1SKC Inc., Eighty Four, PA
There has been a strong focus on benzene personal monitoring in the petrochemical industry due to the health effects of benzene. A point of care test using a fluorescent inhibition assay has been developed to monitor for the metabolite s-PMA in urine. The assay will be less labor intensive and provide a much higher sensitivity to detect some of the lower guidelines that are being proposed. Fluorescently labeled antibodies react with an SPMA conjugate coated on a glass slide. Once the reaction is complete, it can be read on a portable fluorescence reader that will provide results within a few hours of being analyzed. The objective of this study was to provide a user-friendly point of care approach for benzene in urine. Approach should be sensitive enough for the new guidelines, portable for field use, and can provide fast biological monitoring based on the present knowledge of urinary SPMA ELISA. This will enable the users to receive results in a timely fashion to prevent further overexposures in the workplace.
Situation / Problem:
Benzene is a known carcinogen and the 8-hr. TLV guidelines are being lowered. Since workers are concerned about their health from workplace exposures, biomonitoring should be used to address exposures by all routes. Biomonitoring is important for benzene due to the skin notation and to short-term peak exposures that are prevalent. Current biomonitoring methods are not sensitive enough and have a long turnaround time, limiting the potential for immediate response in the workplace. Biomonitoring can be cumbersome and expensive, particularly if you are working on an oil platform in the ocean. Samples must be flown to and from the rig, making this sampling approach very costly. In addition, users wait sometimes 2 to 3 weeks for results. Also, the existing assay using s-Phenylmercapturic acid (SPMA) needs improved sensitivity to achieve some of the lower guidelines being proposed internationally.
A Nexterion glass slide containing a multi-component organic hydrogel was used in this study for the immobilization of the conjugate antigen. The SPMA-BSA conjugate was prepared and immobilized on to the Nexterion slide and placed in a freezer at - 20°C. A portion of the antibody solution was fluorescently labeled with Oyster-550-NHS, to provide better sensitivity during the assay. Binding experiments were performed with the conjugate treated slides and the fluorescent-labeled antibodies. First, the fluorescence properties of the antibodies were tested in solution using a Tecan Fluorescence instrument. The fluorescence properties were good with a maximum emission at 573 nm. Binding experiments were then conducted on the coated glass slides and the coating conditions were optimized to give maximum fluorescence. The slides were glued to 96-well plates for best performance. Antibody standards were then prepared in synthetic urine and were analyzed with some actual urine samples from the field. The Log of the SPMA concentration versus fluorescence absorbance units was plotted.
Results / Conclusions:
The results indicate that the fluorescent immunoassay is reliable and accurate. A calibration curve was plotted and results from previously tested urine samples using traditional SPME methods correlated well with the curve. The sensitivity for this technique is 2 micrograms SPMA per gram of creatinine. The biological exposure index (BEI) for benzene is 25 micrograms per gram of creatine, providing a good increase in sensitivity. The total analysis time has been reduced to 3 hours and the results can be received immediately. The portable fluorescent reader is still in development but is set up for manual slide positioning, an optical path, a controller measuring system with touchscreen, and an amplifier with photodiode, all contained in a light-tight enclosure. These glass slides with reader will allow the user to receive results on workers exposures within 24 hours. This point of care instrument for benzene in urine will assist H&S personnel in maintaining the health and functioning of workers at risk for exposure to benzene. It will provide insights in benzene exposures earlier and at a lower cost, enabling more effective prevention at a personal level.
Hazard Recognition/Exposure Assessment
Total Exposure Health/Total Worker Health®
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Acknowledgements and References
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How will this help advance the science of IH/OH?
This point of care instrument will help us to better characterize benzene exposure in the oil and gas industry.
What level would you consider your presentation content geared towards?
Intermediate: Specific topics within a subject. The participant would have two (2) to ten (10) years experience in industrial hygiene or OEHS and a good understanding of the subject area, but not of the specific topic presented. Prerequisites required: another course, skill, or working knowledge of the general subject.