Dissertation
Polychlorinated biphenyls in human serum: Diet, BMI, and diabetes
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2022
DOI: 10.25820/etd.006529
Abstract
Polychlorinated biphenyls (PCBs), a group of persistent and carcinogenic chemicals, have been suspected to contribute to diabetes risk by acting as endocrine disruptors. Despite a ban on the manufacture of PCBs in 1978 in the U.S., people are still exposed to PCBs through contaminated food and air. The goal of this study was to identify the determinants of serum PCBs, and to identify serum PCB congener profiles associated with diabetes. Specific Aim 1 sought to explore the relation between diet and serum concentrations of PCBs among a total of 76 children and their mothers, by assessing dietary exposure through the Dietary History Questionnaire II (DHQII) and measuring all PCB congeners in their serum and in food from where they shop. The analyses were performed by linear mixed models with households included as the random effect. We estimated a 10-fold decrease in dietary exposure to PCBs over the past two decades. We found that higher diet quality with less processed food, presented by Healthy Eating Index (HEI), was associated with higher serum concentrations of PCBs. Data from the National Health and Nutrition Examination Survey (NHANES) was used for Specific Aims 2 and 3. Specific Aim 2 sought to examine the association between dietary intake and serum levels of PCBs, and whether the association was modified by BMI, by utilizing linear regressions. We found that the association between dietary PCBs intake and serum levels of PCB was modified by BMI, with stronger associations in normal/underweight individuals and no statistically significant association in obese individuals. Specific Aim 3 sought to identify serum PCB congener profiles associated with diabetes, by utilizing classification tree and logistic regression methods. We revealed the combined associations of serum PCBs with diabetes.
In conclusion, this study provides evidence suggesting that the relationships between diet and serum PCB concentrations can vary in time and by BMI and PCB congeners. It also provides new insights into the combined associations of PCBs with diabetes. The findings of this dissertation support further avenues of research including how serum PCBs are associated with inhalation exposure, PCB sulfate metabolites, and PCBs in adipose tissues. Prospective studies with more detailed diabetes information (e.g., type of diabetes) are also needed to confirm the combined associations of PCBs with diabetes.
Details
- Title: Subtitle
- Polychlorinated biphenyls in human serum: Diet, BMI, and diabetes
- Creators
- Tuo Lan
- Contributors
- Peter S. Thorne (Advisor)Wei Bao (Committee Member)Bill Field (Committee Member)Larry Robertson (Committee Member)Kai Wang (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Occupational and Environmental Health
- Date degree season
- Spring 2022
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.006529
- Number of pages
- xii, 97 pages
- Copyright
- Copyright 2022 Tuo Lan
- Language
- English
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 78-85).
- Public Abstract (ETD)
Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants that were widely used as dielectric and heat exchange fluids in industries. Exposure to PCBs can lead to cancer, liver disease, diabetes, and impairment of nervous and immune system functions. People are still exposed to PCBs through contaminated food and air. This study investigated how diet affected serum PCBs, and the risk of diabetes with a mixture of serum PCBs.
This study revealed that dietary exposure to PCBs influenced serum levels of PCBs in underweight or normal-weight individuals but had little effect on serum PCBs in overweight and obese individuals in 2003-2004. In addition, with an estimated 10-fold decrease in dietary exposure to PCBs over the past two decades, current fish, meat and dairy consumption had little effect on serum levels of PCBs. Further, this study found that the risk of diabetes in adults with a higher serum concentration of a PCB or a combination of PCBs was two to three times higher than those with a lower serum concentration, after considering many diabetes-related factors.
This study provides evidence suggesting that the relationships between diet and serum PCB concentrations can vary in time and by BMI. It also provides new insights into the combined associations of PCBs with diabetes.
- Academic Unit
- Occupational and Environmental Health
- Record Identifier
- 9984271355902771
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