National Institute for Occupational Safety and Health
The Hazard Evaluation and Technical Assistance Branch (HETAB) of the National Institute for
Occupational Safety and Health (NIOSH) conducts field investigations of possible health hazards in the
workplace. These investigations are conducted under the authority of Section 20(a)(6) of the Occupational
Safety and Health (OSHA) Act of 1970, 29 U.S.C. 669(a)(6) which authorizes the Secretary of Health and
Human Services, following a written request from any employers or authorized representative of
employees, to determine whether any substance normally found in the place of employment has
potentially toxic effects in such concentrations as used or found.
HETAB also provides, upon request, technical and consultative assistance to federal, state, and local
agencies; labor; industry; and other groups or individuals to control occupational health hazards and to
prevent related trauma and disease. Mention of company names or products does not constitute
endorsement by NIOSH.
This report was prepared by Chandran Achutan and Rick Driscoll of HETAB, Division of Surveillance,
Hazard Evaluations and Field Studies (DSHEFS). Field assistance was provided by Dino Mattorano and
Lynda Ewers of HETAB. Analytical support was provided by DataChem, and Ardith Grote, Robert
Streicher and Kathleen Ernst of the Division of Applied Research and Technology. Desktop publishing
was performed by Shawna Watts. Editorial review was performed by Ellen Galloway.
Copies of this report have been sent to International and Local United Union of Roofers, Waterproofers
and Allied Workers, and management representatives at US Roofing Contractors, and the OSHA
Regional Office. This report is not copyrighted and may be freely reproduced. The report may be viewed
and printed from the following internet address: http://www.cdc.gov/niosh/hhe. Single copies of this
report will be available for a period of three years from the date of this report. To expedite your request,
include a self-addressed mailing label along with your written request to:
NIOSH Publications Office
4676 Columbia Parkway
Cincinnati, Ohio 45226
800-356-4674
After this time, copies may be purchased from the National Technical Information Service (NTIS) at 5825
Port Royal Road, Springfield, Virginia 22161. Information regarding the NTIS stock number may be
obtained from the NIOSH Publications Office at the Cincinnati address.
For the purpose of informing affected employees, copies of this report
shall be posted by the employer in a prominent place accessible to the
employees for a period of 30 calendar days. |
NIOSH conducted an evaluation at US Roofing Contractors, at the request of the United
Union of Roofers, Waterpoofers and Allied Workers. The request asked NIOSH to evaluate exposures to
4,4’-Methylene-bisphenyl isocyanate (MDI) and volatile organic compounds (VOCs) during a roof
installation process.
What NIOSH Did
- We took personal breathing zone (PBZ)
and area air samples for MDI during
polyurethane foam spraying.
- We took PBZ and area air samples for
VOCs during the spray gun cleaning
process.
- We took PBZ air samples for VOCs
during the roof installation process.
- We conducted confidential medical
interviews with seven employees.
What NIOSH Found
- Personal exposure to MDI exceeded
exposure criteria for full-shift and shortterm
samples.
- Personal exposure to VOCs did not exceed
exposure criteria.
- Employees reported symptoms that were
consistent with overexposure to MDI.
- We observed poor hygiene practices such
as eating at the workplace before washing
hands.
- We observed poor work practices such as
improper use of respirators.
What US Roofers Managers Can Do
- Improve their respiratory protection
program.
- Install portable hand washing stations.
- Train employees on hazards associated with MDI and organic solvents.
- Prohibit smoking in the work area.
What the US Roofers Employees Can Do
- Be aware of the chemical contamination
all around them.
- Shave before donning a respirator.
On November 4, 2003, the National Institute for Occupational Safety and Health (NIOSH) received a
request from the United Union of Roofers, Waterproofers and Allied Workers to conduct a health hazard
evaluation (HHE) at US Roofing Contractors in Philadelphia, Pennsylvania. The request asked NIOSH to
evaluate employee exposures to 4,4’-Methylene-bisphenyl isocyanate (MDI) during the spray application
of FastTrack 100® polyurethane foam, and exposures to volatile organic compounds (VOCs) during the
rubber roofing membrane installation and spray gun cleaning. The request stated that employees had
reported respiratory symptoms such as difficulty breathing, coughing, chest tightness, and skin irritation,
which they believe may be work related.
A total of 26 full-shift, task-based, and short-term personal breathing zone (PBZ) samples for MDI and
VOCs were collected on October 13, 2004 and on October 25-28, 2004. Confidential medical interviews
with seven employees were completed on October 14, 2004.
More than 50% of the PBZ samples for MDI exceeded the NIOSH Recommended Exposure Limit of 50
micrograms per cubic meter (µg/m3), and the NIOSH and OSHA ceiling limit of 200 µg/m3. The VOC
PBZ results were all below exposure criteria. Of the seven respondents interviewed using a standard
questionnaire, four reported symptoms that they attribute to FastTrack 100 exposure. These symptoms
ranged in severity from stuffy nose, itchy/watery eyes, to shortness of breath and wheezing. Of the four
workers reporting symptoms, three reported chest tightness, cough, sinus congestion, and shortness of
breath and two workers reported headaches. One worker with no previous history of asthma reported a
combination of wheezing, shortness of breath, and cough that met our case definition for presumptive
work-related asthma; this worker was strongly advised to have his respiratory symptoms evaluated by his
personal physician for possible occupational asthma. In the event that any worker is determined to have
an MDI-associated occupational asthma, he or she must be reassigned to a job that does not involve
exposure to MDI-containing materials.
