Asthma-Like Symptoms in Wood Product Plant Workers Exposed to Methylene Diphenyl Diisocyanate

doi:10.1378/chest.118.4.1183

Chest

Volume 118, Issue 4, October 2000, Pages 1183-1193

https://doi.org/10.1378/chest.118.4.1183 Get rights and content

Background:

Diisocyanates, a group of highly reactivechemicals, have frequently been associated with occupational asthma. Weevaluated respiratory health in workers at a new wood productsmanufacturing plant that uses methylene diphenyl diisocyanate (MDI),and was designed and operated with a goal of minimizing workerexposures.

Methods:

Health surveys using standardizedrespiratory questionnaires were done prior to the initial use of diisocyanates in the plant, and semiannually thereafter for a period of2 years. Other testing included occupational and work practicehistories, serial peak flow measurements, spirometry, methacholinechallenge, and measurement of specific IgE antibodies to MDI-albuminconjugate.

Results:

Of 214 plant employees whoparticipated in at least one health survey, a follow-up survey was alsoavailable from 178 employees (83%). New-onset asthma-like symptoms(NAS) were reported by 15 of 56 workers (27%) in areas with thehighest potential for exposures to liquid MDI monomer and prepolymer, vs 0 of 43 workers in the lowest potential exposure areas(p = 0.001). In the areas with high potential exposure, NAS developedin 47% of workers who had noted MDI skin staining, vs 19% withoutskin stains (p = 0.07). Working around and cleaning up liquid MDIrepresented a significant risk for asthma-like symptoms in both currentsmokers and nonsmokers; work with finished wood products did not. Asthma-like symptoms were associated with variable airflow limitation(odds ratio [OR], 5.0; confidence interval [CI], 1.4 to 18.7) andspecific IgE to MDI-albumin (OR, 3.2; CI, 1.1 to 9.0), but not withskin prick tests to common aeroallergens (OR, 1.1; CI, 0.5 to2.7).

Conclusions:

During the first 2 years of operation, in a plant designed and operated to control exposure todiisocyanates, the development of asthma-like symptoms was reported ina relatively high proportion of the employees who worked with liquidMDI. To prevent asthma symptoms among workers, careful control of respiratory tract exposures associated with liquid MDI is important, especially during cleanup activities. Strict limitation of skin contactwith diisocyanates may also be necessary.

Section snippets

Background

Occupationalasthma has become the most commonly reported occupational respiratorydisease.¹² Diisocyanates, a group of highly reactivechemicals, have been frequently associated with thenewonset of asthma in relation to work exposures, although for industrialsettings in which exposures to these chemicals are well controlled, alow prevalence of symptoms has been reported.³⁴⁵⁶⁷⁸⁹¹⁰¹¹¹²Recently, an opportunity was provided to prospectively study theworkforce at a newly constructed manufacturing

Process Description

The plant produces a laminated wood product. Briefly, logs, primarily yellow poplar, are brought to the plant by individualcontractors, and are stored for subsequent processing in the wood yard. The logs are debarked and placed into stranding machines. The strandingmachines produce thin strands of wood about 12 inches long. The strandspass through a dryer to reduce moisture content and are then placedinto a blender, where they are coated with a liquid diisocyanate resin(monomer and prepolymers)

Materials and Methods

The study protocol was reviewed and approved by the NationalInstitute for Occupational Safety and Health (NIOSH) InstitutionalReview Board, and all participants gave written informed consent.

Study Participants

During the entire 2-year study period, a total of 276 individualswere employed, at least briefly, in the plant. Over the study period, atotal of 214 employees completed the initial questionnaire, with 108enrolling in the study prior to the first delivery of MDI to the plant. Of the 214 participants, 178 also participated in at least onefollow-up survey. Of these 178 workers, a complete occupational historywas available for 144, of whom over half (77 of 144) had completed theinitial health

Discussion

Respiratory disease among workers exposed to the group of commercially useful diisocyanate compounds has been recognized sincethe 1950s, and exposure limits have been established in the UnitedStates and other countries for both ceiling values and time-weightedaverage exposures.¹⁶ However, recent reports continue toimplicate diisocyanates, including MDI, as one of the most frequentcauses of new-onset occupational asthma.³⁴⁵⁶ Weassessed respiratory health among workers during the first 2 years of

Conclusion

Asthma-like symptoms developed in a relatively high proportion of workers during the first 2 years of production at a composite woodproducts manufacturing plant utilizing MDI. Certain job activities, including the cleanup of MDI spills and cleaning the MDI blender, wereassociated with asthma-like symptoms, highlighting the criticalimportance of controlling exposures during those activities. Skinstaining with MDI was also associated with NAS, suggesting that theskin may be a potential site for

ACKNOWLEDGMENT

The authors wish to acknowledge the extensivecontributions to this work made by the NIOSH Field Team members, including Diana Freeland, Ray Petsko, Marty Pflock, Mark Ryan, JimTaylor, Toni Bledsoe, and Judy Mull, as well as Kathy Fedan, JohnOdencrantz, Patrick Hintz, and the Clinical Investigation Branch of ficesupport staff. Dr. David Bernstein (University of Cincinnati) kindlyprovided a high titer serum sample that was invaluable during thedevelopment of the RAST assay for MDI-HSA antigen.

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: Supported by the National Institute for Occupational Safety and Health.

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Chest

Occupational and Environmental Lung DiseaseAsthma-Like Symptoms in Wood Product Plant Workers Exposed to Methylene Diphenyl Diisocyanate

Background:

Methods:

Results:

Conclusions:

Section snippets

Background

Process Description

Materials and Methods

Study Participants

Discussion

Conclusion

ACKNOWLEDGMENT

Chest

Toxicology

Ann Occup Hyg

J Allergy Clin Immunol

Chest

Toxicology

Chest

J Allergy Clin Immunol

Chest

The SHIELD scheme in the West Midlands Region, United Kingdom: Midland Thoracic Society Research Group

Br J Ind Med

Physician based surveillance system for occupational respiratory diseases: the experience of PROPULSE, Quebec, Canada

Occup Environ Med

Occupational asthma

The prevention of occupational asthma in industries

J Investig Allergol Clin Immunol

A state-based surveillance system for work-related asthma

J Occup Environ Med

New developments in occupational asthma

Br Med Bull

Pathomechanisms and pathophysiology of isocyanate-induced diseases: summary of present knowledge

Am J Ind Med

Occupational and Environmental Lung Disease
Asthma-Like Symptoms in Wood Product Plant Workers Exposed to Methylene Diphenyl Diisocyanate