Trisaminohexyl Isocyanurate (TAHI) Levels in Plasma and Urine in Workers Exposed to 1,6-Hexamethylene Diisocyanate (HDI) Monomer and HDI Isocyanurate

Abstract

Identification and quantification of trisaminohexyl isocyanurate (TAHI) as a biomarker of 1,6-hexamethylene diisocyanate (HDI) isocyanurate exposure is a critical step for evaluating the contributions of work environment and personal protective equipment practices in limiting isocyanate exposure. Polymeric HDI isocyanurate is the predominant inhalation and skin exposure in the automotive repair industry, yet, biological monitoring has been limited to metabolites of HDI monomer exposure. We analyzed TAHI and hexamethylene diamine (HDA), a biomarker for HDI monomer exposure, in the plasma and urine of automotive spray-painters. Despite the large number of samples with HDA, daily total urinary HDA and plasma HDA were weakly associated with inhalation exposures to HDI monomer (Urine: r = 0.121, p = 0.1980; Plasma: r = 0.120, p = 0.2146) or HDI isocyanurate (Urine: r = 0.011, p = 0.9112; Plasma: r = 0.065, p = 0.5015). By comparison, correlations for TAHI were strong with both HDI monomer (Urine: r = 0.329, p = 0.0003; Plasma: r = 0.262, p = 0.0062) and HDI isocyanurate inhalation exposures (Urine: r = 0.364, p = <0.0001; Plasma: r = 0.335, p = 0.0004). HDA and TAHI levels in urine and plasma had equally strong correlations with HDI monomer and HDI isocyanurate skin exposures. However, due to the collinearity of HDI monomer (r = 0.475, p = <0.0001) and HDI isocyanurate (r = 0.377, p = <0.0001) inhalation and skin exposures, the contributions of exposure pathways to biological levels is unknown. Workplace factors such as paint-booth type, coverall and glove use, and respirator type may be equally or more important factors for variation in TAHI levels. Using linear mixed modeling in SAS, we are currently investigating the contributions of exposure pathways and workplace factors on HDA and TAHI levels in plasma and urine in this occupationally exposed worker cohort.