Recent Thesis Topics

2017

  • Examining the Association Between Temperature and Mental Health-related Outcomes in California
    Working with the Office of Environmental Health Hazard Assessment in the California EPA, I used a time-series Poisson regression model to determine whether there is a statistically significant association between ambient temperature and mental health outcomes. I obtained counts of ER visits attributed to a mental health disorder, suicide or self-inflicted injury, and homicide or injury purposely inflicted by others in the state of California between 2005 and 2013. I found that seasonally warm temperatures were associated with a 6-9% higher incidence of mental disorder ER visits in the warm season and a 7-11% higher incidence in the cool season. Additionally, warm temperatures were associated with a 24-29% higher incidence of homicide/inflicted injury ER visits in the warm season and an 11-34% higher incidence in the cool season, compared to the reference temperatures. As global temperatures continue to rise and heat waves are predicted to become more frequent, it is important to understand how mental health outcomes may be impacted.

  • Cell Phone Use and Risk of Thyroid Cancer: a Population-based Case Control Study in Connecticut
    Cell phone use, which exposes users to non-ionizing radiation, has substantially increased in the United States over the past decades with millions of current cell phone users. Thyroid cancer incidence has also been increasing over a similar time frame; ionizing radiation is an established risk factor. The carcinogenicity of exposure to non-ionizing radiation from cell phone use is a controversial topic and previous studies have reached inconsistent conclusions, such as with respect to brain cancer. However, no study has directly investigated the association between cell phone use and thyroid cancer. A population-based case-control study was conducted in Connecticut between 2010 and 2011, which recruited 462 histologically confirmed thyroid cancer cases and 498 population-based controls. Several metrics capturing frequency and duration of self-reported cell phone use patterns were constructed, including phone use hours per day, number of phone calls per day, and phone use years. Multivariate unconditional logistic regression models were used to estimate the associations between cell phone use and risk thyroid cancer. Cell phone use was not associated with the risk of thyroid cancer (OR: 1.05, 95% CI: 0.74-1.48). However, a suggestive trend of increased risk of thyroid cancer microcarcinoma was observed for long-term and frequent users. Compared to individuals who never used cell phone, individuals who had used cell phone >15 years (OR: 1.29, 95% CI: 0.83-2.00), who had used cell phone >2 hours per day (OR: 1.40, 95% CI: 0.83-2.35), who had the most cumulative phone use hours (OR: 1.55, 95% CI: 0.93-2.57) and who had the most cumulative phone calls (OR: 1.30, 95% CI: 0.82-2.07) had a non-statistically significantly increased risk of microcarcinoma. Future large prospective studies are warranted to further investigate the association.

  • Understanding the Role of Effect Modification of Maternal Risk Factors on Infant Respiratory Distress Outcomes
    We sought to determine which maternal covariates are most associated with infant respiratory distress outcomes. Similarly, this research analyzes which covariates best predict or determine the total length of time an infant with respiratory distress syndrome requires.

  • Genetic Variations in the AGEs/AGER Pathway and Risk of Pancreatic Cancer
    Previous studies suggested that the engagement of advanced glycation end-products (AGEs) and receptor for advanced glycation end products (AGER, also known as RAGE) is associated with pancreatic cancer by modulating chronic inflammation. We conducted a two-stage case-control study to examine the association between 96 single nucleotide polymorphisms (SNPs) in 21 genes of the AGEs/AGER pathway and risk of pancreatic cancer.

  • Assessment of Volative Organic Compounds (VOCs) and Residential Proximity to Unconventional Natural Gas (UNG) Development in Ohio
    Hydraulic fracturing has played more and more important role in supplying natural gas. However, there are limited studies directly focusing on the ambient air quality impact by this industry. Objective: We conducted a community-based, cross-section study in Belmont county, Ohio to assess the association between the detection of indoor and outdoor VOCs (benzene, ethylbenzene and toluene) and the residential proximity to the unconventional natural gas wells. Methods: There are totally 66 participants involved in our study. We set the indoor air samples inside the participants’ house and place outdoor air samples in front porch for 9 days using passive air monitor and collected them back for further analysis. During the home visiting, we also administered a questionnaire about the demographics, home characteristics and participants’ feeling about the air quality. The Pace Analytical Services Company analyzed the concentration of benzene, ethylbenzene and toluene in both indoor and outdoor samples to calculate the time weighted average concentration. We calculated the residential proximity to the unconventional natural gas wells based on the well locations and geocoded addresses of the participants’ house. Then we calculated the inverse distance weighted (IDW) matrix for 2 km and 5 km. We performed chi-square test and Wilcoxon rank-sum test and univariable logistic regression analysis to assess whether the VOCs were more likely to be detected for the participants living within 2km from the nearest wells compared to the participants living out of 2 km from the nearest wells. Results: The detection rate of indoor VOCs are much high than the outdoor detection rate, which were too low to be considered. Also the detection rate of indoor VOCs among houses within 2 km to the wells are higher comparing to the houses out of 2 km from the wells. Observed both indoor and outdoor toluene and ethylbenzene concentration were below the Reference concentration (RfC) by the U.S. Environmental Protection Agency; however, the maximum indoor concentration detected for benzene is 64µg/m^3 and outdoor is 47µg/m^3. Compared to the Reference concentrations (RfCs) from US EPA, 30µg/m^3, participants may be potential exposed to an unsafe level to benzene both indoor and outdoor. We didn’t observe the obviously statistically significant association between the residential proximity to the unconventional natural gas wells and the detection of indoor VOCs. Conclusions: The results of this study didn’t directly suggest the correlation between the residential proximity to the unconventional natural gas wells and the detection of the indoor VOCs (benzene, ethylbenzene and toluene). These analyses require more refined inverse-distance weighted proximity matrix and longer sampling duration for air samples. Our findings in this pilot study did provide some insights and data base for further investigation in Ohio unconventional natural gas development and air quality impacts.

