1996 

DHHS (NIOSH) Publication Number 96-111 

Preventing Asthma and Death from Diisocyanate 

Exposure DHHS 

Workers exposed to diisocyanates may develop serious or fatal respiratory 

disease.

The National Institute for Occupational Safety and Health (NIOSH) requests assistance in 

preventing asthma, other respiratory disease, and death from diisocyanate exposure. This Alert

summarizes seven case reports of disease and deaths following occupational exposure to 

diisocyanates. Information about preventing adverse health effects from exposure to 

diisocyanates is urgently needed by workers and employers, small businesses, physicians, and 

other health care providers. 

NIOSH therefore requests that editors of trade journals, safety and health officials, labor union

leaders, employers, educators, and diisocyanate suppliers and manufacturers bring this Alert 

to the attention of all workers at risk. Your assistance will help prevent asthma and other 

respiratory disease in the 280,000 U.S. workers potentially exposed to diisocyanates. 

Background 

Diisocyanates are a group of low-molecular-weight aromatic and aliphatic compounds. The 

most common of these are toluene diisocyanate (TDI), methylene bisphenyl isocyanate (MDI), 

and hexamethylene diisocyanate (HDI). Appendix A lists commonly used synonyms for these 

three diisocyanates. They are widely used in the manufacture of flexible and rigid foams, fibers,

coatings such as paints and varnishes, and elastomers. Diisocyanates are increasingly used in 

the automobile industry, autobody repair, and building insulation materials. In this report, 

diisocyanates as a group will be referred to as isocyanates. 

The world production of isocyanates is estimated to be 3 billion pounds annually [Woods 

1987], and 280,000 U.S. workers are potentially exposed [NIOSH 1983; Dunn and Bradstreet 

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1983]. 

The major route of occupational exposure to isocyanates is inhalation of the vapor or aerosol; 

exposure may also occur through skin contact during the handling of liquid isocyanates. 

Occupational exposure normally occurs during the production and use of isocyanates--

particularly during the mixing and foaming processes in the polyurethane foam industry. 

Exposures to airborne isocyanates may also occur from the melting or burning of polyurethane 

foams during fire fighting. 

Current Exposure Limits 

Occupational exposure standards for isocyanates are based on respiratory irritation and 

sensitization and carcinogenesis. Only the exposure standards for TDI and MDI are outlined 

here. 

OSHA 

The current Occupational Safety and Health Administration (OSHA) permissible exposure 

limit (PEL) for TDI is 0.02 part per million parts of air (0.02 ppm), or 0.14 milligram per cubic 

meter of air (0.14 mg/m3) as a ceiling limit [29 CFR* 1910.1000]. When updating its air 

contaminants standard in 1989, OSHA decreased this limit to 0.005 ppm (0.036 mg/m3) as an

8-hour time-weighted average (TWA) and 0.02 ppm (0.14 mg/m3) as a short-term exposure 

limit. However, this standard was rescinded by court order in 1992. 

The OSHA PEL for MDI is 0.02 ppm (0.2 mg/m3) as a ceiling limit. 

*Code of Federal Regulations. See CFR in references. 

NIOSH 

In two separate criteria documents, NIOSH has recommended that TDI exposure be limited to 

0.005 ppm (0.036 mg/m3) as a TWA for up to a 10-hour workday during a 40-hour workweek,

with a ceiling concentration of 0.02 ppm (0.14 mg/m3) for any 10-minute period [NIOSH 

1973, 1978]. This NIOSH recommended exposure limit (REL) was intended to prevent acute 

and chronic irritation and sensitization of workers but not to prevent responses in workers who

are already sensitized. Available data do not indicate a concentration at which TDI vapor fails 

to produce adverse reactions in sensitized persons. NIOSH further recognized the carcinogenic 

potential of TDI and its isomers and recommended that exposures be reduced to the lowest 

feasible concentrations [NIOSH 1989]. 

The NIOSH REL for MDI is 0.005 ppm (0.05 mg/m3) as a TWA and 0.02 ppm (0.2 mg/m3) as

a ceiling limit. 

