Associations between airborne crude oil chemicals and neurological symptoms among workers in the gulf long-term follow-up study

Background: Many volatile organic compounds may be neurotoxic at occupational levels. However, little is known about the neurotoxicity of these chemicals below occupational exposure limits, including among oil spill response and cleanup (OSRC) workers. Objective: We studied associations of neurological symptoms with exposure to benzene, toluene, ethylbenzene, xylenes, and n-hexane (BTEX-H) individually and as a mixture among 23,641 OSRC workers enrolled in the Gulf Long-Term Follow-up (GuLF) Study, a cohort following the 2010 Deepwater Horizon disaster. Methods: At enrollment, participants reported frequencies of neurological symptoms in the preceding 30 days. Cumulative inhalation exposure to the BTEX-H chemicals (ppb-days) and to total hydrocarbons (THC; ppm-days) were estimated using a job exposure matrix linking exposure group estimates to detailed individual OSRC work histories. We calculated adjusted prevalence ratios (PR) and 95 % confidence intervals (CI) for associations across quartiles (Q) of each exposure and each neurological symptom, as well as multiple symptoms, reported all or most of the time, using modified Poisson regression. Quantile g-computation was used to estimate the per-quartile increase in the effects of the BTEX-H mixture on neurological symptoms. Results: Twenty-eight percent of participants reported experiencing at least one, and 5 % reported 2 or more, neurological symptoms. Increased exposure to THC was associated with increased prevalence of two or more neurological symptoms (Q₄ vs. Q₁ PR = 1.94 (95 % CI:1.75, 2.15)), with similar results observed for other BTEX-H chemicals. Exposure to the BTEX-H mixture was associated with a per-quartile increased risk of two or more neurological symptoms of PR = 1.21, (95 % CI: 1.17, 1.25).