Browsing by Subject "Environmental health"

American cutaneous leishmaniasis (CL) is a severely understudied and neglected“disease of poverty” widespread throughout Peru. Transmission dynamics of CL are complex, requiring sandfly vectors and mammalian reservoir hosts to maintain the pathogen in a local environment whereby incidental hosts (people) can become infected. We employed a One-Health approach to understand CL transmission in rapidly changing region of northern Peru. We describe the characteristics of 529 CL positive patients from four participating clinics. Using conditional logistic regression, we assessed risk factors of CL for residents of small urban areas through a matched case-control study with 63 patients who had visited one of the same clinics for CL (cases) or other medical reasons (controls). We later enrolled 343 households as part of a community based study occurring in 15 urban and rural areas of Soritor. We found 256 positive humans (n= 914) as tested via the Montenegro Skin Test; we found 11 positive dogs (n = 236) via an immunofluorescence antibody test. Our results suggest that most- if not all- of CL transmission is occurring in rural areas and that urban women and urban children engage in many high risk activities typically attributed to men. We find evidence that prevalence of past infection is highest among rural residents and men. We believe dogs are unlikely Leishmania reservoirs in either rural or urban settings. It remains unknown if the high number of MST positive children in rural areas is a result of peridomestic or intradomestic transmission.

Air pollution is a common problem. Particulate matter generated from air pollution has been tied to adverse health outcomes associated with cardiovascular disease. Biomass fuels are a specific contributor to increased particulate matter and arise as a result of indoor heating, cook stoves and indoor food preparation. This is a two part cross sectional study looking at communities in the Madre de Dios region. Survey data was collected from 9 communities along the Madre de Dios River. Individual level household PM2.5 was also collected as a means to generate average PM data stratified by fuel use. Data collection was affected by a number of outside factors, which resulted in a loss of data. Results from the cross-sectional study indicate that hypertension is not a significant source of morbidity. Obesity is prevalent and significantly associated with kitchen venting method indicating a potential relationship.

Despite the threats to morbidity, mortality, and human capital accumulation posed by environmental risks, investments in environmental health technologies remain low. This is especially evident in low- and middle-income countries, which disproportionately shoulder the burden of environmental risk exposure and consequence. Households face competing risks associated with poor air and water quality, necessitating choices about how to invest in technologies to reduce the consequences associated with their exposures. Yet, even in areas where access to environmental health technologies such as improved cookstoves, latrines, and insecticide-treated bednets has expanded and products are subsidized to make them more affordable, adoption and use of these technologies often lag. This dissertation examines some of the conditions that impact environmental health technology adoption and use decisions as well as the health implications of low investment.

In Chapter 1, I ask how air pollution exposure drives consumption behaviors and impacts health outcomes. I examine this question in the short term--asking how behavior and health respond to a large, yet transitory, spike in ambient air pollution--as well as over time--considering the responses to average ambient air pollution levels over a period of 19 years. I leverage variation in air pollution resulting from forest fire emissions in Indonesia between 1996 and 2015 to generate short-term exposure spikes and average exposures over time, and I combine these exposures with four waves household and individual-level survey data. I implement a cross-sectional, difference-in-difference analysis to estimate the immediate effects of an unexpectedly severe forest fire season in 2015, finding increased fuel demands among the most-exposed households as well as declines in lung capacity among emissions-affected children. I extend my analysis across the panel using an instrumental variables approach to estimate consequences of average exposure over time. I find that households facing higher average ambient air pollution exposures are more likely to utilize clean cooking fuels such as LPG. Even with these behavioral adjustments, more-exposed individuals face significant reductions in lung capacity. In line with existing literature, I find negative health implications resulting from short-term exposure shocks; however, my analysis demonstrates that these respiratory consequences are not fleeting, particularly in areas that experience elevated average ambient air pollution levels.

In Chapter 2, I turn to environmental risks posed by limited access to improved sanitation technologies to examine how social influences impact household sanitation decisions. Using three waves of data collected immediately before, a few months after, and a few years after a randomized latrine promotion campaign in rural Orissa, India, I evaluate the extent to which social influences impact sanitation choices. I find that a ten percentage point decrease in neighbors' open defecation reduces a household's likelihood of open defecation by 3-4 percentage points. The sanitation intervention decreased open defecation in the short term; however, this treatment was less effective in neighborhoods with higher rates of open defecation due to strong social effects. Disaggregating social effects by gender, I find that both women and men respond to sanitation behaviors among male neighbors in the short term and female neighbors in the longer term, perhaps because men have more control over initial latrine purchasing decisions while women are more influential in sustaining latrine use over time.

Finally, in Chapter 3, I expand on my analysis of social influences and sanitation practices and examine how households make decisions to contribute to collective action for sanitation. In this chapter, I analyze data from an experimental public goods game I designed and implemented among over 1500 households in rural Bihar and Orissa, India. I randomly assigned each of the 70 villages in the sample into groups that are either homogeneous or heterogeneous by gender for game play. In the context of rural India, individuals are more likely to frequently interact with and make decisions in front of others of the same gender. Thus, splitting the groups in this way provides a proxy for peer or social groups. Participants chose how much to contribute to improved sanitation by making decisions in the game that are associated with actual sanitation and hygiene choices they face every day. Payoffs were awarded after each round, and payoff amounts were dependent on both individual contributions and aggregated group contributions, generating a setting in which the benefits participants received were connected. Comparing the game behavior among participants in groups that were homogeneous and heterogeneous by gender, I find evidence that contributions to collective action for sanitation are higher in gender homogenous groups. Female participants drive this difference, and it is more distinct in the first round of game play. I also find evidence that preferences for improved sanitation as elicited during the experimental games are reflective of actual improved sanitation practices at the household level.

This thesis assesses indoor fine particulate matter (PM2.5) levels in homes in Los Angeles County, California and identifies variables that might impact the effectiveness of High-Efficiency Particulate Air (HEPA) filters in reducing PM2.5 levels in residential settings. While research has confirmed that HEPA filters effectively reduce PM in controlled environments, additional research is needed to understand how well HEPA filters work in residential and commercial settings. For this study, twelve homes in Los Angeles County had either HEPA filters (n=6) or sham filters installed in their bedrooms and living rooms for six months. All twelve homes had indoor and outdoor air pollution sensors installed to monitor and report hourly PM2.5 levels. Results showed varying degrees of HEPA filter effectiveness in each home. One home experienced a reduction in the geometric mean PM2.5 from 6.99 (2.13) µg/m3 during the pre-filter period to 3.2 (2.2) µg/m3 during the filter period; four homes experienced reductions between 0.51 and 1.33 µg/m3; one home experienced a 0.09 µg/m3 increase. In homes with sham filters, all experienced increases in PM2.5 between 0.22 and 1.76 µg/m3. I identified temporal patterns in indoor and outdoor PM2.5 levels and investigated whether housing characteristics and behavior patterns influence the concentration of PM2.5 and the indoor/outdoor (I/O) ratio of particles. A relationship is seen between dramatic spikes in outdoor pollution during events such as the 4the of July and indoor PM2.5 levels. While this is a small study, results from this can be used to inform future study design and best practices for HEPA filter use.