ACGIH 

The American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit 

value (TLV) for TDI is 0.005 ppm (0.036 mg/m3) as an 8-hour TWA and 0.02 ppm (0.14 

mg/m3) as a short-term exposure limit. The ACGIH TLV for MDI is 0.005 ppm (0.05 mg/m3) 

as a TWA [ACGIH 1995]. 

Health Effects of Isoyanates 

Irritation 

TDI and other isocyanates are powerful irritants to the mucous membranes of the eyes and 

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gastrointestinal and respiratory tracts [Swensson et al. 1955; Upjohn Company 1970]. Direct 

skin contact with TDI can also cause marked inflammation [Fisher 1967]. Respiratory irritation

may progress to a chemical bronchitis with severe bronchospasm [Williamson 1965]. 

Sensitization and Asthma 

Isocyanates can also sensitize workers, making them subject to severe asthma attacks if they 

are exposed again--even at concentrations below the NIOSH REL [NIOSH 1973, 1978]. Death 

from severe asthma in sensitized subjects has been reported [Fabbri et al. 1988]. 

Hypersensitivity Pneumonitis 

Sporadic cases of hypersensitivity pneumonitis (HP) have also been reported in workers 

exposed to isocyanates [Charles et al. 1976; Fink and Schlueter 1978; Selden et al. 1989]. 

Individuals with acute HP typically develop symptoms 4 to 6 hours after exposure. 

Symptoms are often flu-like, with fever, muscle aches, and headaches. Symptoms may also 

include a dry cough, chest tightness, and difficult breathing. Individuals with chronic HP often 

experience progressively more difficult breathing, fatigue, and weight loss [Parker et al. 1992]. 

Cancer 

Data from recent studies of animals show that cancer is associated with exposure to 

commercial-grade TDI (an 80:20 mixture of 2,4- and 2,6-TDI). The responses of both rats and 

mice treated with TDI meet the OSHA criteria for classifying a substance as a potential 

occupational carcinogen [29 CFR 1990.112]. NIOSH therefore recommends that occupational 

exposure to TDI and its isomers be minimized [NIOSH 1989]. 

The carcinogenic effects of TDI [Loeser 1983; NTP 1986] were also investigated by the 

International Agency for Research on Cancer (IARC) and the World Health Organization 

(WHO) [IARC 1986; WHO 1987]. IARC concluded that data were sufficient to show that TDI 

causes cancer in animals. WHO concluded that TDI should be treated as a potential human 

carcinogen. 

Case Reports 

The following case reports highlight examples of isocyanate-induced asthma, other respiratory 

disease, and death. 

Case No. 1--Spray Painting (One Death)

A 37-year-old male, self-employed car painter was admitted to the hospital with asthma 

symptoms [Fabbri et al. 1988]. These symptoms had first developed 5 years earlier and were 

thought to be related to his occupation. He had been working in the same environment for 

more than 20 years. 

The car painter was diagnosed with occupational asthma induced by isocyanates and advised 

to change his job or avoid the use of polyurethane paints. He nevertheless continued to work as

a car painter and used medications such as bronchodilators, cromolyn, and steroids to treat his

asthma. 

Six years later, he was wearing a mask and spraying a car with 2-component polyurethane 

paint when he developed severe, prolonged asthma. Despite medication, he remained 

symptomatic--especially at night. He returned to work, sprayed the polyurethane paint again, 

and developed severe asthma requiring emergency treatment. He died in the ambulance 

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enroute to the hospital. The manufacturer reported that the paint contained small amounts of

TDI, and a chemical analysis confirmed the presence of TDI mixed with solvents. 

Case No. 2--Highway Spill

Two police officers developed asthma-like illness after a single exposure to TDI in the 

immediate vicinity of a tank car that had overturned on the highway [Luo et al. 1990]. After 

briefly directing traffic at the accident scene, both officers received medical care for severe 

symptoms, including burning eyes, throat irritation, cough, chest tightness, and difficult 

breathing. Treatment included steroids and a bronchodilator. 

