Health Consequences of Exposure to "Green" Polyurethane Spray Foam

| |

Summary Statement

This PowerPoint from a presentation at a 2012 CPWR meeting by Carrie Redlich MD reviews the main findings of a NIOSH-funded study looking at health effects from exposure to spray polyurethane foam as part of green construction. The results point out the strong relationship between this work and occupational asthma and addresses the medical evaluations needed. Case studies are presented of workers who developed sensitivity.
March 27, 2012

Exposure to “Green” Polyurethane Spray Foam

  • What’s in it
  • Potential health effects ‐ isocyanate asthma
  • Challenges
  • Biomonitoring ‐ Isocyanate-specific IgG / IgE
  • CPWR study – preliminary data
  • Questions

Chemical Composition of SPF

    Part A – Isocyanates

    • Methylene diphenyl diisocyanate (MDI) /pMDI

    Part B – variable / proprietary

    • Polyols (petroleum or soy based)
    • Amine catalysts
    • Flame retardants
    • Blowing agents
    • Surfactants

(exothermic reaction)

Major Commercial Isocyanates

    HDI - hexamethylene

      Paints, Coatings Light resistant

    TDI - toluene


    MDI - diphenylmethane or methylene diphenyl

      Less volatile – “safe”
      Foams, adhesives Coatings, wood products

Uses Isocyanates / Polyurethanes in Construction - Growing

  • Foams – soft / hard
    • Insulation – spray foam
    • Simulated wood – doors, posts
  • Adhesives
  • Roofing materials
  • Caulking
  • Sealants
  • Elastomers / coatings
  • Woodbinder – composite wood

Health Effects Isocyanates

  • Potent sensitizer / allergen
  • Occupational asthma
  • One of the most commonly identified causes of occupational asthma
  • Rash / skin irritation - less common, but occurs
  • Hypersensitivity pneumonitis – less common.

Isocyanate asthma – key features

  • Clinically similar to “ordinary” asthma
  • Timing- onset months to years after onset exposure
    • Delayed symptoms 6-8 hours after exposure
  • Once sensitized, exposures to very low levels trigger asthma
  • Diagnosis can be missed – (by patient and doctor)
  • Asthma commonly persists after away from exposure
  • Poor socioeconomic outcomes – unemployment, reduced income
  • Extent problem unknown – especially in end-user settings

Health effects from exposure to other components PU Foam ?

  • Amine catalysts
    • Sensitizers, irritants – asthma, rash
    • Blurry vision (halo vision)
  • Flame retardants
  • VOCs
  • Blowing agents
  • Polyols

Routes of exposure / forms

  • Inhalation
  • Skin – likely contributes to sensitization and asthma

  • Liquid, aerosol, vapor
  • Exothermic reaction
  • Cut & shave foam → dust, particulates


    Healthy 36 y/old construction worker / insulator 1 yr ago started use PU spray foam. Past 5 months -­‐ cough after work / evening – wife concerned. Chest tightness, SOB, wheeze. Better on weekends. Symptoms progress – goes to ER.

    Initial Medical evaluation
    No h/o asthma, allergies. Improves with asthma inhalers. Continues to work, wears PPE, but progressive symptoms.

    Further work‐up
    Spirometry – airflow obstruction ‐ positive BD response MDI‐IgG, MDI‐IgE positive. Told to avoid isocyanates.

Health Effects of Exposure to “Green” Polyurethane Spray Foam

  • What’s in it
  • Potential health effects ‐ isocyanate asthma
  • Major challenges
  • Biomonitoring ‐ Isocyanate ‐specific IgG / IgE
  • CPWR study – preliminary data
  • Questions

Limitations isocyanate exposure assessment and regulation

  • Multiple formulations and forms– vapor / aerosol / particulates
  • Sampling and laboratory analysis can be challenging
  • All methods depend on free NCO – timing critical
  • “Snapshot” of exposure ‐ end‐user settings esp problematic
  • Air sampling does not assess effectiveness personal protective equipment (gloves, respirator)
  • Skin exposure assessment methods limited

  • Current OELs – Not protective

Limitations diagnosis isocyanate asthma

  • Asthma common condition ‐ connection to work frequently missed – especially once asthma more chronic.
  • No simple specific test for isocyanate asthma. Frequently other work (and environmental) triggers.
  • Most clinicians focus on treatment more than cause / prevention
  • Worker may leave causative job / work before diagnosis made, but asthma frequently persists.
  • No mandatory medical surveillance or reporting for isocyanate asthma

Biomonitoring Approaches

  • Direct measurements of isocyanate derivative or metabolite in urine - currently not useful

  • Measurements of physiologic response to exposure (antibodies in blood)

Principles Guiding Isocyanate Serology

    Isocyanate chemicals are “man-made” - don’t exist naturally.

