Isocyanates, polyurethane and childhood asthma.

Isocyanates are the most prominent and well-studied cause of occupational asthma. Over the decades, airborne isocyanates have been regulated to extremely low levels in the workplace, some of the lowest for any organic compound. Yet the incidence of isocyanate-induced occupational asthma remains high and the role of dermal exposure in disease etiology is only slowly being recognized. Almost completely overlooked is the potential relationship between isocyanates in consumer products and increasing prevalence of asthma in the general population, especially children. The steady rise in asthma over the past decades points strongly to a potential role of environmental exposures in its development. Imbalances in the immune system favoring respiratory diseases have been linked to biological and chemical stressor exposures early in life. Evidence for the presence of isocyanates in many polyurethane-containing materials, especially polyurethane foams, is presented as a possible contributor to the increase in asthma. Polyurethane foam is ubiquitous in western societies and used in bedding, furniture, automobile seats, footwear, etc., and numerous medical materials. Theoretical, epidemiologic, experimental and clinical evidence of a role for isocyanates and polyurethanes in the genesis of non-occupational allergy and respiratory disease are reviewed. These data all point to the urgent need for additional research on the links between isocyanates, polyurethanes and the role of the skin in non-occupational asthma.

Polyurethanes and childhood asthma.

BACKGROUND: Asthma is the most common chronic disease of children. Its prevalence in affluent nations has steadily and dramatically increased in recent decades. Genetic and environmental factors play a role in development of atopy and asthma. Imbalance in the immune system favoring respiratory diseases has been linked to exposure to environmental stressors (e.g, biological and chemical) very early in life. Isocyanates, used in the production of polyurethane, can elicit asthma and produce immune responses (e.g, antibodies, cytokines, etc.) typical of atopy. MATERIAL/METHODS: Numerous medical materials that directly contact human neonates are constructed of polyurethanes. A detailed survey and listing of such materials was undertaken in the neonatal unit of a large urban hospital. Representative samples of polyurethane-containing materials were tested for isocyanate residues using a semi-quantitative colorimetric method. RESULTS: Isocyanate residues were detected in wound dressings, adhesive films, oximetry sensors, etc, that directly contact neonatal skin. CONCLUSIONS: Dermal exposure to polyurethane and, thus, to isocyanates could occur early in life through contact with medical materials. In an animal model, dermal exposure to isocyanates leads to dermal sensitization and asthma. We postulate that dermal contact with polyurethane-containing medical materials may be involved in dysregulation of the neonatal immune system and could predispose infants to the development of childhood asthma.