Both police officers developed a chronic bronchospastic disorder after their relatively brief 

exposure to high concentrations of TDI. Though considerable improvement has occurred in 

both cases, symptoms have persisted for more than 7 years. 

Case No. 3--Spray Painting

Occupational asthma was reported in three workers in the paint shops of a large assembly 

plant [Seguin et al. 1987]. When coworkers were also examined, six additional workers showed 

symptoms of occupational asthma. 

Of the nine affected workers (males aged 23 to 59), six had significantly reduced lung function 

after an inhalation test using the paint containing isocyanates. The duration of exposure to 

isocyanates in the paint shops ranged from 3 to 5 years. 

The authors of this study reported a 12% prevalence rate for occupational asthma. 

Case No. 4--Isocyanate Foam Operation (One Death)

A maintenance worker became ill after repairing an MDI foaming system at a plant that 

manufactured artificial plants with polyurethane foam bases [NIOSH 1994a]. The worker later 

suffered recurrent bouts of respiratory illness (diagnosed as isocyanate- induced HP). 

After showing further respiratory symptoms associated with isocyanate exposure, the worker 

quit his job but continued to experience coughing and progressive loss of lung function. His 

illness was eventually complicated by productive cough, weakness, sweats, muscle aches, and 

shortness of breath. Ultimately, he died. 

Worksite evaluations found detectable air concentrations of MDI and inadequate ventilation 

systems in the foaming areas. Vapors and aerosols were observed rising into the faces of 

employees working with the foam. Skin contact with the curing foam was also noted during the

survey. 

Case No. 5--Wood Products Manufacturing

Ten workers at an engineered wood products plant developed occupational asthma from 

exposure to MDI [NIOSH 1993]. The workers were employed 1 to 8 months at the plant before 

their diagnosis of occupational asthma. None of the 10 workers reported preexisting asthma. 

Respiratory symptoms included chest tightness, wheezing, and coughing at night. Six workers 

reported a relationship between symptoms and work: they either reported improved symptoms

while away from work or increased symptoms on their first day back at work. Eight workers 

showed declines in lung function over the workweek or over their period of employment, or 

they showed increased lung function after treatment with a bronchodilator. Eight workers 

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showed bronchial sensitivity when tested (methacholine challenge).

All 10 workers reported respiratory symptoms when they were in areas where MDI was used. 

The physician who examined the 10 workers recommended that they be removed from areas 

with any potential exposure to MDI. 

Case No. 6--Coal Mining

Coal miners at a longwall mine complained of illness after exposure to MDI-based 

polyurethane rock glues [NIOSH 1994b]. These miners had sprayed glues onto rock strata. 

They were supplied with air-purifying respirators (organic vapor cartridges) and chemicalresistant gloves that were not routinely worn. The exposed miners reported respiratory 

difficulties, asthma, shortness of breath, dizziness, headache, sore throat, fatigue, and contact 

dermatitis. Company medical records contained nine reports of health problems attributed to 

rock glue exposure. 

The inappropriate glue-spraying procedure used at this mine was eliminated by the Mine 

Safety and Health Administration (MSHA). The manufacturer's instructions specify that the 

glues are only to be injected for roof support and that workers are to wear supplied-air 

respirators--not air-purifying respirators. Air-purifying respirators are not recommended 

because rock glues are eye irritants and have poor warning properties, and because cartridges 

for these respirators have no end-of-service indicators for MDI. 

Case No. 7--Isocyanate Roofing Foam

Isocyanate exposure has also occurred at nonindustrial worksites such as public schools. The 

management of a large metropolitan school district contacted NIOSH for assistance after a 

university study documented asthma in 13 of approximately 85 staff members from a middle 

school [NIOSH 1994c]. The report further suggested that as many as 34 staff members might 

be asthmatic. 

NIOSH investigators determined that large quantities of polyurethane foams and isocyanate 

coating materials had recently been applied to the school roof on several occasions. School staff

members reported odors during roofing application, suggesting possible exposures to roofing 

materials that included isocyanates. Later air sampling during a test pour of the roofing 

materials at another location indicated the release of isocyanates during roofing and a potential

for exposure. 

