Spices under the microscope: First detection and characterization of microplastics in turmeric, black pepper, and chili

Abstract

Microplastics (MPs) are increasingly recognized as contaminants in various food products, including salt, tea, honey, rice, and seafood; however, data on their occurrence in commonly consumed spices remain scarce. In this study, the presence, abundance, morphology, and polymer composition of MPs were investigated in three widely used spices—turmeric, red pepper, and black pepper—purchased in bulk (loose) and packaged forms from markets in Ahvaz, southwestern Iran. A total of 30 samples (15 bulk and 15 packaged) were analyzed using chemical digestion and density separation, followed by stereomicroscopy and Raman spectroscopy under strict contamination control procedures, including procedural blanks and recovery validation. Method sensitivity and analytical uncertainty were addressed through procedural blanks, recovery validation, and conservative particle confirmation criteria. MPs were detected in all samples, with concentrations ranging from 500 to 1100 particles/kg. Bulk spices consistently exhibited higher MP loads than packaged products, suggesting handling and environmental exposure as important contamination pathways. Fibers (61.7 %) and fragments (35.6 %) were the dominant particle morphologies, while polyethylene (PE), polypropylene (PP), and polystyrene (PS) were the most frequently identified polymers. Most particles were smaller than 100 μm. Among the studied spices, red pepper showed the highest average MP concentration, followed by turmeric and black pepper. Based on typical consumption rates, the estimated annual intake of MPs from spices ranged from approximately 188 to 613 particles per person per year, which is substantially lower than reported intakes from foods such as bottled water or salt, but represents a chronic and recurrent dietary exposure. Although limited in sample size, this study provides the first quantitative evidence of MPs contamination in common spices from Iran and highlights spices as an underreported, chronic dietary source of MP exposure.