Arsenic (As) exposure via groundwater consumption is a global health problem affecting millions. Monitoring exposure is a key step in understanding and predicating future health outcomes. This thesis explores the relationships between arsenic concentrations in toenails and arsenic in water. Three case studies were investigated, with residents from: North Carolina, USA (n=103); the Rift Valley, Ethiopia (n=60); and the Mekong Delta, Vietnam (n=65). Arsenic concentrations above the WHO's recommended 10ppb limit were found in groundwater from the three research sites.

Arsenic in toenails was analyzed by inductively coupled plasma mass spectrometry (ICP-MS).

In the Rift Valley of Ethiopia, 53% of the tested drinking wells (n=34) had As above the WHO's limit. Arsenic concentrations in toenails (n=60) were significantly correlated to As concentrations in groundwater (r=0.72; p<0.001), reflecting the direct exposure of rural communities to As in well water, which is their principle water source. Male minors (<18 years old) were found to have greater nail-As concentrations compared with adults consuming equal amounts of As (p<0.05). Estimated As dose specifically from drinking water sources was also associated with nail concentrations (p<0.01).

In the Mekong Delta of Vietnam (Dong Thap Province), 36 out of the 68 tested wells had As content above the WHO's recommended limit of 10ppb, with levels as high as 981 ppb. Arsenic contents in nails collected from local residents (n=62) were significantly correlated to As in drinking water (r=0.49, p<0.001). Demographic and survey data show that the ratio of As in nail to As in water varies among residents that reflects differential As accumulation in the exposed population. The data show that water filtration and diet, particularly increased consumption of animal protein and dairy and reduced consumption of seafood, were associated with lower ratios of As in nail to As in water and thus could play important roles in mitigating As exposure.

Sixty-one wells were tested from Union County, North Carolina, with 15 out of 61 wells exceeded the WHO's 10 ppb limit. Arsenic values ranged from below the limit of detection (0.07) to 130ppb, with a mean of 11ppb (median=1.5ppb). Nails were collected from county residents (n=103) and were statistically correlated with As-water concentrations (r=0.48, p<0.001).

Integration of the data from the three cases studies across different populations and ethnicities show high correlation between As concentrations in groundwater and As in nails in all the three locations (r(Union County)= 0.48, p<0.001; r(Ethiopia)=0.72 p<0.001; r(Vietnam)=0.49, p<0.001). For As-nail to As-water pairs in which As in water was above 1ppb, these three locations are statistically indistinguishable from one another (r=0.62, p<0.001, n=176). These results support the hypothesis that nails can be used as a biomarker of exposure regardless of geographic or ethnic differences in populations considered. Nutrition (meat, seafood, and milk consumption) rather than gender, ethnicity, or dose is suggested to be the major confounding issue affecting the magnitude of As exposure in the human body.

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals used in a wide array of products and applications (e.g., nonstick cookware, waterproof and water-repellent textiles, firefighting foam). Following their decades of use, PFAS have garnered concern as “forever chemicals” due to their extreme persistence in the environment and in humans. PFAS have further elicited concern because they have been linked to adverse health effects in humans, and their huge number (over 12,000 different chemicals) and complex chemistry make them very challenging to analyze and study for exposure and toxicology. Two particular PFAS chemicals, perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS), are drinking water contaminants that can be found in the blood of the vast majority of people. PFOA and PFOS are also linked to toxic effects like kidney and testicular cancer, increased blood cholesterol, and reproductive outcomes. These two chemicals are being phased out of use and federal drinking water standards are likely upcoming. However, the replacements for these two chemicals are much less well-characterized, and many of these newer, replacement PFAS chemicals can be found in the environment of North Carolina due (at least in part) to industrial pollution.

The overarching goal of this dissertation was to characterize the potential exposure and health effects of PFAS in North Carolina communities. The surface water and drinking water in some areas of North Carolina have been found to be contaminated with PFAS; however, there are additional routes of PFAS exposure beyond drinking water, such as ingestion of house dust or placental transfer during pregnancy. This dissertation explores various routes of PFAS exposure and better characterizes the specific PFAS analytes that can be found in North Carolina and the concentrations in which they are present. Additionally, this dissertation evaluates this exposure and potential associations with some adverse health outcomes in a few North Carolina communities.

In Chapter 2, the relationships between PFAS exposure during pregnancy and birth outcomes are explored. This chapter includes data on PFAS concentrations in placenta samples from 120 participants in Durham, North Carolina and evaluates the subsequent associations between placental PFAS exposure and birth outcomes (e.g., infant birth weight, gestational age). A total of 11 PFAS were measured in placental tissues collected in 2010-2011, and the compounds PFOS, PFOA, PFNA, and PFDA were detected in all placenta samples. A few placental PFAS were associated with birth outcomes. The most striking result was that placental PFOS was associated with changes in birth weight, but the direction of change depended on the sex of the infant. For male infants, placental PFOS was associated with lower birthweight, and in female infants, placental PFOS was associated with higher birthweight.

In Chapter 3, the exposure to PFAS through drinking water is evaluated in a community with known PFAS water contamination. This chapter includes data on PFAS concentrations in blood serum and drinking water samples from 49 participants in Pittsboro, North Carolina. The community receives its drinking water from the Haw River, a part of the Cape Fear River watershed. Blood and water samples were collected at two different timepoints to explore temporal variability in contamination. This community was found to have blood levels of PFAS about two to four times higher than the U.S. average. This chapter also includes results on the associations between PFAS blood level and clinical chemistry measurements, such as serum lipids, as indicators of health. Negative associations were found between serum PFOS and PFHxA with decreased electrolytes and decreased liver enzymes. Positive associations were found between serum PFOA and PFHxS with increased total cholesterol and increased non-HDL cholesterol.

In Chapter 4, the effects and toxicokinetics of PFAS in a pregnant rabbit model are evaluated. This chapter includes data from an animal study of 21 pregnant rabbits provided with drinking water that is representative of the PFAS exposure observed in Pittsboro, North Carolina. Rabbits were exposed to this environmentally-relevant mixture of ten different PFAS during and before pregnancy. After exposure, the wastes and tissues were evaluated to measure the PFAS concentration that accumulated. This provided information on where PFAS are distributed in the body after exposure. The liver of the pregnant rabbit was also evaluated to determine if there was an increase in lipids in the liver, or any changes in liver lipid metabolism. For this study, few differences were noted between treated animals and control animals, indicating that the environmentally-relevant dose had little effect on pregnant rabbits. However, due to the lack of PFAS accumulation in blood, tissue, or in wastes, it is likely that the dose of PFAS given through drinking water was too low.

