A Summary of Health Hazard Evaluations:

Issues Related to Occupational Exposure to

Isocyanates, 1989 to 2002

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

January 2004
ii Hazard Evaluations and Technical Assistance Branch

Individual Health Hazard Evaluations (HHEs) presented in this document may be requested by

referencing the Hazard Evaluations and Technical Assistance (HETA) number listed. To receive

these documents or other information about occupational safety and health topics, contact the

National Institute for Occupational Safety and Health (NIOSH) at

NIOSH Publications Dissemination

4676 Columbia Parkway

Cincinnati, OH 45226–1998

Telephone: 1–800–35–NIOSH (1–800–356–4674)

Fax: 1–513–533–8573

E-mail: pubstaft@cdc.gov 

or visit the NIOSH Web site at www.cdc.gov/niosh

This document is in the public domain and may be freely copied or reprinted.

Mention of any company or product does not constitute endorsement by NIOSH.

DHHS (NIOSH) Publication No. 2004-116

ORDERING INFORMATION
The Health Hazard Evaluations and Technical Assistance (HETA) Program responds to requests

from employers, employees, employee representatives, and other Federal, State, and local agencies. Through a staff of industrial hygienists, engineers, occupational physicians, epidemiologists,

other health professionals, and support personnel, the Hazard Evaluations and Technical

Assistance Branch (HETAB) collaborates with appropriate personnel in other divisions of the

National Institute for Occupational Safety and Health (NIOSH) to respond to approximately 450

requests for assistance each year. The typical HETA response to a request for assistance results in

(l) an evaluation of whether chemical, physical, biological, or other agents are hazardous as used

or found in the workplace and (2) the development of recommendations for control procedures,

improved work practices, and medical programs to reduce exposure levels and prevent adverse

health effects. Health Hazard Evaluation (HHE) site visits are conducted if warranted, and interim

and final reports are developed and distributed to employees, unions, management, and relevant

Federal and State agencies. When the HETA request is from a Federal, State, or local agency for

assistance in investigating another workplace, NIOSH provides only the technical assistance (TA)

requested and does not conduct a complete HHE. The results of individual evaluations may trigger

wider studies of similar exposures in other settings or may stimulate recommendations for implementation or modification of health standards. Approximately 12,000 evaluations have been completed since the inception of the HETA Program in 1972.

Requests received by the HETA Program tend to reflect emerging occupational problems, such as

isocyanate exposure and other priority areas. Forty-six isocyanate-related site visits were conducted

from 1989 to 2002. The HHE requests came from a variety of sources—including manufacturers of

plastic, wood, and automotive products, coal mines, schools, and offices. Sixteen of the requests

were made by management, eleven by union, eleven by three or more employees, six by government, and two by management and employees jointly. This document first presents some background information about isocyanate exposures, health effects, analytical methods, and general

recommendations that are provided for most isocyanate-related HHEs. The analytical methods section is important because of the complexities and limitations associated with measuring isocyanate

exposures. (More detailed information can be gained from the NIOSH Manual of Analytical

Methods.) The major portion of this document presents the titles and summaries of the site visits

related to isocyantes conducted between 1989 and 2002. In most cases multiple exposures were

investigated at the work site; sometimes isocyanate exposures were a primary issue and sometimes not. In many cases, corrective measures were made in response to the evaluation and recommendations made by NIOSH investigators. 

The purpose of this HHE summary document is to amass the past 14 years of isocyanate-related

HHEs in a concise format for easy reference and examination by NIOSH researchers, customers,

and partners. Any individual report or letter of interest can easily be requested. The scope and

presentation of the individual HHEs vary based on the requesters’ needs and the project officers’ professional judgment. The document is not meant to be a state-of-the-art review, but

instead, it is intended to provide general insight into the types of isocyanate HHE requests

received, and HETAB’s response to them. 

John Howard, M.D.

Director

National Institute for Occupational 

Safety and Health

Centers for Disease Control 

and Prevention

Hazard Evaluations and Technical Assistance Branch iii

FOREWORD
Prepared by

Beth Donovan Reh, M.H.S.

Editor

Jane Weber, M.Ed.

Design/Desktop Publisher

Donna Pfirman

NIOSH Printing Office

Penelope Arthur

Web Production

David Wall

Donna Pfirman

Project Officers for Individual Health

Hazard Evaluations

Emily Allen, M.P.H.

Dan Almaguer, M.S.

Bruce P. Bernard, M.D., M.P.H.

Mary E. Brown, D.V.M., M.P.H.

Gina Bueno, M.D.

Joseph E. Burkhart, C.I.H.

Nancy Clark Burton, M.P.H., M.S., C.I.H.

John A. Decker, M.S.

Alan Echt, M.P.H., C.I.H.

Thomas Hales, M.D.

Bruce W. Hills, M.S., C.I.H.

Edward J. Hoekstra, M.D., M.S. 

Bradley Husberg, R.N., M.S.P.H.

Elizabeth Jennison, M.D., M.P.H.

Max Kiefer, M.S., C.I.H.

Stuart Kiken, M.D.

Elizabeth Knutti, R.N., B.S.N.

Greg Kullman, Ph.D., C.I.H.

Ali Lopez, M.D.

Robert Malkin, D.D.S., Dr. P.H.

Dino Mattorano 

Charles S. McCammon, Ph.D.

Mary Newman, Ph.D.

David L. Orgel, M.D., M.P.H. 

Chris Piacitelli, I.H.

Christopher M. Reh, M.S.

Stanley Salisbury, C.I.H.

Bambi Sorensen

Robert Streicher, Ph.D.

Doug Trout, M.D., M.H.S.

Randy L. Tubbs, Ph.D.

Corrado Ugolini, M.D., M.P.H.

Isocyanate

HDI 1,6-hexamethylene diisocyanate 

hexamethylene-1,6-diisocyanate 

1,6-diisocyanate

1,6-diisocyanatohexane

hexamethylene diisocyanate

HDI BT Hexamethylendiisocyanate-biurettrimer 

HMDI Methylene bis (4-cyclohexylisocyanate)

HMTA Hexamethylenetetramine

IPDI Isophorone diisocyanate

MAP 1-(9-anthracenylmethyl)piperazine

MDA 4,4’ methylenedianiline

Methylenedianaline

MDI 4,4'-diphenylmethane diisocyanate

Methyl diphenyl diisocyanate

Methelene bisphenyl isocyanate

Diphenylmethane diisocyanate

Methylene diphenyl diisocyanate

Methylene diphenyl isocyanate

NDI 1,5-naphthalene diisocyanate

PPI 2,6-diisopropylphenyl isocyanate

TDA Toluene diamine

TDI 2,4- and/or 2,6-toluene diisocyanate

Trioxide toluene diisocyanate 

Toluene diisocyanate 

Toluene iisocyanate

TRIG Total reactive isocyanate group

Other

ACGIH American Conference of

Governmental Industrial Hygienists

AHU Air handling unit

°C Degrees Celsius 

CA Carcinogen

CFR Code of Federal Regulations

CI Confidence interval

CL Ceiling limit, an exposure that shall

not be exceeded during any part of

the workday

cm2 Square centimeters

DOP Dioctyl phthalate

ELISA Enzyme-linked immunosorbent

assay

°F Degrees Fahrenheit

FEV Forced expiratory volume in one

second

FVC Forced vital capacity 

GA General area (air sample)

iv Hazard Evaluations and Technical Assistance Branch

CONTRIBUTORS ABBREVIATIONS
HETA Hazard Evaluations and Technical

Assistance

HETAB Hazard Evaluations and Technical

Assistance Branch

HHE Health Hazard Evaluation

HP Hypersensitivity pneumonitis

HPLC High pressure liquid chromatography

HVAC Heating, ventilating, and airconditioning

IAQ Indoor air quality

IARC International Agency for Research 

on Cancer

IEQ Indoor environmental quality

IgE Immunoglobulin E (antibody)

IgG Immunoglobulin G (antibody)

IH Industrial hygiene

LEV Local exhaust ventilation

LFC Lowest feasible concentration

LOD Limit of detection (analytical

method)

LOQ Limit of quantitation (analytical

method)

Lpm Liters per minute

MDC Minimum detectable concentration 

(the smallest amount of a material

which can be reliably detected). 

The MDC is calculated by dividing

the analytical LOD by a 

representative air volume.

MEK Methyl ethyl ketone

mg Milligram

mg/l Milligrams per liter

mg/m3 Milligrams per cubic meter of air

MIBK Methyl ethyl isobutyl ketone

MIK Methyl isobutyle ketone

mL Milliliter

mm Millimeter

MQC Minimum quantifiable concentration

(the smallest amount of a material

which can be reliably measured).

The MQC is calculated by dividing

the analytical LOQ by a representative air volume.

MSDS Material safety data sheet

NA Not applicable

ND Not detected

NDBA Nitosodibutylamine,

NDEA Nitosodiethylamine

NDMA Nitrosodimethylamine

NIOSH National Institute for

Occupational Safety and Health

nm Nanometer

NMOR Nitrosomorpholine

NPIP Nitrosopiperidine

OSHA Occupational Safety and Health

Administration

P Probability factor (statistical)

PBZ Personal breathing-zone air 

sample

PEL Permissible exposure limit

(OSHA)

ppb Parts (of a contaminant) per

billion parts of air

PPE Personal protective equipment

ppm Parts (of a contaminant) per

million parts of air

PRR Prevalence rate ratio

QFF Quartz fiber filter

R Correlation factor (statistical)

REL Recommended exposure limit

(NIOSH exposure criteria)

SIC Standard Industrial Classification

STEL Short-term exposure limit

TA Technical assistance

TLV Threshold limit value (ACGIH

exposure criteria)

TWA Time-weighted average

UK-HSE United Kingdom’s Health and

Safety Executive

VOC Volatile organic compounds

μg Microgram

μg/m3 Micrograms of contaminant per 

cubic meter of air (a unit of concentration) 

μgNCO/m3 Micrograms of isocyanate groups

per cubic meter of air

Hazard Evaluations and Technical Assistance Branch v
The unique feature common to all

diisocyanates is that they consist of two

N=C=O (isocyanate) functional groups

attached to an aromatic or aliphatic parent

compound. Because of the highly unsaturated nature of the isocyanate functional

group, the diisocyanates readily react with

compounds containing active hydrogen

atoms (electrophiles). Thus, the diisocyanates readily react with water (humidity),

alcohols, amines, etc.; diisocyanates also

react with themselves to form either dimers

or trimers. When a diisocyanate species

reacts with a primary, secondary, or tertiary

alcohol, a carbamate (NHCOO-) group is

formed, which is commonly referred to

as a urethane. Reactions involving a

diisocyanate species and a polyol result

in the formation of cross-linked polymers;

i.e., polyurethanes. Hence, they are used

in surface coatings, polyurethane foams,

adhesives, resins, elastomers, binders,

and sealants. Many material safety data

sheets (MSDSs) use isocyanate-related

terms interchangeably. For the purpose of

this report, terms are defined as follows.

Diisocyanates (Monomers): The difunctional isocyanate species from which polyisocyanates and polyurethanes are derived.

Common examples of monomeric isocyanates include 1,6-hexamethylene diisocyanate (HDI), 2,4- and/or 2,6-toluene diisocyanate (TDI), 4,4' diphenylmethane

diisocyanate (MDI), methylene bis (4-cyclohexylisocyanate) (HMDI), isophorone diisocyanate (IPDI), and 1,5-naphthalene diisocyanate (NDI). Commercial-grade TDI is an

80:20 or 65:35 mixture of the 2,4- and

2,6-isomers of TDI, respectively.

Polyisocyanates: Species possessing free

isocyanate groups and derived from

monomeric isocyanates either by directly

linking these monomeric units (a

homopolymer) or by reacting these

monomers with di- or poly-functional alcohols or amines (a copolymer).

Prepolymers: Species possessing free isocyanate groups, prepared from the reaction

of a polyol with an excess of di- or polyisocyanate. Commercially available isocyanate

products frequently contain prepolymers in

lieu of more volatile isocyanate monomers.

Oligomeric Isocyanates (Oligomers):

Relatively low molecular weight polyisocyanates.

Intermediates: Species possessing free

isocyanate groups, formed during use of an

isocyanate product by partial reaction of

the isocyanate species with a polyol. 

In general, the types of exposures

encountered during the use of isocyanates (i.e., monomers, prepolymers,

polyisocyanates, and oligomers) in the

workplace are related to the vapor pressures of the individual compounds. The

lower molecular weight isocyanates tend to

volatilize at room temperature, creating a

vapor inhalation hazard. Conversely, the

higher molecular weight isocyanates do not

readily volatilize at ambient temperatures

but are still an inhalation hazard if

aerosolized or heated in the work environment. The latter is important since many

reactions involving isocyanates are exothermic in nature, thus providing the heat for

volatilization. As exposure limits decrease,

the volatility of solid materials becomes an

issue. To reduce the vapor hazards associated with the lower molecular weight diisocyanates, prepolymer and polyisocyanate

forms of these diisocyanates were developed and have replaced the monomers in

many product formulations. An example is

the biuret of HDI, which consists of three

molecules of HDI monomer joined together

to form a higher molecular weight oligomer

having similar characteristics to those found

in the monomer. Also, many MDI product

formulations consist of a combination of

MDI monomer and a MDI-based polyisocyanate (such as polymethylene polyphenyl

isocyanate). Many prepolymer and polyisocyanate formulations contain a small fraction (usually less than 1%) of unreacted

monomer. 

ISOCYANATES BACKGROUND

INFORMATION

Hazard Evaluations and Technical Assistance Branch 1
Isocyanates exist in many different physical

forms in the workplace. Not only are workers potentially exposed to the unreacted

monomer, prepolymer, polyisocyanate,

and/or oligomer species found in a given

product formulation, they can also be

exposed to partially reacted isocyanatecontaining intermediates formed during

polyurethane production. In addition, isocyanate containing mixtures of vapors and

aerosols can be generated during the thermal degradation of polyurethane coatings

and plastics. The capability to measure all

isocyanate containing substances in air,

whether they are in monomer, prepolymer,

polyisocyanate, oligomer, and/or intermediate forms, is important when assessing a

worker’s total airborne isocyanate exposure. 

