Systematic review on benzene, toluene, ethylbenzene, and xylene (BTEX) emissions; health impact assessment; and detection techniques in oil and natural gas operations

The ONG industry emits VOC such as BTEX, which pose health risks to workers. This study analyzed peer-reviewed research articles to provide BTEX emission profiles from three primary ONG operations and their associated health risks. PRISMA (Preferred Reporting Items for Systematic Reviews) was used to choose relevant articles for this review paper. The analysis revealed that in ONG operation, upstream operations involving gas flaring (benzene: 0.115 ± 0.1 ppmv, toluene: 0.029 ± 0.001 ppmv, ethylbenzene: 0.002 ± 0.001 ppmv, xylene: 0.123 ± 0.001 ppmv) contributed to relatively lower concentration of BTEX emission. Meanwhile, midstream operation involving tanker loading (benzene: 5.391 ± 28.670 ppmv, toluene:10.376 ± 48.929 ppmv, ethylbenzene:1.583 ± 6.563 ppmv, xylene:2.067 ± 9.211 ppmv) contributed to significant BTEX emission. On the other hand, downstream operations involving refinery operation zone (benzene: 3.5 ± 1.69 ppmv, toluene: 4 ± 0.87 ppmv, ethylbenzene: 1.2 ± 0.24 ppmv, xylene: 6.6 ± 1.34 ppmv) and refueling station (benzene: 1.164 ± 0.408 ppmv, toluene: 2.394 ± 1.086 ppmv, ethylbenzene: 1.301 ± 0.779 ppmv, xylene: 1.736 ± 0.898 ppmv) exhibited higher BTEX emissions. The Lifetime Cancer Risk (LCR_i) for benzene was greater than 10⁻⁶ near gasoline pump stations (1400 × 10⁻⁶) and during loading operations (160 × 10⁻⁶). Ethylbenzene also had a significant LCR_i value of 1000 × 10⁻⁶ during loading operations. Other ONG activities like gas flaring, inspection operations, and gasoline station pumps have hazard ratio value of > 1. The study highlights BTEX emissions in all three ONG sectors, with significant contributions from midstream tanker loading and downstream refinery and refueling stations. E-nose techniques are promising for BTEX detection due to their real-time measurement capabilities and ease of use. Some Asian countries have reported benzene concentrations exceeding permissible limits during tanker loading and refueling operations. Overall, BTEX emissions are a cause for concern and should be addressed in ONG operations.