Convenient Self-Heating Instant Food Causes Significant Increasing Human Exposure to Organophosphate Esters

The self-heating lunch box (SHLB) is a kind of popular instant food in China, yet little is known about the associated chemical release risk during its heating process. In this study, we investigated organophosphate esters (OPEs) in original unheated food (UF), SHLB-heated processed food (HF) and potential OPE release from SHLB packaging materials. Significantly higher concentrations of OPEs were observed in HF (267 ± 246 ng/g dry weight (dw)) than in UF (163 ± 211 ng/g dw) (p < 0.001), suggesting an introduction of additional OPEs during heating processes. Tris(2-chloroethyl) phosphate, triethyl phosphate, and tris(2-chloroisopropyl) phosphate exhibited the highest absolute increased amounts, with 137, 48.8, and 149% growth in HF than in UF, respectively. Migration testing revealed that packaging materials were rich in OPEs and can release considerable OPEs into food simulates (range, 14.7–90.8 ng/g; mean, 47.9 ± 21.8). Influencing factors (temperature, contact time, oily food) on OPE migration from packaging materials to food were assessed. Higher temperature and longer contact time increased OPE contents in food simulates. Moreover, the presence of abundant OPEs in UF and significant correlations among different OPEs (p < 0.05) suggested contamination happened during food processing and storage. With one SHLB meal a day, a 12-fold increase of OPE intake was observed for humans compared to those following a traditional dietary habit. In the high-exposure (95th percentile) scenario, hazard quotients of nine OPEs ranged from 0.00005 to 0.05. Our results suggested that the SHLB exposure pathway of OPEs should be particularly paid attention to in specific subpopulations that prefer this dietary habit.