   |      |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+
| **%Beryllium**           | * | \<   |   |     |          |        |
|                          | * | 0.06 |   |     |          |        |
|                          |   |      |   |     |          |        |
|                          | * |      |   |     |          |        |
|                          | * |      |   |     |          |        |
+--------------------------+---+------+---+-----+----------+--------+

# Exposure Controls in Place

## Access Control

The facility operates with the expectation and confidence that beryllium
particles are maintained in a controlled environment. Particles of
beryllium oxide are restricted to the local exhaust ventilation, process
enclosures, and work hoods. Any particles that inadvertently escape
these controlled systems are immediately cleaned up and not available
for migration and/or transport throughout the facility. Therefore,
access to the production area is not rigidly controlled for
office/administrative personnel. Administrative personnel enter the
production areas of the facility in street clothes and shoes without any
special precautions. Workers and are permitted in the office environment
and enter on an infrequent basis. At the start of the shift, workers
change out of personal clothes/shoes and don work uniforms/safety shoes.
The locker room is not designed for personal/work clothing segregation,
therefore, worker co-mingling (personal clothing versus work clothing)
does occur. Showers are available, however, their use is not mandatory.

## Personal Protective Equipment (PPE)

There is no routine or constant use of respiratory protection equipment.
Respirators are reportedly available and used for maintenance and
service tasks having a potential for airborne beryllium exposure.
Workers wear standard cotton/leather work gloves as the work tasks
require for abrasion/cut protection. Occasional use of impermeable
gloves by operators is observed depending on the task and work involved.
Overall, there is no rigid strategy for keeping beryllium off the skin.
The predominate strategy is if beryllium does get on the hands or skin
that it is promptly washed off prior to removal from the local exhaust
ventilation hood and enclosures.

## Work Practice Controls

Worker compliance with company established work practices and procedures
is excellent. Management expectations regarding beryllium health and
safety are clear, certain, and well defined in documentation, training
and ongoing program audits. Procedures are detailed and address
beryllium control expectations throughout the work place. Workers
maintain excellent work practice discipline and attention to beryllium
control detail. Both workers and management described a work environment
and culture where safety and health expectations have always been high
and workers are encouraged and feel free to bring up and address safety
and health issues in an urgent manner.

## Housekeeping

Housekeeping in all zones of the facility is well-organized. The site
has established a daily, weekly, monthly and quarterly schedule of
housekeeping control expectations. This schedule is documented and
activities are tracked to ensure housekeeping requirements are
completed. The site employs one full-time maintenance worker who is
dedicated to and responsible for completing the housekeeping schedule.
All operators are responsible for keeping their work surfaces and
personal self clean throughout the shift and use the final 15 minutes of
the shift to perform a through cleaning of their work area. One central
vacuum system and 4 portable HEPA vacuums are available to facilitate
housekeeping efforts.

## Local Exhaust Ventilation Controls

There are approximately 60 BeO machining centers and each is fully
enclosed a with stainless steel framed/Plexiglas and under negative
pressure. There are approximately 17 work hoods with running water,
drains, and both back and down draft airflow designs. There are 12 high
volume, low velocity HEPA filter collection systems on site providing
negative pressure to the work hoods and processing enclosures. Eight are
rated at 4000 cubic feet per minute (CFM) and four are rated at 2000
CFM. There is one low volume, high velocity HEPA filter collection
system provided in the machining department.

Machine controls are reportedly interlocked with the operation of the
ventilation systems and on critical systems alarms are installed to
indicate system malfunction. Differential pressure gauges across the
filters are installed and checked and recorded routinely. The
ventilation system is serviced and maintained by internal personnel on
an annual basis.

# Discussion

# General Recommendations

OSHA has developed the following general recommendations for all
beryllium workplaces:

*[Engineering Controls]{.underline}*\
\
Employers should use appropriate engineering controls and work practices
to ensure that worker exposures to beryllium are maintained below the
current OSHA PELs to the extent feasible. The following engineering
controls and practices should be used by employers:

-   enclose processes;

-   design and install appropriate local exhaust ventilation;

-   use vacuum systems in machining operations;

-   use pellets instead of powders wherever possible;

-   use product substitution where possible;

-   minimize the number of workers who have access to areas where there
    is a potential for beryllium exposure;

-   monitor employee exposures to airborne beryllium dust and fume,
    using personal sampling techniques, on a regular basis to ensure
    that exposures are below the PELs and that proper respiratory
    protection is being used where necessary.

*[Work Practices to Reduce Beryllium Exposure\
]{.underline}*Employers should ensure that employees use the following
safe practices to reduce their exposure to beryllium:

-   use high-efficiency particulate air (HEPA) vacuums to clean
    equipment and the floor around their work areas;

-   do not leave a film of dust on the floor after the water dries if a
    wet mop is used to clean;

-   do not use long vacuum hoses and do not loop the hoses that are
    used;

-   do not disconnect or disable the vacuum system during any machining
    operation;

-   never use compressed air to clean parts or working surfaces;

-   avoid prolonged skin contact with beryllium particulate; and

-   do not allow workers to eat, drink, smoke, or apply cosmetics at
    their work stations.