NIOSH investigators conclude that a health hazard exists from exposure to MDI during
the polyurethane foam application. Recommendations are provided to reduce exposures
to roofers during the spraying of MDI-containing foam, including respiratory protection. |
Keywords: 1761 (Roofing, Siding and Sheet Metal work), 4,4’-Methylene-bisphenyl isocyanate, MDI,
roofers, volatile organic compounds, respiratory effects
Preface
Acknowledgments and Availability of Report
Highlights of Health Hazard Evaluation
Summary
Introduction
Background
Methods
Industrial Hygiene Evaluation
Epidemiologic Evaluation
Evaluation Criteria
Isocyanates
Xylenes
Toluene
2(2-butoxyethoxy) ethanol
N-methyl-2-pyrrolidinone
Results
Industrial Hygiene Results
Epidemiologic Evaluation Results
Discussion
Conclusions
Recommendations
References
On November 4, 2003, the National Institute for
Occupational Safety and Health (NIOSH)
received a request from the United Union of
Roofers, Waterproofers and Allied Workers to
conduct a health hazard evaluation (HHE) at US
Roofing Contractors in Philadelphia,
Pennsylvania. The request asked NIOSH to
evaluate employee exposures to 4,4’-Methylenebisphenyl
isocyanate (MDI) during the spray
application of FastTrack 100® polyurethane
foam, and to volatile organic compounds
(VOCs) during the installation of the rubber
roofing membrane and solvent cleaning of the
spray gun. The request also stated that
employees had reported respiratory symptoms
such as difficulty breathing, coughing, chest
tightness, and skin irritation, which they
believed may be work related.
An opening conference was held on October 12,
2004, between NIOSH representatives,
management officials, the Local 30 union
representative, and staff members from CPWR – Center for Construction Research and Training (CPWR). The
CPWR was involved at the invitation of union
officials. US Roofing Contractors identified a
hospital roof in Paoli, Pennsylvania, as a
potential work site. NIOSH investigators had
planned to conduct air sampling and medical
evaluations from October 13-15, 2004.
However, due to inclement weather, air
sampling for MDI and VOCs was only
conducted on one day (October 13, 2004).
Medical interviews were conducted on October
14, 2004 to ascertain health issues related to the
work environment. Between October 25-28,
2004, NIOSH investigators returned to this job
site to further assess employee exposures to
MDI and VOCs.
The first step in the roof installation process is to
remove the old insulation and clear the area of
all debris. Patch areas where old insulation has
been removed are first sprayed with adhesive
foam and new board insulation is pressed into
the space and cut to fit. The roofers typically
kneel on the board insulation while fitting it into
place. After repairs are completed, the roof is
ready for the rubber membrane to be applied to
the roof with a foam containing MDI.
As a section of the roof is sprayed with foam,
the roofers wait for a few minutes for the foam
to react with the floor before rolling the
membrane into the foam. Using weighted
rollers, brooms, and hand rollers, the roofers
then push down the membrane covering the
expanding foam.
A “hose-helper” stands behind the foam sprayer
to keep the hose centered on the sprayer’s back,
and to take up the slack. Once the spraying is
completed, the spray gun is detached for
cleaning by the equipment operator. The spray
gun parts are cleaned by heating them in
a crock pot containing a cleaning solvent.
The main constituents of this cleaning
solvent are N- methyl-2-pyrrolidinone and
2(2 butoxyethoxy) ethanol. The equipment
operator cleans the spray gun parts. This
employee also maintains the respirators for the
crew, and on occasion, assists the crew in the
roof application.
The areas sprayed during the NIOSH visits
ranged from approximately 25 to 900 square
feet, with a median of 200 square feet. Five to
eight roofers were present at any one time
during the spraying and roof installation.
Industrial Hygiene
Evaluation
Area air samples (samples collected in fixed
locations) and personal breathing zone samples
(PBZ) were collected for MDI and VOCs. The
PBZ samples included full-shift (samples
collected over the entire workday), task-based
(samples collected during MDI foam spraying),
and short-term (samples collected for
approximately 15 minutes during MDI foam
spraying) samples. MDI was sampled and
analyzed according to the NIOSH Manual of
Analytical Methods (NMAM) 55251. MDI was
collected using spill-resistant impingers
containing 15 milliliters (mL) of 3%
1 (9 anthracenylmethyl) piperazine in butyl
benzoate. The impingers were placed in leather
holders and pinned on the workers’ lapels, to
approximate their breathing zone. The impingers
were connected to a battery-operated personal
sampling pump placed on the workers’ belts.
The pumps were set to a flow rate of 1 liter per
minute. During the October 13, 2004 survey,
this connection was made via Tygon® tubing.
During the subsequent survey, an additional
impinger was connected between the spillresistant
impinger on the worker and the pump,
to trap any excess solution overflowing from the
spill-resistant impinger. In addition, the Tygon
tubing was replaced with chemical-resistant
Fluran® tubing, so that the pooled solution was
not contaminated with the chemical residues in
Tygon tubing.
Full-shift, short-term, and task-based PBZ
samples for MDI were collected from seven
roofers during the October 13, 2004 survey, and
from eight roofers during the October 25-28,
2004 survey for a total of 26 samples. Twenty
area samples were collected over both survey
dates.