  • Chemicals in Crumb Rubber Synthetic Turf Infill Predicted to be the Most Toxic
    Synthetic turf fields have grown in popularity with currently >11,000 in the United States and >13,000 in Europe. Concerns have been raised about potential chemical exposures and adverse health effects resulting from contact with synthetic turf fields, particularly with the infill material (“crumb rubber”), which is fabricated from recycled tires. In particular, it has been hypothesized that prolonged exposure to crumb rubber may increase risk of cancer. The objective of this thesis was to evaluate the carcinogenicity potential of chemicals present in crumb rubber infill. A systematic literature review was conducted to identify chemical constituents of crumb rubber infill. Next, the carcinogenicity of the identified chemicals was evaluated using the Toxicity Module of a predictive computer program (ADMET Predictor™). The focus was on the software-generated toxicity predictions for the “Chronic Carcinogenicity and Mutagenicity” models within the Toxicity Module, which comprise two in vivo and two in vitro models. Specific thresholds were set for each of the four predictive models and the chemicals were prioritized in 15 categories based on the strength and consistency of the predictions. A total of 413 compounds linked to crumb rubber infill based on 20 published studies were identified. Compounds included polycyclic aromatic hydrocarbons (PAHs), very volatile organic compounds (VVOCs), volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), and metals. Of these, 190 chemicals met the threshold criteria and thus were assigned a priority ranking. Eight chemicals were prioritized into the highest ranking: 9,10-dimethylanthracene; dibenzofuran; N-nitrosodiphenylamine; N-nitrosodimethylamine; 1-methyl-1H-benzotriazol-5-amine; 2-dibenzofuranamine; dibenzothiophene; and 1-methyl-pyrene. The results indicate that several components of crumb rubber contain chemicals with carcinogenic potential. The priority rankings can inform the focus and design of future exposure and epidemiologic studies.

  • Toxicology and Pharmacokinetics of Perfluoroorctanoic Acid (PFOA)
    The purpose of this thesis is to convert the environmental PFOA exposures to internal doses in a specific population and to extrapolate the internal dose into estimates of individual risk. Because exposure to PFOA is suspected to cause a number of human health effects, in order to better understand the impact of environmental PFOA exposure, this thesis first reviewed major epidemiology studies on the most frequently reported cancer and non-cancer human health effects. This thesis also demonstrates the utility of pharmacokinetic models and their dependency on the available parameters for model building. Perfluorooctanoic acid (PFOA), a widely used synthetic chemical, is a growing public health concern. Detectable serum levels can be found in most residents of the U.S. The purpose of this thesis is to convert the environmental PFOA exposures to internal doses in a specific population and to extrapolate the internal dose into estimates of individual risk. The thesis also compared one-compartment models using pharmacokinetic parameters from different human studies, and applied them to drinking water data from the State of Colorado. This thesis demonstrates the utility of pharmacokinetic models and their dependency on the available parameters for model building.

2016

  • Residential lifetime drinking water source and thyroid cancer risk: A Connecticut based case-control study 
  • Aldehyde Dehydrogenase in Tumor Clinical Outcomes: Prediction of Cancer Prognosis and Metastasis 
  • Smoking, Genetic Polymorphisms in DNA Repair Genes and Risk of Thyroid Cancer 
  • Exposure to fracking-released air pollutants and reported health symptoms: a two-year environmental health survey in Southwestern Pennsylvania 
  • Cost-effectiveness of multidisciplinary management and exercise training in heart failure treatment 
  • The role of folate in the association between perinatal air pollution exposure and birth outcomes in Lanzhou, China 
  • Residential proximity to industrial manufacturing facilities and risk of thyroid cancer 
  • piRNAs variants and lung cancer risk: a post-GWAS study 
  • Dietary Patterns and Thyroid Cancer Risk: a Population-Based Case-Control Study 
  • All-source exposures to arsenic for residents living near historic gold mine in northwest Romania

2015

  • Association Between Time Since Food Safety Training and Inspection Score
  • Environmental Risk Assessment of Community Acquired Legionellosis from Recycled Water Use in Los Angeles County California
  • Water Quality Near Shale Gas Development Sites in Rural Southwestern Pennsylvania
  • Health Surveillance of Households Near Shale Gas Extraction Sites
  • Assessment of Utility & Educational Value of a Virtual Medical Ops Center
  • Effect of Maternal Arsenic Metabolism on Low Birth Weight in Romania
  • Air Pollution & The Health Impact Associated with Cookstove Replacement
  • Impact of Inorganic Arsenic Exp on Blood Pressure Reactivity
  • Occupational Hazards of Actors in Atlanta Georgia
  • Modeling Co-occurence of Aedes aegypti & Aedes Mediovittatus