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August 2019
Objective Data Collection for Roofing Industry Exposures under 29 CFR 1926.1153
On March 25, 2016, the Occupational Safety and Health Administration (OSHA) released a final
rule on worker exposure to respirable crystalline silica (RCS). The rule became effective June 23,
2016, but enforcement initially was delayed until June 23, 2017, and finally initiated Sept. 23, 2017.
According to OSHA, about 2.3 million workers are exposed to RCS in the workplace—respirable
silica means inhaled particles 10 microns in size or less that can get into critical lung areas and cause
health problems. The at-risk workforce comprises about 2 million construction workers who drill,
cut, crush or grind silica-containing materials such as concrete and stone and 300,000 workers in
general industry operations such as brick manufacturing, foundries and hydraulic fracturing. The
common construction tasks cited by OSHA as involving exposure to RCS may not be performed
extensively by roofing workers, but this objective data compilation has been established to assist
contractors in minimizing roofing worker exposure.
Silica refers to the chemical compound silicon dioxide (SiO2) the most common form of which is
quartz. Sand, a key component in many building products like mortar, clay and concrete tiles or
pavers and brick, mainly is composed of silica in the form of quartz. Hazards develop when
materials containing silica are cut, drilled or ground in a way that produces respirable silica. This
most often is done with powered saws or grinders with diamond blades or silicon carbide cut wheels
that produce airborne particles that can be inhaled. The danger results when the smallest of particles
(those that are respirable) penetrate to the gas exchange area of the lungs; larger particles do not
travel that deep into the lungs and are purged by natural actions of the body. The respirable particles
remain in the lungs and permanently scar lung tissue making breathing increasingly more difficult—
an occupational disease known as silicosis that often does not manifest itself until many years after
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exposures. According to the American Lung Association, silicosis also increases the risk of other
lung issues like tuberculosis, lung cancer and chronic bronchitis.
The construction regulation
Following are key features provided in the construction rule:
• Establishment of an action level and a permissible exposure limit (PEL) for worker exposures
• Specified exposure control methods for construction tasks listed in what OSHA refers to as Table 1 that eliminate the requirement for initial exposure monitoring
• The requirement for a written exposure control plan
• Medical surveillance for workers required to use a respirator for 30 or more days in a year
• Silica hazard communication to workers
• Use of objective data to assess worker exposure to silica
• A specific compliance date for the construction industry
Action level and PEL
Under the OSHA rule, an employer must ensure no worker is exposed to a RCS concentration more
than the PEL of 50 micrograms per cubic meter of air calculated as an eight-hour time weighted
average. The employer also is obliged to assess the exposure of any worker who is or may reasonably
be expected to be exposed to a level of RCS at or above the action level of 25 micrograms per cubic
meter of air calculated as an eight-hour time-weighted average. Performing air monitoring of
workers to assess the exposure to RCS likely is the most burdensome requirement in the regulation
for employer compliance. However, two other elements of the rule may be relied on to minimize the
administrative burdens and financial impact of the rule while keeping workers safe: the provision for
objective data and use of the specified exposure control methods under Table 1.
August 2019
Table 1
Under 29 CFR §1926.1153(c), OSHA sets out specified exposure control methods for a variety of
construction tasks. For those tasks set out in Table 1, if the employer implements the engineering
controls and respiratory protection listed in Table 1 for a specific task, the employer will be
considered in compliance with the rules for exposure to RCS under the rule [29 CFR
§1926.1153(e)(3)]. Initial exposure monitoring would not be required. As an example, Table 1
requires an integrated water delivery system that continuously feeds water to the blade of a handheld
power saw used to cut silica-containing material. For outdoor use of four hours or less with such a
saw, Table 1 does not require a respirator be worn by the operator in conjunction with the water
delivery to the blade. However, if cutting exceeds four hours, a respirator with an assigned
protection factor (APF) of 10 also must be used with the water delivery system. Filtering face piece
respirators (dust masks) are available with an APF of 10 and half-mask or full-face mask air-
purifying respirators with an APF of 10 or greater are suitable alternatives to dust masks but also are
cumbersome and restrict visibility, which is a liability for workers on roofs because such masks may
increase the possibility of other injuries. The use of water to control dust is an area of substantial
concern for worker safety particularly when workers are at elevation on sloped surfaces even when
the slope is relatively low. A greater likelihood of slip, trip or fall injuries as a result of water on a
work surface is a natural consequence of the required engineering controls.
