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Open Access Publications from the University of California

Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2017)

The purpose of this project was determining the exposure of toxic vapors, particularly benzene, toluene, ethylbenzene and xylene (BTEX), to workers during an underground storage tanks (UST) inspection process. BTEX are a group of hydrocarbons that are commonly found as volatile organic compounds (VOCs) in gasoline products. Thousands of other VOCs can also be found in gasoline, some that have been identified and others that have not. For this project, a total of 8 different fillingstations were examined during a UST inspection with the help of a local regulatory agency. The project was conducted during the months of January to April 2017. The exposure assessment was divided into 4 phases(laboratory pre-calibrations, preliminary, secondary and personal sampling) to assess whether high air concentrations of VOCs and BTEX were present at the sites. A Photoionization Detector (ppbRAE 7240) was used to measure total VOC levels. A portable Gas Chromatography (GC) (PetroPRO) was used to measure the levels of BTEX. Integrated personal breathing zone sampling was also done at four sites with time ranges of 60-99 minutes. Personal samples were analyzed by GCMS after desorption of the charcoal tube with carbon disulfide.

VOC levels were at much higher concentrations when compared to the BTEX levels at concentrations ranging from 1.0ppm to 200ppm. BTEX concentrations levels decreased over time at constant cool temperatures and ranged from 118 to 340, 151 to 483, 276 to 926, and 249 to 869 ppb for BTEX, respectively. It was also observed that with higher increasing ambient temperatures, concentrations increased over time from 111 to 769, 81 to 504, 75 to 503, and 68 to 406ppb for BTEX, respectively. BTEX concentrations were overall below OSHA’s PELs and STELs, and NIOSH STELs. For one particular site, concentrations of benzene did exceed NIOSH RELs of 0.1 ppm (100ppb) and was above OSHA’s Action Level (AL) at 0.5 ppm (500ppb).

Overall, BTEX concentrations decreased over time with cooler temperatures and increased with warmer temperatures. VOCs were significantly high based on location and concentrations levels changed based on the time of the day related to temperatures. Turbine sumps showed the highest concentrations for VOCs and BTEX when compared to fillings sumps and dispenser sumps. Personal samples results were basically inconclusive because the samples were not analyzed until 6 months after sampling. Also, exposure assessment was not done for a total 8-hour exposure as required to compare with Cal/OSHA regulations and NIOSH guidelines. Similar concentrations were found for benzene and xylene (benzene being the highest concentration and xylenes being the lowest) as Site 4. All data were lower than 0.1 Cal/OSHA PELs, with the highest concentrations being 40.8 ppb for Site 5 and the lowest at 0.5 ppb for Site 6.In general, exposure levels to BTEX were not of immediate concern but it is still recommended for workers to take preventative measures to reduce exposures.

    Cover page: Exposure Assessment for Toxic Vapors During Underground Storage Tank Inspections
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (2021)
    Anthropogenic warming and ocean acidification are predicted to negatively affect marine calcifiers. While negative effects of these stressors on physiology and shell calcification have been documented in many species, their effects on shell mineralogical composition remains poorly known, especially over longer time periods. Here, we quantify changes in the shell mineralogy of a foundation species, Mytilus californianus, under 60 y of ocean warming and acidification. Using historical data as a baseline and a resampling of present-day populations, we document a substantial increase in shell calcite and decrease in aragonite. These results indicate that ocean pH and saturation state, not temperature or salinity, play a strong role in mediating the shell mineralogy of this species and reveal long-term changes in this trait under ocean acidification.
      Cover page: Shell mineralogy of a foundational marine species, Mytilus californianus, over half a century in a changing ocean
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2022)
      OBJECTIVES: Persistent functional impairment is common in bipolar disorder (BD) and is influenced by a number of demographic, clinical, and cognitive features. The goal of this project was to estimate and compare the influence of key factors on community function in multiple cohorts of well-characterized samples of individuals with BD. METHODS: Thirteen cohorts from 7 countries included n = 5882 individuals with BD across multiple sites. The statistical approach consisted of a systematic uniform application of analyses across sites. Each site performed a logistic regression analysis with empirically derived higher versus lower function as the dependent variable and selected clinical and demographic variables as predictors. RESULTS: We found high rates of functional impairment, ranging from 41 to 75%. Lower community functioning was associated with depressive symptoms in 10 of 12 of the cohorts that included this variable in the analysis. Lower levels of education, a greater number of prior mood episodes, the presence of a comorbid substance use disorder, and a greater total number of psychotropic medications were also associated with low functioning. CONCLUSIONS: The bipolar clinical research community is poised to work together to characterize the multi-dimensional contributors to impairment and address the barriers that impede patients complete recovery. We must also identify the core features which enable many to thrive and live successfully with BD. A large-scale, worldwide, prospective longitudinal study focused squarely on BD and its heterogeneous presentations will serve as a platform for discovery and promote major advances toward optimizing outcomes for every individual with this illness.
        Cover page: Predictors of functional impairment in bipolar disorder: Results from 13 cohorts from seven countries by the global bipolar cohort collaborative.
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2024)
        Deficits in memory performance have been linked to a wide range of neurological and neuropsychiatric conditions. While many studies have assessed the memory impacts of individual conditions, this study considers a broader perspective by evaluating how memory recall is differentially associated with nine common neuropsychiatric conditions using data drawn from 55 international studies, aggregating 15,883 unique participants aged 15-90. The effects of dementia, mild cognitive impairment, Parkinsons disease, traumatic brain injury, stroke, depression, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, and bipolar disorder on immediate, short-, and long-delay verbal learning and memory (VLM) scores were estimated relative to matched healthy individuals. Random forest models identified age, years of education, and site as important VLM covariates. A Bayesian harmonization approach was used to isolate and remove site effects. Regression estimated the adjusted association of each clinical group with VLM scores. Memory deficits were strongly associated with dementia and schizophrenia (p < 0.001), while neither depression nor ADHD showed consistent associations with VLM scores (p > 0.05). Differences associated with clinical conditions were larger for longer delayed recall duration items. By comparing VLM across clinical conditions, this study provides a foundation for enhanced diagnostic precision and offers new insights into disease management of comorbid disorders.
          Cover page: Verbal Learning and Memory Deficits across Neurological and Neuropsychiatric Disorders: Insights from an ENIGMA Mega Analysis.
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