Protein adducts in plasma as biomarkers of exposure to and risk of organic acid anhydrides

Organic acid anhydrides (OAAs) are important industrial chemicals but also potent inducers of airways diseases. Many exposed workers develop specific IgE and IgG antibodies. Hexahydrophthalic anhydride (HHPA) and methylhexahydrophthalic anhydride (MHHPA) are two particularly sensitising OAAs. The aim of this thesis was to develop and evaluate a method for biological monitoring of exposure to and risk of HHPA and MHHPA, using protein adducts in plasma as biomarkers. A total of 141 workers exposed to HHPA and MHHPA and two guinea pigs exposed to HHPA were investigated. Plasma from these were dialysed and the total plasma protein adducts (TPPA) of the anhydrides were hydrolysed. The acids thus formed were extracted, derivatised and analysed by gas chromatography-mass spectrometry (GC-MS). Air levels and urinary metabolite levels of the anhydrides were also analysed by GC methods. Chromatography, electrophoresis and immunological methods were used for separation, identification and quantification of proteins and Igs. Medical histories and symptoms were assessed through questionnaires supplemented with interviews and medical examinations. A quick, simple, accurate, precise and sensitive quantification method for TPPA of OAAs was developed. There were very strong correlations between long-term exposures, as assessed by repeatedly collected urine samples and hemoglobin adducts, and TPPA. Serum albumin (SA) was found to be the major OAA adduct forming protein. Anhydride specific IgE and IgG showed a preferred affinity for SA adducts. There were significant exposure-response relationships for TPPA of HHPA with specific IgE and IgG and symptoms and for TPPA of MHHPA with specific IgG. Thus, the TPPA can be considered to be excellent biomarkers of long-term exposure and of risk. A biological occupational exposure limit for HHPA and MHHPA is suggested.