Air samples for VOCs were collected during the
roof installation, and during the cleaning of the
spray guns used to apply the polyurethane foam.
Air samples were collected using thermal
desorption tubes for qualitative analysis and
charcoal tubes for quantitative analysis. Thermal
desorption tubes were sampled at a flow rate of
50 milliliters per minute (mL/min) and analyzed
per NMAM 2549.2 The charcoal tubes were run
at a flow rate of 200 mL/min, and analyzed by a
combination of NMAM 1302 and NMAM 2501.
Based on the thermal desorption sample results,
xylene, toluene, ethylbenzene and aliphatic
hydrocarbons were identified for quantification
by the charcoal tube samples.
Epidemiologic Evaluation
Confidential interviews were conducted with
each of the seven workers on duty October 14,
2004. In addition, each participant completed a
respiratory symptom questionnaire. The
questionnaire, based upon both the American
Thoracic Society’s Standardized Adult
Questionnaire and the NIOSH Asthma
Questionnaire, asked workers whether they had
ever been diagnosed with asthma, whether they
wheeze when breathing, have a persistent cough,
or experience difficulty breathing. In addition to
the respiratory questionnaire, pulmonary
function records were reviewed. Two workers
had 3 years of records, two had 2 years and one
worker had only 1 year for review.
As a guide to the evaluation of the hazards posed
by workplace exposures, NIOSH field staff
employ environmental evaluation criteria for the
assessment of a number of chemical and
physical agents. These criteria are intended to
suggest levels of exposure to which most
workers may be exposed up to 10 hours per day,
40 hours per week for a working lifetime
without experiencing adverse health effects. It
is, however, important to note that not all
workers will be protected from adverse health
effects even though their exposures are
maintained below these levels. A small
percentage may experience adverse health
effects because of individual susceptibility, a
pre-existing medical condition, and/or a
hypersensitivity (allergy). In addition, some
hazardous substances may act in combination
with other workplace exposures, the general
environment, or with medications or personal
habits of the worker to produce health effects
even if the occupational exposures are controlled
at the level set by the criterion. These combined
effects are often not considered in the evaluation
criteria. Also, some substances are absorbed by
direct contact with the skin and mucous
membranes, and thus potentially increases the
overall exposure. Finally, evaluation criteria
may change over the years as new information on the toxic effects of an agent become
available.
The primary sources of environmental
evaluation criteria for the workplace are: (1)
NIOSH Recommended Exposure Limits
(RELs),3 (2) the American Conference of
Governmental Industrial Hygienists’ (ACGIH®)
Threshold Limit Values (TLVs®),4 and (3) the
U.S. Department of Labor, Occupational Safety
and Health Administration (OSHA) Permissible
Exposure Limits (PELs).5 Employers are
encouraged to follow the OSHA limits, the
NIOSH RELs, the ACGIH TLVs, or whichever
are the more protective criteria.
OSHA requires an employer to furnish
employees a place of employment that is free
from recognized hazards that are causing or are
likely to cause death or serious physical harm
[Occupational Safety and Health Act of 1970,
Public Law 91–596, sec. 5(a)(1)]. Thus,
employers should understand that not all
hazardous chemicals have specific OSHA
exposure limits such as PELs and short-term
exposure limits (STELs). An employer is still
required by OSHA to protect their employees
from hazards, even in the absence of a specific
OSHA PEL.
A time-weighted average (TWA) exposure
refers to the average airborne concentration of a
substance during a normal 8- to 10-hour
workday. Some substances have recommended
STEL or ceiling values which are intended to
supplement the TWA where there are
recognized toxic effects from higher exposures
over the short-term.
Isocyanates
The feature common to all diisocyanates
(monomers) is the presence of two -N=C=O
(isocyanate) functional groups attached to an
aromatic or aliphatic parent compound. These
compounds are widely used in surface coatings,
polyurethane foams, adhesives, resins,
elastomers, binders, and sealants.
Exposure to isocyanates is irritating to the skin,
mucous membranes, eyes, and respiratory
tract.6,7 The most common adverse health
outcome associated with isocyanate exposure is
asthma due to sensitization; less prevalent are
contact dermatitis (both irritant and allergic
forms) and hypersensitivity pneumonitis
(HP).7,8,9 Contact dermatitis can result in
symptoms such as rash, itching, hives, and
swelling of the extremities.6,9 A worker
suspected of having isocyanate-induced
asthma/sensitization exhibits the traditional
symptoms of acute airway obstruction, e.g.,
coughing, wheezing, shortness of breath,
tightness in the chest, and nocturnal
awakening.6,8 An isocyanate-exposed worker
may first develop an asthmatic condition (i.e.,
become sensitized) after a single (acute)
exposure, but sensitization usually takes a few
months to several years of exposure.6,8,10,11,12 The
asthmatic reaction may occur minutes after
exposure (immediate), several hours after
exposure, or a combination of both immediate
and late components after exposure (dual).8,11
The late asthmatic reaction is the most common,
occurring in approximately 40% of isocyanatesensitized
workers.13 After sensitization, any
exposure, even to levels below an occupational
exposure limit or standard, can produce an asthmatic response that may be life threatening.
Diagnosis of isocyanate induced asthma requires
a thorough occupational history. As with other
asthmatic conditions, pulmonary function tests
may be within normal limits between episodes.
In controlled laboratory environments,
provocation testing may be used in diagnosis.