Another Table 1 task listed by OSHA is the use of a handheld grinder for mortar removal, for
example, to facilitate counterflashing installation in the roofing industry. To comply with the
engineering controls, the grinder must be equipped with a shroud and dust-collection system
operated according to the manufacturer’s instructions. OSHA specifies the minimum airflow, filter
efficiency and type under Table 1 for compliance. In addition, an operator using a grinder with the
August 2019
described dust-collection attachment must wear a respirator with an APF of 10 when grinding work
is performed for four hours or less and a respirator with an APF of 25 when grinding is performed
for more than four hours. The National Institute for Occupational Safety and Health (NIOSH) lists
two types of APF 25 respirators in its selection logic: any powered air-purifying respirator equipped
with a hood or helmet and a high-efficiency (HEPA) filter and any continuous flow supplied-air
respirator equipped with a hood or helmet. Extending the time an operator uses a grinder for mortar
joints in excess of four hours triggers required use of the more efficient yet cumbersome respirator,
which also may increase the likelihood of falls or other injuries.
Medical surveillance
The medical surveillance requirement under the rule is tied to the days a worker must use a
respirator. If respirator use will be required on 30 or more days per year, a contractor must make
sure several medical examinations and procedures take place. For example, an initial examination
must focus on a worker’s medical and work history, a physical exam, chest X-ray, pulmonary
function test and tuberculosis test. OSHA requires an initial examination as a baseline evaluation to
be performed within 30 days after the worker’s initial assignment. Periodic examinations covering
the areas listed under the initial examination protocol must be conducted at least every three years or
more frequently if recommended by the physician or other licensed health care professional
(PLHCP).
A contractor must make sure the PLHCP is informed of the worker’s duties as they relate to RCS
exposure; the anticipated levels of occupational exposure to RCS that the worker may expect and
any current or past exposures; a description of personal protective equipment used or to be used by
the worker; and information from work-related medical exams previously provided to the worker
and currently under the control of the employer.
August 2019
A contractor must obtain a written medical opinion from the PLHCP within 30 days of the medical
examination of the worker and must ensure the worker receives a copy of the written medical
opinion from the PLHCP within that same 30 days.
Worker exposure assessment and objective data
Under 29 CFR §1926.1153(d), for construction tasks not listed in Table 1 or where the employer
does not fully and properly implement the engineering controls, work practices and respiratory
protection described in Table 1, the employer must ensure no employee is exposed to an airborne
concentration of RCS more than 50 micrograms per cubic meter of air as an eight-hour time-
weighted average. An employer must assess the exposure of any worker who is or may be reasonably
expected to be exposed to RCS at or above the action level using either of two regulatory options:
the performance option or scheduled monitoring option.
The performance option allows assessment of the eight-hour time-weighted exposure based on any
combination of air-monitoring data or objective data sufficient to accurately characterize the worker
exposure to RCS. The scheduled monitoring option requires the employer to perform initial
monitoring based on one or more personal breathing zone air samples of workers by shift, job
classification and work area. Additional subsequent required monitoring depends on the nature of
the initial results with respect to the action level and PEL under the rule. Regardless of the option
used by the employer, worker exposures must be reassessed whenever a change in the production,
process, control equipment, personnel or work practices may reasonably be expected to result in
exposures at or above the action level. This is true also if the employer has reason to believe
exposures at or above the action level have occurred.
Objective data under the performance option means:
August 2019
“…information, such as air monitoring data from industry-wide surveys or calculations based on the composition of a substance, demonstrating employee exposure to respirable crystalline silica associated with a particular product or material or a specific process, task, or activity. The data must reflect workplace conditions closely resembling or with a higher exposure potential than the processes, types of material, control methods, work practices, and environmental conditions in the employer’s current operations.”
OSHA notes reliance on objective data is intended to provide the same degree of assurance that air
monitoring of worker exposures through personal breathing samples does; so it comes with a
similar, specific recordkeeping requirement as air monitoring data. A contractor must maintain a
record of silica-containing material; source of the objective data; test protocol and results of testing;
description of the process, task or activity on which the objective data were based along with other
data relevant to the foregoing or the exposures on which the objective data were based. Because
OSHA views objective data similar to employee exposure records, the rule requires the data be
maintained for at least 30 years.
