Scand J Work Environ Health 1993:19 ;255-63 Monitoring occupational exposure to styrene from hemoglobin adducts and metabolites in blood by Alex Christakopoulos, PhDY Emma Bergmark, PhD ,2 Vlado Zorcec," Hannu Norppa, PhD,3Jorma Maki-Paakkanen, PhD,3.4 Siv Osterman-Golkar, PhD2 CHRISTAKOPOULOS A, BERGMARK E, ZORCEC V, NORPPA H, MAKI-PAAKKANEN J, OSTERMAN-GOLKAR S. Monitoring occupational exposure to styrene from hemoglobin adducts and metabolites in blood. Scand J Work Environ Health 1993;19:2 55-63. Monitoring occupational ex- posure to styrene was achieved through quantification of adducts of styrene 7,8-oxide to N-terminal valine in hemoglobin (Hb) on the basis of the enrichment of adducted globin chains by ion-exchange chromatography and gas chromatographic-mass spectrometric analysis by the use of the N-alkyl Ed- man method. Application to blood samples from reinforced plastics workers exposed to styrene and from referents showed Hb adduct levels correlating with the blood styrene glycol and urinary man- delic acid concentrations. The blood styrene glycol and styrene 7,8-oxide levels of the exposed work- ers averaged 2.5 !Lmol· I-I (17 subjects) and 0.09 umol . I-I (7 subjects), respectively. The blood styrene glycol and urinary mandelic acid content (mean 9.5 mmol· I-I, 17 subjects) suggested a styrene con- centration of about 300 mg . m' (75 ppm) in the workplace air. The Hb adduct levels were low (mean 28 pmol . s"). indicating rapid detoxification of styrene 7,8-oxide in humans. Key terms: gas chromatography-mass spectrometry, N-alkyl Edman procedure, styrene glycol in blood, styrene 7,8-oxide in blood, urinary mandelic acid. Styrene is used in the production of various plastics, syn- thetic rubber, and polyester resins. The most extensive human exposure to styrene occurs in the reinforced plas- tics industry. The occupational exposure limit is at present 25 ppm in Sweden and 20 ppm in Finland . The metabolism of styrene has been extensively studied in experimental animals (I, 2). The fate of styrene in human s with re spect to upt ake and di spo- sition is also well understood (3- 5). The first step in the major metabolic pathway is the formation of styrene 7,S-oxide (styrene oxide), which is hydrated to styr ene glycol or conjugated with glutathione in enzyme-catalyzed reactions. The major urinary ex- cretion products, mandelic acid, phenylglyoxylic acid and hippuric acid, are related to styrene glycol, in- dicating the intermediate formation of styrene oxide. Styrene oxide has been detected in the blood of ani- mals experimentally exposed to styrene (2). Low levels of this epoxide have also been indicated in hu- man volunteers exposed to styrene and in occupa- tion ally exposed workers (3). I Present address: Reserca AB, S-118 84 Stockholm, Sweden. 2 Departmentof Radiobiology, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden. J Department of Industrial Hygiene and Toxicology, In- stitute of Occupational Health, Helsinki, Finland. 4 Present address: Division of Environmental Health, Na- tional Public Health Institute, Kuopio, Finland. Reprint requests to: Dr S Osterman-Golkar, Department of Radiobiology, Arrhenius Laboratories for Natural Sciences, Stockholm University, S-106 91, Stockholm, Sweden. Hemo globin (Hb) is suitable as a monitor of gen - otoxic agents because of its ready availability and its relatively long life span, which permits cumul ative doses to be determined (6). The measur em ent of Hb adducts has been used for monitoring environmen- tal factors such as occupational exposures to ethyl- ene oxide (7- 11), propylen e oxide (9, 12), and var- ious components of tobacco smoke (13, 14). In the case of ethylene oxide the sensitivity of the analy - sis of adducts to N-terminal valine in Hb by the N- alkyl Edman proc edure (8, 15, 16) has been shown to be high enough to monitor exposures down to levels that may be acceptable with re spect to the en- suing can cer risk (15). In a previous study (17) using the N-alkyl Edman procedure to monitor Hb adducts in styrene-exposed workers, deuterated 2-hydroxyethylvaline was used as the internal standard. Due to the uncert ainty with respect to the relative yields of the free amino ac id versus the modified N-terminal valine re sidue in Hb in the Edman reaction, the results were expressed as proportional values. The expo sures of the workers ranged from 0.6 to 44 ppm . There was a large, though not signifi cant, difference in the levels of Hb adducts of styrene oxide among the exposed workers and ref- erents, primarily as a consequence of a single heav- ily exposed individual with an extremely high level of adducts. In order to make Hb adducts useful for risk esti- mation, quantitative data on adduct levels are re- quired. We have developed a procedure to determine Hb addu cts of styrene oxide quant itatively in work- ers occupationally exposed to styrene. CZHs)Styrene 255