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This summer, new international rules spelled out the end of the short-lived polyurethane swimsuit era in competitive sports. Amid all media splash (what does Michael Phelps think?), one ripple-effect that went unnoticed was the likely benefit of fewer factory workers coming down with asthma from making this high-tech gear.
Polyurethanes comprise a group of chemically synthesized compounds that are all derived from a single type of starting material called an isocyanate. There are several closely related isocyanates, all of which share a potent ability to induce asthma among those who come in close and repeated contact with any of these chemicals. Medical researchers have been actively studying isocyanate-caused asthma and have still not been able to work precisely how it comes about - but a number of facts have become clear. The most important thing is that isocyanates bind chemically with natural molecules in the human body and this reaction leads to allergic sensitization. Once this happens, re-exposure, even to very low levels of the chemical, can induce a full-blown asthma attack.
The reactivity of isocyanate that makes it dangerous is also what makes it attractive commercially. Mixes containing isocyanates combine together, linking up to produce all sorts of textures and surfaces. Like a buoyant but tight-fitting swimsuit, for example. Or the hard surface on a floor or on an automobile body. Or a piece foam insulation molded into a custom shape or simply sprayed into a crawl-space.
Once all of the isocyanate is reacted into the final product and none is left to react with the body's immune system, it can't cause asthma any longer. For that reason, swimmers wearing pre-cured swimsuits have little to worry about. The person making the polyurethane for the swimsuit would be the one most at risk.
But in many (if not most) urethane uses, there is no factory door that marks a threshold beyond which there is no risk. That is because when it comes to urethanes, consumers often are also product manufacturers. Whenever a two-part urethane system is used ("combine Part A with Part B, apply within 15 minutes," etc.) free isocyanate that can be reactive is likely to be there. Even newer "one-part" urethane products also pose a potential hazard. Moreover, new market uses seem to be emerging all the time, such as urethane-based casts instead of plasters for fractures and even over-the-counter urethane glue (www.gorillatough.com).
A few weeks ago I was walking down the corridors of my own hospital when I noticed the custodial staff applying an odd looking coating to the floor of an empty patient room. The windows were closed, the space was fairly confined, and the workers wore no specific skin protection or face masks. Then I noted that the product came in different containers that required mixing just before use. As I feared, it was a urethane. "The coating lasts a long time - that's why we started using this," the supervisor said. I told the supervisor and the crew to get better protective gear and to call in safety experts so that they could reconsider using the product at all. Asthma can last a long time, too.
