Children are commonly exposed to metals in the environment, particularly those living in proximity to steel-producing ferroalloy industry. Exposure to metals, including lead (Pb), manganese (Mn), chromium (Cr) and copper (Cu), impacts neurodevelopment, but less attention has been given to examining associations of metal mixtures with cognitive function in children. Further, recent epidemiological studies have identified iron (Fe) status as a modifier of metals-induced neurotoxicity, such that adverse associations of metals (e.g., Mn or Pb) tend to be stronger among children with Fe deficiency. However, no study to date has quantified the modifying or mediating role of Fe status on a complex metal mixture in relation to any neurodevelopmental outcome. We used data from the Public Health Impact of Metals Exposure Study (PHIME), a cohort of 720 Italian adolescents (10–14 years) to quantify the association of an industry-relevant metal mixture (Pb, Mn, Cr, Cu) with neurodevelopment, and examine the role of Fe status as a modifier or mediator of these associations. Metals were measured in blood (Pb) or hair (Mn, Cr, Cu) using inductively-coupled plasma mass spectrometry, and Fe status was assessed using three clinically relevant biomarkers (ferritin, hemoglobin, transferrin) measured in whole blood or serum using luminescent or immunoassays. Of note, there was no indication of Fe deficiency in the study population. In Chapter 2, we identified associations of the metal mixture with verbal learning and memory, measured using the California Verbal Learning Test for Children (CVLT-C), using Bayesian Kernel Machine Regression (BKMR). In adjusted models, we found that the mixture was jointly associated with higher scores for the recall trials: compared to the 50th percentile, the 90th percentile of the mixture was associated with a 0.12 standard deviation increase (95% credible interval [CI]= -0.27, 0.50) in the number of words recalled on trial 5 recall, indicating better cognitive performance. This association was driven primarily by Cu, which was further modified by Fe status: the beneficial association of Cu with recall was stronger at increasing percentiles of ferritin. In Chapter 3, we found that the metal mixture was jointly associated with self-reported attention-related behaviors measured on the Conners Rating Scales. For example, the 90th percentile of the mixture, compared to the 50th percentile, was associated with a 4.1% increase (β= 0.04; 95% CI= 0.00, 0.08) in self-reported inattention T-scores in BKMR models, reflecting worse cognitive performance. These associations were driven primarily by Mn, though there was no indication of modification by Fe status. Lastly, in Chapter 4, we quantified the mediating role of Fe status on the association between the metal mixture and CVLT-C scores using the newly developed BKMR Causal Mediation Analysis (BKMR-CMA). Though the metal mixture was associated with aspects of Fe status (e.g., ferritin), there was no evidence that Fe status mediated the association between the metal mixture and CVLT-C scores. Overall, the findings from this dissertation suggest that an industry-relevant metal mixture can impact aspects of neurodevelopment, including learning, memory and attention-related behaviors, and that Fe status may be a modifier of these associations. These findings have significant implications for potential public health interventions aimed at improving cognitive development in adolescents. However, the generalizability of our findings in a Fe-replete population of healthy adolescents may be limited, and further research in Fe-deficient populations is warranted. / 2025-04-26T00:00:00Z

BACKGROUND: Children, especially those living near industry sites, are commonly exposed to multiple metals including lead and manganese. These metals are associated with adverse neurodevelopmental outcomes, with evidence of non-linear associations for essential metals. Metals target brain regions involved in cognition and motor function. However, there is a paucity of epidemiological studies focused on early-life exposure to metals, especially in association with less commonly studied neurodevelopmental domains like motor function. OBJECTIVE: To characterize exposure to multiple metals in early life, estimate associations with neurodevelopmental outcomes in adolescence, and examine susceptibility factors including exposure timing, co-exposures, and biological sex. METHODS: Research aims were addressed using data from the Assessing Children’s Environmental Exposures (ACHIEVE) study and the Public Health Impact of Metals Exposure (PHIME) study. The ACHIEVE study included 30 mother-child pairs from the town of Holliston, Massachusetts where naturally shed baby teeth were collected from children ages 5–13 years. In the first aim, we used multivariable linear mixed models to explore sociodemographic, dietary, and behavioral correlates of tooth metal concentrations for children in the ACHIEVE study (N=28). We estimated weekly prenatal and postnatal (up to one year of age) exposure to 12 metals. Tooth metal concentrations were quantified using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). For the second and third aims, we analyzed data from the PHIME study, comprised of 721 Italian adolescents living in proximity to steel production sites. Blood and hair samples were collected at the time of enrollment and analyzed for metals concentrations (manganese, lead, copper, and chromium) using ICP-MS. Teeth were collected for a subset of PHIME participants (N=195) and analyzed for manganese using LA-ICP-MS. A battery of neuropsychological assessments was administered to PHIME participants at enrollment by one of two trained neuropsychologists. In the second aim, we evaluated associations of prenatal, postnatal and childhood manganese levels in teeth with scores of adolescent verbal learning and memory, assessed using an Italian translation of the California Verbal Learning Test for Children (CVLT-C) (N=140). Associations were estimated using multivariable linear and logistic regression, generalized estimating equations and multiple informant models. In the third aim, we estimated associations of a metal mixture (lead, manganese, copper, and chromium) with multiple assessments of motor function (N=612). Statistical methods included generalized additive models, multivariable linear regression, quantile g-computation and Bayesian kernel machine regression. In the second and third aims, we also stratified analysis by sex to examine effect measure modification. Results: In the first aim, we found that temporal trends of tooth metal levels differed by metals and correlates of tooth metal levels included biological sex and primary source of milk during infancy. In the second aim, we estimated manganese-cognition associations that differed by exposure time window: prenatal manganese and childhood manganese for boys was beneficial but postnatal manganese associations were null. In the third aim, we observed sex-specific associations between a metal mixture with motor function scores. The metal mixture was associated with improved motor function scores among females (driven by copper and chromium) whereas the metal mixture was associated with worse motor function scores among males (driven by manganese and copper). CONCLUSION: The association between metal exposure in early life with neurodevelopment is dynamic and complex: associations between metals and neurodevelopment depend on exposure timing, biological sex, and co-exposures. This body of research can be used to inform future research by contributing to the understanding of metal neurotoxicity in critical windows of development and in relation to less studied neurodevelopmental domains, like motor function. / 2025-01-20T00:00:00Z

