Microplastic contamination in salt from two traditional salterns in the Southern Philippines: occurrence and exposure implications

Graph showing a decline in water use per capita in Finland by more than 40% between 1974 and 2014, due to increased water prices. Microplastic contamination in salt production systems presents an emerging concern for water quality, food safety, and environmental management. This study assessed microplastics in two traditional salterns in the southern Philippines to evaluate contamination levels, particle characteristics, and potential human exposure. Salt samples were collected from evaporation ponds prior to harvest at two sites, Zamboanga City and Alubijid, each employing distinct water-handling designs and harvesting methods. Both sites contained microplastics, with Zamboanga City exhibiting lower levels (28 ± 7 particles per kilogram) compared with Alubijid (102 ± 21 particles per kilogram). Particle profiles differed between the salterns: fragments and dark-colored particles were predominant in Zamboanga City, while films and light-colored particles were dominant in Alubijid. Polypropylene and polyethylene were the major polymers in both systems. Higher contamination in Alubijid corresponded with elevated pollution load and potential human intake estimates, suggesting a greater overall risk. The observed differences appear linked to site-specific water flow, pond lining materials, and operational practices. The findings demonstrate that operational and water-handling practices directly affect microplastic accumulation in salt ponds, underscoring the need for enhanced monitoring and targeted process improvements to mitigate contamination.