Exposure to isocyanates is irritating to the

skin, mucous membranes, eyes, and respiratory tract.1,2 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).2,3,4 Contact dermatitis

can result in symptoms such as rash, itching, hives, and swelling of the extremities.1,4

A worker suspected of having isocyanateinduced asthma/sensitization will exhibit the

traditional symptoms of acute airway

obstruction, e.g., coughing, wheezing, shortness of breath, tightness in the chest, and

nocturnal awakening.1,3 An isocyanateexposed 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.1,3,5,6,7 The asthmatic reaction may occur minutes after exposure

(immediate), several hours after exposure

(late), or a combination of both immediate

and late components after exposure

(dual).3,6 The late asthmatic reaction is the

most common, occurring in approximately

40% of isocyanate sensitized workers.8

After sensitization, any exposure, even to

levels below an occupational exposure limit

or standard, can produce an asthmatic

response that may be life threatening.

Experience with isocyanates has shown that

monomeric, prepolymeric and polyisocyanate species are capable of producing

respiratory sensitization in exposed

workers.9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25

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 facilities5,26

to 25% in polyurethane production plants26,27

and 30% in polyurethane seatcover operations.28 The scientific literature contains a

limited amount of animal data suggesting

that dermal exposure to diisocyanates may

produce respiratory sensitization.29,30,31,32

This finding has not been tested in dermally

exposed workers.

HP also has been described in workers

exposed to isocyanates.33,34,35,36 Currently,

the prevalence of isocyanate-induced HP in

the worker population is unknown and is

considered to be rare when compared to

the prevalence rates for isocyanate-induced

asthma.4 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, nonproductive cough, fever, chills, sweats,

malaise, and nausea.3,4 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.3,4 Early diagnosis is difficult since

many aspects of HP, i.e., the flu-like symptoms and the changes in pulmonary function, are manifestations 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

2 Hazard Evaluations and Technical Assistance Branch

HEALTH EFFECTS
isocyanate exposure occurs, or by providing

the worker with supplied-air respiratory protection and preventing any dermal exposures. 

The primary sources of exposure criteria for

workplace inhalation exposures in the

United States follow: (1) the National

Institute for Occupational Safety and

Health (NIOSH) recommended exposure

limits (RELs),37 (2) the American

Conference of Governmental Industrial

Hygienists (ACGIH) Threshold Limit

Values (TLVs®),38 and (3) the U.S.

Department of Labor, Occupational Safety

and Health Administration (OSHA) permissible exposure limits (PELs).39 These include

exposure criteria for diisocyanates. In July

1992, the 11th Circuit Court of Appeals

vacated the 1989 OSHA PEL Air

Contaminants Standard. OSHA is currently

enforcing the 1971 standards, which are

listed as transitional values in the current

Code of Federal Regulations; however,

some States operating their own OSHAapproved job safety and health programs

can have lower limits. Table 1 contains a

comparison of the respective NIOSH RELs,

ACGIH TLVs, OSHA PELs, and United

Kingdom’s Health and Safety Executive

(UK-HSE) exposure criteria for the isocyanates. The UK-HSE has taken a different

approach, i.e., developing a nonspecific

standard based on the total reactive isocyanate groups (TRIGs) in a volume of

air.40 (The TRIGs in air can be determined

using data from NIOSH Method 5522.)

First, the monomer and oligomer concentrations are summed to obtain the total

weight of isocyanate-containing 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 that is contributed by the

TRIGs. For MDI and MDI-based oligomers

the TRIG’s constant is 0.34; for TDI and

TDI-based oligomers the TRIG’s constant is

0.48. Finally, the total weight of isocyanateHazard Evaluations and Technical Assistance Branch 3

EXPOSURE CRITERIA
containing compounds in a given air sample

is multiplied by the TRIGs constant, and the

product is the concentration of TRIGs in air.) 

The standards and limits listed in Table 1

are calculated on the basis of a general

standard that isocyanate exposures

should not exceed the vapor equivalent of

an 8-hour time-weighted average (TWA)

exposure of 5 ppb, or a short-term or ceiling

exposure of 20 ppb. NIOSH recommends

using this standard basis to calculate exposure

limits for diisocyantes not specifically

mentioned in the REL. The NIOSH REL is

for TWA diisocyanate exposures up to

10-hours per workday, and the ACGIH TLV

is an 8-hour TWA exposure. The NIOSH

RELs ceiling limit (CL) and ACGIH shortterm exposure limits (STELs) are based

on 10- and 15-minute TWA exposures,

respectively, and should not be exceeded

during the work shift. The OSHA CL is a

concentration that should never be

exceeded during a workday. OSHA does

not have a full shift, TWA PEL for any of

the diisocyanate species.

In recent years there has been an interest in isocyanate exposures associated

with 2 component polyurethane paints,

especially as related to the autobody

industry. NIOSH has conducted a few

HHEs in these workplaces and expects to

do more in the future. The most common

isocyanate-bearing substances found in

these paints are polyisocyanates based

on HDI. Two forms of HDI-based polyisocyanates exist: an aliphatic form, which

is biuret of HDI, and a ringed compound,

which is HDI trimer. Both are known to

cause respiratory sensitization (occupational asthma), and dermal exposures are

an issue. These paints also contain a very

small residual amount of HDI (monomer).

Currently, there are no NIOSH, OSHA, or

ACGIH evaluation criteria for HDI-based

polyisocyanates. In some past HHEs, NIOSH

has used the Bayer Corporation’s recommended limit of 0.5 mg/m3 for an 8-hour

TWA and 1.0 mg/m3 as a CL, which has

also been adopted by the State of

Oregon.41 A more conservative Swedish

standard appears to be roughly on the

basis of the general diisocyanate recommendation of 5 ppb (TWA) and 20 ppb

(CL). The standard reads as follows: “hexamethylendiisocyanate-biurettrimer” (HDI

BT), 5-minute STEL of 0.2 mg/m3

, TLV TWA

of 0.09 mg/m3.” 

The issues related to determining airborne

isocyanate exposure are presented in detail

in Chapter K of the NIOSH Manual of

Analytical Methods.

42 Portions of that text

are presented below.

Accurate and sensitive determination of isocyanates is complex and difficult. The

advantages and disadvantages of the various

methods must be understood, in order to

choose the most appropriate sampling and

analytical method for a particular workplace

environment. Isocyanates may be in the

form of vapors or aerosols of various particle

size; the species of interest are reactive and

unstable; few pure analytical standards

exist; and high analytical sensitivity is needed.

In addition, numerous points exist in the

sampling and analytical procedures where

errors can be introduced. The selection of

the most appropriate isocyanate method for

a given workplace environment is based

upon an evaluation of measurement

accuracy, specificity, sensitivity, convenience, simplicity, and speed. These factors

must be considered for the entire analytical

measurement process including collection,

derivatization, sample preparation, separation, identification, and quantification. For

example, the faster the isocyanate product

cures (isocyanate systems having half lives

of a few minutes or less are considered fast

cure), the more strongly an impinger is recommended for sampling. Also, an impinger

is recommended for all aerosols having particle diameters greater than 2 μm because

it is believed that the poor mixing on filters

results in poor derivatization efficiency.

However, filters are recommended for sampling particles smaller than 2 μm because

they are collected inefficiently by impingers.

ANALYTICAL METHODS

AND ISSUES

4 Hazard Evaluations and Technical Assistance Branch
Hazard Evaluations and Technical Assistance Branch 5
Another issue is that impingers are considerably less convenient than filters for sampling and, in some cases, are not appropriate for personal sampling. Unfortunately,

the need to measure highly reactive isocyanate species at low levels is many times

in conflict with the desire of industrial

hygienists and chemists to choose methods

that are convenient to use in the field and

are easy to run in the laboratory. 

Table 2 summarizes NIOSH and OSHA isocyanate methods and method selection for a

given workplace environment. The selection

of the most appropriate isocyanate method

depends upon the isocyanate species, its

physical state, its cure rate, the sensitivity

required, and other factors shown in Table 2.

This information is used to select methods

for NIOSH research studies and HHEs and is

also provided when employers, industrial

hygienists, or laboratories request NIOSH

technical assistance on isocyanate methods.

Direct-reading instruments can be used to

measure isocyanate concentrations in the

field, but they have limitations just like the

laboratory methods. The direct-reading instruments use a colorimetric tape with a photoanalyzer to quantify the color change. They

are only appropriate for certain monomers in

the vapor phase, and other isocyanates and

non-isocyanates can interfere.

Obvious from the above discussion, more

research is needed to resolve the limitations

of current sampling and analytical methods.

Such research is ongoing at NIOSH and elsewhere in government, academic, and private

organizations. NIOSH is currently proposing

a new sampling method (NIOSH 5525, see

Table 2)43 that is more sensitive and selective than previous methods and that can be

used for PBZ sampling. This method was

recently evaluated by researchers at the

University of Massachusetts, Lowell,44 and

will be issued in the next supplement for

the NIOSH Manual of Analytical Methods.

Chapter K of this manual (referenced at the

beginning of this section) is currently being

updated by NIOSH chemists to include more

discussion of this new method.

Any HHEs that determine a potential for

isocyanate exposures offer certain recommendations for respiratory and dermal protection, employee education, and

medical surveillance. The recommendations may vary slightly on the basis of

the specific HHE. Often other site-specific

recommendations are made, but the

ones routinely offered are as follows:

1. Whenever there is potential for exposure

to diisocyanates, even concentrations

below the NIOSH REL, NIOSH recommends that employees be supplied with

supplied-air respiratory protection.

(Negative pressure air-purifying respirators are not recommended since

diisocyanates have poor odor warning

properties.) Also, there should be a

respiratory protection program.

2. NIOSH investigators recommend that

dermal exposures to isocyanate-containing substances be prevented.

Employers should provide protective

clothing, gloves, and footwear that is

impervious to isocyanate--containing

compounds. The protective clothing

should either be disposed or laundered

after each use (e.g., at the end of the

work shift). The gloves should be

elbow-length and made of an isocyanateresistant material. Face-shields and

aprons should be used whenever

there is a possibility of a splash or a

spill of liquids containing isocyanatecontaining materials. The open points

at the interface between different

forms of protective clothing, e.g., the

opening that forms between the

sleeve of a protective suit and a glove,

should be sealed to prevent exposure

through the interface. A common and

effective method for sealing these

interfaces is to use duct tape to join

the two different forms of protective

clothing.

6 Hazard Evaluations and Technical Assistance Branch

RECOMMENDATIONS
Hazard Evaluations and Technical Assistance Branch 7

3. NIOSH recommends that employers

provide workers with appropriate

training on the inhalation and dermal

exposure hazards associated with isocyanate-containing materials and on

the proper use of personal protective

equipment (PPE) associated with protection from these exposures.

NIOSH recommends both preplacement and periodic medical surveillance programs for all workers potentially exposed to diisocyanates. 

The preplacement examinations

should consist of detailed medical

and work histories with emphasis on

pre-existing respiratory and/or allergic

conditions, a physical examination

that centers on the respiratory tract, a

baseline pulmonary function test that

measures forced expiratory volume in

one second (FEV1) and forced vital

capacity (FVC), and a judgement on

the worker’s ability to wear a suppliedair respirator. Workers should be provided

with annual examinations that update

the medical and work histories and

measure the worker’s FEV1 and FVC.

4. NIOSH recommends that empoloyers

conduct industrial hygiene (IH) surveys on all workers potentially

exposed to isocyanates. 

These surveys should contain both

inhalation and dermal exposure evaluations and should be conducted on an

annual basis or when there are

changes in the process or engineering

controls. A sufficient number of samples

should be collected to characterize

each employee’s exposure and to

characterize isocyanate emissions

from a given process, operation,

machine, etc. These surveys should

encompass both routine (e.g., normal

operations and scheduled maintenanace) and nonroutine (e.g., repair

activities associated with breakdowns

or malfunctions) work activities. Task

oriented exposure assessments

should be used to determine the isocyanate exposure levels associated

with specific tasks within an operation

or shift.

5. All medical and IH records should be

kept by the employer for a time period

of no less than 30 years.
8 Hazard Evaluations and Technical Assistance Branch

HETA 94ñ0027

May 1994

Requester: Union

Method(s): NA

Range of isocyanates: NA

Purpose: To investigate complaints from

underground coal miners of illness after

exposure to rock glues

Keywords: SIC 1222 (Bituminous Coal

Underground Mining), rock glue, diphenylmethane diisocyanate, isocyanates

Abstract: NIOSH conducted this HHE to

investigate complaints from underground

coal miners of illnesses, including respiratory problems, asthma, and skin irritation,

after exposure to rock glues in the course

of their work duties. NIOSH was requested

to provide guidance in establishing a company medical surveillance program for

those workers with exposure to rock glue

adhesives containing isocyanates. NIOSH

reviewed and concurred with the proposed

safety precautions to be taken during the

application of the rock glue. 

Recommendations included substituting

non-isocyanate-containing products where

feasible and providing protective clothing

made from laminates to protect against

dermal exposure to isocyanates.

HETA 97ñ0217ñ2667

December 1997

Requester: Management

Method(s): NIOSH 5522

Range of isocyanates: two GA samples—

20.1 μg/m3 and 30.7 μg/m3 ppm MDI

Purpose: To investigate workers’ exposures

and symptoms, including dizziness and

sleepiness, that were believed to be related

to a hot melt adhesive process used in the

production of residential doors

*Keywords: SIC 2431 (Millwork), door

manufacturing, hot adhesive, acetone,

methylene bisphenyl diisocyante, methylene

cholride, toulene, sleepiness, dizziness,

ventilation

_______

* at the conclusion of an HHE, the NIOSH investigators

provide keywords for inclusion in the HHE database

Abstract: NIOSH conducted an HHE to

investigate workers’ exposures and symptoms, including dizziness and sleepiness,

that were believed to be related to a hot

melt adhesive process used in the production

of residential doors. Confidential medical

interviews were conducted with employees

in the door assembly area. The two GA air

samples collected for MDI were below

current occupational exposure limits. The

local exhaust ventilation of the roller

machine was operating. There was very

little air movement in the door assembly

area, and the fans that were used were

blowing directly toward the assembly

employees. In addition, solvent vapors from

the adjacent production area were entering

the door assembly area. Because of continued health complaints among employees

and low concentrations of VOCs in the door

assembly area, this company should consider

adding LEV to the area. Additionally, replacement air from a clean area or from outside

should be added to compensate for the air

being exhausted and to provide additional

ventilation.