In Chapter 5, the levels of PFAS in indoor house dust were evaluated. This chapter includes data on PFAS concentrations in indoor dust from 184 homes in Durham, North Carolina, as well as 49 fire stations across the U.S. and Canada. House dust and fire station dust PFAS concentrations were then evaluated for associations with characteristics of the building (e.g., square footage, amount of carpeting, age of building construction). Levels of precursor PFAS, such as fluorotelomer alcohols, were typically higher in dust than the perfluoroalkyl acids. This study, along with previous literature, shows that the legacy PFAS in dust has been decreasing, but the precursor PFAS has been increasing in U.S. house dust. Few associations were found between building characteristics and dust PFAS. However, one notable result was that higher 8:2 FTOH was found in dust from buildings with more carpeting, indicating that carpets may be an important source of exposure to fluorotelomer alcohols (possibly from stain-proofing treatment).

Collectively, this dissertation provides important information on the potential exposure and health effects of PFAS in North Carolina communities.

Azobenzene disperse dyes are the fastest-growing category of commercial dyestuffs, accounting for 70% of the 9.9 million tons of industrial dye colorants used annually. Azobenzene disperse dyes are intended to be applied to synthetic fabrics such as polyester, nylon, and acrylic; however, azo dyes may also be used in cosmetic products such as hair dyes, and in fashion accessories such as leather goods. Recently, our group and others have detected azobenzene disperse dyes in dust particles collected from the indoor environment, and raising concerns about the release of these chemicals from products and human exposure. Although extensive literature characterizes these chemicals as toxic contaminants in aquatic environments, to date there exists little data on levels, exposures, and hazards associated wit exposures to azobenzene disperse dyes in the indoor environment. The presence of these dyes in the indoor environment is concerning. House dust is a sink for many contaminants that leach out or off-gas from products in the home. Due to children’s unique behaviors (e.g. crawling and hand to mouth activity) they have higher exposure to chemicals associated with dust. Azobenzene disperse dyes are implicated in literature as potentially allergenic: they are known to be present in clothing that elicits allergic reactions such as skin sensitization. Therefore, it is of crucial importance to support research that seeks to characterize children’s exposure in the home environment, and evaluate the in vitro effects of azobenzene disperse dyes. The hypothesis of this research dissertation is that azobenzene disperse dyes are prevalent in dust collected from the indoor environment at concentrations of concern for human health. In the first aim of this thesis research, azobenzene disperse dyes were characterized in commercial mixtures and in children’s polyester clothing. Azo dyes were first purified from dyestuffs by Soxhlet extraction and flash chromatography and then analyzed using ultra-high-performance liquid chromatography (UHPLC) coupled with high resolution mass spectrometry (HRMS), as well as by 1H and 13C NMR for structural elucidations. Nineteen total azobenzene dyes were detected in dyestuffs via a non-targeted analysis approach, including Disperse Blue 79:1, Disperse Blue 183:1, Disperse Orange 44, Disperse Orange 73, Disperse Red 50, Disperse Red 73, and Disperse Red 354. Samples of children's polyester clothing (n=X) were then analyzed via UHPLC-HRMS. In clothing, 21 azobenzene disperse dyes were detected, 12 of which were confirmed and quantified via reference standards. Individual dyes in apparel were quantified at concentrations up to 9230 μg dye/g shirt, with geometric means ranging 7.91–300 μg dye/g shirt. Total dye load in apparel was quantified at up to 11,430 μg dye/g shirt. This research supported the development of reference standards and library mass spectra for azobenzene disperse dyes previously absent from standard and spectral libraries. This study was the first to confirm and quantify these azo compounds in children’s products, facilitating a more robust understanding of sources of azobenzene disperse dyes in the indoor environment. The second aim of this thesis research investigated the presences and quantities of azobenzene disperse dyes and related compounds in indoor house dust (n=188) collected from homes in Durham, NC. Using a targeted approach, we quantified 12 azo disperse dyes and quantified at least one dye in every house dust sample. Detection frequencies ranged from 11% to 89%; of the dyes that were detected in at least 50% of the samples, geometric mean levels ranged from 32.4 to 360 ng/g. HRMS suspect screening analysis identified an additional eight azobenzene compounds in dust that are present at high relative abundances. This study indicates that azo disperse dyes and related compounds are ubiquitous in the indoor environment. To support quality assurance and control during the analysis, a house dust Standard Reference Material (NIST SRM 2585) was extracted and analyzed with the samples. Based on the detection and abundance of azo dyes in SRM 2585, which was prepared from hundreds of dust samples collected in the mid 1990s, azo dye levels in the indoor environment may be increasing over time. To our knowledge, this is the most comprehensive quantitative study of azo disperse dyes in house dust to date. Future studies are needed to quantify additional dyes in dust, particularly those identified here via suspect screening, and to examine exposure pathways of dyes in the indoor environment where children are concerned. The third aim of this thesis research examined the binding reactivity of azobenzene disperse dyes to nucleophilic peptide residues in order to understand their potential reactivity as electrophilic allergenic sensitizers. The Direct Peptide Reactivity Assay (DPRA) was utilized via both a spectrophotometric method and a high-performance liquid chromatography (HPLC) method. Dyes isolated from the commercial dyestuffs, and several potential transformation products, were tested. All dyes were found to react with nucleophilic peptides in a dose-dependent manner with pseudo-first order (kobserved) activity, but overall to react more potently with cysteine than with lysine: EC10 values for cysteine binding were determined as low as 0.005mM and pseudo-first order rate constants as high as 0.04 hr-1 (as observed for Disperse Blue 79:1). Observed rate constants were correlated to metrics of structural features such as Hammett constants and electrophilicity indices, indicating that binding reactivity may be related to structural properties of azobenzene disperse dyes. In addition to examining dyes, the reactivity of extracts of polyester shirts were also examined; shirt extracts with high relative abundances of azobenzene disperse dyes were observed to induce greater peptide reactivity. Results suggest that azobenzene disperse dyes may function as immune sensitizers, and that clothing containing azobenzene disperse dyes may pose risks for skin sensitization. Collectively, this thesis research suggests that azobenzene disperse dyes are common in clothing, and appear to be near ubiquitous in house dust. Given their reactivity in vitro, this may present health consequences, particularly for young children.