NRCA’s compilation of objective data is intended to provide a source of exposure data for roofing
tasks that may involve contact with silica as suggested primarily from information found in Section 3
of manufacturers safety data sheets (SDSs) for the products being handled. In addition, data has
been captured for other tasks that may or may not be listed in Table 1 and for which silica exposure
was possible based on assumptions about the nature of the task and the material being disturbed.
The goal of the collection is to provide dependable, quality data to help roofing contractors protect
their workers from harmful exposures to RCS.
August 2019
Sampling Results
RCS and Total Respirable Particulate or Dust
Various Roofing Industry Tasks September 7, 2018
August 2019
Asphalt shingle removal project #1701
Date: July 5, 2017
Location: Munster, IN
Structure type: Church
Project description: Removal of 5,000 square feet of approximately 25 year old, three-tab shingle removal using hand tools
Lab analysis of removed material: 9.9% quartz
Crew members sampled: 5.
Sample results for RCS in micrograms per cubic meter of air during removal phase:
9.0 µg
9.2 µg
9.3 µg
9.4 µg
9.4 µg
RCS as a full shift TWA:
9.2 µg
9.3 µg
9.3 µg
9.4 µg
9.4 µg
Sample results for respirable particulate in milligrams per cubic meter of air during removal phase:
0.090 mg
0.092 mg
0.093 mg
0.094 mg
0.094 mg
August 2019
Respirable particulate as a full shift TWA:
0.092 mg
0.093 mg
0.093 mg
0.094 mg
0.094 mg
August 2019
Asphalt shingle installation project #1702
Date: July 6, 2017
Location: Munster, IN
Structure type: Church
Project description: Installation of ice and water barrier and laminated asphalt shingles on 5,000 square foot roof area
Products installed: Carlisle WIP® 100 water and ice protection and Certainteed Landmark® asphalt shingles
Crew members sampled: 5.
Sample results for RCS in micrograms per cubic meter of air during installation phase:
9.4 µg
9.5 µg
9.4 µg
9.4 µg
9.4 µg
RCS as a full shift TWA:
9.2 µg
9.3 µg
9.3 µg
9.4 µg
9.4 µg
Sample results for respirable particulate in milligrams per cubic meter of air during installation phase:
0.094 mg
0.095 mg
0.094 mg
0.094 mg
0.094 mg
August 2019
Respirable particulate as a full shift TWA:
0.092 mg
0.093 mg
0.093 mg
0.094 mg
0.094 mg
August 2019
Asphalt shingle removal project #1703
Date: September 6, 2017
Location: Fairfield, OH
Structure type: Residence
Project description: 1,400 square feet of asphalt shingle and underlayment removal using hand tools
Lab analysis of removed material: 9.9% quartz
Crew members sampled: 5.
Sample results for RCS in micrograms per cubic meter of air during the removal phase:
18.0 µg
17.0 µg
19.0 µg
18.0 µg
22.0 µg
RCS as a full shift TWA:
10 µg
11 µg
11 µg
11 µg
19 µg
Sample results for respirable particulate in milligrams per cubic meter of air during the removal phase:
0.18 mg
0.17 mg
0.19 mg
0.18 mg
0.32 mg
August 2019
Respirable particulate as a full shift TWA:
<0.10 mg
<0.11 mg
<0.11 mg
<0.11 mg
<0.14 mg
August 2019
Asphalt shingle installation project #1704
Date: September 6, 2017
Location: Fairfield, OH
Structure type: Residence
Project description: Installation of synthetic underlayment, water barrier and laminated asphalt shingles on 1,400 square foot roof area using pneumatic nail guns.
Products installed: Atlas Summit® 60 Synthetic underlayment; Atlas Weathermaster® granular self-adhesive ice and water barrier; Atlas StormMaster® shingles.
Crew members sampled: 5.
