Protecting Worker Health Through Biological Monitoring: Urinary S-Phenylmercapturic Acid (SPMA) as a Tool for Assessing Barriers and Control Efficacy

Abstract

Abstract Benzene is a common component of some petroleum streams. It is causally related to acute myelogenous leukemia (AML) and aplastic anemia and is associated with myelodysplastic syndrome. Depending on the country and regulator, the current occupational exposure limit (OEL) for an 8 hr TWA (Time Weighted Average) is between 0.5 – 1.0 ppm. Biological monitoring for benzene may be performed as part of regular medical surveillance as well as post-incident. Given the continuous lowering of the OEL, it is imperative that a sensitive and specific biomarker be used. Urinary S-Phenylmercapturic Acid (S-PMA) was used as a biomarker to assess absorption of benzene and to provide assurance that engineering, personal protective including respirator controls are effectively utilized for all tasks. Smoking status of participants was assessed to review impact on S-PMA results. Results showed that S-PMA levels are low and often below the laboratory cutoff value of 5μg/L in non smokers performing routine work, reflecting effective engineering and personal protective equipment (PPE) controls. About 25% of smokers performing routine tasks had S-PMAs results above 5μg/g of creatinine. This is likely due to benzene in cigarette smoke. Therefore, one must consider smoking status when interpretating workplace benzene absorption. During an incident, where there is a potential for benzene exposure, a careful review of smoking status along with other relevant factors, such as air monitoring, material of exposure, and use of PPE including respirators should be considered to determine effectiveness of controls. Past studies and this data shows that biomarkers can accurately assess worker exposures and controls in protecting workers both for long and short-term exposures. During incidents where hydrocarbons containing benzene are released, early and proper use of personal protective equipment (PPE) and respirators can prevent absorption. This also suggests that US OSHA regulations for post incident biomonitoring currently requiring the non specific and less sensitive biomarker urinary phenol reflects older technology and science and should be updated to a specific and more sensitive biomarker for benzene such as urinary S-PMA.