Roadside Open Sun Drying in Nigeria: Food Safety Risks and Potentials of Solar Drying technologies as mitigating strategies

Roadside open sun drying remains the dominant post-harvest food preservation method among smallholder farmers and rural agro-processors across Nigeria, driven by zero operational cost, cultural tradition and the absence of possible alternatives. Despite its economic rational, the practice systematically exposes commodities to dangerous arrays of chemical, microbial and physical contamination hazards. Chemical risks often arise from vehicular emissions depositing heavy metals, polycyclic aromatic hydrocarbons and volatile organic compounds on the drying produce, while direct contact with bituminous road surfaces introduces hydrocarbon residues. Microbial hazards include contamination by pathogenic bacteria, mycotoxigenic fungi, and zoonotic vectors, compounded by slow and interrupted drying cycles that aid conditions favorable to aflatoxin-producing fungi and enteric pathogens. Physical contaminants including dust, insect fragments and animal droppings further compromise product safety, quality and marketability. These cumulative hazards impose a great public health concern on Nigerian consumers, particularly vulnerable populations including children and women. Improved solar drying technologies like cabinet, tent, direct, indirect, and hybrid solar-biomass systems represent evidence-based mitigation strategies that address these hazards while preserving the solar-powered, low-operational-cost nature of traditional drying. These enclosed systems achieve increased drying temperatures, rapid moisture removal, and exclusion of environmental contaminants and thermal inactivation of pathogens, producing commodities that consistently meet NAFDAC, SON, and international food safety standards, thereby unlocking premium domestic and export market access currently unavailable to open sun-dried products. Despite these demonstrated food safety and economic benefits, adoption of improved solar dryers among Nigerian smallholders remains critically low, constrained by high initial capital costs, limited technical awareness, inadequate extension services and weak regulatory enforcement. This review consolidates current evidence on the food safety risks of roadside open sun drying, evaluates the mitigating role of improved solar drying technologies and opportunities necessary to safeguard public health across Nigeria's food value chain.