Experience with isocyanates has shown that
monomeric, prepolymeric and polyisocyanate
species are capable of producing respiratory
sensitization in exposed workers.
14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30 Since the
intermediates may be chemically similar to these
compounds, it is reasonable to assume that they
may also produce this condition. Prevalence
estimates for isocyanate-induced asthma in
exposed worker populations vary considerably:
from 5% to 10% in diisocyanate production
facilities10,31 to 25% in polyurethane production
plants31,32 and 30% in polyurethane seatcover
operations.33 The scientific literature contains a
limited amount of animal data suggesting that
dermal exposure to diisocyanates may also
produce respiratory sensitization.34,35,36,37 This
finding has not been tested in dermally exposed
workers.
Hypersensitivity pneumonitis (HP) also has been
described in workers exposed to
isocyanates.38,39,40,41 Currently, the prevalence of
isocyanate-induced HP in the worker population
is unknown, and is considered rare compared to
the prevalence rates for isocyanate-induced
asthma.9 Whereas asthma is an obstructive
respiratory disease usually affecting the bronchi,
HP is a restrictive respiratory disease affecting
the lung parenchyma (bronchioles and alveoli).
The initial symptoms associated with
isocyanate-induced HP are flu-like, including
shortness of breath, non-productive cough,
fever, chills, sweats, malaise, and nausea.8,9
After the onset of HP, prolonged and/or repeated
exposures may lead to an irreversible decline in
pulmonary function and lung compliance, and to
the development of diffuse interstitial fibrosis.8,9
Early diagnosis is difficult since many aspects of
HP, i.e., the flu-like symptoms and the changes
in pulmonary function, are common to many
other respiratory diseases and conditions.
The only effective intervention for workers with
isocyanate-induced sensitization (asthma) or HP
is cessation of all isocyanate exposure. This can
be accomplished by removing the worker from
the work environment where isocyanate
exposure occurs, or by providing the worker
with supplied-air respiratory protection and
preventing dermal exposures.
NIOSH and OSHA have established a ceiling
concentration of 200 micrograms per cubic
meter of air (µg/m3) as a ceiling (10-minutes)
concentration not to be exceeded. NIOSH has
also established a REL of 50 µg/m3 as a timeweighted
exposure not to be exceeded as an
average during any work period of up to 10
hours. The ACGIH has established a TLV of
51 µg/m3 as a time-weighted average not to
exceed 8 hours.
The United Kingdom Health and Safety
Executive (UK-HSE) has developed a standard
based on the concentration of total reactive
isocyanate groups (TRIG) in a volume of air.42
Airborne TRIG concentrations can be
determined using data from NMAM 5525. First,
the monomer and oligomer concentrations are
summed to obtain the total weight of isocyanatecontaining
compounds in a given air sample.
Next, the molecular weight of the isocyanate
functional groups in the parent compound is
divided by the molecular weight of the parent
compound. This yields a constant that reflects
the percentage of a compound’s molecular
weight contributed by the TRIGs. For MDI and
MDI-based oligomers, the TRIG constant is
0.34. Finally, the total weight of isocyanate
containing compounds in a given air sample is
multiplied by the TRIG constant. The product is
the concentration of TRIGs in air. The UK-HSE
ceiling limit for TRIGs is 70 µg/m3 and the fullshift
TWA is 20 µg/m3.
Xylenes
Xylene is a colorless, flammable organic liquid
with a molecular structure consisting of a
benzene ring with two methyl group (CH3)
substitutions. Xylene is used in paints and other
coatings, and as a raw material in the synthesis
of organic chemicals, dyes, and pharmaceuticals.
The vapor of xylene has irritant effects on the
skin and mucous membranes, including the eyes
and respiratory tract. This irritation may cause
itching, redness, inflammation, and discomfort.
Repeated or prolonged skin contact may cause
erythema, drying, and defatting which may lead
to the formation of vesicles (liquid-filled sacs).
At high concentrations, repeated exposure to
xylene may cause reversible damage to the
eyes.43
Acute xylene inhalation exposure may cause
headache, dizziness, incoordination, drowsiness,
and unconsciousness.44 Previous studies have
shown that concentrations from 60 to 350 ppm
may cause giddiness, anorexia, and vomiting.43
At high concentrations, exposure to xylene has a
narcotic effect on the central nervous system (CNS), and minor reversible effects on the liver
and kidneys.43,44,45
Historical accounts of hematopoietic (formation
of blood cells) toxicity as a result of xylene
exposure are likely due to the high concentration
of benzene contamination in xylene prior to
1940. These effects are not associated with
contemporary xylene exposure.44,46,47
The current OSHA PEL, NIOSH REL, and
ACGIH TLV for xylene are 100 ppm as an
8-hour TWA. In addition, OSHA and NIOSH
have published STELs for xylene of 150 ppm
averaged over 15 minutes.
Toluene
Toluene is a colorless, aromatic organic liquid
containing a six carbon ring (a benzene ring)
with a methyl group (CH3) substitution. It is a
typical solvent found in paints and other
coatings, and used as a raw material in the
synthesis of organic chemicals, dyes, detergents,
and pharmaceuticals.
