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Penetration patterns of monomeric and polymeric 1,6-hexamethylene diisocyanate monomer in human skin.

Authors
Thomasen-JM; Nylander-French-LA
Source
J Environ Monit 2012 Mar; 14(3):951-960
NIOSHTIC No.
20040899
Abstract
We investigated penetration patterns of monomeric and polymeric 1,6-hexamethylene diisocyanate (HDI), experimentally and as part of commercial products, in excised full-thickness human skin at 5, 10, 30, or 60 min after exposure. We observed that both monomeric and polymeric HDI were readily absorbed into the skin and that the clearcoat composition affects the penetration rate of the individual isocyanates. The short-term absorption rates for HDI monomer, biuret, and isocyanurate were determined and used to estimate the exposure time required to reach a body burden equal to the American Conference of Governmental Industrial Hygienists (ACGIH) inhalation threshold limit value (TLV) or Oregon State occupational exposure limit (OEL). Oregon is the only government entity in the United States to promulgate a short-term exposure limit (STEL) for HDI-based polyisocyanates biuret and isocyanurate. Based on these absorption rates for a slow-drying clearcoat after 10 min (1.33 g cm(-2) h(-1)) or 60 min (0.219 g cm(-2) h(-1)), we calculated that 6.5 and 40 min dermal exposure, respectively, is required to achieve a dose of HDI equivalent to the ACGIH TLV. For biuret, the time to achieve a dose equivalent to the Oregon OEL for slow-drying clearcoat was much shorter (<31 min) than that for fast-drying clearcoat (618 min). Isocyanurate had the shortest skin absorption times regardless of clearcoat formulation (14 s-1.7 min). These results indicate that the dose received through dermal exposure to HDI-containing clearcoats has a significant potential to exceed the dose equivalent to that received through inhalation exposure at established regulatory limits. A critical need exists to monitor dermal exposure quantitatively in exposed workers, to use proper protective equipment to reduce dermal exposure, and to re-evaluate regulatory exposure limits for isocyanates.
Keywords
Humans; Skin-exposure; Isocyanates; Skin-absorption; Monomers; Polymers; Body-burden; Exposure-assessment; Exposure-limits; Absorption-rates; Threshold-limit-values; Short-term-exposure; Dose-response; Coatings
Contact
Leena A. Nylander-French, Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, CB #7431, Rosenau Hall, Chapel Hill, NC, 27599-7431, USA
CODEN
JEMOFW
CAS No.
822-06-0; 108-19-0
Publication Date
20120301
Document Type
Journal Article
Email Address
leena_french@unc
Funding Type
Grant
Fiscal Year
2012
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-T42-OH-008673; Grant-Number-T42-CCT-422952; B06202012
Issue of Publication
3
ISSN
1464-0325
Source Name
Journal of Environmental Monitoring
State
NC
Performing Organization
University of North Carolina, Chapel Hill, North Carolina
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