Sample results for RCS in micrograms per cubic meter of air during the installation phase:
7.3 µg
8.6 µg
7.5 µg
7.7 µg
18.0 µg
RCS as a full shift TWA:
10 µg
11 µg
11 µg
11 µg
19 µg
Sample results for respirable particulate in milligrams per cubic meter of air during the installation phase:
0.073 mg
0.086 mg
0.075 mg
0.077 mg
0.073 mg
August 2019
Respirable particulate as a full shift TWA:
<0.10 mg
<0.11 mg
<0.11 mg
<0.11 mg
<0.14 mg
August 2019
Asphalt shingle removal project #1705
Date: September 8, 2017
Location: Portland, OR
Structure type: Residence
Project description: 1,000 square feet of asphalt shingle and underlayment removal using hand tools
Crew members sampled: 2
Sample results for RCS in micrograms per cubic meter of air during removal phase:
33.0 µg
11.0 µg
RCS as a full shift TWA:
21.0 µg
11.0 µg
Sample results for respirable particulate in milligrams per cubic meter of air during removal phase:
1.2 mg
<0.11 mg
Respirable particulate as a full shift TWA:
0.64 mg
0.11 mg
August 2019
Asphalt shingle installation project #1706
Date: September 8, 2017
Location: Portland, OR
Structure type: Residence
Project description: Installation of roofing felt and asphalt shingles on approximately 1,000 square foot roof area using pneumatic nail guns.
Product installed: GAF Timberline HD® asphalt shingles
Crew members sampled: 2
Sample results for RCS in micrograms per cubic meter of air during installation phase:
12.0 µg
12.0 µg
RCS as a full shift TWA:
21.0 µg
11.0 µg
Sample results for respirable particulate in milligrams per cubic meter of air during installation phase:
<0.12 mg
<0.12 mg
Respirable particulate as a full shift TWA:
0.64 mg
0.11 mg
August 2019
Modified bitumen removal and installation project #1721
Date: August 1, 2017
Location: Munster, IN
Structure type: Church
Project description: Removal of granulated modified bitumen cap sheet and asphalt underlayment and installation of Certainteed Black Diamond self-adhering base sheet and torch -applied Certainteed GTA cap sheet (Desert Tan).
Crew members sampled: 5
Sample results for RCS in micrograms per cubic meter of air:
<10 µg
<7.1 µg
<7.1 µg
<10 µg
<7.2 µg
RCS as a full shift TWA:
<5 µg
<5.2 µg
<3.6 µg
<5.1 µg
<5.2 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
<0.10 mg
<0.071 mg
<0.071 mg
<0.10 mg
<0.072 mg
August 2019
Respirable particulate as a full shift TWA:
<0.05 mg
<0.052 mg
<0.036 mg
<0.051 mg
<0.052 mg
August 2019
Modified bitumen installation project #1723
Date: August 8, 2017
Location: Madison, WI
Structure type: School
Project description: Installation of 4,000 square feet of torch-applied SBS modified bitumen
Product installed: Siplast Paradiene® 20 PR TG.
Crew members sampled: 6
Sample results for RCS in micrograms per cubic meter of air as full shift TWA:
4.6 µg
4.7 µg
4.8 µg
5.0 µg
4.6 µg
4.7 µg
Sample results for respirable particulate in milligrams per cubic meter of air as full shift TWA:
0.046 mg
0.047 mg
0.081 mg
0.050 mg
0.046 mg
0.047 mg
August 2019
BUR/Modified removal and modified bitumen and gypsum roof board installation project #1725
Date: December 15, 2017
Location: Berwyn, IL
Structure type: Bank
Project description: Removal of a gravel-surfaced BUR with modified bitumen roof flashings and installation of approximately 450 square feet of gypsum roof board and modified bitumen base and cap sheets. Tools used included a powered roof cutter, gas axe, grinder, roof spade, prybar, crowbar, razor knives, hammers, roofing torch, brooms and wheelbarrows. The bulk sample of the roofing material removed was analyzed to have <0.24 % quartz and <0.24% Cristobalite and <0.96% Tridymite.
Product installed: Densdeck® gypsum roof board; Johns-Manville SBS modified bitumen base sheet and Johns-Manville Dynaweld Cap 250 FR.