Inhalation and skin absorption are the major
occupational routes of entry. Toluene can cause
acute irritation of the eyes, respiratory tract, and
skin. Since it is a defatting solvent, repeated or
prolonged skin contact will remove the natural
lipids from the skin which can cause drying,
fissuring, and dermatitis.43,48
The main effects reported with excessive
(inhalation) exposure to toluene are
CNS depression and neurotoxicity.43 Studies
have shown that subjects exposed to 100 ppm of
toluene for six hours complained of eye and
nose irritation, and in some cases, headache,
dizziness, and a feeling of intoxication
(narcosis).49,50,51 No symptoms were noted below
100 ppm in these studies. There are a number of
reports of neurological damage due to deliberate
sniffing of toluene-based glues resulting in
motor weakness, intention tremor, ataxia, as well
as cerebellar and cerebral atrophy.52 Recovery is
complete following infrequent episodes;
however, permanent impairment may occur after
repeated and prolonged glue-sniffing abuse.
Exposure to extremely high concentrations of
toluene may cause mental confusion, loss of
coordination, and unconsciousness.10,531154
Originally, there was a concern that toluene
exposures produced hematopoietic toxicity
because of the benzene ring present in the
molecular structure of toluene. However, toluene
does not produce the severe injury to bone
marrow characteristic of benzene exposure as
early reports suggested. It is now believed that
simultaneous exposure to benzene (present as a
contaminant in the toluene) was responsible for
the observed toxicity.12,48,55
The NIOSH REL for toluene is 100 ppm as an
8-hour TWA. NIOSH has also set a
recommended STEL of 150 ppm for a 15-minute
sampling period. The OSHA PEL for toluene is
200 ppm as an 8-hour TWA. The recently
adopted ACGIH TLV® is 50 ppm for an 8-hour
exposure level. This ACGIH TLV® carries a
skin notation, indicating that cutaneous exposure
contributes to the overall absorbed inhalation
dose and potential systemic effects.
2(2-butoxyethoxy) ethanol
2(2-butoxyethoxy) ethanol is a colorless liquid
with a mild odor. It may cause irritation to the
respiratory tract. Symptoms may include
coughing, sore throat, labored breathing, and
chest pain. Prolonged skin contact causes mild
to moderate local redness and swelling. The
chemical can be absorbed through the skin with
prolonged and widespread contact. It can also
cause eye irritation, redness, and pain. Small,
repeated exposures of this material are generally
more toxic than single, large exposures. Chronic
exposures may produce central nervous system
and kidney effects.
N-methyl-2-pyrrolidinone
N-methyl-2-pyrrolidinone is a colorless liquid
with a mild odor. The acute effects of the
chemical include irritation to the eyes, skin, and
respiratory tract. Prolonged or repeated skin
contact with the liquid may lead to drying or
cracking skin, and possible dermatitis.
Overexposure may cause nausea, headache,
dizziness, vomiting and weakness.
Industrial Hygiene Results
The PBZ results are provided in Table 1. Taskbased
results for MDI monomer were compared
to the TWA by extrapolating the results to
reflect an 8-hour workday. Sample IMP 37 was
compared to a 300-minute workday to reflect
actual length of time worked. When MDI
containing polyurethane foam was not being
sprayed, the worker’s exposure was assumed to
be zero. The extrapolated results are listed under
the column “MDI Time-Weighted Average” in
Table 1.
Of the 26 personal samples, 8 exceeded the
NIOSH REL of 50 µg/m3 and 6 exceeded the
NIOSH ceiling limit of 200 µg/m3 for MDI
monomer. The sprayer had the highest exposure
(76.5-178 µg/m3 for the NIOSH REL;
78.2 328 µg/m3 for the NIOSH Ceiling limit),
while the operator had the lowest (exposures
ranged from non-detected to 0.29 µg/m3). MDI
oligomers were detected in 24 of 26 samples,
including two samples in which MDI monomer
was not detected.
For the full-shift (TWA) samples and short-term
samples, the TRIG was calculated by adding the
“MDI monomer as NCO” and “MDI oligomer as
NCO” columns, and multiplying it by 0.34.
NCO refers to the nitrogen-carbon-oxygen
functional group for isocyanates. For the taskbased
results, the sum of the “MDI monomer as
NCO” and “MDI oligomer as NCO” columns is
first extrapolated to reflect the TWA, and then
multiplied by 0.34. The results are displayed in
the “TRIG” column of Table 1. The UK-HSE
criteria for TWA of 20 µg/m3 was exceeded
once, and the UK-HSE short-term limit of
70 µg/m3 was exceeded twice.
Area sample results (Table 2) indicate that MDI
monomer is not present in the environment up to
2 hours after the spraying has ceased. However,
MDI-oligomers are present in the environment
up to 2 hours after spraying has ceased. An area
sample collected during employee lunch break
showed detectable levels of MDI oligomers, but
not the monomer.
The VOC PBZ results, presented in Table 3,
were below all applicable criteria for toluene,
xylene, and ethylbenzene. There are no exposure
criteria for N-methyl-2-pyrrolidinone and
2(2 butoxyethoxy) ethanol.
Epidemiologic Evaluation
Results
All seven employees completed the respiratory
questionnaire at the worksite. Participants had
worked with FastTrack 100 from 2 weeks to 5
years. Three workers reported no health
problems or symptoms. Four of the seven
respondents reported symptoms they attribute to
the FastTrack 100 exposure. These symptoms
ranged in severity from stuffy nose, itchy/watery
eyes to shortness of breath and wheezing. Of the
four workers reporting symptoms, three reported
chest tightness, cough, sinus congestion, and
shortness of breath and two workers reported
headaches. One worker, with no previous history
of asthma, reported a combination of wheezing,
shortness of breath, and cough that met our case
definition for presumptive asthma. This worker
was referred to his personal physician to be
evaluated for possible occupationally-induced
asthma.
