Biomonitoring of exposure to ethylene oxide and propylene oxide by determination of hemoglobin adducts: correlations between airborne exposure and adduct levels

Objectives: Ethylene oxide (EO) and propylene oxide (PO) are important indu strial chemicals. Exposure to these directly acting mutagens may be monitor ed by determination of their adducts to hemoglobin (Hb). This study establi shes correlations between airborne concentrations of EO and PO and their Hb adducts in petrochemical workers. Methods: In three different studies cond ucted during maintenance Shutdown of petrochemical plants the external occu pational exposure to EO and PO was assessed by personal air monitoring (PAM ). The internal exposure to EO and PO was con; comitantly assessed by deter mination of N-(2-hydroxyethyl)valine (HOEtVal) and N-(3-hydroxypropyl)valin e (HOPrVal) in blood samples of the operators using the N-alkyl-Edman degra dation method. Results: In the first study, PAM was applied once a month at random over a period of 4 months. Blood samples for Hb-adduct determinatio n were collected at the end of this period. No significant correlation was found between PAM and Hb-adduct data. In the next two studies, PAM was appl ied to the operators during the entire shift on every working day during th e shutdown. Blood samples were collected before and immediately after the s hutdown period. Highly significant correlations were found between the incr ement in the concentration of HOEtVal and HOPrVal over this period and the total exposure to EO and PO, respectively. Conclusions: Time-integrated exp osure to EO or PO can be readily and reliably assessed by measurement of th e concentration. of HOEtVal or HOPrVal in a small blood sample. In workers occupationally exposed to low concentrations of EO or PO, good correlations were found between these Hb adducts and the airborne concentrations of EO and PO. These correlations allow the calculation of tentative biological ex posure limits (BELs) for EO and PO. At the current Dutch occupational expos ure limit (OEL) for EO (0.84 mg m(-3), X-h TWA) the EEL is 3.2 nmol HOEtVal /g globin. At the value of 10 mg m(-3) (8-h TWA), which is currently being investigated as the new Dutch OEL for PO, the corresponding EEL is 5.3 nmol HOPrVal/g globin.