Accumulating evidence is suggesting that exposure to some environmental contaminants may alter adipogenesis, resulting in accumulation of adipocytes, and often significant weight gain. Thus these types of contaminants are often referred to as obesogens. Many of these contaminants act via the activation (i.e. agonism) of the peroxisome proliferator activated receptor γ (PPARγ) nuclear receptor. To date, very few chemicals have been identified as possible PPAR ligands. In the thesis, our goal was to determine the PPARγ ligand binding potency and activation of several groups of major semi-volatile organic compounds (SVOCs) that are ubiquitously detected in indoor environments, including flame retardants such as polybrominated diphenyl ethers (PBDEs) and Firemaster 550 (FM550), and other SVOCs such as phthalates, organotins, halogenated phenols and bisphenols. Additional attention was also given to the potential activity of the major metabolites of several of these compounds. Since the primary sink for many of these SVOCs is dust, and dust ingestion has been confirmed as an important pathway for SVOCs accumulation in humans, the potential PPAR binding and activation in extracts from environmentally relevant dust samples was also investigated.

Previous studies have also shown that SVOCs sorbed to organic matrices (e.g., soil and sediment), were only partially bioaccessible (bioavailable), but it was unclear how bioaccessible these compounds are from indoor dust matrices. In addition, bioactivation of SVOCs (via metabolism) could exacerbate their PPAR potency. Therefore, to adequately assess the potential risk of PPARγ activation from exposure to SVOC mixtures in house dust, it is essential that one also investigates the bioaccessibility and bioactivation of these chemicals following ingestion.

In the first research aim of this thesis, the bioaccessibility and bioactivation of several important SVOCs in house dust was investigated. To accomplish this, Tenax beads (TA) encapsulated within a stainless steel insert were used as an infinite adsorption sink to estimate the dynamic absorption of a suite of flame retardants (FRs) commonly detected in indoor dust samples, and from a few polyurethane foam samples for comparison. Experimental results demonstrate that the bioaccessibility and stability of FRs following ingestion varies both by chemical and by matrix. Organophosphate flame retardants (OPFRs) had the highest estimated bioaccessibility (~80%) compared to brominated compounds (e.g. PBDEs), and values generally decreased with increasing Log Kow, with <30% bioaccessibility measured for the most hydrophobic compound tested, BDE209. In addition, the stability of the more labile SVOCs that contained ester groups (e.g. OPFRs and 2-ethylhexyl-tetrabromo-benzoate (TBB)) were examined in a simulated digestive fluid matrix. No significant changes in the OPFR concentrations were observed in this fluid; however, TBB was found to readily hydrolyze to tetrabromobenzoic acid (TBBA) in the intestinal fluid in the presence of lipases.

In research aims 2 and 3, two commercially available high-throughput bioassays, a fluorescence polarization PPAR ligand binding assay (PolarScreenTM PPARγ-competitor assay kit, Invitrogen, Aim 2) and a PPAR reporter gene assay (GeneBLAzer PPARγ non-DA Assay, Invitrogen, Aim 3) were used to investigate the binding potency and activation of several groups of SVOCs and dust extracts with human PPARγ LBD; respectively. In the PPAR binding assay (Aim 2), most of the tested compounds exhibited dose-dependent binding to PPARγ. Mono(2-ethylhexyl) tetrabromophthalate (TB-MEHP), halogenated bisphenol/phenols, triphenyl phosphate and hydroxylated PBDEs were found to be potent or moderate PPARγ ligands, based on the measured ligand binding dissociation constant (Kd). The most potent compound was 3-OH-BDE47, with an IC50 of 0.24 μM. The extent of halogenation and the position of the hydroxyl group strongly affected binding. Of the dust samples tested, 21 of 24 samples showed significant PPAR binding potency at a concentration of 3 mg dust equivalents (DEQ)/mL. In the PPAR reporter assay (Aim 3), many SVOCs or their metabolites were either confirmed (based on previous reports) or for the first time were found to be potential PPARγ agonists with various potency and efficacy. We also observed that 15 of 25 dust extracts examined showed an activation percentage more than 8% (calculated activation threshold) of the maximal activation induced by rosiglitazone (positive control). In some cases, activation was as high as 50% of the rosiglitazone activation for the dust extracts with the highest efficacy. Furthermore, the correlation between the reporter assay and the ligand binding assay among the house dust extracts was significant and positive (r = 0.7, p < 0.003), suggesting the binding potency was predicting activation. In research aim 2, the effect of bioactivation on the PPARγ binding potency was also investigated. In vitro bioactivation of house dust extracts incubated with rat and human hepatic S9 fractions was used to investigate the role of in vivo biotransformation on PPAR gamma activity. The result showed that metabolism may lead to an increased binding affinity, as a 3-16% increase in PPARγ binding activity was observed following bioactivation of the dust extracts.

In research aim 4, an effect-directed analysis (EDA) was used to identify compounds likely contributing to the observed PPAR activity among the dust extract. Three dust extracts which showed significant PPAR activity with approximately 25, 30, and 50% of the maximal response induced by rosiglitazone at the highest efficacy were fractionated using normal phase high-performance liquid chromatography (NP-HPLC) and each fraction was individually tested for PPAR activity. Active fractions were then analyzed using gas-chromatography mass spectrometry (GC-MS) and possible compounds identified. Three dust extracts showed a similar PPAR activity distribution among the NP-HPLC fractions. In the most active fractions, fatty acids (FAs) were identified as the most active chemicals. The concentrations of four FAs were measured in the house dust extracts, and the concentrations were found to be highly correlated with the observed PPAR activity. These four FAs were also tested for PPAR activity and found to be partial PPAR agonists, particularly oleic and myristic acid. To tentatively identify sources of FAs, FAs in human/animal hair, dead skin cells, and two brands of cooking oil were analyzed. We found the same FAs in those samples and there concentrations were relatively abundant, ranging from 186 to 14,868 µg/g. Therefore, these results suggest that FAs are likely responsible for the observed PPAR activity in indoor dust. Also, this is the first study reporting on the level of FAs in dust samples. The source of these FAs in dust may be either from the cooking or accumulation of human/animal cells in indoor dust.

In conclusion, this research demonstrates that many SVOCs ubiqutiously detected in house dust, and/or their metabolites, can be weak or moderate PPAR ligands. In addition, chemical mixtures in house dust can effectively bind to and activate PPAR. However, our results suggest FAs are probably responsible for these observations, and likely outcompeting the synthetic environmental contaminants present in the dust extract. Furthermore, bioactivation of contaminants present in house dust can potentially increase their affinity for PPAR. And lastly, the bioaccessibility and stability of SVOCs in house dust after ingestion are likely to modulate the PPAR activity in the environmental mixtures and should be considered in future risk assessments.