Conclusion 

The cases described here reveal the potentially serious nature of respiratory disease after 

exposures to isocyanates. The following recommendations are intended to reduce the potential 

for exposed workers to develop adverse health effects. Because NIOSH regards TDI as a 

potential occupational carcinogen, appropriate engineering controls† and work practices‡ 

should be used to reduce worker exposures to the lowest feasible concentration. 

†Engineering controls are hazard controls designed into equipment and workplaces. 

‡Work practices are procedures followed by employers and workers to control hazards. 

Recommendations 

Product Substitution 

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When feasible, employers should substitute a less hazardous material for isocyanates.

Closed Systems and Ventilation 

Engineering controls such as closed systems and ventilation should be the principal method for

minimizing isocyanate exposure in the workplace. Exhaust ventilation systems should be 

designed to capture and contain vapors and particulates. Ventilation equipment should be 

checked for adequate performance at least every 3 months. 

Worker Isolation 

Areas containing isocyanates should be restricted to essential workers. If feasible, these 

workers should avoid direct contact with these chemicals by using automated equipment 

operated from a control booth or room with separate ventilation. 

Protective Clothing and Equipment 

When there is potential for isocyanate exposure, workers should be provided with and required

to use appropriate personal protective clothing and equipment such as coveralls, footwear, 

chemical-resistant gloves and goggles, full faceshields, and suitable respiratory equipment. 

Respiratory Protection 

The use of respirators is the least preferred method of controlling worker exposures. 

Respirators should not be used as the primary control for routine operations, but NIOSH 

recognizes that they may be used during situations such as implementation of engineering 

controls, some short-duration maintenance procedures, and emergencies. Only the most 

protective respirators should be used for situations involving exposures to isocyanates that 

have poor warning properties, are potent sensitizers, or may be carcinogenic. These respirators

include any self-contained breathing apparatus with a full facepiece operated in a pressuredemand or other positive-pressure mode, and any supplied-air respirator with a full facepiece 

operated in a pressure-demand or other positive-pressure mode in combination with an 

auxiliary self-contained breathing apparatus operated in a pressure-demand or other positivepressure mode. 

Any respiratory protection program must, at a minimum, meet the requirements of the OSHA 

respiratory protection standard [29 CFR 1910.134]. Respirators must be certified by NIOSH 

and MSHA according to 30 CFR or by NIOSH (effective July 19, 1995) according to 42 CFR 84. 

A complete respiratory protection program should include (1) regular training and medical 

evaluation of personnel, (2) fit testing, (3) periodic environmental monitoring, (4) periodic 

maintenance, inspection, and cleaning of equipment, (5) proper storage of equipment, and (6) 

written standard operating procedures governing the selection and use of respirators. The 

program should be evaluated regularly. The following publications contain additional 

information about selection, fit testing, use, storage, and cleaning of respiratory equipment: 

NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a] 

NIOSH Respiratory Decision Logic [NIOSH 1987b] 

Worker and Employer Education 

Worker education is vital to a good occupational safety and health program. OSHA requires 

that workers be informed about materials that may contain or be contaminated with 

isocyanates, and the nature of the potential hazard [29 CFR 1910.1200]. Employers must 

transmit this information through container labeling, material safety data sheets (MSDS), and 

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worker training. 

Exposure Monitoring 

Each employer who manufactures, transports, packages, stores, or uses isocyanates or 

products containing isocyanates should determine whether the potential exists for worker 

exposure. 

Decontamination and Waste Disposal 

Procedures for decontamination, waste disposal, and transport should be established for 

isocyanate-contaminated materials or equipment. 

Medical Monitoring 

A medical monitoring program should be established for the early detection and prevention of 

the acute and chronic effects of exposure to isocyanates. The worker's physician should be 

given information about the adverse health effects of exposure to isocyanates and the worker's 

potential for exposure. 