Adhesives

ISOCYANATE HHE SUMMARIES

ORGANIZED BY PROCESS
Hazard Evaluations and Technical Assistance Branch 9

Decomposition Products

HETA 89ñ0360

December 1991

Requester: Union

Method(s): NA

Range of isocyanates: NA

Purpose: To investigate health complaints

from operators in a trilaminator department

and adjacent departments

Keywords: SIC 2396 (Automotive

Trimmings, Apparel Findings, and Related

Products), urethane foam, antimony, TDI

Abstract: NIOSH conducted an HHE at an

automobile seat manufacturer to investigate

health complaints from operators in the

trilaminator department and sewing

machine operators in an adjacent department. Workers reported that they were

experiencing chronic skin and eye irritation

and acute and chronic respiratory problems.

NIOSH reviewed environmental sampling

completed by the manufacturer, and

conducted laboratory experiments on bulk

samples of the urethane foam and powder

adhesives. At the time of the NIOSH site

visit, 10 workers operated two trilaminator

units. Past IH surveys had found TDI air

concentrations to be low during normal

operation of the trilaminators. However, the

potential for worker exposure was increased

during fires (which occurred about once a

month) because the LEV system was deactivated until the fire was extinguished. The

data from the NIOSH laboratory analyses,

along with the data from the previous studies

provided by the manufacturer, clearly

demonstrated that TDI is released when

urethane foam is heated, that the concentration of TDI released increases as the

temperature increases, and that high

concentrations may be released during

fires. In addition, the NIOSH analyses show

that other chemicals are released when

urethane foam and powder adhesive are

heated. As with TDI, concentrations of the

other compounds increase as the temperature

increases. The acute respiratory symptoms

and mucous membrane irritation reported

during fires in the trilaminator and Lincoln

Base departments were consistent with

exposure to smoke and other fire-generated

emissions (e.g., TDI, formaldehyde,

acetaldehyde, acrolein, benzene, which are

known respiratory and mucous membrane

irritants). Chronic respiratory problems

(e.g., asthma-like symptoms and bronchitis)

may have been related to exposure to

smoke and fire-generated emissions. It was

also possible that a few individuals may

have developed TDI-related occupational

asthma. NIOSH recommended that the

manufacturer investigate alternatives to the

present system that results in fires and

contamination of workplace air, that there

be a better fire-emergency plan, and that

the company follow all the standard isocyanate recommendations if isocyanate

exposures are not eliminated from this

workplace.

HETA 91ñ0053ñ2320

May 1993

Requester: Union

Method(s): NIOSH 5521

Range of isocyanates: <1.7 μg/m3

(below MDC)

Purpose: To investigate possible employee

exposures to hazardous residues during

railroad tank car repair

Keywords: SIC 4789 (Transportation

Services, not elsewhere classified),

railroad car repair, tank cars, arsenic,

chromium, welding, cutting, air arc

gouging, isocyanates

Abstract: NIOSH conducted this HHE to

evaluate possible employee exposures to

hazardous residues during railroad tank car

repair. Ten GA air samples were collected

during cutting and burning on polyurethane

foam-insulated chlorine cars, but no isocyanates were detected (<1.7 μg/m3

).

However, investigators determined from the

bulk samples that there was potential for

exposure to polyisocyanate foam decomposition products. NIOSH provided recommendations for engineering and administrative controls to prevent isocyanate and

other hazardous exposures.
10 Hazard Evaluations and Technical Assistance Branch

HETA 94ñ0312ñ2512

June 1995

Requester: Joint Employee-Management

Method(s): NIOSH 5522 and NIOSH 2535

Range of isocyanates: ND (TDI)

Purpose: To investigate respiratory

symptoms potentially associated with

isocyanate exposures during brazing and

welding operations

Keywords: SIC 3677 (Electronic Coils,

Transformers, and Other Inductors), isocyanates, diisocyanates, TDI, transformers,

occupational asthma, brazing, welding 

Abstract: NIOSH conducted this HHE to

investigate respiratory symptoms potentially

associated with isocyanate exposures during

brazing and welding operations. In addition,

a variety of other health effects were reported.

The industrial hygienists reviewed MSDSs

and manufacturing processes and evaluated

employee exposure to TDI. PBZ air samples

were collected during simulated brazing

operations at the entrance of the flexible

duct of the portable filtration unit, one foot

prior to the entrance, and in and near the

exhaust. TDI was ND in any of the air samples. The medical investigators distributed

and reviewed respiratory symptom/allergy

questionnaires, reviewed the OSHA illness

and injury log, workers’ compensation

claims, and employee medical records, and

interviewed workers. From January 1992

through December 1994, six incidents

occurred involving respiratory problems—

two were described as asthma attacks, two

were for smoke inhalation, one was recorded

as “respiratory problems,” and one was

recorded as allergic pneumonitis. In the

past year, 20 (14%) of the 138 respondents

reported experiencing three or more

respiratory symptoms including shortness of

breath, difficulty breathing, chest tightness,

and wheezing; 9 (7%) reported physiciandiagnosed asthma; 21 (15%) respondents

reported dermatologic symptoms. The

NIOSH medical investigators interviewed

20 workers. The most prevalent symptoms

among the 15 (75%) symptomatic workers

were upper respiratory irritation and skin

problems such as rashes, hives, and

eczema. On the basis of the data collected

during this survey, the NIOSH investigators

did not find evidence of a current health

hazard from brazing-related TDI exposure

and were unable to determine the frequency

and severity of past TDI exposures.

Workers did appear to have respiratory

symptoms that could be associated with

the brazing and welding operations.

Exposure to the many constituents of welding and brazing fumes is a possible cause

of these symptoms. Recommendations

were offered to reduce workers’ exposures

when performing these operations including

(1) all welding and brazing operations /

stations should be equipped with fixedstation LEV systems that exhaust the air

outside of the workplace and (2) a qualified

heating, ventilation, and air conditioning

firm should be contracted to conduct a

mechanical system audit of the ventilation

system to verify that the system is adequately

sized and designed for current application.

Foaming

HETA 89ñ0278ñ2035

April 1990

Requester: Government

Method(s): Proposed NIOSH 5525 (currently

in review)43

Range of isocyanates: ND to 0.2 μg/m3 MDI

Purpose: To evaluate exposures and health

effects from MDI among workers of a jewelry

facility

Keywords: SIC 3911(Misc. Manufacturing

not classified elsewhere e.g., jewlrey, silverware etc.), MDI, isocyanates, foam insulation,

asthma, HP, MDI-induced respiratory disease 

Abstract: NIOSH responded to a local health

department request to evaluate exposures

and health effects among workers of a

jewelry facility where foam insulation

containing MDI had been applied. Five days

after the application ceased, NIOSH

investigators collected air samples,

administered questionnaires, and offered
medical evaluations to those who reported

asthma-like symptoms on the selfadministered questionnaires. Seven of

the sixteen GA air samples had detectable

quantities of MDI, ranging from 0.1 to

0.2 μg/m3, which were all well below the

relevant exposure limits. Because of the

timing of the request, it was not possible to

estimate exposures during the spraying

application. Ninety-six percent (75/78) of

the workers that worked during the week of

application completed theself-administered

symptom questionnaire, and 13 were

identified as having probable MDI-induced

respiratory disease. Investigators concluded

that MDI exposures probably occurred

during the insulation application, and

they provided recommendations for the

prevention of future exposures and

guidance for workers with persistent

respiratory symptoms.

HETA 89ñ0312

April 1990

Requester: Government

Method(s): NIOSH 5521

Range of isocyanates: ND for MDI monomer

and MDI-based polyisocyanates but there

were problems with the MDI-based polyisocyanate analyses

Purpose: To evaluate worker exposure to

MDI at an animal taxidermy manufacturer

Keywords: SIC 2759 (Commercial Printing,

not elsewhere classified), MDI, fluorinated

hydrocarbons, diisocyanates

Abstract: This HHE was conducted to evaluate worker exposure to MDI at a manufacturer that makes animal head forms for use

in big game taxidermy. The heads are made

using a 2-part foam system. Part ”A” contains MDI, and Part “B” contains fluorinated

hydrocarbons and tertiary aliphatic amines.

The two liquids are mixed in a bucket,

poured into molds, and allowed to sit at

room temperature while windows and doors

are kept open to provide ventilation. NIOSH

collected 5 GA air samples in the building.

No MDI was detected in any of the air

samples. The sampling and analytical

LOD was reported to be about 2 μg/m3

.

Investigators reported that it should not be

assumed that there is no exposure to MDI

despite the results of the test; this analytical

method was still questionable for detecting

MDI-based polyisocyanate at the time of the

survey. Also, once a person becomes sensitized to MDI, exposure at very low concentrations may trigger illness, and therefore

any future exposures must be avoided.

Guidance included the standard isocyanate

recommendations and also the addition of

engineering controls such as process enclosures or LEV to reduce risk of exposure.

HETA 90ñ0011ñ2034

April 1990

Requester: Management

Method(s): NIOSH 5521

Range of isocyanates: ND to 320 μg/m3 MDI

(short-term samples), ND for MDI-base polyisocyanate

Purpose: To characterize worker exposure

to isocyanates during use of a polyurethane

foam system in the shipping department

Keywords: SIC 3491 (Industrial Valves),

MDI, polyurethane foam, Instapak 40TM,

respiratory protection, short-term exposures

Abstract: NIOSH conducted this HHE to

determine the exposures to workers using a

polyurethane foam system in a shipping

department. The foam was a two-component

system that contained MDI and MDI- based

polyisocyanate, and was applied with a

spray gun. The actual packaging of valves

took approximately 30 to 45 minutes, during

which the foam system was used for about

5 minutes. Thus, MDI entered the work

atmosphere as a point source emission and

the exposure was intermittent in nature.

TWA and short-term exposure monitoring

was performed in the packaging area using

NIOSH Method 5521. TWA air sampling

equipment was located in the packaging

station work area and in surrounding work

areas at varying distances from the

polyurethane foam application area. All of

the TWA air samples measured nondetectable levels of MDI and MDI-based polyHazard Evaluations and Technical Assistance Branch 11
12 Hazard Evaluations and Technical Assistance Branch

isocyanate. Conversely, the short-term

exposure sampling did measure substantial levels of MDI but did not detect any

MDI-based polyisocyanate. Concentrations

of MDI ranged from ND to 320 μg/m3

,

with 2 of the 7 samples being above the

OSHA and NIOSH CLs for MDI of 200 μg/m3.

On the basis of this survey, the NIOSH

investigators concluded that a health hazard

existed from short-term exposure to MDI

when applying the foam. Recommendations

were made in this report to either eliminate

the use of the polyurethane foam system,

or to use engineering controls and PPE to

protect the workers. All the standard isocyanate recommendations were made.

HETA 90ñ0175

August 1992

Requester: Employee

Method(s): NIOSH 5521

Range of isocyanates: ND (MDI monomer

and MDI-based polyisocyanate)

Purpose: To investigate employee exposures

to MDI in the foam operations and adjacent

departments

Keywords: SIC 3632 (Household

Refrigerators and Home and Farm Freezers)

MDI

Abstract: NIOSH conducted this HHE at a

refrigerator manufacturer to investigate

employee exposures to MDI in the foam

operations and assembly and subassembly

operations in adjacent departments

because some workers had developed

occupational asthma as a result of exposures

to MDI. Investigators conducted full-shift

and short-term GA air monitoring to

characterize exposures to MDI and MDIbased polyisocyanate in the foam application

and adjacent departments. Full-shift sampling

was performed by placing area air sampling

equipment in foam application areas and

in adjacent departments. The short-term

exposure monitoring was performed by

holding the air sampling equipment in or

near the breathing zone of the workers or

by placing the equipment as close as possible

to the foam fixture head. Because the

sampling equipment contained liquid

solutions of toluene, the equipment was

not placed directly on the workers. Efforts

were made to obtain samples at either

worst-case locations or at workstations

where workers spent most of their time. On

the basis of the limits of detection (LOD)

for the analytical method, neither MDI nor

MDI-based polyisocyanate was present at

concentrations above 1 μg/m3 on full-shift

air samples or 20 μg/m3 on short-term

(10 to 15 minute) air samples. Subsequent

resampling by a consultant showed similar

results. Although the overall level of MDI

exposure appeared to be low, workers

who are sensitized to MDI may suffer

effects even at levels below NIOSH LOD.

NIOSH recommended that workers with

potential for exposure to MDI should have

preplacement and periodic medical examinations to determine if any medical conditions exist that could be aggravated by

exposure to isocyanates. Also, all of the

other standard isocyanate recommendations were provided.

HETA 90ñ0277ñ2487

February 1995

Requester: Union

Method(s): NA

Range of isocyanates: NA

Purpose: To investigate exposures potentially

related to halovision in workers at a

polyurethane foam production plant

Keywords: SIC 2531 (Seats: Automobile),

polyurethane foam, organic amines,

diethanol amine, triethylene diamine,

DABCO, bis(2-dimethylaminoethyl) ether,

NIAX® A99, triethyl urea, halovision, visual

disturbance, diisocyanates, TDI, asthma

Abstract: NIOSH conducted this HHE

because workers exposed to amine catalysts

used in polyurethane foam production were

experiencing halovision. Although isocyanate

sampling was not requested, investigators

noted that the foam manufacturing process

used resins that contained TDI and that the

employee questionnaire revealed that

greater than 30% of the respondents reported
Hazard Evaluations and Technical Assistance Branch 13

experiencing respiratory symptoms that

were consistent with isocyanate exposure.

For those reasons, NIOSH provided the

standard isocyanate HETA Program recommendations to this facility.