Background: Silver nanoparticles (AgNPs) act as antimicrobials by releasing monovalent silver (Ag+) and are increasingly used in consumer products, thus elevating exposures in human and environmental populations. Materials and Methods: We evaluated Ag+ in a standard model of neuronal cell replication and differentiation, and then determined whether there were similar effects of the ion in vivo using zebrafish. Next, we compared Ag+ and AgNP exposures in the same two models and incorporated the effects of particle coating, size and composition. Conclusions: This work is the first to show that both Ag+ and AgNPs are developmental neurotoxicants in vitro and in vivo. Moreover, although both the soluble ion and the particles impair measures of neurodevelopment, the outcomes and underlying mechanisms of each toxicant are often wholly distinct. Superimposed on the dichotomies between Ag+ and AgNP exposures are clear effects of particle coating, size and composition that will necessitate evaluation of individual AgNP types when considering potential environmental and human health effects. The results presented here provide hazard identification that can help isolate the models and endpoints necessary for developing a risk assessment framework for the growing use of AgNPs.

Introduction: This study explores the cytotoxic effects of Per- and polyfluoroalkyl substances (PFAS), specifically focusing on Perfluorooctanoic acid (PFOA) and its industrial substitute, Gen-X, on a set of human cancer cell lines. PFAS are synthetic chemicals with widespread use and environmental persistence, raising concerns over their potential bio accumulative properties and toxicity. Research aims to elucidate the mechanistic impact of PFOA and Gen-X exposure on cell viability, gene expression, and protein signaling pathways including TGF-β/SMAD, p53 signaling across melanoma (A375), renal (SN12C), liver (HepG2), and colon (SW620) cancer cells.

Method: Employing a comprehensive experimental approach, the study assessed cytotoxicity using the CCK-8 assay, protein expression via Western blot analyses, and gene expression changes through RT-PCR. Four human cancer cell lines were exposed to varying concentrations of PFOA and Gen-X to determine their semi-inhibitory concentrations (IC50) and to analyze the subsequent biological effects.

Result: The results highlighted distinct cytotoxic profiles for PFOA and Gen-X across the examined cell lines, revealing variations in cellular susceptibility and resistance. Melanoma cancer cells (A375) displayed high sensitivity to PFOA but greater tolerance to Gen-X, while renal cancer cells (SN12C) showed significant resistance to both compounds. Molecular analyses indicated that exposure to PFOA and Gen-X modulates the TGF-β/SMAD signaling pathway and activates DNA damage response markers. Furthermore, alterations in the expression of genes related to the cell cycle, apoptosis, and metabolic processes were observed, suggesting potential genotoxic and carcinogenic effects.

Conclusion: The study provides insights into the differential cytotoxic effects of PFOA and Gen-X on human cancer cell lines, underscoring the complex interaction between these PFAS and cellular mechanisms. The findings indicate that PFAS exposure can significantly impact cell viability, gene expression, and protein signaling pathways, contributing to our understanding of their toxicological profile. Given the environmental persistence and widespread use of PFAS, these results underscore the need for further research into their biological impacts and the development of targeted intervention strategies to mitigate their health risks.

Non-essential trace metals (lead, mercury, arsenic, and cadmium) are ubiquitous in our environment and have overlapping routes of exposure, yet mixed trace metal exposures are rarely considered in epidemiological studies. Instead, research often follows a single research question that focuses on a single trace metal of concern and does not incorporate potential co-exposures. The published literature of artisanal small-scale mining in the Amazon is a prime example as it has predominantly focused on mercury exposure, due to its use in the mining process. Once exposures of concern are identified, further studies evaluate health outcomes; however, the health effects cannot be accurately determined without accounting for co-exposures. This verification is becoming more important as there is a growing recognition that mixed trace metal exposures are more common than previously believed.To address the prevalence of mixed trace metal exposures and their health effects in the Peruvian Amazon region of Madre de Dios, I use epidemiological data from the COhorte de NAcimiento de MAdre de Dios (CONAMAD) birth cohort study (2018-Present), and two cross-sectional epidemiological studies (Amarakaeri Communal Reserve study (ACR, 2015), and Etiology and Toxic Metals study (EATM, 2018)). CONAMAD collected survey data along with maternal and cord blood samples at birth, which were processed for minerals and trace metals. The cross-sectional studies collected venous blood for trace metal analysis and hair samples for total hair mercury. Blood samples from the ACR were also processed for amino acids. In-depth demographic and health survey data were collected in all three studies. Structural equation models and random mixed effect models were used to evaluate research questions. The cross-sectional studies demonstrate a high correlation of lead and mercury exposure in communities that rely on wild fish and wild game as protein sources, which is prevalent throughout the Amazon. Consuming a meal of wild game resulted in an estimated lead dose of 500 µg, with those who eat wild game (Yes/No) associated with 1.41 µg/dL (95% CI: 1.20 – 1.70) higher blood lead levels compared to those who do not. This furthers the notion that mixed exposures are likely more common than previously believed. Mixed exposures target the same toxicological pathway, which may lead to synergistic or antagonistic effects. My research found that lead disrupts the arginine pathway and is associated with increased blood pressure. Mercury exposure was a modifier of the arginine pathway, with high blood mercury levels changing the effect of global arginine bioavailability from 17.16 (95% CI: 9.09 – 25.84) to -14.17 (95% CI: -31.88 - -0.33) on systolic blood pressure. Interestingly, mercury was not directly associated with the arginine pathway. Results from the birth cohort demonstrate the importance of nutrition and prenatal care for fetal development, which had a large positive effect on birthweight and gestational age. However, even low maternal lead exposure had detrimental effects on fetal health. A 1% increase in maternal blood lead was associated with a shorter gestational age of 0.05 days (β: -0.75, 95% CI: -1.51 - -0.13), even with the CONAMAD birth cohort having lower blood lead levels than other birth cohorts. There is a need for an integrated approach of nutritional and exposure assessments to better understand neonatal health outcomes.

This paper utilizes a mixed methods approach to evaluate household demand for reduced diarrhea risk through an assessment of willingness to pay (WTP) for water and sanitation technologies in Udaipur, India. Using data from a survey of 900 households, responses to a contingent valuation scenario were analyzed using multivariate logit regression to determine WTP for a water purification device. Furthermore, transcripts from 10 focus groups were analyzed for specific determinants of WTP for a ceramic filter, an open well chlorination tank, and a composting latrine by identifying preferences based on the frequency and type of responses given by group participants. The mean WTP estimated from the logit model was $1.03; this is the monthly WTP amount per person in this sample. The specific determinants for WTP include the randomized price levels, and factors like education level and household socio-economic characteristics. In addition, the qualitative work did not reveal a clear preference by all groups for any one of the three offered technologies, but demonstrated the influence of factors such as perceived health improvement and increased convenience on demand. Understanding what drives demand for these technologies could help implementers in designing more effective behavior change interventions, educational campaigns or social marketing schemes.

