Abstract
Mosquitoes are one of the most deadly creatures on Earth through their ability to transmit vector-borne illnesses. Diseases such as malaria, dengue fever, Zika virus, chikungunya, and West Nile virus affect hundreds of millions of people around the world annually, with an estimate of 240 million cases of malaria alone in 2022 (World Health Organization, 2023). Personal protection with insect repellents derived from locally sourced plants plays a major role in global public health strategy, particularly in tropical and subtropical regions with proximity to mosquito populations. N,N-diethyl-meta-toluamide (DEET) has been the gold standard since the 1940s due to its safety and efficacy validated by the Environmental Protection Agency (EPA) and Centers for Disease Control and Prevention (CDC), though it has become contested heavily, often being seen as synthetic, and culturally accepted as unnatural and therefore risky, giving rise to “chemophobia” – a public fear about the risks of industrial chemicals. This cultural movement has given rise to a naturalness bias where consumers link botanical origins with safety. This divergence between scientifically validated evidence and consumer behavior brings to light a critical problem for public health as well as for chemical engineers: how to develop effective protection that also earns public trust. This portfolio addresses this sociotechnical problem by engineering a scalable production process for para-menthane-3,8-diol (PMD), which is an EPA-recognized plant-based repellent, and it also explores the psychological and social drivers that shape consumer preference for such alternatives over synthetic standards.
The technical report proposes a pilot-scale manufacturing facility in Kalsi, India, to produce a PMD-based topical repellent spray as a sustainable alternative to DEET. This site was strategically selected for its proximity to essential-oil feedstocks and its elevation, which lowers the boiling point of water and protects the molecular integrity of heat-sensitive components. The proposed process begins with the steam distillation of lemon eucalyptus leaves to recover essential oil, followed by enrichment of citronellal through consecutive sub-atmospheric distillation columns. Purified citronellal is then cyclized into PMD via a batch acid-catalyzed reactor designed to achieve an 80 mol% conversion. The plant is designed to produce 1.71 million units per year, accounting for 25% of the projected PMD-based repellent market. While an on-site fermentation pathway was evaluated to improve vertical integration, economic analysis revealed that purchasing commercial ethanol yields a higher after-tax return on investment of 55.4% and a 10-year net present value of $27.8 million. Consequently, the report recommends pursuing PMD production while forgoing the non-economical fermentation and drying units to maximize profitability and operational simplicity.
The STS research paper investigates the social causes behind consumers' preference for natural insect repellents and the impact of these perceptions on technology development. The study identifies a tension between technical consensus upheld by institutions like the EPA and CDC, and public trust, which is driven more by moral framing and familiarity than by quantitative risk data. Through an analysis of regulatory discourse and marketing materials, the research finds that “natural” functions as a cognitive shortcut and moral signal. For example, the pervasive “DEET-free” claim used by brands such as Cutter and OFF! Botanicals serves as a proxy for safety, even when scientific evidence demonstrates that the synthetic alternative is safe when used properly. The paper argues that naturalness bias leads consumers to follow a different decision rule: “natural” branding signifies a responsible, eco-conscious identity, while DEET signifies industrial risk. This cultural context necessitates the development of repellent technologies that can bridge the gap between perceived safety and laboratory efficacy. Ultimately, the research concludes that successful repellent design must account for these public risk perceptions and environmental values within the broader sociotechnical system.
Together, these projects demonstrate that effective chemical engineering solutions must be integrated with an understanding of social context. The technical report provides a robust, economically attractive pathway for PMD production that directly addresses the market gap created by social resistance to synthetic chemicals. Simultaneously, the STS analysis provides critical insights for technology developers to navigate the psychological drivers of “naturalness bias” and “chemophobia.” By coupling technical feasibility with social perception, this portfolio offers a comprehensive approach to advancing insect repellent technology in a way that respects both chemical engineering rigor and public environmental priorities.
