Development, validation and characterization of an analytical method for the quantification of hydrolysable urinary metabolites and plasma protein adducts of 2,4- and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate and 4,4'-methylenediphenyl diisocyanate

Abstract

Occupational exposure to diisocyanates within the plastic industry causes irritation and disorders in the airway. The aim of this study was to develop, validate and characterize a method for the determination of 2,4-toluenediamine (2,4-TDA), 2,6-toluenediamine (2,6-TDA), 1,5-diaminonaphthalene (1,5-NDA) and 4,4'-methylenedianiline (4,4'-MDA) in hydrolysed urine and plasma, and to study the correlation between the plasma and urinary levels of these potential biomarkers of 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), 1,5-naphthalene diisocyanate (1,5-NDI) and 4,4'-methylenediphenyl diisocyanate (4,4'-MDI), respectively. Samples were hydrolysed with 0.3 M NaOH at 100 degrees C for 24 h. The diamines were extracted, derivatized with pentafluoropropionic acid anhydride, and quantified by selected ion monitoring on gas chromatography-mass spectrometry. The repeatability and reproducibility of the method were 7-18% and 7-19%, respectively. Dialysis experiments showed that the metabolites of 2,4-TDI, 2,6-TDI, 1,5-NDI and 4,4'-MDI in plasma were exclusively protein adducts. No free diamines were found in urine, indicating that all diisocyanate-related metabolites were in a conjugated form. For each diisocyanate-related biomarker, there were strongly significant correlations (p<0.001) between individual levels of metabolites in plasma and urine, with Spearman's rank correlation coefficient (rs) values of 0.74-0.90. The methods presented here will be valuable for the development of biological monitoring methods for diisocyanates.

Biomarkers of exposure in Monday morning urine samples as a long-term measure of exposure to aromatic diisocyanates

“…The biomarker levels in the urinary and plasma samples were analyzed according to Sennbro et al (2003). In principle, the biological samples were hydrolyzed for 24 h in 0.3 M NaOH in order to release the diisocyanate-related diamines 2,4-toluene diamine (TDA), 2,6-TDA, methylene dianiline (MDA) and naphthalene diamine (NDA).…”

“…When diisocyanates are inhaled they react with biomolecules (Sennbro et al 2003). In the blood it has been shown that the diisocyanates are mainly bound to serum albumin (Lind et al 1997a;Johannesson et al 2004) and the half-life of the adducts in plasma has been reported to be 21 days which is similar to that of albumin (Lind et al 1997b).…”

“…The adducts will be excreted in urine as low-molecular weight conjugates (Lind et al 1996) when the proteins are degraded. These are analyzed as diisocyanate derived amines in hydrolysed fluids (Sennbro et al 2003) or can be analyzed as such (Sabbioni et al 2012). …”

Biological monitoring of exposure to 1,5–naphthalene diisocyanate and 4,4’-methylenediphenyl diisocyanate

“…Absorbed NDI and MDI form protein adducts in blood , Sennbro et al 2003, preferentially with serum albumin in plasma (Johannesson et al 2004). MDI metabolites are excreted in urine as low-molecular weight conjugates (Lind et al 1996a).…”

“…By hydrolysis of biological samples from exposed subjects, the NDI-and MDI-related metabolites are released as 1,5-naphthalenediamine (NDA) and 4,4'-methylenedianiline (MDA), respectively. Methods for the quantification of MDA in hydrolysed biological fluids have been described (Brunmark et al 1992, Schütze et al 1995, Dalene et al 1997, Kääriä et al 2001, Sennbro et al 2003, but few studies have concerned biological monitoring of exposure to MDI (Skarping et al 1996, Kääriä et al 2001. For NDA, one method for determination in hydrolysed urine and plasma has been described (Sennbro et al 2003), and no studies on biological monitoring of NDI have been reported.…”