HETA 91ñ0386ñ2427

May 1994

Requester: Government

Method(s): NIOSH 5521

Range of isocyanates: <1.6 μg/m3 MDI

monomer (below MQC)

Purpose: To investigating a possible health

hazard from exposure to MDI at an artificial

plant manufacturing facility

Keywords: SIC 3999 (Manufacturing

Industries, not elsewhere classified), artificial flower arrangements manufacturing,

polyurethane foam, diphenylmethane

diisocyanate, HP, MDI

Abstract: NIOSH conducted this HHE to

investigate a possible health hazard from

exposure to MDI at an artificial plant manufacturing facility. The request was prompted by the death of a former employee who

had developed a disease consistent with HP

after working with MDI at the plant. The

facility used a MDI-based polyurethane foam

to provide a rigid support for artificial plant

arrangements. NIOSH investigators found

detectable concentrations of monomeric

MDI in two of the five full-shift GA air samples collected in impingers; however,

these concentrations were below the LOQ.

The MDC was 0.6 μg/m3

, and the MQC

was 1.6 μg/m3 for the samples. The six

impingers used for short-term personal

sampling did not detect monomeric MDI.

The detection limit for these samples

was about 20 μg/m3. Vapors/aerosols were

observed rising into the faces of workers

working with the foam. This observation

and a chemical smoke tube test indicated

that the ventilation systems in the foaming areas were not adequate for preventing

worker exposure to MDI. Skin contact with

the curing foam was also noted during the

survey. The medical portion of the survey

consisted of a medical questionnaire, occupational and exposure histories, spirometry,

and serial peak flow measurements. 

Individuals who reported high exposure to

the polyurethane foaming process were

more likely to report work-related nasal and

eye irritation than were individuals in the

other exposure categories. Self-reported

exposure to the foaming process was not

associated with any other symptoms, nor was

it related to pulmonary function, as

measured by spirometry and serial peak

flow monitoring. Thirty-five prior workers

participated in a separate medical questionnaire. Sixteen prior workers had spirometry

testing, and all had normal results, including

two of the four who said they had left work

because of a respiratory problem. There

was no evidence of impaired pulmonary

function among former workers who

participated in this study. There was no

apparent relationship between chronic

pulmonary impairment, as assessed by

spirometry, or reactive airway disease, as

measured by peak flow variability, and

working with the foaming system. Current

workers who work directly with the

polyurethane foaming system were found to

have a substantial prevalence of work-related

nasal and ocular irritation, suggesting that

there is ongoing exposure to an irritant.

The air sampling did not indicate concentrations of MDI above the exposure standards,

but because of the potential for isocyante

exposures, investigators provided all the

standard isocyanate recommendations.
14 Hazard Evaluations and Technical Assistance Branch

HETA 94ñ0055

July 1996

Requester: Employee

Method(s): GMD Sure-SpotTM Test cards and

OSHA 47 (by a consultant prior to the HHE)

Range of isocyanates: 15-minute samples

ranged from ND to 37.8 6 μg/m3 MDI

monomer (Note: OSHA 47 often underestimates concentrations)

Purpose: To evaluate exposures and possible health effects associated with the

use of a two-component polyurethane

foam system

Keywords: SIC 3585 (Air-Conditioning and

Warm Air Heating Equipment and

Commercial and Industrial Refrigeration

Equipment), MDI, asthma, respiratory sensitization, polyurethane foam, soft drink

dispensers, ice chests

Abstract: NIOSH conducted this HHE to

evaluate exposures and possible health

effects associated with the use of a twocomponent polyurethane foam system,

which contained MDI and MDI-based

polyisocyanates. An independent consultant

had performed two types of isocyanate

short-term air sampling prior to the HHE, and

the results ranged from ND to 37.8 μg/m3

MDI. NIOSH investigators did not perform

any air sampling because the consultant

data documented the presence of isocyanates,

and previous NIOSH HHEs and other studies

had documented MDI and MDI-based polyisocyanate exposures and work-related

asthma from injection foaming processes.

Based upon the employee interviews and

review of medical records, at least two

workers had occupational asthma, one

employee possibly had occupational

asthma, and one employee had underlying

asthma that was reportedly exacerbated by

the workplace. Investigators provided the

standard isocyanate recommendations.

HETA 94ñ0124ñ2470

November 1994

Requester: Employee

Method(s): NIOSH 5522

Range of isocyanates: ND to 6 μg/m3

MDI monomer, 2 to 13 μg/m3 TRIG,

ND to 38 μg/m3 MDI oligomer

Purpose: To evaluate potential chemical

exposures from polyurethane foam injection

processes

Keywords: SIC 3632 (Household

Refrigerators and Home and Farm Freezers)

MDI, blowing agents, fluorotrichloromethane,

condensation aerosol

Abstract: NIOSH conducted this HHE to

evaluate potential chemical exposures from

polyurethane foam injection processes. The

request stated that health effects among

some workers, including eye and throat irritation, asthma, emphysema, cancer, and

heart disease, resulted from exposure to

workplace chemicals and environmental

tobacco smoke. NIOSH investigators

conducted site-visits and area air sampling

for monomeric and oligomeric MDI at six

locations where polyurethane foam was

being injected into refrigerator doors and

cabinets. At each location, six sampling

trains were used to differentiate between

MDI vapor and condensation aerosol.

Monomeric MDI concentrations ranged from

ND to 6 μg/m3

, less than the NIOSH REL of

50 μg/m3. TRIG concentrations were

calculated (range: 2 to 13 μg/m3); these

concentrations were less than the 8-hour

TWA UK-HSE Common Control Limit of

20 μg/m3. The highest concentration

(13 μg/m3) was found at the foam-in-place

injection area. Considering the possible low

analytical recovery for oligomeric MDI, the

concentrations of oligomer and TRIG may

be underestimated. However, if a worst-case

60% recovery is assumed, only the sample

collected at the foam-in-place location

could be near the exposure limit. No MDI

was found on the treated filters or back-up

bubblers (except one bubbler), suggesting

little or no condensation aerosol was present. 
Hazard Evaluations and Technical Assistance Branch 15

A health hazard from overexposure to

MDI was not determined during the NIOSH

evaluation.

*HETA 97ñ0084ñ2669

December 1997

Requester: Management

Method(s): NIOSH 5522

Range of isocyanates: Spray painting—

5.1 to 9.6 μg/m3 2,4-TDI monomer, 7.4 to

17.9 μg-NCO/m3 TRIGs, ND 2,6-TDI monomer;

packaging—ND MDI monmer, ND to 15.5 μg/m3

MDI oligomer, <9.8 μg-NCO/m3 TRIGs

Purpose: To document worker exposure to

isocyanates during spray painting and

packaging processes

Keywords: SIC 3519 (Internal Combustion

Engines, not elsewhere classified), noise,

isocyanates, metal working fluids, TDI and

MDI, total reactive isocyanate TRIG,

toluene, xylene, formaldehyde, inorganic

acids, ammonia, lead

_______

*also included in surface coating processes

Abstract: NIOSH conducted this HHE to

document worker exposure to isocyanates

during spray painting and packaging of

engine control devices. Monitoring for TDI

and MDI monomers and oligomers and

TRIGs was conducted. Area air sampling

results for TDI during spray-painting

operations ranged from 5.1 to 9.6 for

2,4 TDI monomer, and 7.4 to 17.9 μg NCO/m3

for TRIGs. No 2,6-TDI monomer was

detected. These data indicate that area

14 isocyanate levels are low for spray-painting

operations, especially when compared to

the ACGIH TLV for TDI (8-hour TWA of

36 μg/m3

) and the UK-HSE standard for TRIG

(8-hour TWA of 20 μg NCO/m3). The low levels

indicated that the spray booth was effectively

containing the isocyanates. Area air samples

collected for MDI during packaging operations

did not detect MDI monomer but detected

oligomer concentrations ranging from ND

to 15.5 μg/m3

. The TRIG concentrations

were all below 9.8 μg NCO/m3

. Although MDI

concentrations were low, the design of the

local exhaust systems for the packaging

needed improvements. NIOSH provided the

standard isocyanate recommendations.

HETA 98ñ0011ñ2801

July 2000

Requester: Union

Method(s): Proposed NIOSH 5525 (currently

in review)43

Range of isocyanates: 1.40 μg/m3 to

2.75 μg/m3 TDI in air; 1.74 μg/l and

1.77 μg/l TDA in urine (creatinine-corrected).

Purpose: To evaluate potential exposures to

TDI in a plant that produced flexible

polyurethane foam cushions for automobile

seats

Keywords: SIC 3714 (Motor vehicle parts

and accessories), diisocyanates, occupational asthma, diisocyanate-induced sensitization, allergic contact dermatitis, TDI, TDA,

formaldehyde, hydrocarbon solvents, Bis

(2-dimethylaminoethyl) ether, NIAX®, respiratory irritants, foam-manufacturing 

Abstract: NIOSH investigated a plant that

produced flexible polyurethane foam cushions for automobile seats. The union

request indicated that five workers had

been diagnosed with cancer over the last

4 years, and that current workers were concerned that these cancers might be caused

by workplace exposures, especially to TDI,

the primary chemical constituent used to

make the flexible foam used for automotive

seat cushions. The union later noted that

83 workers had recently completed a health

and safety survey and that various health

symptoms were reported that were consistent with exposure to diisocyanates.

Two initial site visits involved interviews,

process and work practice observations,

records reviews, and air sampling for

hydrocarbons. Some hydrocarbon sampling

was conducted during the subsequent visit

in May 1999, but the major study was to

evaluate TDI exposures and their relationship to the prevalence of occupational

asthma, airway hyper-responsiveness, allergic sensitization to TDI, and diisocyanaterelated allergic contact dermatitis. NIOSH

investigators also conducted an evaluation

of the five reported cancers.
16 Hazard Evaluations and Technical Assistance Branch

One hundred fourteen (39%) of the 290

workers completed medical questionnaires,

100 provided blood samples for measuring

TDI-specific antibodies, 65 provided serial

peak flow records for assessing airway

hyper-responsiveness, and 26 participated

in skin patch testing to assess allergic contact dermatitis. 

Asthma and work-related asthma were

defined from questionnaire responses

using standard epidemiologic definitions;

cases defined in this way may not meet

standard clinical definitions of asthma.

Twenty-two percent (25/114) of the

participants met the case definition for

asthma, and 18% (20/114) met the case

definition for work-related asthma.

Production work (PRR=3.40; 95%

CI=0.92-39.52) and ever working with TDI

(PRR=2.31; 95% CI=0.34-123.20) were

both associated with asthma. Production

work (PRR=2.66; 95% CI=0.65-29.16)

and ever working with TDI (PRR=1.83;

95% CI=0.25-92.75) were also associated

with work-related asthma. However, these

associations were not statistically significant

(p<0.05). Of the 59 peak flow participants

whose peak flow records were suitable

for analysis, 25 (42%) met the definition

for airway hyper-responsiveness. Of the

25, 8 had a work-related pattern, 5 had a

non-work related pattern, and no pattern

could be discerned for the remaining 12. 

Eighty-two (72%) of participants met the

case definition for work-related mucous

membrane (nose and eye) irritation symptoms. Production line work (PRR=1.57; 95%

CI=1.05-10.05) and ever working with TDI

(PRR=1.88; 95% CI 0.97-23.08) were

associated with mucous membrane

symptoms (p<0.05).

Antibody test and skin patch testing results

did not show an immune response to TDI or

the presence of TDI-related allergic contact

dermatitis. Of the 100 individuals providing

blood for antibody testing, two had an

elevated TDI-specific immunoglobulin class

G (IgG) antibody level, and none had an

elevated TDI-specific immunoglobulin

class E (IgE) antibody level. Of the 26 individuals participating in skin patch testing,

none developed skin reactions to any of the

test allergens either 48 or 96 hours after

patch test application. 

PBZ air samples were calculated for each

worker participating in the medical evaluation. Additionally, PBZ samples were

obtained for a random sample of workers

who did not participate in the medical

evaluation. TDI area air sampling was also

conducted. Workers who participated were

also asked to provide an end-of-shift urine

sample, which was analyzed for a metabolite of TDI exposure, TDA.

The highest TDI (2,4-, 2,6- and total TDI)

exposures were found among production

line workers. Demold workers had the highest mean total TDI exposures (2.75 μg/m3

),

followed by insert workers (2.37 μg/m3),

mechanics (1.49 μg/m3), and utility

workers (1.40 μg/m3). However, TDI concentrations for all PBZ and area samples

were below the current ACGIH TLV of

36 μg/m3. A sample stability problem

arose when TDI air samples collected in

May 1999 underwent storage for a 3-month

period; a 12% to 14% decline in TDI concentration between analysis in September

and October 1999 was identified in these

samples. However, reanalysis of the samples did not support a continuous sample

stability problem, and only minor concentration declines were identified between the

initial and subsequent TDI analyses.

Analysis of urine TDA concentrations in

workers demonstrated that production

line workers (primarily demold and insert

workers) had the highest TDA levels; creatinine-corrected mean urine total TDA

levels among demold workers and insert

workers were 1.77 mg/l and 1.74 mg/l,

respectively. Statistically significant correlations were found between total TDI

exposure and both uncorrected (R=0.30,

P=0.007) and creatinine-corrected

(R=0.35, P=0.002) urine 2,4-TDA levels.

Although airborne exposures to TDI were

below RELs, respiratory, mucous membrane,

and skin problems were noted in this worker

population and these symptoms were
Hazard Evaluations and Technical Assistance Branch 17

associated with indicators of TDI exposure.

The strength of this association, however,

was limited by the low participation rate of

the study. Insert and demold workers had

higher environmental TDI exposure levels

compared with offline workers and nonproduction personnel, and subsequently

demonstrated higher urine TDA levels. The

reported cancers among workers were not

consistent with a work-related etiology,

because of the variety of cancers noted,

the limited carcinogenic potential of the

compounds identified, and the low exposure

levels measured for each compound.

Recommendations included following proper

medical surveillance procedures for workers

exposed to TDI, improving ventilation,

improving the availability and usage of

PPE, and following existing safety and health

guidelines.