Crew members sampled: 5
Sample results for RCS in micrograms per cubic meter of air as full shift TWA:
<4.4 µg
<4.4 µg
<4.4 µg
<4.4 µg
<4.4 µg
Sample results for respirable dust in milligrams per cubic meter of air as full shift TWA:
0.14 mg
0.096 mg
0.064 mg
0.044 mg
0.11 mg
August 2019
Built-up roofing removal project #1744
Date: August 8, 2017
Location: Clackamas, OR
Structure type: School
Project description: 1,500 square feet of built up roofing system removal (half day) using powered roof cutter, shovels, brooms and wet/dry vacuum
Crew members sampled: 3
Sample results for RCS in micrograms per cubic meter of air:
23 µg
10 µg
10 µg
RCS as a full shift TWA:
17 µg
10 µg
10 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
1.8 mg
0.34 mg
0.25 mg
Respirable particulate as a full shift TWA:
1.31 mg
0.57 mg
0.18 mg
August 2019
Built-up roofing installation project #1745
Date: August 8, 2017
Location: Clackamas, OR
Structure type: School
Project description: 1,000 square feet of built up roofing system installation (half day)
Product installed: Johns Manville Dynabase®
Crew members sampled: 3
Sample results for RCS in micrograms per cubic meter of air:
11 µg
11 µg
11 µg
RCS as a full shift TWA:
17 µg
10 µg
10 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
0.81 mg
0.8 mg
0.11 mg
Respirable particulate as a full shift TWA:
1.31 mg
0.57 mg
0.18 mg
August 2019
Built-up roofing removal and installation project #1746
Date: October 10, 2017
Location: Mendota Heights, MN
Structure type: Commercial structure
Project description: 3,000 square feet of built up roofing system removal (half day). Workers removed a built-up roof system with a motorized roof cutter, shovels and wheelbarrows and debris was loaded into a dumpster using a crane. Fine asphalt debris was cleaned up using a gas-powered gravel sweeper. After clean-up, two workers drilled approximately 100 holes into concrete using a ¼-inch drill bit to a depth of 2-3 inches. Workers then installed rigid insulation, a cover board, Grace Ice & Water Shield, Johns Manville GlasPly®IV using Trumbull Trulo® Low Odor Asphalt and Johns Manville Dynaflex SBS Mineral Surfaced Flashing Sheet.
Crew members sampled: 3
Sample results for RCS in micrograms per cubic meter of air:
9.1 µg
9.4 µg
12 µg
RCS as a full shift TWA:
7.3 µg
7.5 µg
9.6 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
0.17 mg
0.15 mg
0.26 mg
Respirable particulate as a full shift TWA:
0.14 mg
0.12 mg
0.21 mg
August 2019
Built-up roofing removal and installation project #1747
Date: September 29, 2017
Location: Milwaukee, WI
Structure type: Public utility building
Project description: Approximately 1,000 square feet of built up roofing system was removed and a new built-up roof system installed. Workers removed a built-up roof system with a roof cutter, roof plow and manual tools. Fine asphalt debris was cleaned up using a blower. After clean-up, workers fastened Densdeck® gypsum roof board into the metal deck over which a two-ply roofing felt was installed followed by use of a chain mop to flood coat the two-ply system.
Product installed: Johns Manville GlasPly® Premier
Crew members sampled: 3
Sample results for RCS in micrograms per cubic meter of air:
<8.5/14 µg
<9.3/15 µg
<8.1/14 µg
RCS as a full shift TWA:
<11.0 µg
<11.0 µg
<10.0 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
<0.085/0.14 mg
<0.093/0.15 mg
<0.081/0.14 mg
Respirable particulate as a full shift TWA:
<0.106 mg
<0.115 mg
<0.103 mg
August 2019
Sheet metal and flashing installation project #1766
Date: September 12, 2017
Location: Chicago, IL
Structure type: Apartment building
Project description: Drilling and sawing into concrete and masonry to install 100’ of base tie-in and 50’ aluminum termination bar; drilled for fasteners every 12 inches (approximately 150 holes)
Crew members sampled: 2
Eight-hour TWA concentration for RCS in micrograms per cubic meter of air:
5.8 µg
5.7 µg
Eight-hour TWA concentration for respirable dust in milligrams per cubic meter of air:
0.13 mg
0.095 mg
August 2019
Fastener installation into concrete for waterproofing project #1767
Date: September 12, 2017
Location: Fridley, MN
Structure type: Commercial structure
Project description: Drilling of approximately 200 holes in concrete walls to insert fasteners for installation of approximately 1,000 square feet of waterproofing membrane. Holes were ¼-inch in diameter and drilled to a depth of 2 inches. The drill was not equipped with dust collection.
