Asthma Induced by Exposure to Spray Polyurethane Foam Insulation in a Residential Home

Abstract

Spray polyurethane foam (SPF) has recently become a popular “green” solution for insulation systems in residential homes and office buildings in the United States because of its high efficiency, low cost, and eligibility for federal energy tax credits in 2011. All SPFs contain isocyanates that are known to cause occupational asthma,1 but the occurrence of asthma in occupants of homes and building in which SPF is used for energy retrofits has not been reported. CASE A 36-year-old man and a 38-year-old woman living in the same household presented to the pulmonary clinic for evaluation of persistent cough and dyspnea upon exertion. They had moved into a home 18 months previously and had SPF installed in the attic. The patients followed the recommended precautions by evacuating the home for 4 hours. On returning, the patients noted a strong noxious odor, and almost immediately they developed cough, dyspnea, dizziness, nausea, headache, and watery eyes. Several attempts were made to abate the odor by venting the attic, keeping the windows open, and eventually removing the SPF, but the symptoms persisted. After 3 months, the family finally vacated the home. Neither patient had significant medical history. Both were nonsmokers and worked in office-based professions with no exposure to occupational hazards. Both had normal physical examinations, normal routine laboratory tests, including complete blood count and metabolic panels, and normal pulmonary function tests. Both patients showed a positive methacholine challenge test with the methacholine concentration that causes a 20% decrease in forced expiratory volume in 1 second (PC20) of 8 mg/mL for the male patient and 1 mg/mL for the female patient (Fig. 1). The SPF used in our patients' home was a two-component SPF system (Sealection® 500; Dimilec USA, LLC, Arlington, TX) that contained polymeric diphenylmethane diisocyanate (MDI) (50% to 60%), 4,4′-MDI (35% to 45%), and 2,4′-MDI (1% to 5%) in side A. Both patients were diagnosed with asthma or reactive airway dysfunction syndrome induced by exposure to isocyanates and were treated with bronchodilators and inhaled steroids.2FIGURE 1: Results of methacholine challenge tests for the two patients. The tests were done 16 months after the initial exposure. A, For the male patient, the PC20 is 8 mg/mL. B, For the female patient, the PC20 is 1 mg/mL. The dashed line indicates a decrease of 20% in forced expiratory volume in 1 second.DISCUSSION Isocyanates are traditionally used in the automotive, aerospace, metal-working, and wood-working industries.3 They are the most common cause of new onset work-related asthma.4 The use of isocyanates in nonoccupational settings has increased recently, primarily because of the popularity of SPF as an insulation material for residential homes. The home occupants may unknowingly be exposed to isocyanates and be at increased risk for adverse health effects. The “curing” rate of SPF, that is, the time for chemicals in the product to react to produce polyurethane foam, is an important determinant for health effects and varies from 7 to 72 hours depending on the type of SPF product, applicator technique, foam thickness, temperature, and humidity. This curing rate will impact the “re-entry time.” Our patients were told to return 4 hours after the application was completed, and thus were likely exposed to high concentrations of MDI. The clear exposure history, symptoms/signs of asthma, and positive methacholine challenge test established the diagnosis of isocyanate-induced asthma. To our knowledge, this report is the first to describe asthma associated with household exposure to isocyanates contained in SPF. The use of SPF in residential homes likely will continue to increase. This new source of exposure potentially puts a large population at risk for adverse health effects. In response to a growing number of complaints about adverse health effects from homeowners and occupants of office buildings, the US Environmental Protection Agency has recently published an action plan to control exposure to MDI for homeowners and “do-it-yourselfers.”5 Clinicians should be vigilant about this novel exposure scenario to isocyanates when managing patients with new-onset or worsening asthma. Wayne Tsuang, MD Yuh-Chin T. Huang, MD, MHS, FCCP Department of Medicine Duke University Medical Center Durham, NC