HETA 99ñ0065ñ2780

December 1999

Requester: Employee

Method(s): Proposed NIOSH 5525 (currently

in review)43

Range of isocyanates: 1.1 μg/m3 and

2.3 μg/m3 MDI

Purpose: To evaluate exposures to MDI

during the use of an Instapak® foam-in-bag

packaging system

Keywords: SIC 3714 (Motor Vehicle

Parts and Accessories); isocyanates,

MDI, polyurethane foam, packaging,

automobile parts

Abstract: NIOSH investigated an Instapak®

foam-in-bag packaging system, marketed

under the trade name of Speedy PackerTM,

at a manufacturer of truck transmissions.

The plant began packaging parts in

polyurethane foam in 1988 using an

Instapak® foam-in-place system. An employee

using the foam-in-place packaging system

had to be removed from the job after 2 days

due to respiratory symptoms described by

the affected employee as “constricting of

the throat and wheezing.” A different person

began using the system and worked without

incident. In February 1999, the foam-in-place

system was replaced with the foam-in-bag

system currently used in the warehouse.

NIOSH investigators conducted a site visit

in April 1999 to observe how the packaging

system was used, learn about the occupational health programs in place for users of

the packaging system, and obtain environmental measurements for MDI and MDI

oligomers. One person worked directly with

the foam-in-bag system and several workers worked adjacent to the foaming area at

distances of approximately 30 feet. Batches

of parts were periodically delivered to the

foaming area by a fork truck. The number

of parts and the rate at which they were

delivered varied considerably. LEV was in

place in the foaming area. The foamer wore

shorts and a tee shirt throughout the shift.

Chemical goggles and full-length Sol-Vex

nitrile gloves (model 37-185) were worn

while using the Speedy PackerTM.

Respiratory protection was not used. The

plant’s corporate health and safety department had a written medical surveillance

program for workers who worked with

isocyanates that provided guidelines for

pre-placement and periodic medical

evaluations of workers who work with

isocyanates. The medical evaluations were

to emphasize the respiratory system. Six

area samples were collected over the full

shift, and two PBZ samples were collected

over 15-minute periods to measure peak

exposures to MDI and MDI oligomers while

the foamer was using the foam-in-bag

system. Wipe samples also were obtained

for MDI on surfaces in the foaming area.

MDI was detected in 4 of 8 air samples at

concentrations below applicable exposure

criteria. Oligomeric MDI was not detected

in any sample. The greatest concentrations,

1.1 μg/m3 and 2.3 μg/m3

, were measured

in two short-term PBZ samples collected

while the foamer used the foam-in-bag

system. Other detectable MDI concentrations were measured near where the bags

of foam were placed into boxes and in an

area sample collected 10 feet from the

foaming operation. The data from this survey

indicated that MDI airborne exposures may

occur in the foaming area during periodic

peak episodes, and that the concentration

decreased to non-detectable levels beyond

the foaming area, at a distance greater
18 Hazard Evaluations and Technical Assistance Branch

than 10 feet from the source. None of the

concentrations were near the NIOSH CL of

200 μg/m3

. Surface wipe tests, conducted

immediately after the foam-in-bag system

was used, did not identify measurable levels of MDI. As long as the plant was following

the corporate written medical surveillance

program, NIOSH investigators concluded

that an immediate health hazard for persons performing polyurethane foam packaging did not exist at the time of the survey. Recommendations were made for the

use of PPE to prevent dermal exposures,

and for the establishment of an isocyanate

work zone in which only workers medically

cleared to work with isocyanates should be

permitted. 

*HETA 99ñ0196ñ2860

August 2001

Requester: Management

Method(s): Proposed NIOSH 5525 (currently

in review)43

Range of isocyanates: 5.1 μg/m3 and

10.7 μg/m3 HDI; <1.6 μg/m3 HDI-based

polyisocyanate

Purpose: To evaluate potential exposures to

isocyanate containing paints and

polyurethane packing foam, and cleaning

solvents during cleaning, repairing, and

reassembling aircraft parts

Keywords: SIC 3721 (Aircraft and Parts),

solvents, naphtha, isocyanates, headache,

irritation,polyurethane packing foam,

ventilation

________

*also included in surface coating processes

Abstract: NIOSH evaluated a plant that

provided repair and service operations

for the airline industry. Health problems

identified in the request included headaches

and eye irritation, and potential exposures

included emissions from isocyanate

containing paints and polyurethane

packing foam, and cleaning solvents during

cleaning, repairing, and reassembling aircraft parts. An initial site visit involved an

inspection of the facility, observation of

work practices and chemical handling

activities, and monitoring petroleum solvent

exposures, all of which were below the

applicable NIOSH RELs on the day of

monitoring. 

Then, a follow-up site visit was conducted

to measure exposure to isocyanate-containing

compounds during the spray-painting and

foam packaging operations. Two PBZ

exposure measurements were collected

from the painter. No HDI monomer was

detected, and the HDI-based polyisocyanate

exposures were 10.7 μg/m3 and 5.1 μg/m3

.

HDI was detected in only one of the seven

area air samples collected during spraypainting; a concentration of 0.4 μg/m3 was

found at the curing oven doors. Also, HDIbased polyisocyanate concentrations were

below the MDC of 1.6 μg/m3 in the area air

samples. 

Foam packaging occurred three times

during the second site visit. A 10-minute

PBZ exposure measurement was collected

each time the foam system was used. The

foamer’s MDI exposures were 3.5 μg/m3

,

5.2 μg/m3, and ND (< 2.6 μg/m3). MDI-based

polyisocyanate was not detected in any

sample. Peak exposure was assessed by

sampling only when MDI was being dispensed. These sampling times included

short samples during each of the three

packaging jobs, and a 1-minute period that

began when the gun malfunctioned and a

small volume of MDI spilled into a box.

The results of this sample indicated an

average peak exposure of 7.5 μg/m3

.

These exposure concentrations are all

well below the NIOSH REL of 200 μg/m3

as a 10-minute CL. Neither MDI nor MDIbased polyisocyanates were detected at

any of four GA sampling locations near the

foam packaging station.

All measured exposures were below

applicable NIOSH limits, but several

recommendations were provided for

improved PPE use (glove use, eye protection,

respiratory protection program, hearing

conservation program). Also, minimizing

skin contact with the polyurethane foam

used in the shipping and receiving department was encouraged, and management
was reminded that engineering controls

(e.g., containment, ventilation) or work

practice changes (eliminating use of compressed air, depressurization, etc.) should

be a first consideration to reduce the potential for exposure. 

Foundry Applications

HETA 98ñ0237ñ2872

April 2002

Requester: Employee

Method(s): Proposed NIOSH 5525 (currently

in review)43

Range of isocyanates: ND to 0.25 μg/m3

MDI

Purpose: To evaluate MDI exposures and

respiratory symptoms in the Pepset and

No-Bake areas, among other concerns, at

an iron foundry

Keywords: SIC 3321 (Gray and Ductile Iron

Foundries), cancer, lung disease, respiratory

irritation, core making, molding, Stoddard

solvent, phenol, ammonia, formaldehyde,

cumene, toluene, trimethylbenzene, MDI,

HMTA

Abstract: NIOSH conducted an HHE at an

iron foundry where workers expressed

concern over exposures to formaldehyde,

phenol, xylene, isocyanates, toluene,

naphthalene, carbon monoxide, trimethyl

benzene, cumene, lead, and silica in the

Pepset, No- Bake, shell core, green sand,

and iron pouring areas; silica and iron dust

in the cleaning room, shell core, green

sand, and machining areas; oil mist from

hydraulic tanks; and asbestos from the

concrete plant floors. The HHE request

listed respiratory symptoms and possibly

increased cancer rates as health concerns.

On March 31-April 1, 1999, NIOSH investigators conducted a walk-through survey,

reviewed MSDSs and environmental sampling

data, and interviewed 22 workers about the

work environment and possible work-related

health effects. Employer records were

examined to determine the number of

cancer cases among workers. On August 8

to 9, 2000, environmental monitoring was

conducted for phenol, volatile organic

compounds, Stoddard solvent, formaldehyde, toluene, cumene, ammonia, trimethyl

benzene isomers, MDI, and HMTA. The five

MDI samples collected in the Pepset and NoBake areas ranged from ND to 0.25 μg/m3

,

below occupational exposure limits.

Twenty-one (4.4% of the 475 production

workers) were interviewed. Among those

interviewed, most workers who had prolonged exposure to emissions from the

Pepset and No-Bake coremaking/molding

operations reported transient respiratory

irritation. The workers who worked in these

areas on a regular basis generally did not

report persistent respiratory illnesses that

they associated with their workplace

exposures. Review of the medical records

of six workers who reported work-related

respiratory illnesses found that some

workers had worsening of pre-existing

chronic respiratory conditions, although the

cause of this was not determined.

Information concerning cancer diagnosed

among workers did not reveal an unusual

number or pattern of cancers, and it was

not possible to determine the cause of the

cancers that developed among the workers.

Recommendations were provided for

additional monitoring for MDI, formaldehyde,

and phenol; use of gloves, reporting of

health symptoms to medical personnel;

and adding LEV in the shell core area.

Hazard Evaluations and Technical Assistance Branch 19
20 Hazard Evaluations and Technical Assistance Branch

Molding

HETA 89ñ0198ñ2133

September 1991

Requester: Union

Method(s): NIOSH 5521

Range of isocyanates: <1.1 to 9.8 μg/m3

MDI monomer, 2.0 to 12.2 μg/m3 MDI polymer, ND to 253.6 μg/m3 NDI

Purpose: To characterize exposures to 

NDI, MDI, and possible isocyanate-related

respiratory problems

Keywords: SIC 3089 (Plastic Products, not

elsewhere classified), isocyanate-related

asthma, cumulative trauma disorder, carpal

tunnel syndrome, thoracic outlet syndrome,

MDI, NDI, 2-methoxyethanol

Abstract: NIOSH conducted this HHE to

characterize exposures to NDI, MDI, and

possible isocyanate-related respiratory

problems. Site visits were conducted, and

respiratory questionnaires were administered to the workers. NIOSH investigators

performed pulmonary function tests and

conducted an exposure assessment to

determine the workers’ exposures to MDI

and NDI. In addition, the NIOSH investigators reviewed employee medical records

and the OSHA 200 Logs from 1985 to

1989 and conducted a telephone survey

of selected workers. The average MDI

concentration measured by this sampling

was 3.9 μg/m3

, with concentrations ranging

from less than 1.1 μg/m3 to 9.8 μg/m3.

The average polyisocyanate concentration

was 5.6 μg/m3

, with a range from 2.0 to

12.2 μg/m3. Three samples for NDI were

ND, three had detectable concentrations

but were below the NIOSH REL of 40 μg/m3,

and one sample was 253.6 μg/m3. This high

sample was collected within a laboratorytype hood that was used as the mixing

station. Smoke tube tests indicated that the

hood effectively removed the contaminants

from the workers weighing out NDI. About

half (7) of the workers previously evaluated

for respiratory symptoms had evidence

suggestive of NDI-related asthma. Just

under half of the workers at the facility who

participated in the NIOSH survey reported

respiratory symptoms consistent with

occupational asthma. On the basis of the

data collected during this investigation,

NIOSH investigators concluded that a

potential health hazard existed from MDI

exposure to workers filling the molds and

from hot molds exiting the oven. The

medical findings further indicate that an

isocyanate-related occupational asthma

hazard existed at the facility between 1987

and 1988 and that some workers continue

to be affected. Investigators provided the

standard isocyanate recommendations.

HETA 91ñ0094

March 1994

Requester: Management

Method(s): NIOSH 2535 initially, then

NIOSH 5522 during 1994 followup

Range of isocyanates: ND for TDI monomer;

ND to 37 μg/m3 TDI oligomer

Purpose: To evaluate TDI and other exposures during the manufacture of

polyurethane timing belts for copying

machines

Keywords: SIC 2296 (Textile Mill), MDA,

TDI, DOP

Abstract: NIOSH conducted this HHE to

evaluate TDI and other exposures during

the manufacture of polyurethane timing

belts by an injection molding process.

Initial sampling was performed in April 1991,

but because of problems analyzing diisocyanate oligomers at that time, further

sampling was delayed until January 1994,

subsequent to development of a new analytical method (NIOSH 5522). The 1994 GA

air sampling did not detect any TDI

monomer (<0.3 μg/m3) but measured an

average of 19 μg/m3 TDI oligomer (range

ND to 37 μg/m3

). The highest concentrations were near the main mixing area and

the table-top mixing area. However, the GA

samples probably overestimated worker

exposures since workers spent limited time

at these areas. Recommendations were

made to add LEV to the mixing areas, and

the general isocyanate recommendations

were also provided.
Hazard Evaluations and Technical Assistance Branch 21

HETA 93ñ0885

December 1993

Requester: Government

Method(s): NIOSH 5521 and 5522 (under

development)

Range of isocyanates: ND to 200 μg/m3 MDI

Purpose: To evaluate potential occupational

health problems from exposure to MDI

during hot tub manufacture

Keywords: SIC 3088 (Plastics Plumbing

Fixtures) hot tub, isocyanates, MDI, air

sampling

Abstract: NIOSH conducted this HHE at a

hot tub manufacturing company to evaluate

potential occupational health problems

from exposure to MDI. Most of the air

concentrations were near the NIOSH REL of

50 μg/m3 but only as a TWA for 30 to 45

minutes. When averaged over 10 hours, the

effective TWA is well below the REL. One of

the air samples was equal to the NIOSH,

OSHA, and ACGIH CL of 200 μg/m3.

Investigators provided the standard isocyanate recommendations, as well as one

for posting signs that warn of the danger of

exposure to diisocyanates at the entrance

to the spray area.

HETA 94ñ0072ñ2648

August 1997

Requester: Union

Method(s): NIOSH 5522

Range of isocyanates: ND

Purpose: To determine isocyanate exposures

during a liquid composite molding process,

as well as other exposures in other areas of

the facility

Keywords: SIC 3061(Molded, extruded,

lathe cut Mechanical rubber goods) rubber,

rubber vehicle sealing, sheet molding

compound, liquid composite molding,

nitrosamines, nitrosodimethylamine, NDMA,

nitrosopiperidine, NPIP, nitrosomorpholine,

NMOR, nitosodiethylamine, NDEA,

nitosodibutylamine, NDBA, nitrosodipropylamine, NDPA, nitrosopyrrolidine, NPYR,

DNA Adducts, N7 methyldeoxyguanosine, 

O6 methyldeoxyguanosine, O6 alkylguanineDNA alkyltransferase, AGT, VOCs, isocyanates, MDI

Abstract: NIOSH conducted this HHE to

determine health hazards in a facility that

manufactured automotive parts, including

rubber vehicle sealing, sheet molding compound, and liquid composite bumper

beams. During the liquid composite molding process, a two-component polyurethane

coating system was injected into the mold. 