    Humans don’t normally make antibodies to isocyanate modified albumin; they are triggered by exposure.

    Antibody Graph
    Without ongoing exposure, specific antibodies are cleared from blood in a time dependent manner.

Isocyanate Immunoassays

    Measures human response to exposure

    • Detect in human serum
    • Isocyanate-specific IgG and IgE responses
    • Integrated measurement over time
      • IgG serum1/2 life = 30 days
      • IgE serum 1/2 life ~ 2 days
    • Response highly specific for isocyanate
    • Can vary depending upon form of isocyanate used as the “antigen”

Biomonitoring hexamethylene diisocyanate (HDI) exposure based on serum levels of HDI-specific IgG

HDI Exposure
Wisnewski. Ann Occup Hyg 2012; 10: 1-10

Case: PU spray foam sprayer MDI-IgG over time

PU spray foam sprayer MDI-IgG over time

Assessment and Prevention of Isocyanate Exposures in the Construction Industry Funded by NIOSH / CPWR

    Aim 1) Assess respiratory and skin isocyanate exposures in the construction industry

    Aim 2) Implement a surveillance program for construction workers who work with or around PU products.

    Aim 3) implement an intervention program to reduce isocyanate exposures in construction workers.

Characteristics Construction Workers Recruited who use Isocyanate Products (n= 60) Preliminary Data

    Gender: Male 58 (97%)
    Current smoker 22 (37%)
    Job Category  
      Insulator 20 (33%)
      Other 40 (67%)
      Glazier / taper 9 (15%)
      Energy conservation 7 (12%)
      Other construction 24 (40%)
      None 19 (32%)
      Non-specific 24 (40%)
      Asthma, work-related 15 (25%)
    Spirometry - airflow obstruction 16 (27%)

Worker Self Reported Exposure (n= 60) Preliminary Data

    Other spray near you  
      No 7 (12%)
      Monthly or less 14 (23%)
      Daily / weekly 39 (65%)
    Get Isocyanate product on skin  
      Never 4 (7%)
      Occasionally 22 (37%)
      Frequently 34 (57%)
    Where on skin  
      Hands, arms, wrists 24 (40%)
      Head, neck, face 15 (25%)

Work-related symptoms preliminary data (n = 60)

Work-related symptoms preliminary data graph

Possible Asthma: prior diagnosis vs study diagnosis preliminary data (n = 60)

Possible Asthma: prior diagnosis vs study diagnosis graph

Prevalence of isocyanate-specific-IgG Comparison to autobody workers preliminary data

Prevalence of isocyanate-specific-IgG graph

MDI specific-IgG titres (mean) preliminary data (n = 60)

MDI specific-IgG titres (mean) graph

PU Construction Worker Project – Initial Preliminary Conclusions

  • Work‐related asthma symptoms are common in the PU spray foam workers – may represent isocyanate asthma
  • High prevalence MDI‐IgG positive titers in PU spray foam workers
  • MDI skin exposure is commonly reported
  • Traditional IH monitoring does not appear to be adequate

Health Effects of Exposure to “Green” Polyurethane Spray Foam

  • What’s in it
  • Potential health effects ‐ iIsocyanate asthma
  • Major challenges
  • Biomonitoring ‐ Isocyanate‐specific IgG / IgE
  • CPWR study – preliminary data
  • Questions


    Yale Occupational and Environmental Medicine Program
    Adam Wisnewski, PhD
    Meredith Stowe, PhD
    Judy Sparer, CIH

    Dhimiter Bello, PhD

    CPWR-NIOSH Construction Center Grant “Assessment and Prevention of Isocyanate Exposures in the Construction Industry”