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Patterns of infectious disease in human populations result from complex interactions between the infectious agent, the disease host, and the environment in which host and agent interact. Many environmental factors influence infectious disease dynamics including characteristics of the natural and built environments and social systems. This dissertation focuses on key environmental factors associated with two timely infectious diseases in the United States (US): acute gastrointestinal illness (AGI) following overflow discharge from combined sewer systems (CSS) in Massachusetts (MA), and patterns of COVID-19 outcomes in relation to the spatial distribution of essential workers in MA. CSS exist in over 700 municipalities in the US as well as cities in Canada, Europe, Asia, and Australasia. When heavy rainfall or snowmelt occurs, CSS discharge untreated or undertreated wastewater into nearby waterways in combined sewer overflow (CSO) events. The association between CSO events and health has been understudied, and critical gaps in knowledge remain, including which exposure pathway(s) may be most relevant in communities downstream of CSO releases, whether CSO events and precipitation are independently associated with AGI, and which subpopulations may be at greatest risk of developing AGI following CSO events. The rapid spread and severity of COVID-19 disease led to widespread stay-at-home orders in the US beginning in March of 2020. In MA, only a designated set of essential businesses remained open during the stay-at-home orders (March through May 2020). During this period, essential workers who performed their duties in person were at higher risk of contracting COVID-19 than people who worked from home, but among essential workers, risk varied by industry- and worksite-specific factors. While differential risk of COVID-19 mortality and outbreaks are documented among essential workers, risk of COVID-19 infection among essential workers has been difficult to ascertain because occupation is frequently missing from state and federal COVID-19 surveillance efforts. The overall objective of this dissertation is to assess the associations between these two infectious diseases in MA and key environmental factors that influence how pathogens and susceptible hosts interact. The relationship between CSO events and AGI was investigated in a geographic region of MA where sewage discharges impact a river that is both a drinking water source and recreational destination for hundreds of thousands of people. Statewide patterns of COVID-19 cases and deaths were evaluated in relation to relative representation of categories of essential workers in MA census tracts. This dissertation relies on health outcome data from administrative and surveillance datasets, all analyses employ ecologic study designs with individual-level data aggregated to small areas, and methods incorporating geospatial and temporal data are included in each study. In Chapter 2, the association between extreme CSO events and AGI was assessed in MA municipalities bordering the CSO-impaired Merrimack River with a secondary analysis evaluating differences in the associations between CSO and AGI based on municipal drinking water source. In the 4-days following 95th percentile upstream CSO discharge events, the cumulative risk ratio (CRR) of AGI increased by 17% and CRR increased by 62% after 99th percentile CSO events. Stratification by drinking water source suggests that the association between CSO events and AGI is most pronounced among municipalities that do not have river-sourced drinking water, but there is elevated risk of AGI among all municipalities regardless of drinking water source following the largest CSO events. These findings suggest that CSO discharge volume is a critical factor in the association between CSO events and AGI, and that exposure to CSO discharge may occur through multiple pathways. Chapter 3 extends the work of Chapter 2 to an evaluation of the strength of the association between CSO events and AGI across subpopulations defined by age, sex, healthcare payer type, area-level social vulnerability, and drinking water source. The CRR of AGI was most pronounced among young people ages 5–19 and people living in areas of low social vulnerability relative to cumulative risk for the population as a whole. The results of this study suggest that the association between CSO events and AGI differs among subpopulations characterized by both physiological and social characteristics. In Chapter 4, categories of essential workers were defined from the broad set of essential occupations defined in the MA emergency response to COVID-19. The association between census-tract-resolution populations of essential worker categories and COVID-19 cases and deaths was evaluated, adjusting for multiple sociodemographic risk factors for COVID-19. Elevated COVID-19 case incidence was observed among census tracts with the highest populations of workers in construction, building maintenance, transportation, production, and public-facing sales and service occupations. Reduced case incidence was observed in tracts with the highest populations of essential workers able to work from home. These findings suggest that occupational composition of census tracts in MA may have influenced community-level COVID-19 transmission, possibly through spread from essential workers to those in their households and communities. Overall, the findings of this dissertation provide insight into the environmental factors associated AGI and COVID-19 in MA. In both cases, consideration of environmental factors provides opportunities to inform public health intervention measures for infectious diseases that are 1) influenced by climate change, and 2) symptomatic of globalization. / 2026-01-03T00:00:00Z