Component A was MDI monomer and

polyisocyanate, and component B was a

polyol/glycol blend. GA samples did not

detect any measurable MDI, and it was

concluded that the LEV was effectively

controlling emissions. 
22 Hazard Evaluations and Technical Assistance Branch

HETA 97ñ0138ñ2677

February 1998

Requester: Management

Method(s): NIOSH 5522

Range of isocyanates: ND to 130 μg/m3

MDI; ND to 320 μg/m3 MDI oligomer

Purpose: To identify and control headache

and nausea-causing chemicals during pours

of bronze castings

Keywords: SIC 3366 (Castings, except

die-castings: brass, bronze, copper, and

copper-base alloy), foundry, phenol, MDI

Abstract: NIOSH conducted an HHE at this

bronze-casting facility to help identify and

control headache and nausea-causing

chemicals during pours of bronze castings.

The company identified the sand mold resin

bonding system as the suspected source of

the irritating chemicals. Air sampling was

conducted for MDI and other suspected

exposures, including aldehydes, phenol,

and VOCs. Only one MDI sample was

above the analytical LOD (3 μg/sample).

The airborne concentration measured by that

sample was 130 μg/m3 over a 32-minute

period, which is below the NIOSH REL as

a ceiling of 200 μg/m3. One oligomer sample

was detectable and equated to an air

concentration of 320 μg/m3 for a 19-minute

sample. Recommendations for exhaust

ventilation and PPE were provided to

reduce exposures to other chemicals at

the work site.

Surface Coating

HETA 89ñ0010

January 1990

Requester: Management

Method(s): NIOSH 5521 with modifications

Range of isocyanates: 4.9 to 113.9 μg/m3 TDI

Purpose: To investigate potential exposure

to isocyanates in floor coatings

Keywords: SIC 1752 (Floor Laying and

Other Floor Work, not elsewhere classified),

isocyanates, formaldehyde, wood dust

Abstract: NIOSH was requested to conduct

an HHE to evaluate exposures during floor

refinishing operations. NIOSH conducted air

sampling for isocyanates during floor

refinishing operations that used a urethane

finish. PBZ concentrations of TDI ranged

from 4.9 μg/m3 to 113.9 μg/m3. GA samples ranged from 14.2 to 85.4 μg/m3.

NIOSH investigators provided the standard

isocyanate recommendations, as well as

recommendations to reduce other exposures

HETA 89ñ0071

May 1990

Requester: Employee

Method(s): NIOSH 5521

Range of isocyanates: ND for MDI monomer,

semi-quantitative results of ND to 55 μg/m3

MDI equivalents (prepolymers)

Purpose: To evaluate exposures to isocyanates and VOCs potentially released

when removing and applying an encapsulant

used to protect telephone cable splices

Keywords: SIC 1731 (Electrical Work)

diisocyanates, VOCs, polyurethane

encapsulants

Abstract: NIOSH conducted this HHE to

evaluate exposures to isocyanates and

VOCs potentially released when removing

and applying an encapsulant used to

protect telephone cable splices. Workers

reported symptoms of raspy voice, shortness

of breath, and headaches. NIOSH had
Hazard Evaluations and Technical Assistance Branch 23

conducted two previous HHEs related to

polyurethane encapsulants in underground

cable vaults and had not documented any

isocyanate exposures. Similarly, no MDI was

detected during this survey. However, the

laboratory provided semi-quantitative

results for MDI oligomers, reported as the

equivalent amount of MDI monomer that

could supply the same concentration of

reactive isocyanate groups. These concentrations ranged from ND to 55 μg/m3 MDI

equivalents. Investigators hypothesized that

the residual MDI monomer in the encapsulant

activator is not released because it quickly

reacts with the polyol during mixing.

Recommendations were made for respiratory

protection for individuals who experience

irritation and for hazard communication.

HETA 89ñ0276ñ2093

January 1991

Requester: Union

Method(s): NIOSH 5521

Range of isocyanates: 14 to 34 μg/m3 HDI

Purpose: To evaluate exposures to epoxy and

polyurethane paints being sprayed in open

areas on an aircraft assembly line

Keywords: SIC 3721 (Aircraft Manufacture)

paint, solvents, organic vapor, trace metals,

HDI, isocyanates

Abstract: NIOSH conducted this HHE to

evaluate exposures to epoxy and

polyurethane paints being sprayed in open

areas on an aircraft assembly line. Some

of the assembly line workers had reported

breathing difficulties and respiratory problems. Sampling for HDI monomer and

oligomers detected concentrations of 14 to

34 μg/m3, just above the analytical LOD

Investigators concluded that there was a

minimal risk of HDI exposure to nonpainters

but did recommend that open spraying practices be limited to times when the building

is mostly unoccupied or that spraying operations be controlled by LEV. They also provided standard isocyanate recommendations.

HETA 90ñ0368ñ2137

September 1991

Requester: Management

Method(s): NIOSH 5521

Range of isocyanates: ND for HDI monomer,

<3.6 to 162.6 μg/m3 HDI oligomer

Purpose: To investigate possible employee

exposures to paint solvents and aerosols

Keywords: SIC 3714 (Motor Vehicle Parts

and Accessories), axle housings and

shafts, HDI, isocyanates, diisocyanates,

MIK, MEK, xylene, chromium, cobalt,

polyurethane paint, epoxy paint

Abstract: NIOSH conducted this HHE in the

axle painting area of this motor vehicle

parts manufacturing facility to investigate

possible employee exposures to paint

solvents and aerosols. Full-shift PBZ

monitoring for solvent vapors and GA air

monitoring for metals and diisocyanates

were conducted throughout the axle painting

line. The paint booth systems were

observed, employee interviews were

conducted, and health symptom questionnaires were distributed to the affected

workers. Area sampling for HDI showed

concentrations above the NIOSH REL TWA

criteria of 35 μg/m3 in the paint kitchen,

near the hook touch-up painter (who used a

spray bottle), behind a paint robot, and at

the exit to a touch-up booth. One measurement behind the paint robot (162.6 μg/m3

HDI oligomer) was above the NIOSH STEL

of 140 μg/m3. Respirators were not being

used in these areas. Because of a problem

with high field blank values, a photodiode

array ultraviolet detector was used to

corroborate HDI oligomer data. Ten workers

were either interviewed or completed

questionnaires regarding possible health

symptoms in the axle painting area. Several

of the workers reported sinus and respiratory

symptoms, dizziness, and drowsiness. Of

the four workers who reported sinus or

respiratory problems, three indicated that

they had allergies or often had sinus

problems when not at the plant. One

employee reported headaches while at

work, and one reported occasionally feeling
“flush to the face.” This investigation

identified a potential health hazard from

exposure to HDI in specific areas of the

axle painting area. Investigators provided

standard isocyanate recommendations and

ones for improving engineering controls and

work practices.

HETA 93ñ0842

February 1995

Requester: Employee

Method(s): NA

Range of isocyanates: NA

Purpose: To investigate the occurrence of

occupational asthma in workers exposed to

diisocyanates during the spray painting of

vehicles

Keywords: SIC 4911 (Electric Services),

electric utilities, vehicle repair, diisocyanates,

styrene, liver function tests, HDI

Abstract: NIOSH conducted this HHE to

investigate the occurrence of occupational

asthma in workers exposed to diisocyanates

during the spray painting of vehicles. An

initial medical investigation resulted in the

following recommendations: that workers

potentially exposed to diisocyanates should

receive annual medical examinations

(including spirometry); that workers handling

liquid chemicals wear gloves, protective

clothing, and safety goggles; and that all

workers receive hazardous communication

training. A follow-up survey by an industrial

hygienist was conducted to observe the

spray-painting operations. On the basis of

the observations made during the NIOSH

site visit and the existing data in the

scientific literature on these exposures and

processes, the NIOSH investigators did not

believe that any further evaluation was

necessary. The combination of the sidedraft painting booth, supplied-air respiratory

protection, and PPE were deemed adequate

measures for protecting workers from

hazardous exposure to the diisocyanates

(HDI monomer and prepolymers) and other

chemicals found in the paints. The NIOSH

investigators recommended that the mixing

of the polyurethane paint be moved from

the work bench to the side-draft painting

booth to control any diisocyanate vapors

that could emanate during this task and to

prevent secondary exposure to nearby

workers.

HETA 95ñ0065

August 1995

Requester: Union

Method(s): OSHA 42 by an independent

consultant prior to the HHE

Range of isocyanates: 0.05 to 0.2 μg/m3 MDI

Purpose: To determine whether employee

health problems could be related to a

floor-tile encapsulation process

Keywords: SIC 4311 (Postal Service),

isocyanates, diisocyanates, MDI, respiratory

disease

Abstract: NIOSH conducted this HHE to

investigate employee complaints of health

problems (respiratory problems, abdominal

pains, vomiting, heart attacks, skin rashes

and hair loss) possibly related to chemical

encapsulation of floor-tile the prior year.

NIOSH reviewed background information

about the health complaints and the

chemicals used in the encapsulation

process. Prior to the HHE, an independent

consultant conducted air monitoring near

the encapsulation area to estimate exposures

to monomeric MDI. Area air concentrations

ranged from 0.05 to 0.2 μg/m3

, expressed

as 8-hour TWAs. The NIOSH REL is 50 μg/m3

as a 10-hour TWA and 200 μg/m3 as a CL.

A review of the data by NIOSH investigators

revealed that the sampling was performed

on a day when a sealer that did not contain

MDI was being used. Investigators also

pointed out that the OSHA 42 method can

underestimate MDI monomer exposures

and does not measure oligomeric MDI or

phenyl isocyanate, which were also present

in the encapsulants. NIOSH investigators

concluded that during the encapsulation

project, exposures to monomeric and

oligomeric isocyanates could potentially

have caused chemical induced mucosal

irritation and or respiratory symptoms

among some workers. 

24 Hazard Evaluations and Technical Assistance Branch
Hazard Evaluations and Technical Assistance Branch 25

HETA 95ñ0311ñ2593

August 1996

Requester: Management

Method(s): NIOSH 5522.1

Range of isocyanates: ND for HDI monomer,

ND to 482 μg/m3 for HDI oligomer

Purpose: To assess worker exposures to

isocyanates during spray painting of automobiles

Keywords: SIC 7532 (Top, Body, and

Upholstery Repair Shops and Paint Shops),

isocyanates, solvents, total dust, carbon

monoxide, noise, respirators, HDI

Abstract: NIOSH conducted an HHE at this

autobody repair shop to help assess worker

exposure to isocyanates during spray painting of automobiles. Two site visits were

conducted several months apart to assess

effects of seasonal variation. Activities in

the repair shop included fume straightening, panel repair/replacement body filling,

and final painting and detailing. Workers

used isocyanate-catalyzed paints composed

of a base coat, a reducer, and a hardener.

The paints contained HDI polymer and very

small amounts of the monomer (<0.006%).

Some of the hardeners also contained IPDI

polymer and monomer. PBZ (collected by

attaching the impingers to workers’ belts)

and GA airborne levels of isocyanate (HDI

only) monomer and oligomers were measured. All of the oligomer and most of the

monomer samples collected during the first

visit were below the analytical LOD of 2 μg

per sample. One area sample collected

within the spray booth found a trace

amount of the oligomer. One personal

sample collected on the head painter at

the end of the day when he was applying

clear coat paint measured 99 μg/m3

,

which is above the NIOSH REL of 35 μg/m3

for an 8-hour TWA but below the 140 μg/m3

ceiling REL. The head painter’s TWA for the

day was 29 μg/m3

. The samples from the

second visit showed all monomer exposures

as below the analytical LOD; most oligomer

samples had detectable results. These

ranged from 83 to 482 μg/m3

. Although

isocyanate exposures were below the

various evaluation criteria, NIOSH recommends air-supplied respirators whenever

there is the potential for exposure to

isocyanates, and thus, all the standard

isocyanate recommendations were provided.

HETA 95ñ0405ñ2600

September 1996

Requester: Management

Method(s): NIOSH 5522

Range of isocyanates: ND to 750 μg/m3 HDI

monomer, ND to 667 μg/m3 HDI oligomer

Purpose: To assess worker exposure to

isocyanates during spray painting of

automobiles

Keywords: SIC 7532 (Top, Body, and

Upholstery Repair Shops and Paint Shops),

isocyanates, solvents, total dust, carbon

monoxide, noise, respirators, HDI

Abstract: NIOSH conducted an HHE at this

autobody repair shop to help assess worker

exposure to isocyanates during spray

painting of automobiles. Two site visits

were conducted several months apart to

assess effects of seasonal variation.

Activities in the shop included frame

straightening panel repair/replacement,

body filling, painting, and detailing. Workers

used isocyanate-catalyzed paints containing

HDI polymer and very small amounts of the

monomer (>0.006%). Some of the hardeners

also contained isophorone diisocyanate

polymer and monomer. PBZ (collected by

attaching the impingers to workers’ belts)

and GA airborne concentrations of isocyanate (HDI only) monomer and oligomers

were measured. All but one of the

monomer samples collected in both time

periods were below the analytical LOD of

2 μg per sample. One personal sample for

HDI monomer collected was 750 μg/m3 for

an 8-minute sample, which is in excess of

the NIOSH ceiling REL of 140 μg/m3. The

oligomer samples from both time periods

ranged from below the LOD (2 μg per

sample) to 667 μg/m3 (TWA concentrations for the two painters ranged from

38 to 65 μg/m3). The TWA concentrations

were below the industry recommended
TWA of 500 μg/m3

. Although isocyanate

exposures were below the various evaluation

criteria, NIOSH recommends air-supplied

respirators whenever there is the potential

for exposure to isocyanates, and thus, all

the standard isocyanate recommendations

were provided.