Crew members sampled: 3
Sample results for RCS in micrograms per cubic meter of air:
5.8 µg
10.0 µg
16.5 µg
RCS as a full shift TWA:
5.8 µg
10 µg
16.5 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
0.26 mg
0.15 mg
0.13 mg
Respirable particulate as a full shift TWA:
0.26 mg
0.15 mg
0.13 mg
August 2019
Hammer drilling into concrete wall for insulation and membrane attachment #1768
Date: October 9, 2017
Location: Minneapolis, MN
Structure type: Commercial structure
Project description: One worker drilled approximately 80 holes in concrete wall to insert fasteners for installation of approximately 1,500 square feet of insulation board and waterproofing membrane. Holes were ¼-inch in diameter and drilled to a depth of 3 inches. The drill was not equipped with dust collection.
Crew members sampled: 1
Sample results for RCS in micrograms per cubic meter of air:
7.1 µg
RCS as a full shift TWA:
5 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
0.071 mg
Respirable particulate as a full shift TWA:
0.049 mg
August 2019
Densdeck® gypsum roof board installation #1769
Date: September 7-8, 2017
Location: Charlotte, NC
Structure type: Commercial structure
Project description: Four workers installed approximately 700 square feet of Densdeck® gypsum roof board using a motorized roof sawzall, drills, hand saw, and razor knife. Gypsum roof board debris was cleaned up using a leaf blower
Crew members sampled: 4
Sample results for RCS in micrograms per cubic meter of air:
4.9 µg
<4.4 µg
<4.4 µg
<4.5 µg
RCS as a full shift TWA:
4.9 µg
<4.4 µg
<4.4 µg
<4.5 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
0.10 mg
0.14 mg
<0.064 mg
0.30 mg
Respirable particulate as a full shift TWA:
0.10 mg
0.14 mg
0.064 mg
0.30 mg
August 2019
Densdeck® gypsum roof board installation #1770
Date: October 12, 2017
Location: Schaumburg, IL
Structure type: Commercial structure
Project description: Eight workers installed approximately 6,500 square feet of Densdeck® gypsum roof board with fasteners into a metal deck. Two of the eight workers also installed perimeter flashing by drilling into a concrete parapet wall using a hammer drill and fasteners.
Crew members sampled: 8
Sample results for RCS in micrograms per cubic meter of air:
<5.0 µg <5.0 µg
<5.0 µg <5.0 µg
<5.0 µg <5.0 µg
<5.0 µg <5.0 µg
RCS as a full shift TWA:
5.3 µg 5.3 µg
5.3 µg 5.3 µg
5.3 µg 5.3 µg
5.3 µg 5.3 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
<0.053 mg <0.053 mg
<0.053 mg <0.053 mg
<0.053 mg <0.053 mg
<0.053 mg <0.053 mg
Respirable particulate as a full shift TWA:
0.053 mg 0.053 mg
0.053 mg 0.053 mg
0.053 mg 0.053 mg
0.053 mg 0.053 mg
August 2019
Roof ballast removal (shoveling and vacuuming) #1781
Date: October 19, 2017
Location: Brooklyn Park, MN
Structure type: Commercial structure
Project description: Two workers removed approximately 8,000 square feet of roof ballast using shovels and a vacuum connected to a long suction tube that disposed the materials into the bed of a dump truck.
Crew members sampled: 2
Sample results for RCS in micrograms per cubic meter of air:
6.0 µg
8.2 µg
RCS as a full shift TWA:
5.2 µg
7.1 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
<0.06 mg
<0.06 mg
Respirable particulate as a full shift TWA:
0.05 mg
0.05 mg
August 2019
Hot asphalt and gravel installation #1782
Date: October 20, 2017
Location: Milwaukee, WI
Structure type: Public utility building
Project description: The project involved coating of an approximately 8,500 square foot roof surface with hot asphalt and dispersing gravel over the freshly applied hot asphalt. Equipment used for dispersing the gravel included a gravel spreader, shovels and brooms. Hot asphalt was spread with mops and asphalt wagons. 5 workers were performing tasks on the roof while two worked on the ground to load gravel from roll-off boxes to a gravel bucket that was lifted to the roof with a crane. One sampling pump failed so only 6 samples are reported below.
