Isocyanates, polyurethane and childhood asthma

Abstract

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.

Skin Exposure to Isocyanates: Reasons for Concern

“…Isocyanate releases from end-users, such as auto body shops located in or near residential neighborhoods, are also possible but rarely reported. It has been hypothesized that environmental skin exposure to polyurethanes in childhood has contributed to the increased prevalence of childhood asthma (Krone and Klingner 2005), but human isocyanate exposure from such products has not been documented, and there are numerous other likely causative factors.…”

Isocyanate Exposure Assessment Combining Industrial Hygiene Methods with Biomonitoring for End Users of Orthopedic Casting Products

“…The most likely explanation of positive results in some of our samples is that a low level of bioburden was present in our worker population that is unrelated to use of MDI. Other investigators have researched other potential sources of isocyanates that members of the public may be exposed to such as foodstuffs with epoxy-based resins (Damant et al , 1995; Lambert, 1997), cooking utensils (Mortensen et al , 2005), and polyurethane foams (Krone and Klingner, 2005) but none provide a conclusive link between such exposures and the presence of MDA in vivo .…”

Isocyanates and Human Health

“…3–6 Consumers may also apply products containing isocyanates, or may be incidentally exposed to commercial- or professional-grade products used by contractors or maintenance staff in their home or workplace. 7,8 Isocyanate compounds can also be generated from thermal decomposition of polyurethane materials, from activities such as heating or grinding polyurethane materials, welding of metal with polyurethane coating, cutting polyurethane foams using hot wire cutting methods, or drilling, soldering, sawing, or sanding of polyurethane materials. 9 …”