Our changing climate is intensifying the public health threat of extreme heat. Heat morbidity and mortality disproportionately burden those made most vulnerable by social, environmental, and structural factors manifesting heightened exposure and sensitivity as well as reduced adaptive capacity to heat. In order to address and prevent these negative impacts, cities are developing heat adaptation plans. There are several approaches by which researchers have positioned their work as informing decision-making, including vulnerability assessments and participatory action research. However, there remains a need to assess these approaches as applied to heat vulnerability and adaptation, with a lens towards the roles of researchers, decision-makers, and residents. This dissertation uses mixed-methods (qualitative and quantitative) to characterize heat vulnerability and understand perceptions and priorities of participants at multiple levels of assessment (individual, community, city, state). First, we assessed the decision-making implications of, and socio-spatial context for, developing HVIs for city- and state-levels. We found that the choices made in constructing an HVI, including those regarding geographic scale and presentation, influence its results and interpretation. The strong spatial association between HVI scores constructed for the Boston area and redlining maps reinforces the challenges in interpreting sociodemographic and land use covariates absent an historical context, and broadly, the challenges of developing nuanced interpretation from publicly available covariates. Moving from the state and city levels, we then focused in on the levels of community and individual, in the context of neighboring environmental justice and urban heat island communities: Chelsea and East Boston. We evaluated the responses of decision-makers to residents’ experiences, perspectives, and priorities around heat adaptation presented via photovoice. We engaged Chelsea and East Boston decision-makers through interviews with nineteen representatives of local government, public health, and policy organizations. Questions combined with viewing the photovoice exhibit and report elicited interviewees’ nuanced responses and valuable insights. Interviewees described how their work aligns with called-for actions by photovoice participants. They also identified barriers and challenges in taking action, gained insights from the photovoice project, and offered recommendations to expand and build on the called-for actions. Finally, we characterized and contextualized individual-level experiences of heat exposure, sensitivity, and adaptive capacity by integrating quantitative and qualitative data for a sample of ten Chelsea and East Boston residents. Across and within each of these participants’ data, we found high variability in exposures defined by time spent under thermal comfort thresholds, as well as in experiences of sensitivity and adaptive capacity. Participants described both taking on and trying to avoid a number of costs related to thermal comfort, in addition to the significant financial/economic costs, including impacts of heat on health and sleep disturbances, coping strategies around transportation, and other behaviors, including either leaving or staying at home on hot days. We demonstrated the value of mixed-methods analysis at an individual level and offer a framework that centers heat adaptation needs and accessibility in positioning interventions. This dissertation provides evidence for integrating qualitative and quantitative methods in community-engaged, participatory action research approaches that link heat vulnerability assessments to heat adaptation actions. / 2026-01-04T00:00:00Z

Thesis (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes survey instruments. Includes bibliographic references (ℓ. 129-138)

Thesis (MPH. (Health Measurement)) -- Universtity of Limpopo, 2012 / The purpose of this study was to establish the community’s knowledge, attitudes and practices regarding environmental health services (EHS) in the informal settlement of Hospital Hill. A qualitative, cross-sectional study was conducted using focus group discussions among study participants that satisfied the inclusion criteria. Each focus group discussion had varying duration ranging from one hour to one-and-half hours. The study revealed that there was lack of knowledge about EHS, with participants citing provision of water and sanitation facilities as the various roles that EHPs played. Participants’ attitude towards EHS and EHPs showed marked dissatisfaction due to their inaccessibility and unavailability. The lack of consultation, follow-up and community initiatives fuelled their negative attitudes towards EHS. Culture and beliefs, school dropout, human resources and lack of access to information discouraged the community from using EHS. A number of suggestions were made which revealed the community’s need and desire for EHS provision because environmental health problems were dealt with in different ways and these varied from one household to the other further signifying the need for a uniform approach was needed to deal with environmental health problems. The community of Hospital Hill was found to be experiencing discrimination evidenced by inexistence of EHS and consequent limited knowledge of EHS, negative attitudes and practices regarding EHS.