*[Hygiene and Personal Protective Clothing\
]{.underline}*\
OSHA is aware of CBD cases that have occurred among family members of
beryllium-exposed workers. To reduce \"carry-home\" exposures, employers
should provide showers, clean work clothes, and clean areas for storing
street clothes**.** Protective clothing should be provided to employees
who work in areas where beryllium-containing powders are used and where
there is a potential for spills. In addition, employers should ensure
that employees:

-   change into work uniforms before entering their work area;

-   place their uniforms in a labeled bin with a cover at the end of the
    work shift;

-   shower and change into street clothes prior to leaving the facility;

-   wash their face, hands, and forearms before eating, smoking, or
    applying cosmetics;

-   keep their work clothes as clean as possible during the workshift;

-   wipe off their shoes before leaving the work area; and

-   do not wear their work uniform (including their work shoes) outside
    of the facility.

*[Respiratory Protection]{.underline}*\
\
Recent data suggest that exposures to beryllium even at levels below the
2 micrograms/m^3^ PEL may have caused CBD in some workers. Therefore,
employers should consider providing their beryllium-exposed workers with
air-purifying respirators equipped with 100-series filters (either N-,
P-, or R-type) or, where appropriate, powered air-purifying respirators
equipped with HEPA filters, particularly in areas where material
containing beryllium can become airborne.\
\
*[Training\
]{.underline}*\
Employers should give employees exposed to beryllium training and
information about the following items:

-   material safety data sheets (MSDSs) for beryllium;

-   the fatal lung disease that may occur as a result of exposure;

-   the availability of the BeLPT blood test to determine whether an
    exposed worker has become sensitized to beryllium;

-   the potential for developing lung cancer as a result of exposure;

-   the importance of avoiding skin contact;

-   the engineering controls the employer is using to reduce worker
    exposures to beryllium;

-   specific work practices that can be used to reduce exposure to
    beryllium;

-   the use of appropriate protective equipment, including the use of
    respirators;

-   the results of any industrial hygiene sampling for levels of
    beryllium in the workplace; and

-   a copy of all pertinent Hazard Information Bulletins from OSHA.

*[Health Screening Methods for Beryllium sensitization and Chronic
Beryllium Disease]{.underline}*\
\
Employers should consider sending beryllium-exposed employees to a
physician or other licensed health care professional to be evaluated for
beryllium sensitization or the presence of CBD. The screening
examination for CBD usually begins with a chest x-ray and a blood test
for beryllium sensitization, namely, the BeLPT, plus any further
evaluation considered appropriate by the health care professional. The
blood test can detect an adverse health response to beryllium exposure
earlier than breathing tests or chest x-rays can. The BeLPT is not
routinely done in most medical laboratories; however, the health care
professional may order this test from any laboratory that has overnight
courier service to one of the Medical Research Centers listed below. If
a worker is sent to a health care professional for health screening, a
copy of OSHA's Hazard Information Bulletin 19990902, *Preventing Adverse
Health Effects From Exposure to Beryllium on the Job* should accompany
the employee.

Employees who work in a place where beryllium is used and have developed
any of the symptoms listed below, should inform their health care
professional of their past beryllium exposure, or seek information from
a health care professional who specializes in occupational lung diseases
to determine whether they may have developed CBD:

-   unexplained cough,

-   shortness of breath,

-   fatigue,

-   weight loss or loss of appetite,

-   fevers, and/or

-   skin rash.

If they do not have any of the above symptoms but are concerned that
they may have become sensitized to beryllium, they should inform their
health care professional that they would like to be tested with the
blood BeLPT. They should also take a copy of the above-mentioned Hazard
Information Bulletin with them.

####### Specific Recommendations

This site visit was not intended to serve as a comprehensive industrial
hygiene review. Thus, investigators did not evaluate all possible
hazards at this facility. To optimize migration control, the design
layout and sequence of work practices are important during transitions
from controlled plant areas to designated offices or administrative
areas outside the control zone. The following considerations should be
incorporated into current or future re-designs:

-   Ideally, there should only be one designated/routine entry into
    controlled work areas where PPE is required.

-   A transition zone should be established between the controlled work
    area and non-controlled area (administrative offices, break areas,
    etc.)

-   The transition zone should be designed and constructed to facilitate
    the use of tack mats, donning and doffing respirators, gloves, and
    coveralls, dirty PPE disposal, seating, and clean PPE storage.

-   Tack mat floor covering should be designed for 3-foot falls per foot
    to increase effectiveness of particle removal from work shoes at the
    transition area.

-   Disposable protective gloves should be on before handling any
    potentially contaminated articles or work surfaces.

