Environmental Contaminants and Diabetes Mellitus
Open AccessAbstract of Dissertation Environmental Contaminants and Diabetes MellitusDiabetes Mellitus is a significant global public health problem with increasing incidence and prevalence over the past few decades (GBD, 2015). The global prevalence (age-standardized) of diabetes mellitus has almost doubled since 1980, rising from 4.7% to 8.5% among adults (WHO, 2016). Overall, this disease caused 1.5 million deaths in 2012, globally. Additionally, it is a risk factor for other chronic diseases, such as cardiovascular disease, which causes an additional 2.2 million deaths globally (WHO, 2016). Known risk factors of diabetes mellitus consist of genetic, behavioral (e.g., low physical activity), and environmental factors (e.g., diet,), however these factors alone cannot explain the global rise in diabetes mellitus during the last few decades (ADA, 2014). More recently animal studies have reported exposures to certain environmental contaminants have a role in developing diabetes mellitus (ADA, 2014).Humans are exposed to a wide range of chemicals present in the environment. Although a number of adverse impacts to human health have been linked to environmental contaminant exposures, limited research has focused on the association between pesticides and diabetes mellitus or the association between environmental contaminants and gestational diabetes mellitus. Given the global concern about diabetes mellitus and related consequences, further evaluations are required to determine the relationships between environmental contaminants and their adverse consequences to diabetes mellitus.In this dissertation, we conducted three studies. First, we investigated the association between pyrethroid pesticides and diabetes mellitus among 3,849 adults (age≥20 years) from the National Health and Nutrition Examination Survey (NHANES) 2007-2010. In this cross-sectional study, we evaluated the association between four pyrethroid urinary metabolites (3PBA(3-phenoxybenzoic acid); 4F3PBA(4F3PBA 4-fluoro-3-phenoxybenzoic acid); trans-DCCA(trans-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid); and cis-DBCA(cis-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid)) and self-reported physician diagnosis of life time diabetes mellitus status. Results indicated a positive association between one pyrethroid metabolite, 3PBA, and diabetes mellitus, after adjusting for potential confounders. Second, we explored the association between organophosphate pesticides and diabetes mellitus among 1,817 adults (age≥20 years) from the NHANES 2007-2008. In this cross-sectional study, we evaluated the association between five organophosphate urinary metabolites (dimethylphosphate(DMP); diethylphosphate(DEP); dimethylthiophosphate (DMTP); diethylthiophosphate(DETP); and dimethyldithiophosphate(DMDTP)) and self-reported physician diagnosis of life time diabetes mellitus status. Results indicated no significant association between any organophosphate urinary metabolites and diabetes mellitus, after adjusting for potential confounders. Finally, we evaluated the effects of environmental contaminants on gestational diabetes mellitus. In this systematic review, we reviewed the literature to identify human studies following the Navigation Guideline (Woodruff & Sutton, 2011). We identified relevant human studies, evaluated the risk of bias in each study, and determined the quality and strength of the evidence across studies. We identified nine studies that evaluated a total of 35 different contaminants. Among these contaminants, 17 had positive associations, 10 had negative associations, and eight had no associations with gestational diabetes mellitus. After identifying and reviewing all of the available studies, we assigned moderate quality to the evidence across all studies, and concluded that there were insufficient evidence that environmental contaminants affect gestational diabetes mellitus.
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