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Appendix: Background Paper and Chapter Authors’ Workshops for the Global Value Chain Development Report 2025
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Cellular communities reveal trajectories of brain ageing and Alzheimer’s disease
No full textAlzheimer’s disease (AD) has recently been associated with diverse cell states, yet when and how these states affect the onset of AD remains unclear. Here we used a data-driven approach to reconstruct the dynamics of the brain’s cellular environment and identified a trajectory leading to AD that is distinct from other ageing-related effects. First, we built a comprehensive cell atlas of the aged prefrontal cortex from 1.65 million single-nucleus RNA-sequencing profiles sampled from 437 older individuals, and identified specific glial and neuronal subpopulations associated with AD-related traits. Causal modelling then prioritized two distinct lipid-associated microglial subpopulations—one drives amyloid-β proteinopathy while the other mediates the effect of amyloid-β on tau proteinopathy—as well as an astrocyte subpopulation that mediates the effect of tau on cognitive decline. To model the dynamics of cellular environments, we devised the BEYOND methodology, which identified two distinct trajectories of brain ageing, each defined by coordinated progressive changes in certain cellular communities that lead to (1) AD dementia or (2) alternative brain ageing. Thus, we provide a cellular foundation for a new perspective on AD pathophysiology that informs personalized therapeutic development, targeting different cellular communities for individuals on the path to AD or to alternative brain ageing.Accepted Manuscrip
The Illusion of Time in Physical Performance: Manipulating Timing Cues to Improve Plank Endurance in Trained Adults
No full textBackground: Deceptive timing feedback has been shown to enhance performance in endurance tasks, though its applicability to isometric exercises and interactions with approach motivation remains unclear. This study explores whether manipulated timing cues influence plank endurance and the role of motivation in these effects.
Methods: Fifty-seven active adults (63.1% male) participated in three maximal effort plank holds under different timing conditions: (1) accurate, (2) slowed, and (3) accelerated timing cues. Plank endurance was the primary outcome. Participants also completed the Approach-Avoidance System Questionnaire (AASQ) and the International Physical Activity Questionnaire - Long Form (IPAQ-LF) to assess motivation and fitness levels. Perceived exertion was evaluated using the Borg CR-10 RPE Scale.
Results: Timing cues significantly influenced plank endurance, with participants holding planks significantly longer in the slowed condition compared to the accelerated condition (p .001). Descriptive improvements in plank endurance from accurate to slowed conditions were not significant (p = .073). RPE did not significantly differ across conditions, indicating that performance gains were achieved without increased subjective effort. Motivation did not moderate the relationship between timing cues and endurance.
Conclusions: These findings suggest that altering time perception can influence endurance without affecting perceived exertion, though future research should explore whether different exercise modalities or greater variations in approach-oriented motivation may produce stronger effects.Extension Studie
Trends and Disparities in Contamination by Per- and Polyfluoroalkyl Substances in United States Community Water Systems
No full textPer- and polyfluoroalkyl substances (PFAS) are a large class of anthropogenic compounds that have been widely used in consumer products and industrial processes for decades. Exposures to PFAS are ubiquitous and can occur through many routes. Hundreds of millions of United States (US) residents are estimated to be exposed to PFAS in drinking water and PFAS are detectable in the blood of nearly all US residents. Associations between PFAS exposures and several adverse health outcomes—including measures related to hepatotoxicity, immunotoxicity, and metabolic disruption—are well established. Despite the ubiquity of PFAS drinking water contamination and human exposure, past assessments have been limited by a lack of comprehensive PFAS drinking water monitoring and high reporting limits in drinking water datasets. Recently available statewide drinking water monitoring datasets provide an opportunity not only to re-examine the relationships between PFAS contaminated sites and drinking water concentrations in public water systems, but also to pursue environmental justice issues posed by PFAS contamination, which have been generally underexamined within the context of PFAS exposure routes and health risks. This dissertation first compiles a statewide monitoring dataset to examine sociodemographic disparities in PFAS contamination, further uses this dataset to investigate associations between PFAS-contaminated drinking water and COVID-19 mortality, and examines disparities in infrastructure to remedy PFAS contamination among water systems affected by PFAS contamination and at the national level.