-   Disposable gloves should be on at all times inside the transition
    room and the plant area. Gloves should only be removed just before
    exiting the transition room into an adjacent office/support area.

-   Work shoes should be covered, removed, or otherwise cleaned prior to
    leaving the transition room into an adjacent office or support area.

-   Foot cross over designs and techniques should be considered in the
    transition area to control transfer of shoe contamination from the
    work area to the office area.

-   All reusable PPE should be placed in covered storage containers.

-   Glove disposal containers should be located at any transition point.

-   Containers of clean disposable gloves should be available at the
    entrance into the plant area and at operator workstations.

-   Hand wipes should be available wherever clean gloves are stored to
    facilitate hand washing prior to donning clean gloves.

-   Beryllium contaminated waste containers should have lids with foot
    pedals. This will alleviate the temptation of workers to throw
    potentially contaminated trash from any distance and will also make
    it unnecessary to touch the lid to open it.

-   All porous surfaces should be eliminated to the extent feasible,
    unless they are disposable and are disposed of regularly, in that
    they may accumulate beryllium dust. This especially includes
    fabric-covered chairs in the work area.

-   Showers should be taken by all workers at the end of the work shift.

-   Workers and management should closely study the work practice
    sequences at transition and locker room areas. Identify all articles
    having a potential for contamination and develop work practice
    sequences that minimize migration of beryllium particles from the
    plant into the office or locker room areas.

-   Dry sweeping and/or compressed air used for cleaning in beryllium
    work area should be prohibited. Vacuum hoses and wet cleaning
    capabilities should be in place at every work location for clean up
    when necessary.

-   Workers should be instructed to check with the appropriate hygiene
    staff when designing their own controls. These controls should be
    thoroughly tested before work begins.

It is recommended that an alternative to the current layout of the
factory be considered. A new design would consist of four zones which,
for ease of referral, will be coded by color; red, orange, yellow and
green.

-   The red zone will be that area in which active beryllium machining
    work is done. This zone will require the strictest controls and
    limited access to all but essential personnel. Company work clothes
    will be required in this area.

-   The orange zone will have no active beryllium work but will be
    considered a contaminated zone. Company work clothes will be
    required in this area. This is the area where support workers
    interface with workers who enter the red zone, but do not come in
    contact with active work surfaces. Some decontamination should be
    done before removing any material from the red zone into the orange
    zone. Nothing should leave the red or orange zones without thorough
    decontamination. Paper and porous materials may not be able to be
    adequately decontaminated. Therefore, its use in the red zone should
    be minimized. Preferably there should be a barrier separating these
    zones. Coming from the red zone into the orange zone should require
    the donning of some protective covering, including shoe covers to
    limit migration of beryllium from the red zone. This protective
    covering should be removed and remain in the orange zone. While one
    time disposable use of the outer garment would be best, cost
    effectiveness may require some reuse. Care should be taken if this
    garment needs to be stored not to transfer contamination from the
    interior of the garment to the exterior. Windows and intercom
    systems should be available between all zones. As little as possible
    should be physically transferred between them. The level of personal
    protective equipment used in these zones should be a matter of
    confidence based on the engineering controls and a history of
    industrial hygiene sampling. A lunchroom and restrooms in the orange
    zone should be provided for the red zone workers.

-   The yellow zone should be that area by which workers leave the
    orange zone. In the yellow zone, showers should be required before
    exiting, as well as a change of work clothes and shoes.

-   The green zone can contain the workers' lockers with their street
    clothes and clean work clothes into which they can change at the
    beginning of the shift.

-   Offices can be placed in either the green or orange zones depending
    on the level of personal protective equipment that is preferable. It
    is assumed that airborne levels of beryllium can be made negligible
    in the orange zone and that the primary concern will be surface
    contamination and skin protection.

-   To encourage workers to use the shower and change facilities,
    privacy should be considered. The number of workers involved in
    beryllium machining is small enough that private shower and changing
    cubicles might be made available for most. Workers should be given
    time as part of their shift to make the transition between areas.
    Company clothes can be worn without disposable covering in the red
    zone, but laundry facilities used to clean these clothes should be
    made aware of the potential for beryllium contamination.
    Alternatively, a cover garment could be worn over the company
    clothes to limit the amount of contamination that occurs, but the
    company should be aware that this covering might not be completely
    effective and some contamination may remain on the clothes
    underneath. In either case, the clothes that are worn should be
    company clothes so that the workers are required to change before
    leaving the plant.

# References

1.  Occupational Safety and Health Administration (OSHA) - Health
    Intelligence Bulletin. *Preventing Adverse Health Effects From
    Exposure to Beryllium on the Job.* September 2, 1999.

2.  McCawley, M.A., M.S. Kent and M.T. Berakis. Ultrafine beryllium
    number concentration as a possible metric for chronic beryllium
    disease risk. Appl. Occupational and Environ. Hyg. 16(5): 631-638
    (2001)