Surveillance and Disease Reporting 

NIOSH encourages surveillance of occupational asthma by State health departments. To 

enhance the uniformity of reporting, NIOSH recommends reporting guidelines and an asthma 

surveillance case definition (see Appendix B). These guidelines and the case definition are 

recommended for public health surveillance of work-related asthma reported by physicians 

and other healthcare providers. As of 1996, four State health departments--California, 

Massachusetts, Michigan, and New Jersey--are actively engaged in occupational asthma 

surveillance activities. 

Acknowledgments 

The principal contributors to this Alert are Karl Musgrave; Chris Piacitelli; Gregory Kullman; 

Steve Berardinelli, Jr.; Al Dieffenbach; and John Parker. Please direct comments, questions, or 

requests for additional information to the following: 

Director 

Division of Respiratory Disease Studies 

National Institute for Occupational Safety and Health 

1095 Willowdale Road 

Morgantown, WV 26505-2888 

Telephone number: 1-304-285-5750 or 1-800-35-NIOSH (1-800-356-4674). 

We greatly appreciate your assistance in protecting the lives of U.S. workers. 

Linda Rosenstock, M.D., M.P.H. 

Director, National Institute for Occupational Safety and Health 

Centers for Disease Control and Prevention 

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chronic obstructive pulmonary disease (COPD) and asthma. Am Rev Respir Dis 136:225-244.

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asthma. MMWR 39(7):119-123. 

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the Federal Register. 

Chan-Yeung M, Lam S [1986]. Occupational asthma. Am Rev Respir Dis 133:686-703. 

Charles J, Bernstein A, Jones B, Jones DJ, Edwards JH, Seal RME, et al. [1976]. 

Hypersensitivity pneumonitis after exposure to isocyanates. Thorax 31:127-136. 

Dunn and Bradstreet [1983]. Dunn's Market Index File. New York, NY: Dunn and Bradstreet 

Corporation. 

Fabbri LM, Danieli D, Crescioli S, Bevilacqua S, Meli S, Saetta M, et al. [1988]. Fatal asthma in 

a subject sensitized to toluene diisocyanate. Am Rev Respir Dis 137: 1494-1498. 

Fink JN, Schlueter DP [1978]. Bathtub refinisher's lung: an unusual response to toluene 

diisocyanate. Am Rev Respir Dis 118: 955-999. 

Fisher AA [1967]. Contact dermatitis. Philadelphia, PA: Lea and Febiger, pp. 134-135. 

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Organization, International Agency for Research on Cancer, pp. 287-323. 

Loeser E [1983]. Long-term toxicity and carcinogenicity studies with 2,4/2,6-toluene 

diisocyanate (80/20) in rats and mice. Toxicol Lett 15:71-81. 

Luo J-C J, Nelsen KG, Fischbein A [1990]. Persistent airway dysfunction syndrome after 

exposure to toluene diisocyanate. Br J Ind Med 47:239-241. 

NIOSH [1973]. Criteria for a recommended standard: occupational exposure to toluene 

diisocyanate. Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public 

Health Service, Center for Disease Control, National Institute for Occupational Safety and 

Health, DHEW (NIOSH) Publication No. HSM 73-11022. 

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Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public Health Service, 

Center for Disease Control, National Institute for Occupational Safety and Health, DHEW 

(NIOSH) Publication No. 78-215. 

NIOSH [1983]. National Occupational Exposure Survey (NOES), 1981-1983: estimated total 

and female employees, actual observation and trade-named exposure to toluene diisocyanate 

and methyl benzene diamine. Cincinnati, OH: U.S. Department of Health and Human Services,

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and Health, Division of Surveillance, Hazard Evaluations and Field Studies, Surveillance 

Branch. Unpublished database. 

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National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-116.

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Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-108. 

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toluenediamine (TDA); evidence of carcinogenicity. Cincinnati, OH: U.S. Department of Health

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Deerwood, MN. Morgantown, WV: U.S. Department of Health and Human Services, Public 

Health Service, Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, NIOSH Report No. HETA 93-0436, Interim Report. 