All records, with one exception, showed normal
spirometry results. The one abnormal result
showed borderline obstruction. Overall, the
spirometry results showed excessive variability
(greater than 5% variability) between spirometry
trials, making it difficult to validly interpret the
test results. In one case, pulmonary function
parameters improved rather than declined (as
would be expected with age).
The results from all of the October 2004 surveys
show high exposures to MDI. The October 13,
2004 survey may have underestimated the MDI
levels because of sample loss from the impingers. In these samples some fluid was lost
when the impingers were tilted during increased
worker activity. To minimize sample oss during
the subsequent survey, personal sampling was
limited to the time period when polyurethane
foam was sprayed (task-based sampling). The
TWA was determined by extrapolating the
results to the actual number of hours worked. In
addition, a back-up impinger was used during
the second survey to collect overflow.
Chemically inert tubing connected the impingers
and, in the event of an overflow, the liquids from
both the impingers would be pooled. However,
sample loss during the second survey was
minimal, and in most cases did not require
solutions to be pooled.
The impinger method used in this survey
(NMAM 5525) is suitable for collecting the fastcuring
MDI monomer and the slower-reacting
MDI oligomer. This method is more versatile
than methods that employ filters as the
collection medium, because the latter does not
effectively capture the MDI monomer,
potentially underestimating total MDI levels in
the environment. The disadvantages of NMAM
5525 as a personal sampling method are that the
impingers are bulkier to wear than the filters,
and they are prone to spill or overflow if the
employees are twisting, turning, and lying on
their backs.
The results from the area samples show that no
MDI monomer was present in the environment
immediately after spraying. This is because MDI
monomer is a fast-curing compound. However,
the slower reacting MDI oligomer was present in
the environment 2 hours after spraying was
completed.
Roofers were potentially exposed to MDI via the
inhalation, dermal, and ingestion routes. Roofers
were observed wearing Protech® full face air
purifying respirators with combination
cartridges (chlorine, organic vapors, acids, and
particulates), which if worn properly, can reduce
MDI exposure through inhalation. However, for
respirators to be effective and protect workers
from harmful exposures they must be selected,
inspected, and maintained properly. Respiratory
protective devices should never be worn when a
satisfactory face seal cannot be obtained. There
are many conditions that may prevent a good
seal between the worker’s face and the
respirator. Some of these conditions include
facial hair, glasses, or an unusually structured
face. We noticed many employees with facial
hair donning respirators. In addition, employees
were also observed partially removing the
respirator to communicate with their coworkers.
These actions may expose workers to potentially
hazardous levels of MDI. US Roofing
subcontracts the qualitative fit testing of
respirators. Employees noted that when an
employee with facial hair is fit tested, he might
hold his breath to pass the fit-test. A computerbased
quantitative test is more desirable because
it is objective and more accurate. US Roofing
Contractors has designated one employee to be
responsible for cleaning and maintaining the
respirators each day. Respirator cartridges are
changed every other day on the respirator worn
by the sprayer, and once a week on the
respirators worn by the other roofers.
Most employees were wearing long-sleeved
shirts while spraying foam. In the warmer
months, we were told that employees either wear
a short-sleeved shirt or are shirtless, all of which
can increase the potential for dermal exposure.
In addition, employees were observed wearing
cotton gloves while spraying polyurethane foam
during the rubber membrane installation. While
cotton gloves provide dexterity, they may not
adequately protect workers’ hands from MDI
exposure. Neoprene, nitrile, or butyl rubber
gloves provide better protection against MDI
than cotton gloves.
NIOSH investigators observed employees
transferring chemicals from their original
containers to smaller, improperly labeled soda
containers. This practice creates the potential for
someone to accidentally drink from the wrong
container. This practice also violates the OSHA
Hazard Communications Standard (CFR
1910.1200).56
Employees were observed eating, drinking, and
smoking in the workplace without first washing their hands. They were also observed spreading
chemicals with their bare hands. These practices
can increase MDI exposure through ingestion of
chemicals from hand to mouth. In addition,
smoking in the presence of flammable liquids
presents a safety hazard.
The insulation process employed by US Roofing
Contractors involves spraying a layer of
isocyanate-containing polyurethane foam, then
installing insulation material. NIOSH staff was
told that in some processes, multiple layers of
polyurethane foam are sprayed in lieu of the
insulation material. Isocyanate exposure to
employees utilizing this latter process is
expected to be higher than what was observed
during this survey.
Sensitization to workplace materials can lead to
occupational asthma in susceptible individuals.
At least one of the seven workers interviewed
was found to have symptoms consistent with
MDI-associated occupational asthma; he was
referred to his personal physician for evaluation.
MDI levels exceeded the NIOSH and OSHA
full-shift and short-term standards. Employees
wore their respirators improperly and had poor
work practices and personal hygiene, which
increased their exposure to MDI. If any worker
is diagnosed with occupational asthma caused
by exposure to MDI-containing roofing
compounds, that worker should be immediately
accommodated in a job that does not involve
MDI exposure. Occupational asthma can be a
life threatening condition, and workers who
report wheezing or shortness of breath following
exposure to MDI-containing materials should be
referred for medical follow-up.
