Too hot to handle: an unusual exposure of HDI in specialty painters

Hexamethylene Diisocyanate (HDI) is a color stable aliphatic isocyanate that is used in specialty paints as a hardener. Due to the lower vapor pressure of its commercial biuret form, it is considered a relatively "safe" isocyanate from an exposure standpoint. This case series reports on an unusual toxic exposure to HDI. Between November 1993 and May 1994, seven specialty painters and one boiler maker who were working at three different power plants were examined at the Institute of Occupational and Environmental Health at West Virginia University. At their respective work sites, HDI was applied to the hot surfaces of boilers that were not shut down, and allowed sufficient time to cool. Consequently, these workers were exposed to volatile HDI and its thermal decomposition products.

All of these workers underwent a complete physical examination, spirometry, and methacholine challenge testing.

All 8 workers complained of dyspnea, while 4 of the 8 also complained of rash. On examination 3 workers were methacholine challenge positive and 2 had persistent rash. At follow-up 4 years later, 5 workers still had to use inhalation medication and one had progressive asthma and dermatitis. All 8 workers, by the time of the follow-up, had gone through economic and occupational changes.

This case series reports on an unusual exposure to HDI. It is unusual in that: 1) There were two simultaneous sentinel cases with two different Material Safety Data Sheets (MSDS) for the same product, 2) Exposure was to volatile HDI and its decomposition products and 3) Hazardous conditions of exposure occurred at three different sites.