Semi-volatile organic compounds (SVOCs) are used in consumer products in a wide variety of applications such as flame retardants, plasticizers, pesticides, preservatives, and fragrances. Due to their extensive use in everyday products, SVOCs are widely detected in indoor environments, and human exposure is common and often chronic. As the wealth of toxicological data examining the negative health impacts of these compounds grows, the need for reliable tools to accurately measure human exposure becomes increasingly more crucial. In the past few decades, external exposure to these compounds have been evaluated through measurements in indoor air, house dust, and hand wipes, all of which have been shown to be associated with internal dose (e.g., concentrations in urine or blood). However, there are significant limitations to using each of these approaches to characterizing exposure. In recent years, silicone wristbands have been used as personal passive samplers for evaluating ambient exposure to a wide array of consumer product and industrial compounds. While over a thousand chemicals have been reported to be detected on the wristbands, very few studies have measured the concentrations on wristbands and determined how well they correlate to established biomarkers of exposure. This dissertation research sought to evaluate the use of silicone wristbands for measuring personal exposure to three classes of SVOCs- organophosphate esters (OPEs), brominated flame retardants (BFRs), and phthalates. The central hypothesis is that wristbands are an effective tool for evaluating personal exposure to SVOCs and provide more accurate measures of exposure compared to tools currently in use.

Within the first aim of this dissertation research, paired samples of polyurethane foam (collected from sofas), house dust, and serum were analyzed for flame retardants (FRs) chemicals and associations were evaluated. The detection of two FR mixtures, PentaBDE and FM 550, in foam was significantly associated with 4 to 6.5 times as high concentrations of their primary components in house dust (p<0.01). These relationships were modified by the size of the sofa footprint within the room and dust-loading rates. PentaBDE in foam was also associated with higher levels of individual PBDE congeners in serum, particularly two of the primary congeners BDE-47 and -153. Participants who lived in a home with a sofa containing PentaBDE had serum BDE-47 levels that were 2.5 times as high as participants whose sofa did not contain PentaBDE (p<0.01). This study was the first to relate a specific FR application in a consumer product with house dust and a known biomarker of exposure.

For the second aim of this research, adult exposure to OPEs and BFRs were evaluated using silicone wristbands. OPEs quantified on the wristbands were significantly associated with metabolites from pooled urine samples, and polybrominated diphenyl ethers (PBDEs) on the wristbands were similarly correlated to PBDE levels in serum (rs=0.4-0.6, p<0.05). Several novel BFR compounds which lack verified biomarkers of exposure were also measured on the wristbands and reported for the first time. These two studies were the first to evaluate FR concentrations on wristbands with known biomarkers and represent two of now four published manuscripts providing evidence that measurements on wristbands are predictive of internal dose.

In the third aim of this research, children’s exposure to OPEs, phthalates, and BFRs were examined using silicone wristbands. The ability of the wristband measurements to predict urinary metabolite levels of OPEs and phthalates was compared to that of hand wipes and house dust. Across the three classes, the children’s wristband concentrations were positively and significantly associated with a number of their corresponding biomarkers in both urine and serum, similar to observations in our adult cohort. For OPEs, phthalates, and PBDEs, the wristbands were found to have similar or an improved utility, compared to hand wipes and dust, for evaluating children’s exposures to these compounds. For instance, one of the OPEs, 4-tertbutylphenyl diphenyl phosphate (4tBPDPP), on wristbands was more strongly correlated to its urinary metabolite, tert-butyl phenyl phenyl phosphate (tb-PPP), compared to that on hand wipes and dust (rs=0.35, p<0.01, compared to rs=0.16 and 0.05 for hand wipes and dust, respectively). For the phthalate benzyl butyl phthalate (BBP), wristbands and hand wipes were similar associated with the urinary metabolite, mono benzyl phthalate (MBzP), but both were stronger than the dust correlation (rs=0.56 for wristbands and hand wipes, p<0.001; rs=0.23 for dust, p<0.05). Similar results were observed among the PBDEs on the three exposure mediums and their serum biomarkers, although the magnitudes of correlation with serum were more similar for wristbands and dust.

Taken together this dissertation research provides some of the first insights on the evaluation of personal exposures to SVOCs using silicone wristbands. It includes six distinct studies evaluating human exposure to sixty-five chemicals from three classes of compounds. Further, this research offers novel contributions to the field of exposure science, evaluating the relationship between wristbands and established biomarkers of exposure and comparing them to the existing tools used in standard exposure assessments. Wristbands have the potential to serve as an inexpensive and non-invasive medium for evaluating human exposure to chemical mixtures, and this work provides support for their use in large-scale research efforts to characterize SVOC exposures. Additional research should continue to assess wristbands for their ability to measure meaningful exposures for additional classes of chemicals, and importantly, identify the pathways of exposure (e.g., dermal absorption, inhalation, etc.) that are captured by the wristbands.

Parabens are environmental phenols that are most commonly found in personal care products (PCPs) worldwide. Though used widely, there is some contradictory information and data in the peer reviewed literature regarding their safety. To support informed risk assessment, more detailed information on exposure, exposure sources, and behaviors that contribute to exposure are needed. Current approaches for assessing exposure to parabens typically utilize urine samples that may not reflect average chronic exposure due to their short half-lives in the body. Wearable sensors, such as the silicone wristband (SWB), hold promise for improving exposure research in this area, particularly for chemicals that are quickly metabolized in the body. The overarching goal of this dissertation was to determine if SWBs could be an effective tool for measuring individual level exposure to parabens as a result of PCP use. Four parabens are examined herein: methylparaben, ethylparaben, propylparaben, and butylparaben. These compounds are often measured in exposure measurement matrices as a proxy for PCP exposure. Current research suggests that SWBs integrate both inhalation and dermal routes of exposure, the two major exposure routes for parabens. This dissertation therefore set out to determine if SWBs could provide more precise measures of exposure compared to more traditional approaches that utilize house dust samples, hand wipes, or spot urine samples. Aim 1 of this thesis sought to investigate the relationships between environmental and biological samples for phenols, including parabens and triclosan, in the home environment . This involved analysis of paired house dust, hand wipes, children’s urine, and SWBs collected from children in North Carolina. Guardians of these children (aged 3-6 years) completed questionnaires on habits and behaviors. All questionnaires and samples were collected between 2014 and 2016. Positive correlations for methyl-, ethyl-, and propylparaben were observed frequently in all matrices investigated. Exposure measurements from the sampled abiotic matrices were significantly correlated to associated urinary biomarkers for these parabens , although correlations with urine were higher for hand wipes and SWBs compared to dust. Everyday lotion use was also associated with significantly higher levels of urinary paraben biomarkers in children. These results demonstrated that lotion is a predictor of paraben exposure in children, and that SWBs may be a suitable tool for assessing children’s exposure to both parabens and triclosan. Aim 2 was designed to determine if SWBs could provide a quantitative estimate of total paraben internal dose by comparing their predictive ability compared to a spot urine sample. Uptake of parabens onto SWBs was assessed by asking 10 adults from central North Carolina to wear five SWBs, with one removed each day over five days. 24-hour urine samples and random spot urine samples were also collected daily to evaluate paraben biomarkers of exposure for methyl-, ethyl-, propyl-, and butylparaben. The concentrations of parabens and triclosan in SWB and spot urine samples were compared to measures of the total mass excreted over five days. Results demonstrated that butylparaben had a significant and positive linear uptake over five days, while methyl- and ethylparaben displayed an apparent steady state concentration over five days. SWBs and spot urine samples were similarly correlated to total mass excreted for parabens. Due to the advantages of SWBs over spot urine samples, such as higher sensitivity (i.e. greater detection rates), reduced participant burden, and less dependency on the timing of sample collection, SWBs may be a more suitable tool for assessing exposure to PCPs. Lastly, Aim 3 investigated the sensitivity of SWBs in their ability to detect paraben exposures resulting from the use of a specific PCP (lotion) and whether concentrations observed in SWBs correlate with the total mass of parabens excreted in urine. To support this aim, 20 adults from central North Carolina were asked to participate for two, three-day periods over two weeks. Participants were asked to keep PCP use identical between the two periods, but during one period (randomized as first or second period per participant) participants were asked to apply one pump of a body lotion (containing a known about of parabens) to the arm on which they wore the wristband. During both periods, participants wore a single SWB and collected three 24-hour urine samples. Results demonstrate that wristbands were able to differentiate paraben exposure between Lotion and No Lotion periods as well as urinary biomarkers of exposure. This study provides evidence that SWBs can detect chemical exposures originating from use of PCPs, and suggest that SWBs are a promising and sensitive tool to capture differences in PCP use in individuals. Collectively, this dissertation provides evidence that SWBs are a promising method to measure exposure to chemicals found within PCPs. Accurate exposure classification is critical for both epidemiological studies of health effects and risk assessments used for chemical regulation. This dissertation supplies the first evidence that SWBs can be used to measure common exposures, such as those from PCPs like lotions, and that these measurements realistically correlate to common measurements of internal dose.