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Inc., Brookwood, AL. Morgantown, WV: U.S. Department of Health and Human Services, 

Public Health Service, Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, NIOSH Report No. HETA 94-0027. 

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Dallas, TX. Morgantown, WV: U.S. Department of Health and Human Services, Public Health 

Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety 

and Health, NIOSH Report No. HETA 94-0265. 

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grade 2,4(80%)- and 2,6(20%)-toluene diisocyanate (CAS No. 26471-62-5) in F344/N rats and 

B6C3F1 mice (gavage studies). Research Triangle Park, NC: U.S. Department of Health and 

Human Services, Public Health Service, National Institutes of Health, National Toxicology 

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syndrome. Immunol and Allergy Clin of North America 12(2):279-290. 

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Occupational respiratory diseases. Cincinnati, OH: U.S. Department of Health and Human 

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Occupational Safety and Health, DHHS (NIOSH) Publication No. 86-102. 

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painters exposed to several types of isocyanates, including polymethylene 

polyphenylisocyanate. J Occ Med 29 (4):340-344. 

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report of a probable case and prevalence of specific immunoglobulin G antibodies among 

exposed individuals. Scand J Work Environ Health 15:234-237. 

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Upjohn Company [1970]. Urethanes: engineering, medical control and toxicologic 

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Woods G [1987]. The ICI polyurethanes book. Netherlands: ICI Polyurethanes. 

Appendix A 

Diisocyanate synonyms 

TDI 

MDI 

HDI 

z 2,4-Diisocyanato-1-methylbenzene 

z 2,4-Diisocyanatotoluene 

z 2,4-TDI 

z 2,4-Tolylene diisocyanate 

z 4-Methyl-phenylene diisocyanate 

z Di-iso-cyanatoluene 

z Isocyanic acid, 4-methyl-m-phenylene ester 

z Isocyanic acid, methylphenylene ester 

z m-tolylene diisocyanate 

z Toluene-2,4-diisocyanate 

z Toluene diisocyanate 

z 1,1-Methylenebis(4-isocyanatobenzene) 

z 4,4'-Diisocyanatodiphenylmethane 

z 4,4'-Diphenylmethane diisocyanate 

z 4,4'-Methylenebis(phenyl isocyanate) 

z 4,4'-Methylenediphenyl diisocyanate 

z Bis(1,4-isocyanatophenyl)methane 

z Bis(4-isocyanatophenyl)methane 

z Diphenylmethane 4,4'-diisocyanate 

z Diphenylmethane diisocyanate 

z Methylenebis(4-isocyanatobenzene) 

z Methylenebis(4-phenylene isocyanate) 

z Methylene bisphenyl isocyanate 

z Methylene-di-p-phenylene isocyanate 

z Methylene di(phenylene isocyanate)

z 1,6-Diisocyanatohexane 

z 1,6-Hexamethylene diisocyanate 

z 1,6-Hexanediol diisocyanate 

z Hexamethylene-1,6-diisocyanate 

z Hexamethylene diisocyanate 

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References 

Lewis RJ Sr. [1993] Hazardous chemicals desk reference, 3rd ed. New York, NY: Van Nostrand 

Reinhold Publishers. 

NIOSH [1995] Registry of toxic effects of chemical substances. Cincinnati, OH: U.S. 

Department of Health and Human Services, Public Health Service, Centers for Disease and 

Control and Prevention, National Institute for Occupational Safety and Health. 

Sax NI, Lewis RJ Sr. [1987] Hawley's Condensed Chemical Dictionary, 11th ed. New York, NY: 

Van Nostrand Reinhold Publishers. 

Appendix B 

Surveillance Guidelines for State Health Departments: Occupational Asthma 

Reporting Guidelines 

State health departments should encourage providers to report all suspected or diagnosed 

cases of occupational asthma. These should include persons with: 

State health departments should collect appropriate clinical, epidemiologic, and workplace 

information on reported cases to set priorities for workplace investigations. 

