Neurological Effects of Environmental Styrene and BTEX Exposure in a Gulf of Mexico Cohort

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Abstract Styrene is neurotoxic at occupational levels, but has received little study at environmental levels experienced by the general population, despite widespread exposure. Our study team has found that annual average ambient styrene levels are adversely associated with neurologic function and symptoms, including decrements in visual, sensory, and vestibular function. Exposure to styrene in the general population occurs primarily through inhalation of industrial and vehicle emissions, tobacco smoke, and off-gassing of building materials. It is produced from petroleum-derived benzene and ethylbenzene, which explains why over half of US styrene production occurs near oil and gas operations in the Gulf states. Benzene, ethylbenzene, toluene, and xylenes (i.e., BTEX) are also neurotoxic at occupational levels. The proposed study is significant because there are virtually no data describing the safety of most of these neurotoxicants at general population levels, despite widespread exposure. The objective of this study is to investigate the acute and chronic neurotoxicity of styrene and BTEX at levels relevant to the general population. Our central hypothesis is that, even at general population levels, higher ambient styrene/BTEX levels are associated with reduced peripheral nerve and neurobehavioral function and increased neurologic symptoms. We will test this in a prospective, well-characterized cohort of 23,370 Gulf state residents enrolled in the Gulf Long-Term Follow-up Study in 2011-2013—a socioeconomically disadvantaged, medically underserved, and racially diverse population with significant unexplained health disparities. This population has average blood styrene levels 2-3 times higher than those observed in the general population, but much lower than the ~25-fold higher levels typically observed in occupationally exposed populations. We have extensive information on all cohort members, from enrollment and follow-up interviews, on demographic, lifestyle, occupational, and health factors; geocoded residential histories; measured blood levels of styrene and BTEX from 965 cohort members during the last year of enrollment; and results of extensive peripheral neurologic function and neurobehavioral tests administered to 3,403 members 2-4 years after enrollment. We propose to: (1) Generate high resolution temporally- and spatially-referenced ambient (air) styrene and BTEX concentrations in the Gulf region over a 6 year follow-up period, (2) Evaluate estimated ambient styrene and BTEX concentrations against measured blood styrene and BTEX levels, and (3) Determine associations of styrene and BTEX exposures, both individually and as a mixture, with neurologic symptoms and neurobehavioral and peripheral neurologic function, accounting for other neurotoxic air pollutants. This study is innovative because we will be the first to investigate the neurotoxicity of styrene at general population levels and we will do so using state-of-the-art air quality exposure data fusion methods that have not previously been applied to styrene or BTEX. The Public Health Impact of this research is high because exposure to styrene and BTEX is widespread and these chemicals are known to be neurotoxic at occupational levels.