Evidenced-based biomonitoring program development for the oil industry

Introduction
Bio-monitoring is an important instrument of exposure assessment in industry. However, lack of practical guidelines might have prevented a more extensive use in the developing world. We developed evidence-based recommendations for the use of BTX bio-monitoring in the oil industry.

Methods
Exposure assessment applications of bio-monitoring were identified based on the needs of a large oil company in Colombia. We conducted a review of available biomarkers in urine, blood, exhaled air and saliva for these identified applications. ACGIH documentation was complemented with a systematic search of relevant literature in Citation Indexes, Medline, EBSCO HOST and Embase. Specific biomarkers were then recommended for specific applications based on sensitivity, expected concentrations in the absence of exposure in the population of interest and specificity; the easiness of sampling, stability of the sample, and availability of the analytic technique in the country were also considered.

Results
Decision-making procedures for frequency of sampling, analytical techniques and acceptable risk of exposure were developed for four bio-monitoring applications: 1) Dedicated bio-monitoring, appropriate where there is a suspicion of exposure routes different from inhalation; 2) Routine bio-monitoring, appropriate to complement air monitoring of exposures; 3) After-accident bio-monitoring, appropriate to check for potential exposures after accidental spoils or leakages; and 4) Control bio-monitoring, appropriate to follow-up the effectiveness of interventions. Thirteen different biomarkers reported in 100 relevant documents were considered. In the case of benzene, s-phenylmercapturic acid in urine is recommended for applications 1, 3 and 4; while tt-muconic acid in urine is recommended for application 2. In the case of toluene and xylene, o-cresol and methyl hippuric acid in urine are recommended for all applications, respectively. For exposures occurring during short periods of time, it is recommended to measure BTX in urine.

Discussion
Provided recommendations should be evaluated critically before being extrapolated to other industrial operations.