HETA 95ñ0406ñ2609

October 1996

Requester: Management

Method(s): NIOSH 5522

Range of isocyanates: ND to 40 μg/m3 HDI

monomer, ND to >500 μg/m3 HDI oligomer

Purpose: To assess worker exposure to

isocyanates during spray painting of

automobiles

Keywords: SIC 7532 (Top, Body, and

Upholstery Repair Shops and Paint Shops),

isocyanates, solvents, total dust, carbon

monoxide, noise, respirators, HDI

Abstract: NIOSH conducted this HHE to

assess worker exposure to isocyanates

and other hazards during spray painting

of automobiles. Two site visits were conducted

several months apart to assess effects of

seasonal variation. Measurements included

PBZ (collected by attaching the impingers

to workers’ belts) and GA airborne levels

of HDI monomer and oligomers. All HDI

monomer samples were below the analytical limit of detection (3 to 5 μg/sample),

except one. This was an area sample at

40 μg/m3

, collected in the paint booth

for 4 hours. The 8-hour TWA exposure in

the booth was below the NIOSH REL of

35 μg/m3. The oligomer samples from

the first visit ranged from below the LOD

(3 μg/sample) up to 261 μg/m3. PBZ

oligomer samples collected during the

second visit were higher, often, if briefly,

exceeding the industry recommendation

of 500 μg/m3. However, when time-weighed

over the full shift, all exposures were

below 500 μg/m3. Although HDI monomer

exposures were below the various evaluation

criteria, NIOSH recommends air-supplied

respirators whenever there is the potential

for exposure to isocyanates, and thus all

the standard isocyanate recommendations

were provided.

HETA 96-0266-2702

August 1998

Requester: Management

Method(s): NIOSH 5522

Range of isocyanates: <1.6 μg/m3 (below

the MDC)

Purpose: To evaluate workers’ exposure to

isocyanates from a two-component, waterbased polyurethane paint

Keywords: SIC 3061 (Molded, Extruded,

and Lathe-Cut Mechanical Rubber Goods),

vehicle sealing, automotive/truck rubber

seals, water-based polyurethane paint, polyfunctional aziridine, N-methyl pyrrolidone,

isocyanates, skin patch testing, allergic

contact dermatitis

Abstract: NIOSH conducted this HHE to

evaluate workers’ exposure from a twocomponent, water-based polyurethane

paint (water-based polyurethane paint

with polytetrafluoroethylene and a polyfunctional aziridine cross-linker) that was

applied to automotive truck rubber seals

(vehicle sealing) on the dual durometer

extrusion lines. Health effects described

in the request included skin and upper

respiratory problems. NIOSH investigators

conducted a site visit during which they

administered a questionnaire, performed

skin patch testing, and collected air samples

for nitrosamines, VOCs, and isocyanates

at various locations on the extrusion

lines. All isocyanate concentrations were

below the MDC of 1.6 μg/m3. Although

isocyanate exposures were below NIOSH

REL, recommendations were provided to

reduce exposure to other workplace hazards.

26 Hazard Evaluations and Technical Assistance Branch
*HETA 97ñ0084ñ2669

December 1997

Requester: Management

Method(s): NIOSH 5522

Range of isocyanates: Spray painting—

5.1 to 9.6 μg/m3 2,4-TDI monomer, 7.4 to

17.9 μg-NCO/m3 TRIGs, ND 2,6-TDI

monomer; packaging—ND MDI monmer, ND to 15.5 μg/m3 MDI oligomer,

<9.8 μg-NCO/m3 TRIGs

Purpose: To document worker exposure to

isocyanates during spray painting and packaging processes

Keywords: SIC 3519 (Internal Combustion

Engines, not elsewhere classified), noise,

isocyanates, metal working fluids, TDI

and MDI, TRIG, toluene, xylene, formaldehyde, inorganic acids, ammonia, lead

__________

*also included in surface coating processes

Abstract: NIOSH conducted this HHE to

document worker exposure to isocyanates

during spray painting and packaging of

engine control devices. Monitoring for TDI

and MDI monomers and oligomers and

TRIGs was conducted. Area air sampling

results for TDI during spray painting

operations ranged from 5.1 to 9.6 for

2,4-TDI monomer, and from 7.4 to

17.9 μg NCO/m3 for TRIGs. No 2,6-TDI

monomer was detected. These data indicate

that area isocyanate levels are low for

spray painting operations, especially when

compared to the ACGIH TLV for TDI (8-hour

TWA of 36 μg/m3

) and the UK-HSE standard

for TRIG (8-hour TWA 20 μg NCO/m3

). The low

levels indicated that the spray booth was

effectively containing the isocyanates. Area

air samples collected for MDI during

packaging operations did not detect

MDI monomer but detected oligomer

concentrations ranging from ND to

15.5 μg/m3. The TRIG concentrations were 

all below 9.8 μg NCO/m3

. Although MDI

concentrations were low, the design of the

local exhaust systems for the packaging

needed improvements. NIOSH provided the

standard isocyanate recommendations.

HETA 97ñ0157

October 1997

Requester: Employee originally, but then a

TA to the U.S. Coast Guard

Method(s): OSHA 42, performed by a

consultant prior to the HHE

Range of isocyanates: ND (HDI)

Purpose: To characterize employee health

effects, including throat pain, coughing at

night, chest tightness and gastrointestinal

problems, from isocyanate-containing

paints used to paint barges

Keywords: SIC 4449 (Water Transport of

Freight), HDI

Abstract: NIOSH provided TA to the U.S.

Coast Guard to characterize employee

health effects from isocyanate-containing

paints used to paint barges. Workers at the

site complained of throat pain, coughing at

night, chest tightness, and gastrointestinal

problems possibly associated with isocyanate painting operations. Investigators

reviewed painting procedures, products,

PPE, and hazard communication and medical

management policies. In addition, investigators reviewed employee medical records

and interviewed workers. It was apparent

that the company had enacted policies in

an effort to reduce worker paint exposures,

such as the implementation of PPE, the

restriction of spray painting, and education

in health hazards. Air monitoring done

previous to the HHE by an independent

consultant did not detect any HDI, but the

method used was OSHA 42 and a real-time

monitor that are only for HDI monomers,

not the HDI polyisocyantes in the barge paints.

The Coast Guard closed the investigation

with the standard isocyanate recommendations, which would have been necessary

with or without additional air sampling. 

Hazard Evaluations and Technical Assistance Branch 27
HETA 97ñ0226

December 1998

Requester: Employee

Method(s): NIOSH 5522

Range of isocyanates: ND (MDI)

Purpose: To investigate the occurrence of

isocyanate-induced asthma in an employee

and to evaluate potential exposures to

solvent-containing and dust-producing

materials in a woodworking facility

Keywords: SIC 3999 (Manufacturing

Industries, not elsewhere classified), manufacturing, asthma HP, isocyanate,

polyurethane, solvents, dust

Abstract: NIOSH conducted an HHE at this

woodworking facility to investigate the

occurrence of isocyanate-induced asthma in

an employee and to evaluate potential

exposures to solvent-containing and dustproducing materials. Investigators conducted

a site visit, met with management and

employee representatives, and reviewed

medical records of the symptomatic

employee. PBZ and area air samples were

taken for isocyanates, solvents, and dust.

While the symptomatic worker was shown

to have airflow obstruction and a clinical

picture suggestive of isocyanate-related

asthma, of additional concern was the

abnormality in diffusing capacity test results

implying a disorder other than asthma. In

situations involving exposure to isocyanates, these results could represent

interstitial lung disease or HP. Air sampling

did not indicate overexposure to any of the

air contaminants measured. It should be

noted that there have been cases of isocyanate sensitization where sampling

measured only minimal concentrations. The

standard isocyanate exposure recommendations were provided as well as these

specific ones: parts to be sprayed in the

spray room should be positioned to avoid

overspray that can cause vapor to travel

toward the worker’s breathing zone; the

resin casting bench should be repositioned

in the room to avoid this same problem for

the casting worker as well as the spraying

worker (since he is downstream of the casting

operation), and the addition of LEV should

be considered for the task of sanding

wooden mounts.

HETA 98ñ0073

March 2000

Requester: Union

Method(s): None reported (reviewed

company sampling results)

Range of isocyanates: <1.4 μg/m3 to

.062 μg/m3 HDI

Purpose: To evaluate, among other things,

the exposure to HDI during the manufacture

of tape with an acrylate and polyurethane

coating

Keywords: SIC 3083 (Laminated Plastic

Plate Sheet, and Profile Shapes), tape, laminated tape, dimethyl acrylamide, hexandiol,

diacrylate, isooctyl acrylate, HDI, isocyanates, dermatitis, respiratory symptoms

Abstract: At the request of the local union,

NIOSH conducted a walk-through survey

and reviewed IH sampling results and medical records at a plant that produced various tapes. The union said that workers

were experiencing respiratory, dermal, and

nervous system health effects that might

be related to the various cleaners, adhesives, and tape coatings used in the tape

making departments. The HDI exposures

(<1.4 μg/m3 to 0.62 μg/m3

) were only on

one line and were well below the NIOSH

REL of 35 μg/m3. No sampling was done for

HDI-based polyisocyante. Most other sampling results from the department were low,

except for an overexposure to dimethyl

acrylamide in the Mill/Mix area from

improper use of the LEV. The lower respiratory symptoms and skin irritation were

consistent with exposure to many of the

chemicals in the department, including HDI.

Employee and company nurse interviews,

as well as review of medical records, indicated that workers who had experienced

potentially work-related health effects were

being appropriately referred for medical follow-up. Also, workers diagnosed with workrelated symptoms by the occupational medicine consultant were appropriately

28 Hazard Evaluations and Technical Assistance Branch
reassigned. Skin protection was inadequate

in some cases, most importantly with one

employee handling the isocyanate solution.

Many of the chemicals in the department

could cause dermal sensitization, but investigators pointed out that dermal contact

with isocyanates has been shown to cause

respiratory sensitization in animals, further

emphasizing the need for adequate skin

protection. Recommendations were provided

for continued development and appropriate

use of engineering controls, use of appropriate PPE, proper hygiene practices,

improved hazard education, medical surveillance, and further IH monitoring, especially for HDI-based polyisocyanate.

HETA 98ñ0347ñ2758

November 1999

Requester: Joint employee and management

Method(s): NA

Range of isocyanates: NA

Purpose: To investigate office workers’

exposures to diisocyanate-containing

paints, primers, solvents, and cured and

uncured composite materials used during

the manufacture of fighter jets in the production area below the office

Keywords: SIC 381 (Search, Detection,

Navigation, Guidance, Aeronautical, and

Nautical Systems, Instruments, and

Equipment) IEQ, IAQ, ventilation, tracer

gas, sulfur hexafluoride, composites, diisocyanate-containing paints, MEK, MIBK, isopropanol, occupational asthma, chemical

sensitization, mucous membrane irritation

Abstract: NIOSH conducted an HHE at a

manufacturer of fighter jets to investigate

office workers’ exposures to diisocyanatecontaining paints, primers, solvents, and

cured and uncured composite materials

used in the production area below the

office. Employee interviews revealed that

approximately 88% of the workers (14/16)

reported symptoms, which included eye,

nose, and throat irritation, cough, wheezing,

shortness of breath, chest pain, headache,

nausea, dizziness, fatigue, numbness /

tingling of the extremities, and skin rashes.

Thirteen of the fourteen symptomatic

workers reported that symptoms diminished

when away from work, and nine of the

thirteen were diagnosed by a pulmonary

specialist with a variety of respiratory

conditions attributable to chemical

exposures in the work place. The symptoms

were consistent with exposures to isocyanates and irritative solvents that were

used in the production area. NIOSH

conducted a tracer gas study to evaluate

the effectiveness of newly implemented

engineering controls and concluded that

the changes had successfully controlled

emissions from the paint spray booth and

core-clean room, but that exposures generated near the AHU in the production area

could potentially reach office workers.

Investigators provided recommendations

to address the IEQ concerns, including

ventilation changes, hazard communication,

and production area/office area/management

communication.

HETA 99ñ0122ñ2798

June 2000

Requester: Management

Method(s): Proposed NIOSH 5525 (currently

in review)43

Range of isocyanates: 300 μg/m3 to

1364 μg/m3 MDI; 304 μg/m3 to 1080 μg/m3

MDI-based polyisocyanate; 1.9 μg/m3 HDI;

164 μg/m3 HDI-based polyisocyanate; and

83 μg-NCO/m3 to 831 μg-NCO/m3 TRIG

Purpose: To evaluate worker exposures to

isocyanate-containing compounds during

spray-painting operations at a plant that

manufactured military aircraft

Keywords: SIC 3721 (Aircraft), spray

painting, polyurethane surface coating,

isocyanates, HDI, MDI, polyisocyanates

Abstract: NIOSH received a management

request to assess worker exposures to

isocyanate-containing compounds during

spray painting operations at a plant that

manufactured military aircraft. On

February 17 to 18, 1999, investigators from

NIOSH conducted a site visit and exposure

assessment for these compounds. Air

Hazard Evaluations and Technical Assistance Branch 29
sampling was conducted during polyurethane

spray painting operations in two paint

booths (219 and L-64). Two different

isocyanate-containing polyurethane paints

were used in these spray painting operations.

Both paints were two-component formulations,

and were identified by the in-house

designations of code 36 and code 46. The

code 36 paint contained 40% by weight

HDI-based polyisocyanate, and less than

0.15% HDI. The code 46 paint contained

40% by weight of MDI, and 50% MDI-based

polyisocyanate. During spray painting, the

painters wore a full-face air-purifying

respirator with combined particulate and

organic vapor cartridges, and a TyvekTM

suit. PBZ and area air sampling were

collected to determine short-term, taskbased exposures and general airborne

concentrations to the isocyanate-containing

compounds found in the paints. All area air

samples were collected using midget

impingers containing 15-ml of MAP in butyl

benzoate, followed by a 37-mm diameter

QFF impregnated with MAP. PBZ air samples

were collected using the MAP-impregnated

QFFs. Filter samples were analyzed by

HPLC with ultraviolet and fluorescence

detection for both the monomer and polyisocyanate components of the paints. The

impinger samples underwent solid-phase

extraction, followed by the same analysis

used for the filter samples. Monomers were

quantified based on comparison of their

fluorescence peak heights to those of

monomer standards. If detected, polyisocyanates/oligomers were quantified

based on the comparison of their ultraviolet

peak areas to those of monomer standards. 

