Quantification of insecticides in commercial seafood sold in East Asian markets: risk assessment for consumers

**Background:** The Pearl River Delta (PRD) in southern China has experienced rapid industrialization and agricultural expansion, leading to widespread contamination with organochlorine pesticides (OCPs). Despite bans on many OCPs, their persistence and continued use of compounds like dicofol and lindane have resulted in ongoing environmental pollution. Seafood is a major dietary component in Macao and Hong Kong, with per capita consumption in Hong Kong reaching 66.5 kg in 2017. This study aimed to quantify 21 insecticides (including OCPs and the carbamate fenobucarb) in commonly consumed seafood species from local markets and assess the potential health risks to consumers.

**Methods:** Seven seafood species were collected from seven markets (four in Hong Kong, three in Macao) between June and August 2018: three bivalves (*Meretrix meretrix*, *Anadara subcrenata*, *Perna viridis*), three crustaceans (*Portunus pelagicus*, *Scylla serrata*, *Metapenaeus ensis*), and one fish (*Boleophthalmus pectinirostris*, mudskipper). A total of 138 samples were analyzed. A modified QuEChERS extraction method followed by GC-MS/MS was used to quantify 21 insecticides. Method validation followed SANTE/11813/2017 guidelines. Lipid content was determined using the Bligh & Dyer method. Non-carcinogenic risk was assessed using hazard quotients (HQ) for acute (HQ_ST) and chronic (HQ_LT) exposure, and hazard index (HI) for cumulative risk. Carcinogenic risk (CR) and total cancer risk (TCR) were calculated using cancer slope factors. Consumption rates were 17.1 g/day for bivalves, 8.3 g/day for crustaceans, and 105 g/day for fish for adults; 50 g/day for fish for toddlers. Body weights were 63 kg (adult) and 14 kg (toddler).

**Key Results:** All validated compounds except lindane (γ-HCH) were detected. The highest median concentrations were found in *P. viridis* from Hong Kong (30.33 ng/g WW) and *B. pectinirostris* from Macao (23.90 ng/g WW), both significantly above the legal limit of 10 ng/g WW (p < 0.05). Mudskippers had the highest detection frequency (38%). In bivalves, heptachlors were most abundant (median 52.55 ng/g WW in Macao), and HCHs were also high (ca. 38 ng/g WW in both sites). In crustaceans, DDTs dominated (median 27.06 ng/g WW in Macao, 39.38 ng/g WW in Hong Kong). In fish, fenobucarb (median 222.66 ng/g WW), heptachlors (99.50 ng/g WW), and DDTs (53.06 ng/g WW) were prominent. No significant correlation was found between lipid content and pesticide concentrations (r² = 0.029, p ≥ 0.05). For non-carcinogenic risk, all HQ_ST values were < 1. For chronic exposure, heptachlor epoxide in fish had HQ_LT > 1 for both adults (3.45) and toddlers (1.61). HI exceeded 1 for fish (3.52) and bivalves (1.00) in adults. For carcinogenic risk, individual CR values for heptachlor epoxide in fish (1.92E-03 for toddlers, 8.80E-04 for adults) and β-HCH in fish (1.56E-04 for toddlers) exceeded 10⁻⁴. TCR values were above 10⁻⁴ for all matrices (fish: 2.15E-03 for toddlers, 9.80E-04 for adults; bivalves: 7.08E-04; crustaceans: 2.31E-04). Median concentrations of fenobucarb, DDTs, and HCHs were 13-, 4.6-, and 3.8-fold above the 10 ng/g WW limit, respectively (p < 0.0001).

**Clinical Implications:** The study demonstrates that commercial seafood from Macao and Hong Kong markets contains insecticide residues at levels that may pose chronic non-carcinogenic and carcinogenic health risks to consumers, particularly for fish (mudskippers) and bivalves. The presence of banned OCPs like DDTs and HCHs indicates ongoing environmental contamination. The lack of acute reference doses for several compounds limits the acute risk assessment. The findings underscore the need for rigorous monitoring and control of pesticide residues in seafood sources to protect public health, especially for vulnerable populations such as toddlers.