Abstract
Vector-borne diseases account for nearly 17% of all infectious illnesses worldwide,
causing more than 700,000 deaths annually. In Sri Lanka alone, more than 38,000 dengue cases
were reported by week 38 of 2024, despite growing awareness and prevention campaigns.
Protection against insect-borne disease is deeply unequal: the repellent a family uses is often
determined less by choice than by what is affordable, locally stocked, and institutionally
endorsed. This sociotechnical study asked how regulatory classification, procurement and retail
infrastructures, and public health communication shape the affordability and availability of
PMD-based repellents relative to DEET in low-income urban communities in Sri Lanka. PMD
(para-menthane-3,8-diol) is a biodegradable, plant-derived alternative to the petroleum-based
standard DEET, and review evidence suggests PMD can provide long-lasting repellency
comparable to DEET in many contexts. Yet in many settings, plant-derived repellents remain
positioned as premium or niche products, leaving them inaccessible to the populations most
burdened by dengue.
The chemical engineering project proposes a commercial manufacturing process for a
PMD-based topical mosquito repellent spray as an alternative to products dominated by DEET.
The plant is designed to produce approximately 1.71 million units per year for sale to an
American market, where pricing reflects higher disposable income. The proposed process begins
with biomass preparation and essential-oil recovery from lemon eucalyptus leaves, followed by
citronellal enrichment, acid-catalyzed batch cyclization to PMD, and final purification.
Economic analysis shows the project is attractive overall, with an after-tax ROI of 43–69%.
However, a product priced for American consumers would likely exceed what low-income Sri
Lankan households could afford.
Together, these reports demonstrate that PMD can be manufactured at scale economically
and performs comparably to DEET as an active ingredient. The remaining sociotechnical
challenge is not technical feasibility but whether regulatory classification, procurement
infrastructure, and public health communication will position PMD as an accessible tool for low-
income Sri Lankan communities rather than a premium product priced for Western markets.