Following the phase-out of polybrominated diphenyl ethers (PBDEs) in the early 2000s, organophosphate esters (OPEs) emerged as PBDE substitutes and have been applied to furniture foam, electronics, building materials, and some plastics to reduce their flammability. Although they have been used for quite some time in hydraulic fluids, isopropylated and tert-butylated triaryl phosphate esters (ITPs & TBPPs) have been more recently introduced as flame retardant (FR) replacements for the pentaBDE mixture in polyurethane foam (PUF). In addition to their use as FRs, ITPs and TBPPs are also used as plasticizers.

ITPs and TBPPs comprise a family of aryl organophosphate esters with varying degrees of isopropylation and tert-butylation. Individual ITP and TBPP isomers have been widely detected in indoor house dust, and recent biomonitoring studies demonstrate that human exposure to these compounds is widespread. Due to concerns about their persistence, bioaccumulation, and potential toxicity (P, B, & T), the U.S. Environmental Protection Agency (EPA) listed ITPs as one of five high priority chemicals fast-tracked for expedited risk assessment under the 2016 Toxic Substances Control Act (TSCA) reform.

As such, studying the exposure, metabolism, and in vitro effects of these compounds is especially timely. The hypothesis of this research dissertation is that ITP and TBPP isomers may exhibit some of the same P, B, & T properties that motivated the phase out of PBDEs. The main objectives of this research project were to generate meaningful data to fill gaps in our knowledge of ITP and TBPP isomers, and to contribute to the ongoing risk assessment of these compounds.

In the first aim of this thesis research, the maternal transfer of Firemaster® 550 (FM 550), a commercial mixture containing ITP isomers and brominated FRs, was investigated in dosed Wistar rats. Gestational and lactational transfer were examined separately, with dams orally exposed to 300 or 1000 µg of FM 550 for 10 consecutive days during gestation (gestational day [GD] 9-18) or lactation (postnatal day [PND] 3-12). Levels of parent compounds were measured in dam and pup urine. The two brominated components of FM 500, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB) and bis (2-ethylhexyl)-2,3,4,5-tetrabromophthalate (BEH-TEBP), underwent both gestational and lactational transfer. Triphenyl phosphate (TPHP) and ITPs were rapidly metabolized by the dams and were not detected in whole tissue homogenates. However, diphenyl phosphate (DPHP) and mono-isopropylphenyl phenyl phosphate (ip-PPP) were detected in urine from the dosed animals. This study was the first to confirm ip-PPP as a urinary metabolite of ITPs and establish a pharmacokinetic profile of FM 550 in a mammalian model.

In the second aim of this thesis research, the contribution of individual ITP and TBPP isomers was quantified in four commercial flame retardant mixtures: FM 550, Firemaster® 600 (FM 600), an ITP mixture, and a TBPP mixture. Findings suggested similarities between FM 550 and the ITP mixture, with 2-isopropylphenyl diphenyl phosphate (2IPPDPP), 2,4-diisopropylphenyl diphenyl phosphate (24DIPPDPP), and bis(2-isopropylphenyl) phenyl phosphate (B2IPPPP) being the most prevalent ITP isomer in both mixtures. FM 600 differed from FM 550 in that it contained TBPP isomers rather than ITP isomers. ITP and TBPP isomers were also detected and quantified in house dust standard reference material, SRM 2585, demonstrating their environmental relevance.

The third aim of this thesis research investigated phase I and II in vitro metabolism of TPHP, 4-tert-butylphenyl diphenyl phosphate (4tBPDPP), 2-isopropylphenyl diphenyl phosphate (2IPPDPP), and 4-isopropylphenyl diphenyl phosphate (4IPPDPP) at 1 and 10 µM doses using human liver subcellular fractions. Parent depletion and the formation of known metabolites, including DPHP, hydroxyl-triphenyl phosphate (OH-TPHP), ip-PPP, and tert-butylphenyl phenyl phosphate (tb-PPP), were monitored via gas chromatography/mass spectrometry (GC/MS) and liquid chromatography tandem mass spectrometry (LC/MS/MS). Tb-PPP and its conjugates were identified as the major in vitro metabolites of 4tBPDPP, accounting for up to 33% of the initial parent dose. While the mass balance between parents and metabolites was conserved for TPHP and 4tBPDPP, approximately 20% of the initial parent mass was unaccounted for after quantifying metabolites of 2IPPDPP and 4IPPDPP that had authentic standards available. Two novel ITP metabolites, mono-isopropenylphenyl diphenyl phosphate and hydroxy-isopropylphenyl diphenyl phosphate, were tentatively identified by high-resolution mass spectrometry (HRMS) and screened for in recently collected human urine. This study provided insight into recent human biomonitoring and epidemiological studies and contributed to our understanding of the biological fate of ITP and TBPP isomers.

