Emerging contaminants in microalgae-based sustainable foods: occurrence patterns and dietary risk implications

Microalgae-based foods are gaining attention as sustainable protein sources, but information on the occurrence of emerging contaminants in commercial products remains limited. Here, we investigated the occurrence patterns and dietary risk implications of three classes of emerging contaminants, including parabens, per- and polyfluoroalkyl substances (PFAS), and p-phenylenediamine antioxidants (PPDs), in 77 commercially available microalgae-based food samples from China, including spirulina powder, chlorella powder, and microalgae-processed food products. Target analytes were quantified using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry, and probabilistic dietary exposure was assessed using Monte Carlo simulation. Parabens, PFAS, and PPDs were widely detected across the analyzed samples, with methylparaben and butylparaben dominating the paraben profiles, PFBA dominating the PFAS profiles, and 6PPD overwhelmingly dominating the PPD profiles. Despite their frequent occurrence, parabens and PPDs posed limited dietary risks through microalgae consumption, with hazard index values far below 1. Moreover, PFAS showed relatively higher dietary risk. This risk was not driven by the most abundant PFAS, but by trace-level PFDA, PFHxS, and PFOA, whose extremely low reference doses made them the dominant contributors to overall risk. These findings document the co-occurrence of three contaminant classes in microalgae-based foods and provide evidence-tiered priorities for screening-level dietary risk management. SYNOPSIS: Dietary risk estimates for microalgae-based foods were low for parabens and PPDs but sensitive to the toxicity benchmarks selected for trace PFAS congeners.