Based on the observations and the results of this
survey, the following recommendations are
made to improve employee health and safety.
- Refer employees who wheeze or become
short of breath following exposure to MDI
roofing compounds to their personal physicians
immediately to be evaluated for occupational
asthma.
- Assign employees diagnosed with MDIassociated
occupational asthma to jobs that do
not expose them to MDI-containing compounds.
- Train employees on proper respirator use.
Respirators should not be removed until
spraying is complete. Employees who use
respirators must be clean-shaven.
- Perform quantitative fit testing of
respirators. Quantitative fit testing is more
objective than qualitative fit testing.
- Install portable hand washing units in
workplaces without easy access to restrooms.
- Train employees on the hazards associated
with chemicals in the work environment
consistent with paragraph (h) of OSHA’s Hazard
Communication Standard [Code of Federal
Regulations 910.1200].56
- Encourage employees to stop smoking.
Offer smoking cessation classes and literature on
harmful effects of cigarette smoke.
- Work with the manufacturers of the
polyurethane foam to substitute MDI with a less
toxic compound.
- Prohibit eating, smoking, and drinking in the
work area.
- Use proper personal protective clothing,
including butyl rubber gloves, neoprene, nitrile,
and protective suits to decrease dermal
exposures
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Table 1
Personal sampling results (µg/m3) for MDI from October 13, 2004 and 26-28, 2004
US Roofing Contractors, Philadelphia, PA
Date |
Sample ID |
Job Description |
Sample Type |
Duration (min) |
MDI monomer |
MDI monomer as NCO |
MDI oligomer as NCO |
TRIG |
MDI Time Weighted Average |
10/13/04 |
IMP 1 |
Sprayer/Installer |
Time-Weighted Average |
451 |
89.1 |
31.1 |
14.7 |
15.6 |
89.1 |
10/13/04 |
IMP 7 |
Sprayer/Installer |
Task-Based Sample |
234 |
343 |
114 |
65.4 |
29.8 |
167 |
10/13/04 |
IMP-10 |
Sprayer/Installer |
Short-Term Sample |
10 |
298 |
101 |
44.0 |
49.2 |
NA |
10/13/04 |
IMP-11 |
Sprayer/Installer |
Short-Term Sample |
3 |
78.2 |
26.2 |
ND |
8.90 |
NA |
10/13/04 |
IMP 2 |
Hose-helper/Installer |
Time-Weighted Average |
398 |
62.5 |
7.27 |
5.06 |
4.19 |
62.5 |
10/13/04 |
IMP 3,9 |
Installer |
Time-Weighted Average |
579 |
68.1 |
23.1 |
20.5 |
14.8 |
68.1 |
10/13/04 |
IMP 4 |
Installer |
Time-Weighted Average |
426 |
101 |
34.4 |
21.3 |
19.0 |
101 |
10/13/04 |
IMP 5 |
Installer |
Time-Weighted Average |
431 |
66.4 |
22.8 |
16.1 |
13.2 |
66.4 |
10/13/04 |
IMP 6 |
Installer |
Time-Weighted Average |
435 |
26.1 |
8.91 |
4.80 |
4.66 |
26.1 |
10/13/04 |
IMP 8 |
Operator |
Time-Weighted Average |
374 |
0.29 |
0.10 |
ND |
0.03 |
0.29 |
10/26/04 |
IMP 15 |
Sprayer/Installer |
Task-Based Sample |
122 |
282 |
99.5 |
71.3 |
14.8 |
71.7 |
10/26/04 |
IMP 16 |
Hose-helper/Installer |
Task-Based Sample |
107 |
152 |
49.5 |
52.0 |
7.69 |
33.9 |
10/27/04 |
IMP 28 |
Sprayer/Installer |
Short-Term Sample |
16 |
328 |
115 |
88.8 |
69.4 |
NA |
10/27/04 |
IMP 29 |
Sprayer/Installer |
Short-Term Sample |
18 |
260 |
86.8 |
48.9 |
46.1 |
NA |
10/27/04 |
IMP 30 |
Hose-helper/Installer |
Short-Term Sample |
25 |
ND |
ND |
8.87 |
3.02 |
NA |
10/27/04 |
IMP 31 |
Hose-helper/Installer |
Short-Term Sample |
20 |
299 |
102 |
64.9 |
56.8 |
NA |
10/27/04 |
IMP 26 |
Installer |
Short-Term Sample |
16 |
503 |
170 |
108 |
94.6 |
NA |
10/27/04 |
IMP 27 |
Installer |
Short-Term Sample |
18 |
407 |
133 |
111 |
83.0 |
NA |
10/27/04 |
IMP 24 |
Installer |
Short-Term Sample |
16 |
35.7 |
12.2 |
54.0 |
22.5 |
NA |
10/27/04 |
IMP 25 |
Installer |
Short-Term Sample |
18 |
27.9 |
9.29 |
11.6 |
7.11 |
NA |
10/28/04 |
IMP 37 |
Sprayer |
Task-Based Sample |
219 |
109 |
37.6 |
27.9 |
16.2 |
79.6 |
