Sulfur Dioxide and Volatile Organic Compound Exposure to a Community in Texas City, Texas Evaluated Using Aermod and Empirical Monitoring Data

Abstract

According to emissions data reported to the United States Environmental Protection Agency (USEPA) and the Texas Commission on Environmental Quality (TCEQ), the BP Products North America Inc. (BP) Texas City Refinery is the worst polluter of all the industries in Texas City and is one of the worst polluting refineries in the country. The facility has reported releasing substantial emissions of Sulfur Dioxide (SO2) and Volatile Organic Compounds (VOCs). Air dispersion modeling of the emissions from the facility can be used to assess contamination in the community surrounding the BP Texas City Refinery. In the present study, air dispersion modeling of SO2 and VOCs was performed using AERMOD, the EPA-preferred regulatory dispersion model, to determine the impact of BP's contribution to local air pollution on residents of Texas City and La Marque. SO2 emissions reported to be released by the facility were modeled using AERMOD and it was determined that geographical locations inside this plume experienced ambient air concentrations of SO2 meeting or exceeding 50 micrograms per cubic meter (µg/m 3 ) in 2009 and 2010. Data collected by six active SO2 air monitors located in Texas City support the air dispersion modeling results. Additional modeling was conducted for VOCs emitted by the facility in 2010. The AERMOD analysis of SO2 concentrations in and around the BP facility produced results consistent with data collected by the air monitoring network in Texas City. This confirms the accuracy of AERMOD's estimations and its reliability as an emissions modeling tool. VOC concentrations available for analysis from the air monitoring network in Texas City are extremely limited in terms of the quantity of VOCs sampled for. This evidence affirms the ability of AERMOD to demonstrate comprehensive contaminant impacts that surpass the ability of the current air monitoring network.

Residential exposure to petroleum refining and stroke in the southern United States

“…PPR is concentrated within the southeastern US and emits multiple airborne pollutant classes that have been implicated in stroke pathogenesis, including PM, NO x , SO 2 , PAH, and VOCs [15][16][17]. These constituent pollutants may travel sufficient distances to expose residents of adjacent communities [17,19]. Effluent may contain hydrocarbons and related derivatives, affecting the quality of adjacent soil and potable water supplies [14].…”

“…The moderate correlation between X AQS and SO 2 at 2.5 km and 5 km buffer distances may support the use of our exposure metrics as a proxy for at least air pollution. (American Meteorological Society/ Environmental Protection Agency Regulatory Model) (AERMOD), an EPA's recommended regulatory dispersion model, revealed that SO 2 and VOCs are dispersed over 10 km in Texas City [19] and SO 2 may be coupled with air pollutants such as VOCs and particles smaller than PM 2.5 (e.g. secondary particles) close to oil refineries [17], although X AQS is less correlated with SO 2 at 10 km buffer distance in our study.…”

“…We specified a consistent control group for each threshold distance, consisting of census tracts located at distances >5 km and <11.1 km from a refinery. The distance thresholds were specified a priori and informed by measured levels of SO 2 near refineries and their patterns of decay with distance from smokestacks [19]. Selection of the control group was informed by visual inspection on spatial correlation of stroke prevalence using semi-variograms (figure S2) and by the distribution of stroke prevalence over proximity to refineries to adjust for unmeasured spatial confounding by spatial matching because census tracts within 11.1 km from a refinery have more spatial similarity (see section 2.6).…”

“…As mentioned above, we selected distance thresholds a priori based on patterns of decay with distance from smokestacks [19]. We further considered measured levels of ambient SO 2 when establishing a priori buffer distance thresholds.…”

Adjustment for Unmeasured Spatial Confounding in Settings of Continuous Exposure Conditional on the Binary Exposure Status: Conditional Generalized Propensity Score-Based Spatial Matching

“…We calculated X ct values corresponding to 5-km buffers. This threshold was chosen based on air pollution dispersion from smokestacks of refineries and empirical correlation between petroleum production and measured levels of SO 2 , which is a byproduct of petroleum production and refining (48).…”