Document B5Koe2xOqeYmRg2Z0GKERaE8j
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INDUSTRIAL HYGIENE FOUNDATION O F AM E RICA, I N C. Mellon Institute. 440 0 Fifth Avenue
,Pittsburgh 13 Pa.
Report on
EVALUATION OF THE ASBESTOS DUST HAZARD IN TYLER, TEXAS PLANT
of the
PITTSBURGH CORNING CORPORATION
July 8, August 6, 7, 1963
Field Investigation By: Jacob Cholak
Lawrence J, Schafer William J. Schreibeis
Samples Analyzed By: The Kettering Laboratory
Cincinnati, Ohio
William J. Schreibeis, P.E. Industrial Hygiene Engineer
Robert T. P. deTreville, M.D. Managing Director
AN ASSOCIATION or INDUSTRIES FOR THE ADVANCEMENT OF HEALTHFUL WORKINO CONDITIONS
1.
INTRODUCTION
On July 8, the plant of the Pittsburgh Corning Corporation, Tyler, Texas was visited by Messrs. Jacob Cholak and William J. Schreibeis in order to review the potential health hazards of handling asbestos during manufacture of asbestos pipe insulation. On August 6 and 7, 1963, sampling was conducted at the plant by Mr. Lawrence J. Schafer and an evaluation made of the airborne dust concentrations.
DISCUSSION OF RESULTS
In Table 1, the concentrations of particulate matter, when possible, are expressed both on a weight basis and as the number of particles present in one cubic foot of air. Samples collected with the high volume sampler and the electrostatic precipitator were suitable for gravimetric and other analysis while samples collected on membrane filters were suitable for dust counting only. The number of particles present in the air as total particulate matter and as asbestos fibers were determined. Any rod like particle with length definitely greater than width was considered as asbestos fiber. It may be seen that the per cent of fibers in the dust varied from a low of 29% to a high of 56%. The dust in the sawing area contained a slightly higher content of asbestos fibers than did the airborne dust in the production area. It will also be noted that more parti cles of dust and fibers of asbestos were present in the air near the scrap crushers
2.
than, surprisingly, was the case for air in the sawing area. The values in
Table 1 followed by an asterisk are estimated counts taken from the straight lines
in Figure 1,' fitted to the data by the method of least squares. It may be seen,
"that the dust counts and the'masV'conc ehtrations are closely related. Figure 1
offers the plant a rather simple method for estimating the numbers of total
'particles and of the fibers of asbestos present per cubic foot of air from the mass
weight data and volumes of air sampled.
*
Highest dust counts, at the threshold limit, were obtained in the case
of samples collected at the scrap crusher. The highest concentration of dust oc
curred for the five-minute period that the three-unit dust collector in the saw
area was being cleaned. The air at the take-off areas of the building machines
was the least contaminated with dust.
It should be noted that the threshold limit for asbestos, (5 mppcf) is
assumed to apply only to asbestos fibers while dust in the air of the plant will
contain other particulates, including filler materials used in the process. Since
there is some evidence that the most active particles are those fibers between 20
and 50 microns in length, the numbers of fibers present in various size categories
ivere also determined. These data are given in Table 2. Data in Table 2 and the
asbestos fiber counts in Table 1 were used to derive the data in Table 3. As may
be seen from Table 2, the fibers in the air of the sawing area were generally
shorter than were those in the process area.
In Table 4 are tabulated the per cent of the numbers of the fibers of
asbestos or, more properly, bundles of fibers varying from 5 microns to less
3.
than 1 micron in diameter. The fibers in the air of the sawing area appear to have slightly smaller diameters than was the case for fibers in the air of the pro cess area.
The results of other analytical work performed on these samples are given in Table 5. As may be seen dusts or fibers^ removed from the air in the production and sawing areas did not contain any free crystalline silica. Two dif ferent samples of Dacolite contained variable small amounts of quartz and cristobalite. In view of the warning printed on each bag, the low concentrations of free silica in this material were rather surprising.