10/28/04 |
IMP 38 |
Installer |
Task-Based Sample |
220 |
50.5 |
16.8 |
10.5 |
4.25 |
23.2 |
10/28/04 |
IMP 39 |
Installer |
Task-Based Sample |
219 |
43.2 |
14.4 |
10.2 |
3.82 |
19.7 |
10/28/04 |
IMP 35 |
Installer |
Task-Based Sample |
219 |
62.5 |
21.0 |
12.1 |
5.14 |
28.5 |
10/28/04 |
IMP 36 |
Operator |
Task-Based Sample |
155 |
ND |
ND |
0.54 |
0.06 |
NA |
10/28/04 |
IMP 34 |
Installer |
Task-Based Sample |
218 |
29.3 |
9.98 |
5.93 |
2.46 |
13.3 |
ND: Not Detected; NA: Not Applicable
MDI: 4,4’-Methylene-bisphenyl isocyanate
NCO: Nitrogen-Carbon-Oxygen
TRIG: Total Reactive Isocyanate Group
Table 2
Area sampling results (µg/m3) for MDI from October 13,2004 and October 26-28, 2004
US Roofing Contractors, Philadelphia, PA
Date |
Sample ID |
Sample Location |
Duration (min) |
MDI monomer |
MDI monomer as NCO |
MDI oligomer as NCO |
10/13/04 |
IMP 12 |
About 5 feet from ground |
10 |
107 |
36.0 |
ND |
10/25/04 |
IMP 13 |
Sample collected 2 hours after spraying |
59 |
ND |
ND |
3.24 |
10/25/04 |
IMP 14 |
Sample collected 2 hours after spraying |
60 |
ND |
ND |
1.24 |
10/26/04 |
IMP 17 |
Sample collected 2’from ground-employee BZ |
114 |
146 |
48.7 |
45.0 |
10/26/04 |
IMP 18 |
Sample collected immediately after spraying |
232 |
ND |
ND |
ND |
10/26/04 |
IMP 19 |
Sample collected 2’from ground |
357 |
27.6 |
9.47 |
7.50 |
10/26/04 |
IMP 20 |
Sample collected 2’from ground |
349 |
86.4 |
29.2 |
21.8 |
10/26/04 |
IMP 21 |
Sample collected 2’from ground |
353 |
33.4 |
11.1 |
9.00 |
10/26/04 |
IMP 22 |
Sample collected 2’from ground |
226 |
ND |
ND |
0.18 |
10/26/04 |
IMP 23 |
Sample collected 2’from ground |
354 |
22.1 |
7.62 |
4.81 |
10/27/04 |
IMP 32 |
Sample collected 2’from ground |
144 |
78.7 |
26.8 |
27.7 |
10/27/04 |
IMP 33 |
Sample collected 2’from ground |
144 |
351 |
117 |
82.9 |
10/28/04 |
IMP 40 |
Sample collected 2’from ground |
231 |
25.8 |
9.01 |
6.61 |
10/28/04 |
IMP 41 |
Sample collected 2’from ground |
222 |
4.59 |
1.53 |
0.71 |
10/28/04 |
IMP 42 |
Sample collected immediately after spraying |
23 |
ND |
ND |
2.24 |
10/28/04 |
IMP 43 |
Sample collected 2’from ground |
221 |
16.2 |
5.44 |
3.13 |
10/28/04 |
IMP 44 |
Sample collected 2’from ground |
227 |
10.5 |
3.59 |
0.88 |
10/28/04 |
IMP 45 |
Sample collected 2’from ground |
233 |
14.1 |
4.76 |
2.23 |
10/28/04 |
IMP 46 |
Collected when employees were having lunch |
30 |
ND |
ND |
4.57 |
10/28/04 |
IMP 47 |
Sample collected 2' from ground |
214 |
9.69 |
3.27 |
2.00 |
ND: Not Detected
Table 3
Area and personal sampling results for Volatile Organic Compounds
from October 13, 2004 and October 26-28, 2004
US Roofing Contractors, Philadelphia, PA
Date |
Sample ID |
Sample Location |
Sample duration (min) |
N-methyl-2- Pyrrolidinone (ppm) |
2(2- butoxyethoxy) ethanol (ppm) |
C7 as Heptane (ppm) |
Ethylbenzene (ppm) |
Xylenes (ppm) |
Toluene (ppm) |
10/13/04 |
Roofer 7 |
Personal |
330 |
NR |
NR |
NA |
NA |
NA |
NA |
10/13/04 |
Area |
Trailer |
420 |
0.06 |
ND |
NA |
NA |
NA |
NA |
10/13/04 |
Roofer 4 |
Personal |
105 |
NA |
NA |
12.8 |
0.12 |
0.47 |
20.3 |
10/26/04 |
Roofer 4 |
Personal |
170 |
NA |
NA |
5.01 |
ND |
0.14 |
6.79 |
10/26/04 |
Roofer 5 |
Personal |
184 |
NA |
NA |
5.07 |
ND |
0.14 |
7.03 |
10/27/04 |
Roofer 7 |
Personal |
36 |
0.17 |
ND |
NA |
NA |
NA |
NA |
10/27/04 |
Roofer 7 |
Personal |
267 |
0.03 |
ND |
NA |
NA |
NA |
NA |
NR: Not Reported (Sample destroyed during shipping)
ppm: parts per million
ND: Not Detected
NA: Not Applicable
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To receive NIOSH documents or information
about occupational safety and health topics
contact NIOSH at:
1-800-35-NIOSH (356-4674)
Fax: 1-513-533-8573
E-mail: pubstaft@cdc.gov
or visit the NIOSH web site at:
http://www.cdc.gov/niosh
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