Date of Award

January 2012

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Meredith H. Stowe

Abstract

Isocyanate (NCO) skin contact may contribute to sensitization and the development of isocyanate asthma. Unbound NCO can persist on polyurethane (PU) spray-coated car parts and other surfaces, after appearing dry. Whether human isocyanate skin exposure can result from handling such surfaces remains unclear. To assess NCO transfer potential to human skin from surfaces recently sprayed with aliphatic isocyanate coatings used in collision repair work, quantitative surface and skin wipe sampling for total NCO was performed on test panels sprayed with such coatings and on skin samples obtained from participants who had rubbed the recently dried surfaces. 18 workers in 5 auto body shops participated. Surface and skin samples were prepared following NIOSH method 5525 (modified for skin samples) and isocyanate species (HDI, pHDI, pIPDI and total NCO) analyzed using high-performance liquid chromatography (HPLC) with ultraviolet (UV) and fluorescence (FLD) detectors. Quantifiable unbound NCO species were detected on 84.2% of all sprayed surfaces sampled when initially considered dry (n= 38 samples). A significant (p < 0.001) decay in free NCO was observed over 24 hours. For all 104 skin samples obtained after contact with recently dried coatings only 6.7% (7 out of 104) had detectable quantities of free NCO. The 7 positive samples were all obtained at the initial sampling time (t0) and had a geometric mean of 0.016 micrograms NCO per square cm (range: 0.002-0.88 micrograms NCO per square cm). Only 1 of the 12 (8.3%) skin samples obtained after compounding was positive for free NCO. All study control (pre-contact) skin samples were negative. Limited transfer of free NCO from surfaces with detectable NCO levels to the skin of workers handling them was documented. The risk of substantial human isocyanate skin exposure from contact with the dry appearing (yet potentially semi-cured) isocyanate coatings evaluated in this study appears to be low, although other products and tasks may pose a more substantial dermal NCO exposure potential.

Comments

This is an Open Access Thesis.

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