It would appear from the analysis of the samples that were collected intentionally only at those processes that appeared to be the principal producers of dust, that the number of asbestos fibers present in the air, with few exceptions, were well below the threshold limit of 5 mppcf. One significant exception was the brief period of time during which a collector system was being cleaned. Dur ing this period, excessive quantities of dust and fiber were being dispersed into the air for a period of about 5 minutes. It would appear, from an examination of the total numbers of particles and of fibers as well as observation of the operations, that the crusher and the sawing operation may at times produce large quantities of dust. However, the dust, because of its physical characteristics, appears to settle out of the air rapidly. Particles of particulates in samples collected at breathing level heights, were well below threshold limits, even though some operations were observed to produce what appeared visually to be large clouds of dust.
4.
The type of asbestos used in the plant is "amosite" an iron-magnesium silicate. The specific gravity of this material is 3.45 as compared to 2.55 for chrysotile, the material more widely used in this country.
The fibers of chrysotile are also much smaller in diameter than are those of amosite, the minimum diameters being 0.5 micron and 0.03 micron respectively for amosite and chrysotile. Another factor in favor of the rapid settling of the fibers from the air of the plant is that the asbestos bundles are not given the drastic shredding as in the textile industry.
RECOMMENDATIONS
At no time during the survey was the air of the plant contaminated with dust to the point to affect visibility, and one could always see down the entire length of the rather long building in which the operations were being conducted. Nevertheless, our observation of the operations leads us to make the following recommendations:
1. There was an obvious need to institute a better housekeeping pro gram, especially in the sawing area. Floors, equipment and other structures should be cleaned regularly and frequently according to a definite supervised schedule. Dry sweeping should be avoided and only vacuum cleaning equipment provided with suitable collectors should be used.
2. Hoods and ducts should be maintained in good working order and all breaks and leaks in connecting ducts, etc. should be repaired promptly.
5.
3. The hoods and the exhaust system at the wheel cutter in the saw ing room should be improved.
4. More space should be provided between the sawing equipment to reduce cross-contamination of the air with dust.
5. It is suggested that the crusher be fed by means of a short con veyor system in order to keep the operator clear of the cloud of dust produced when the machine is in operation.
6. Operators should be educated in respect to working habits Which will reduce the dispersion of dusts. For example (a) carts of crushed material should be moved from the crusher only after the crusher has been turned off and a brief period has elapsed to permit dust to settle, (b) Work should be removed from the large slitter only after the exhaust system has cleared the dust from the interior of the piece being cut. A wait of only a few seconds would accomplish this, (c) Bag collectors should be opened only when the discharge end of the col lector is closed.
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Table 1 - - C oncentrations o f P a rtic u la te M a tte r in the A tm o sp h e re at V arious L o ca tio n s in the P lant o f the P itts b u rg h C orning C o rp o ra tio n at T y le r, Texas
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10.
Table 3 -- The Numbers of Asbestos Fibers (mppcf) Present in the Air According to the Range of the Lengths of the Fibers
Sample No. 2 3 4 5
6 8
9 11 12 13 14 15 16 17 19 20
Millions of Fibers Per Cubic Foot of Air
5-50 Microns
10 - 50 Microns
in Length
in Length
0.68 0.43 1.50
0.39 0.25 1. 10
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20.70 3.06 0.25 0. 14 0.20 0.60
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Table 5 -- Free Silica Content of a Number of Samples Collected in the Plant
Description of Sample
Per Cent Free Crystalline Silica
Quartz
Cristobalite
Tridymite
A sample of Dacolite collected on 7-10-63
3.0
2.5
Absent
A sample of Dacolite collected
on 8-5-63
1.2 <(2.0
Absent
General air sample collected in the sawing area between the large slitting saw and the large edging saw.
<2.0
Absent
Absent
General air sample collected 5 feet from the scrap crusher.
<2.0
Absent
Absent
General air sample collected in the feed area.
<.2.0
Absent
> Absent
F igure