Surveillance Case Definition 

*Asthma is a clinical syndrome characterized by increased responsiveness of the 

tracheobronchial tree to a variety of stimuli [ATS 1987]. Symptoms of asthma include episodic 

wheezing, chest tightness, and dyspnea, or recurrent attacks of "bronchitis" with cough, 

sputum production, and rhinitis [Chan-Yeung and Lam 1986]. The primary physiologic 

manifestation of airways hyper-responsiveness is variable or reversible airflow obstruction, 

z HMDI (4,4' dicyclohexylmethane diisocyanate) 

z Isocyanic acid, hexamethylene ester 

z A physician diagnosis of asthma AND 

z An association between symptoms of asthma and work. 

z A physician diagnosis of asthma* 

z An association between symptoms of asthma and work† and any one of the 

following: 

1. Workplace exposure to an agent or process previously associated with 

occupational asthma§ OR 

2. Significant work-related changes in FEV1 or PEFR 

3. Significant work-related changes in airways responsiveness as measured 

by nonspecific inhalation challenge¶ 

4. Positive response to inhalation provocation testing with an agent to which 

patient is exposed at work. Inhalation provocation testing with workplace 

substances is potentially dangerous and should be performed by 

experienced personnel in a hospital setting where resuscitation facilities 

are available and where frequent observations can be made over sufficient 

time to monitor for delayed reactions. 

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Centers for Disease Control and Prevention 1600 Clifton Rd. Atlanta, GA 30333, USA 

800-CDC-INFO (800-232-4636) TTY: (888) 232-6348, New Hours of Operation 8am-8pm ET/Monday-Friday 

which may be demonstrated by significant changes in the forced expiratory volume in 1 second 

(FEV1) or peak expiratory flow rate (PEFR). Airflow changes can occur spontaneously, with 

treatment, with a precipitating exposure, or with diagnostic maneuvers such as nonspecific 

inhalation challenge. 

†Patterns of association can vary. The following examples are patterns that may suggest an 

occupational etiology: symptoms of asthma develop after a worker starts a new job or after new

materials are introduced on a job (a substantial period of time may elapse between initial 

exposure and development of symptoms); symptoms develop within minutes of specific 

activities or exposures at work; delayed symptoms occur several hours after exposure, during 

the evenings of workdays; symptoms occur less frequently or not at all on days away from work

and on vacations; symptoms occur more frequently on returning to work. Work-related 

changes in medication requirements may have similar patterns, also suggesting an 

occupational etiology. 

§Many agents and processes have been associated with occupational asthma [Chan-Yeung and 

Lam 1986, Salvaggio et al. 1986], and others continue to be recognized. 

¶Changes in nonspecific bronchial hyperactivity can be measured by serial inhalation challenge

testing with methacholine or histamine. Increased bronchial reactivity (manifested by reaction 

to lower concentrations or methacholine or histamine) following exposure and decreased 

bronchial reactivity after a period away from work are evidence of work-relatedness. 

Reprinted from CDC [1990], p. 121. 

Employers should take the following steps to protect workers from diisocyanate exposure: 

Workers should take the following steps to protect themselves from diisocyanate exposure: 

z Make workers aware of the serious health effects that may result from diisocyanate 

exposures. 

z Make workers aware of any materials that may contain or be contaminated with 

diisocyanates. 

z When feasible, substitute a less hazardous material for diisocyanates. 

z If substitution is not possible, use engineering controls such as closed systems and 

ventilation to minimize exposures. 

z Provide appropriate respiratory protection to workers exposed to diisocyanates. 

z Be aware that the highest diisocyanate concentrations may occur inside containment

structures. 

z Use appropriate respiratory protection when working with diisocyanates. 

z Wash hands and face before eating, drinking, or smoking outside the work area. 

z Shower and change into clean clothes before leaving the worksite. 

z Participate in medical monitoring and examination programs, air monitoring 

programs, or training programs, offered by your employer.

View/Download Entire Document: Preventing Asthma and Death from Diisocyanate 

Exposure DHHS (Summary) [PDF - 273KB] 

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