At the time of the NIOSH survey, two

painters were painting parts in booth 219.

The painter on the right side of the booth

used the code 46 paint, the painter on the

left side used the code 36 paint. The MDI

and MDI-based polyisocyanate exposure

concentrations were 300 μg/m3 and

304 μg/m3 for the right side (code 46)

painter, respectively. For the left side

(code 36) painter, the HDI and HDI-based

polyisocyanate exposures were 1.9 μg/m3

and 164 μg/m3, respectively. Only one

painter worked in the L-64 booth. This

painter used the code 46 paint, and the

MDI exposure was 1364 μg/m3 and the

MDI-based polyisocyanate exposure was

1080 μg/m3. In addition, the TRIG exposures

for painters in booth 219 were 206 μg-NCO/m3

and 83 μg-NCO/m3, and the TRIG exposure

for the L-64 painter was 831 μg-NCO/m3.

Finally, significant airborne concentrations

of the various isocyanate-containing

compounds were found by the area air

sampling conducted in both spray-painting

booths. Considering the MDI, MDI-based

polyisocyanate, HDI-based polyisocyanate,

and TRIG exposure concentrations, the

NIOSH investigators concluded that a health

hazard existed in the spray-painting

booths/operations evaluated during this

study. Recommendations were provided to

increase the level of protection for workers

in the spray-painting operations that

included respiratory protection, protective

clothing, medical surveillance, and IH

surveillance.

*HETA 99ñ0196ñ2860

August 2001

Requester: Management

Method(s): Proposed NIOSH 5525 (currently

in review)43

Range of isocyanates: 5.1 μg/m3 and

10.7 μg/m3 HDI; <1.6 μg/m3 HDI-based

polyisocyanate 

Purpose: To evaluate potential exposures to

isocyanate containing paints and

polyurethane packing foam, and cleaning

solvents during cleaning, repairing, and

reassembling aircraft parts

Keywords: SIC 3721 (Aircraft and Parts),

solvents, naphtha, isocyanates, headache,

irritation,polyurethane packing foam,

ventilation

__________

*also included in foaming processes

Abstract: NIOSH evaluated a plant that

provided repair and service operations for

the airline industry. Health problems

identified in the request included

headaches and eye irritation, and potential

exposures included emissions from iso30 Hazard Evaluations and Technical Assistance Branch
cyanate containing paints and polyurethane

packing foam, and cleaning solvents during

cleaning, repairing, and reassembling aircraft

parts. An initial site visit involved an

inspection of the facility, observation of

work practices and chemical handling

activities, and monitoring petroleum solvent

exposures, all of which were below the

applicable NIOSH RELs on the day of

monitoring. 

Then, a follow-up site visit was conducted

to measure exposure to isocyanate-containing

compounds during the spray-painting and

foam packaging operations. Two PBZ

exposure measurements were collected

from the painter. No HDI monomer was

detected, and the HDI-based polyisocyanate

exposures were 10.7 μg/m3 and 5.1 μg/m3

.

HDI was detected in only one of the seven

area air samples collected during spray

painting; a concentration of 0.4 μg/m3 was

found at the curing oven doors. Also, HDIbased polyisocyanate concentrations were

below the MDC of 1.6 μg/m3 in the area air

samples. 

Foam packaging occurred three times

during the second site visit. A 10-minute

PBZ exposure measurement was collected

each time the foam system was used. The

foamer’s MDI exposures were 3.5 μg/m3

,

5.2 μg/m3, and ND (< 2.6 μg/m3). MDI-based

polyisocyanate was not detected in any

sample. Peak exposure was assessed by

sampling only when MDI was being dispensed. These sampling times included

short samples during each of the three

packaging jobs, and a 1-minute period

that began when the gun malfunctioned

and a small volume of MDI spilled into a

box. The results of this sample indicated

an average peak exposure of 7.5 μg/m3.

These exposure concentrations are all

well below the NIOSH REL of 200 μg/m3 as

a 10-minute CL. Neither MDI nor MDI-based

polyisocyanates were detected at any of

four GA sampling locations near the foam

packaging station. 

All measured exposures were below

applicable NIOSH limits, but several

recommendations were provided for

improved PPE use (glove use, eye protection,

respiratory protection program, hearing

conservation program). Also, minimizing

skin contact with the polyurethane foam

used in the shipping and receiving department was encouraged, and management

was reminded that engineering controls

(e.g., containment, ventilation) or work

practice changes (eliminating use of

compressed air, depressurization, etc.)

should be a first consideration to reduce

the potential for exposure. 

Other

HETA 89ñ083ñ2134

September 1991

Requester: Employee

Method(s): Not reported

Range of isocyanates: ND for MDI, 39 to

53 μg/m3 PPI, ND to trace 2,4 TDI, and ND

for 2,6-TDI

Purpose: To investigate respiratory complaints (including asthma) at a plastics manufacturer

Keywords: SIC 3052 (Rubber and Plastics

Hose and Belting), asthma, peak flow

testing, isocyanates, Radioallergosorbent

tests (RAST), ELISA testing, TDI, PPI

Abstract: NIOSH conducted this HHE to

investigate respiratory complaints (including

asthma) at a plastics manufacturer.

Investigators conducted a respiratory symptom

questionnaire, which was completed by

72% of hourly workers and revealed a high

prevalence of respiratory symptoms.

Environmental sampling was performed to

assess possible exposures to respiratory

irritants or asthma-producing compounds.

The IH survey found trace amounts of

airborne TDI during urethane extrusion and

12 inches from a locally ventilated glue pot. 

In addition, quantifiable amounts of PPI

were identified in the same two areas, as

well as 12 inches from a glue pot without

local ventilation. Subsequent medical

evaluations attempted to determine the

Hazard Evaluations and Technical Assistance Branch 31
32 Hazard Evaluations and Technical Assistance Branch

prevalence of occupational asthma and to

assess the potential relationship between

cases of asthma and exposure to either TDI

or PPI. Peak flow testing was abnormal in

23% of those tested, and markers of

immunologic response to PPI and TDI were

positive in 14% to 45%. Although the

immunologic responses did not prove that

the symptoms were related to these

chemicals, they do indicate that exposure

has occurred and in some individuals may

be the cause of the symptoms. The standard

isocyanate recommendations were provided. 

HETA 89ñ318ñ2273

November 1992

Requester: Union

Method(s): OSHA 47

Range of isocyanates: ND because of

analytical limitations (LODs of 185 and

1230 μg/m3, respectively, for MDI and MDI

polyisocyanate)

Purpose: To evaluate possible health

effects and lack of adequate personal

protection among workers exposed to

MDI in encapsulation systems used to seal

joints in underground gas mains

Keywords: SIC 4932 (Gas and Other

Services Combined), SIC 4931

(Electric and Other Services

Combined), MDI, MDI polyisocyanate

Abstract: NIOSH received a request for an

HHE to evaluate possible health effects

and lack of adequate personal protection

among workers exposed to MDI in encapsulation systems used to seal joints in

underground gas mains. NIOSH investigators

performed medical interviews and PBZ and

GA air sampling at three application sites

where a total of five joints were being

sealed. Air sampling was conducted above

and below road level for MDI and MDI polyisocyanate. One of these sites contained

12 inch mains and the other sites had 6 inch

mains. At each application site, two GA air

samples for MDI and MDI polyisocyanate

were collected, one below road level and

one above road level approximately 3 to

4 feet from the hole. No MDI or MDI polyisocyanate was detected in any of the air

samples collected during the NIOSH

survey. However, the minimum detectable

concentrations of MDI polyisocyanate in

the encapsulation systems were high due

to sampling and analytical limitations

(185 and 1,230 μg/m3

, respectively).

Therefore, workers who enter the holes may

be exposed to hazardous levels of MDI polyisocyanate that were ND due to limitations

in the method used in this survey. Exposure

limits for MDI polyisocyanate have not

been defined by OSHA or NIOSH. Twelve of

21 workers interviewed reported experiencing

eye, nose, and throat irritation when they

used the paint primer. Cramped work

spaces, especially when repairing pipes

below street level, made it difficult to avoid

inhalation and dermal exposure to the

chemicals. No worker interviewed could

confirm that he had been fit tested or properly

trained to wear respiratory protection.

Observations made onsite indicated the

workers had not been trained in the

appropriate procedures for donning

respiratory protective devices. In addition,

the latex gloves provided by the manufacturers

of the encapsulation systems were inadequate

to protect workers from dermal exposure to

the liquid chemicals in these systems. All of

the standard isocyanate recommendations

were provided.

HETA 90ñ0174ñ2231

July 1992

Requester: Management

Method(s): NA

Range of isocyanates: NA

Purpose: To investigate exposures associated

with a powder-coating operation and evaluate

the possibility that workers’ long-term

health problems may be linked to the isocyanates used in some of the powder

coatings

Keywords: SIC 3479 (Coating, Engraving,

and Allied Services, not elsewhere classified),

powder coating, epoxy, polyester, aldehyde,

caprolactam, isocyanate

Abstract: NIOSH conducted this HHE to

investigate exposures associated with a

powder-coating operation and evaluate the
possibility that workers’ long-term health

problems may be linked to the isocyanates

used in some of the powder coatings.

Technical problems with isocyanate sampling

and analytical methodology had made it

impractical to sample for isocyanates in the

work place, and therefore, investigators

could not determine if workers were overexposed to isocyanates. Potentially hazardous

exposures were documented to other

compounds, but a questionnaire survey of

current workers did not reveal any significant

association between current exposures

and current symptoms or diseases.

Recommendations were provided to reduce

or control potential isocyanate and other

hazardous exposures, and to improve the

safety and health conditions in general.

HETA 93ñ0436ñ2569

March 1996

Requester: Employee

Method(s): NIOSH 5522 (when an interim

method)

Range of isocyanates: ND to 81.8 μg/m3

MDI, ND to 181.4 μg/m3 MDI oligomer

(10-minute sample), ND to 54.9 μg/m3 TRIG

(10-minute sample) 

Purpose: To evaluate the occurrence of

occupational asthma, apparently related to

isocyanate exposure

Keywords: SIC 2493 (Reconstituted

Wood Products), oriented strand boards,

MDI, NCO, MDA, aspen, wood dust, lumber,

asthma, HP

Abstract: NIOSH investigators conducted an

HHE at this parallel strand lumber plant to

evaluate the occurrence of occupational

asthma, apparently related to isocyanate

exposure. The company manufactured

lumber products using long strands of

aspen wood bound together with a MDI

resin, and ten workers at the facility had a

physician’s diagnosis of occupational

asthma attributed to MDI exposure. NIOSH

conducted an environmental and medical

survey at the facility. The environmental

survey consisted of area air sampling for

MDI, TRIG, and MDA. During the medical

survey, a health, symptoms, and occupational history questionnaire was administered

to current workers. Two area air samples

had monomeric MDI concentrations that

exceeded the NIOSH REL and ACGIH TLV

for personal exposure of 50 μg/m3

. The

samples were from an area that is primarily

unoccupied but is used for access to the

blenders. The samples also had TRIG

concentrations that exceeded the UK

control limit of 20 μg/m3. At least 18 workers

had developed respiratory illness that met

the NIOSH case definition for occupational

asthma since the plant began production

in October 1991. Although changes in

ventilation took effect in 1993, 9 (50%) of

these 18 cases developed after this change,

and 4 of these cases were in workers who

began their employment after the ventilation

changes were made. On the basis of the

information collected during this evaluation,

NIOSH investigators concluded that a

health hazard existed from exposure to

isocyanates at this facility. Investigators

provided all the standard isocyanate

recommendations. 

HETA 94ñ0134

April 1994

Requester: Government

Method(s): NIOSH 5521, 5522

Range of isocyanates: ND (MDI monomer

and oligomers)

Purpose: To provide assistance to a health

department in measuring MDI at a manufacturer of window shades

Keywords: SIC 2591(Drapery Hardware)

MDI, methylene diisocyanate

Abstract: NIOSH provided TA to a local

health department to measure MDI concentrations at a manufacturer of window

shades. Samples collected using NIOSH

method 5521 were all below the LOD of

0.3 μg/sample. Since methods 5521 and

5522 have similar LODs, the samples

Hazard Evaluations and Technical Assistance Branch 33
34 Hazard Evaluations and Technical Assistance Branch

collected using method 5522 were not

analyzed and assumed to be ND. NIOSH

concluded, based on this sampling, that no

measurable airborne MDI exposures existed

at this facility.

HETA 99ñ0039

April 1999

Requester: Government

Method(s): NA

Range of isocyanates: NA

Purpose: To investigate a reported case

of work-related asthma related to exposure

to isocyanates at a surgical supplies

manufacturer

Keywords: SIC 3842 (Orthopedic,

Prosthetic, and Surgical Appliances

and Supplies), asthma, isocyanates,

MDI, orthopedics, casts, surgical casting

wraps

Abstract: NIOSH conducted an HHE to

investigate a reported case of work-related

asthma and resulting concerns that other

workers were at risk of exposure and disease.

The health department requested information

about the following: chemicals in use;

severity of inhalation exposures; the

potential for dermal absorption; the

adequacy of ventilation, engineering

controls, and work practices used to limit

exposure; the employer’s hazard communication program; and employee training

related to exposures and exposure controls.

NIOSH collected information to answer

these questions, and they found that the

orthopedic casting wraps that the case

and coworkers tested for product

research and development contained

MDI. The employer had extensive programs

and controls in place to protect workers

from exposure to isocyanates. However, the

protective gloves provided by the employer

were not protective against isocyanate

exposure. NIOSH recommended that the

employer choose the most appropriate

type of glove to protect workers from skin

exposure and use glove breakthrough

indicators to detect glove penetration. 

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Hazard Evaluations and Technical Assistance Branch 37