In Chapter 1, I use monitoring data from 7,873 US community water systems (CWS) in 18 states and find that PFAS detections were positively associated with the number of PFAS sources and proportions of people of color served by these water systems. Numerous contamination sources, including industrial facilities, military fire training areas, airports, municipal solid waste landfills, and wastewater treatment plants, were associated with increases in drinking water concentrations of multiple PFAS (including perfluorooctanoic acid [PFOA], perfluorooctanesulfonic acid [PFOS], perfluorohexanesulfonic acid [PFHxS], and perfluorobutanesulfonic acid [PFBS]). These associations were similar in directionality to prior work, despite differences in geographies, inclusion of a greater proportion of CWS serving smaller populations, and lower uniform detection limits. CWS sharing watersheds with PFAS sources served higher proportions of Hispanic/Latino and non-Hispanic Black residents compared to those without PFAS sources. CWS serving higher proportions of Hispanic/Latino and non-Hispanic Black residents had significantly increased odds of detecting several PFAS, which is likely a reflection of disparities in the siting of PFAS contamination sources. Results of this work suggest addressing environmental justice concerns should be a component of risk mitigation planning for areas affected by drinking water PFAS contamination.
In Chapter 2, I examine associations between PFAS contamination of US CWS and county-level COVID-19 mortality records prior to widespread availability of the COVID-19 vaccines. These analyses leverage two datasets: one at the subnational scale (5,371 CWS serving 621 counties; derived from the dataset compiled in Chapter 1) and one at the national scale (4,798 CWS serving 1,677 counties; derived from the US Environmental Protection Agency's (EPA) Third Unregulated Contaminant Monitoring Rule). These datasets are analyzed in parallel using multilevel quasi-Poisson regressions. In the subnational analysis, detection of at least one PFAS over 5 ng/L was associated with 12% higher [95% CI: 4%, 19%] COVID-19 mortality. In the national analysis, detection of at least one PFAS above the reporting limits (20-90 ng/L) was associated with 13% higher [95% CI: 8%, 19%] COVID-19 mortality. These findings support a positive association between county-level drinking water PFAS contamination and COVID-19 mortality. They also bolster the importance of systematic federal drinking water monitoring efforts for PFAS and remediation of contaminated areas for public health protection, potentially including infectious disease epidemics.
In Chapter 3, I evaluate whether water system characteristics and sociodemographic composition are associated with early adoption of advanced water treatment processes effective for PFAS removal (reverse osmosis, ion exchange, and activated carbon) among US CWS. I use time-to-event statistical methods to analyze US EPA treatment records available over the 2004-2022 period for 2,697 CWS with known PFAS detections and 36,611 CWS nationally. I find that, among systems not reporting use of the target treatment processes at baseline, 5.1% of systems (serving an estimated 20% of the population) reported adoption by the end of the follow-up period. Among systems with known PFAS detections and systems nationally, large and very large systems (serving larger populations) were significantly more likely to report adoption of the treatment processes. Racial/ethnic disparities were observed and were consistent across system sizes, particularly for the proportion of non-Hispanic Black residents. In contrast, disparities related to area-level socioeconomic status measures varied significantly by system size and I observed evidence of non-linear relationships for these measures. This study can inform ongoing national efforts to treat drinking water contamination by PFAS and its study design can be adopted to analyze the progress of drinking water regulations.
My dissertation presents evidence of sociodemographic disparities in PFAS contamination, the siting of PFAS-contaminated sites, and access to the treatment processes that can be used to remedy contamination. It also presents new evidence on the population health impacts of widespread PFAS drinking water contamination. Conclusions from this thesis further highlight not only the problem of PFAS contamination, but also the necessity of drinking water monitoring and national efforts to remediate contamination while ensuring environmental justice.Population Health Science
Economic and Environmental Sustainability of Smallholder Agriculture: The Case of Maize Monocropping in North Thailand
No full textThe northern region of Thailand is known for upland maize monoculture due to the crop’s demand-price stability and resilience to the arid hot season. Due to the scarcity of economically viable alternatives, smallholder farmers manage crop residue by burning, causing hazardous air quality in the surroundings. My thesis aimed to determine if and how upland smallholder farmers could farm more sustainably without reducing their income. To do so, I estimated the net present value (NPV) and benefit to cost ratio (BCR) of farm income over 15 years for maize monoculture (Bm), maize-mungbean intercrop (Bbi), avocado mono (Am), greenhouse tomato (Tg), macadamia mono (Mm), and macadamia-coffee intercrop (Mci). The study was conducted in Pang Hin Fon, Kong Bot, and Huay Fa villages of Chiang Mai’s Mae Chaem district.