Finally, the fourth aim of this thesis research evaluated ITPs, TBPPs, and related commercial mixtures for their effect on the activity of purified human liver carboxylesterase (hCE1). Four of the 15 OPEs tested had IC50 values lower than 100 nM, including TPHP, 2-ethylhexyl diphenyl phosphate (EHDPP), 4-isopropylphenyl diphenyl phosphate (4IPPDPP), and 4-tert-butylphenyl diphenyl phosphate (4tBPDPP), as did four commercial flame retardant mixtures tested. Because hCE1 is critical for the activation of imidapril, an ACE-inhibitor prodrug prescribed to treat hypertension, the most potent inhibitors, TPHP and 4tBPDPP, and an environmentally relevant mixture (house dust) were further evaluated for their effect on imidapril bioactivation in vitro. TPHP and 4tBPDPP were potent inhibitors of hCE1-mediated imidapril activation (Ki = 49.0 and 17.9 nM, respectively), as were extracts of house dust (100 µg/ml), which caused significant reductions in imidapril activation. Combined, these data suggest that exposure to OPEs can affect pharmacotherapy.

Collectively and in context of other recently published findings, this thesis research suggests that ITPs and TBPPs may be regrettable substitutes for PBDEs.

Following the phase out of polybrominated diphenyl ethers (PBDEs), manufacturers turned to several alternative flame retardants (FRs) to meet flammability standards. Organophosphate FRs (OPFRs), and in particular tris (1,3-dichloropropyl) phosphate (TDCPP), have been increasingly detected in textiles and foam padding used in a variety of consumer products including camping equipment, upholstered furniture, and baby products. Like PBDEs, OPFRs are additive, meaning that they are not chemically bound to the treated material and can more readily leach out into the surrounding environment. Indeed, OPFRs have been detected in numerous environmental and biological matrices, often at concentrations similar to or exceeding that of PBDEs.

Although OPFRs have been in use for several decades, relatively little is known regarding their potential for adverse human and environmental health consequences. However, based on their structural similarity to OP pesticides, they may have analogous mechanisms of toxicity. OP pesticide toxicity is classically associated with cholinesterase inhibition, resulting in cholinergic intoxication syndrome. OPFRs have been shown to be ineffective cholinesterase inhibitors, however chlorpyrifos (CPF) and other OP pesticides have been shown to elicit adverse effects on developing organisms through other mechanisms.

The main objective of this research project was to evaluate the toxicity of four structurally similar OPFRs (TDCPP; tris (2,3-dibromopropyl) phosphate, (TDBPP); tris (1-chloropropyl) phosphate (TCPP) and tris (2-chloroethyl) phosphate (TCEP)) in comparison to chlorpyrifos (CPF), a well-studied OP pesticide. A combination of in vitro and in vivo models was used to elucidate potential mechanisms as well as functional consequences of exposure in developing organisms.

In the first research aim, a series of in vitro experiments with neurotypic PC12 cells was used to evaluate the effects of four structurally similar OPFRs (TDCPP, TDBPP, TCEP, or TCPP) and CPF on neurodevelopment. The effects of TDCPP were also compared to that of BDE-47, a major component of the commercial PentaBDE mixture. In general, TDCPP elicited similar or greater effects when compared to an equimolar concentration of CPF. All OPFRs tested produced similar decrements in cell number and altered phenotypic differentiation, while BDE-47 had no effect on cell number, cell growth, or neurite growth.

For the second research aim, zebrafish (Danio rerio) were used to evaluate the effects of the same suite of chemicals on early development. TDCPP, TDBPP, and CPF elicited overt toxicity (e.g., malformations or death) within the concentration range tested (0.033-100 µM). TDBPP was the most potent with 100% mortality by 6 days post fertilization (dpf) at ≥3.3 µM. CPF and TDCPP showed equivalent toxicity with malformations observed in at 10 µM and significant mortality (≥75%) at ≥33 µM. There was no overt toxicity among TCEP- and TCPP-exposed fish. All test chemicals affected larval swimming behavior on 6 dpf at concentrations below the overt toxicity threshold. Parent chemical was detected in all in embryonic (1 dpf) and larval (5 dpf) tissues. TDCPP and TDBPP showed rapid and extensive metabolism.

Finally, for the third aim, juvenile (45-55 dpf) zebrafish were exposed to CPF (1 µg/g food) or TDCPP (Low TDCPP = 1 µg/g food; High TDCPP = 40 µg/g food) via diet for 28 days followed by a 7 day depuration period where all treatments received clean food. A dietary exposure was chosen to more closely recapitulate exposure in humans. Samples were collected at seven time points throughout the experiment: days 0, 7, 14, 21, 28, 30, 35. Whole tissues were collected for tissue accumulation and histopathology endpoints. Viscera and brain were dissected and flash frozen separately for DNA damage analyses.

Tissue measurements of CPF, TDCPP, and the metabolite bis (1,3-dichloropropyl) phosphate (BDCPP) were often below the method detection limit, however when present there was a trend towards increased accumulation with treatment and time. On Day 7 Low TDCPP caused a dramatic but transient increase in DNA damage in both viscera and brain that returned to control levels by Day 14. Similar results have been seen previously with other genotoxicants and may be due to CPF and High TDCPP inducing an adaptive response prior to the 7 day sampling point. All treatments shifted the neurohypophysis to adenohypophysis ratio (NH/AH; Day 7 only) and significantly increased thyroid follicle activation (Day 14). Finally High TDCPP affected gonad maturation, causing a significant increase in ovary follicle development (Day 14) and a transient but marked decrease in testes maturity (Day 7). Taken together these data suggest that dietary exposure to TDCPP and CPF elicits DNA damage in brain and viscera and alters endocrine function in juvenile zebrafish. Importantly, analyses were restricted to the first three time points (Days 0, 7, and 14) due to the emergence a disease among the experimental colony. Although these samples were collected prior to the disease becoming apparent, it remains a potential confounder of the current results.

Background: Approximately 3.8 million people die annually from illnesses caused by household air pollution (HAP). Cooking related HAP is the second leading cause of disease in Madagascar. Our exploratory study aims to examine the effect of cooking fuel smoke exposure on lung function and respiratory symptoms.Methods: A cross-sectional study was conducted in Mandena, Madagascar from 2016 through 2018. Adults aged ≥18 years completed a survey on respiratory symptoms and cooking habits and performed spirometry for FEV1 and FEV6 values. Results: Of the 140 participants, 95 individuals were included in the multiple regression model. Being the primary cooks was significantly associated with decreasing FEV1 (-0.30; 95% CI: -0.57, -0.04) and FEV6 (-0.32, 95% CI: -0.57,-0.06). Cooking indoors significantly decreases FEV6 compared to cooking outdoors (-0.26, 95% CI: -0.50,-0.03). Conclusion: Reduced lung function and increased respiratory disease are most common among primary cooks. Reduced lung function was associated with cooking indoors. Further studies are essential to investigate HAP’s effect on Madagascar communities.