Crew members sampled: 7
Sample results for RCS in micrograms per cubic meter of air:
<6.7 µg
<6.7 µg
<6.7 µg
<7.1 µg
<7.0 µg
<6.8 µg
RCS as a full shift TWA:
<5.3 µg
<5.3 µg
<5.3 µg
<5.6 µg
<5.6 µg
<5.4 µg
Sample results for respirable particulate in milligrams per cubic meter of air:
<0.067 mg
<0.067 mg
<0.067 mg
0.30 mg
August 2019
0.12 mg
0.13 mg
Respirable particulate as a full shift TWA:
<0.053 mg
<0.053 mg
<0.053 mg
0.24 mg
0.096 mg
0.104 mg
August 2019
Hammer drilling into concrete deck for installation of roof board insulation #1790
Date: December 14, 2017
Location: South Bend, IN
Structure type: Hotel
Project description: Six workers installed approximately 1200 square feet of roof board insulation drilling into a concrete deck with a hammer drill that was not equipped with dust collection. Approximately 200 fasteners were installed to secure the insulation.
Crew members sampled: 6
RCS in micrograms as an 8-hour TWA concentration:
<5.5 µg
<5.4 µg
<5.4 µg
<4.3 µg
<5.4 µg
<6.5 µg
Respirable dust in milligrams per cubic meter of air as an 8-hour TWA concentration:
0.054 mg
0.049 mg
0.042 mg
0.15 mg
0.043 mg
<0.065 mg
August 2019
Removal of concrete roof tiles #1795
Date: September 19, 2017
Location: Diamond Bar, California
Structure type: Residence
Project description: Five workers removed concrete roof tiles using hand removal methods and the following tools: hammers, nail pullers and push brooms.
Crew members sampled: 5
RCS in micrograms as an 8-hour TWA concentration:
<5.0 µg
<12.0 µg
<9.0 µg
<5.0 µg
<20.0 µg
Respirable dust in milligrams per cubic meter of air as an 8-hour TWA concentration:
0.09 mg
0.10 mg
0.09 mg
0.10 mg
0.14 mg
August 2019
Perlite-based cover board removal #1801
Date: July 13, 2018
Location: Bradley, IL
Structure type: Public elementary school
Project description: The project involved manual and mechanical removal of the roofing membrane, perlite-based coverboard and polyiso insulation in a roof area of approximately 1,400 square feet. Safety data sheets for commercial perlite report various percentages of crystalline silica content according to the National Institutes of Health. The removal process involved cutting of the rubber roof membrane with utility knives and peeling back and removing the membrane to expose the cover board and insulation. A gas-powered roof cutter was used to cut through the perlite and insulation to produce smaller squares of material for ease of disposal. Manual tools were used to pry up the squares of cut material for transport to the chute at the edge of the roof. Eleven crew members were sampled but one sampling pump fell into the trash chute and broke.
Crew members sampled: 11
Sample results for RCS in micrograms per cubic meter of air as an 8-hour TWA concentration:
<4.7 µg
<4.5 µg
<4.5 µg
<4.7 µg
<4.7 µg
<4.6 µg
<4.6 µg
<4.7 µg
<4.7 µg
<4.7 µg
Sample results for respirable dust in milligrams per cubic meter of air:
0.064 mg
0.22 mg
0.053 mg
0.14 mg
<0.047 mg
August 2019
0.061 mg
0.14 mg
0.054 mg
0.089 mg
0.081 mg
August 2019
Gravel-surface built-up roofing removal and installation project #1948
Date: June 26, 2019
Location: Park Ridge, IL
Structure type: Public high school building
Project description: Eight workers removed two large sections of a gravel-surfaced built up roofing system and the bulk sample of the removed material indicated a 10% concentration of quartz. Workers removed the built-up roof system with powered roof cutters, Sawzall and hand cutter in addition to using a leaf blower, rollers, roof spade, prybar, crowbar, razor knives, push broom, hammer, shovels and wheelbarrow. After clean-up, workers installed a two-ply layer of roofing felt in hot asphalt. Although 8 workers had personal breathing zone sampling equipment attached to each of them, only 7 readings are shown below since one sample was considered “not representative” because the sample inlet was moved away from the worker’s breathing zone by the worker during the work shift. .
Product installed: Johns Manville GlasPly IV and Trumbull Type III asphalt.
Crew members sampled: 8
RCS as an 8-hour TWA concentration:
<4.6 µg/m3
<4.6 µg/m3
9.1 µg/m3
7.1 µg/m3
8.9 µg/m3
<4.7 µg/m3
17 µg/m3
Respirable dust as an 8-hour TWA:
0.30 mg/m3
0.15 mg/m3
0.25 mg/m3
0.12 mg/m3
1.2 mg/m3
0.11 mg/m3
1.1 mg/m3