I hypothesized that incorporating legumes with maize (Bbi), replacing maize with vegetables (Tg), and replacing with perennials (Am and Mm) would increase NPV by 20%, 30%, and 70% respectively, and that multi-crop agroforestry (Mci) would add another 30% on top of the perennial monoculture (Mm). I found the NPVs of Bm, Bbi, Am, Tg, Mm, and Mci to be 21,136 (BCR 1.9), 483,025 (BCR 4.9), 75,557 (BCR 6.2) respectively. This was much higher than expected: a minimum increase of 53% (Bbi vs Bm) and more than 3,000-fold increase in NPV under Tg (vs expected 30% for vegetables). Mci had a 35% higher NPV than Mm, slightly more than the expected 30%. Meanwhile, the payback periods for Am, Tg, Mm, and Mci were four, one, seven, and three years respectively.
My second goal was to determine variables affecting farm income the most. The results met expectations—market prices affected income the most for Bm, Bbi, Tg, and Am, followed by yield for Mm and food loss for Mci. I also evaluated the NPVs under optimistic and pessimistic scenarios by jointly varying the yield and price. Tg was the most volatile, with a net loss of $85,247 (-118%) in the worst scenario (78% less yield; 74% less selling price). The risk of disease (wilt) outbreak caused a higher variance in the NPV of Am; however, it remained healthy even in the worst scenario. Finally, I compared the climate change and human health impacts of Bm and Bbi production using a life cycle assessment (LCA) approach. The LCA included the footprints of equipment, agricultural inputs, and open burning of residue. Bm had a climate change impact of 2.62 tonne (T) CO2eq and human health impact of 36.99*10-3 DALY. Eliminating open burning reduced the climate change impact of Bbi by 29% (1.87 T CO2eq) and the human health impact by 71% (10.65*10-3 DALY) compared to Bm. Human health was most impacted by open burning and climate change by fertilizers. Since legumes improve soil health, agricultural inputs could be optimized to further reduce the environmental impact.
I found that multi-cropping systems integrating perennial trees, understory crops, vegetables, and legumes improved farm income, resilience, and external impact. The farmers I met were aware of and open to alternatives, but held back due to insufficient water and road infrastructure, weak supply chains, demand uncertainty, and lack of institutional support. To overcome these barriers, I recommend improving the upland water and road infrastructure, incentivizing novel supply chains and farm-to-fork solutions, institutional support for credit and training, and research into nature-based solutions for water conservation, crop protection, and yield increase of alternate crops.Extension Studie
Chemical Occupations: Anti-Colonial Reactions in the Desert
No full text“Chemical Occupations” examines how landscape architects can disassemble traditional ecological principles of growth, succession, and restoration to reconfigure landscape through chemical agency. It positions toxic landscapes, not merely as disturbed sites awaiting an idyllic fix, but rather as uncontained, reactive, and existing through multiple states of matter. In Fayoum, an oasis in the Sahara Desert, layers of occupation have toxified the landscape far beyond the presence of its original colonial agents. Here, ecology is co-opted as the final act of the colonial “exquisite corpse,” as a device to delineate and falsely restore through the foreign typology of the national park. Sets of chemical chromatograms, prioritized over Cartesian ecological tools, serve as a methodology to unveil, dissolve, and reconfigure the toxic residues of the former park. “Chemical Occupations” advances the “anti-park,” myths of reactive sovereignty, actualized through new rituals, markers, and stewardship practices, whereby Fayoumis reclaim toxicity toward new futures.Department of Landscape Architectur