Toxic Heavy Metals and Their Risk Assessment of Exposure in Selected Freshwater and Marine Fish in Thailand

Overview

Sirisangarunroj et al. measured total arsenic, cadmium, mercury, and lead in 15 commonly consumed fish species (7 freshwater, 8 marine) purchased from three local fish markets in or near Bangkok, Thailand. All analyses used ICP-MS-MS (Agilent 8800 triple-quadrupole) following microwave acid digestion and AOAC Official Method 2015.01; concentrations are reported as mg/kg fresh weight (FW) with n=3 markets per species. No HPLC-ICP-MS speciation was performed; all arsenic values are total arsenic (tAs), not inorganic arsenic. The study found grouper to be the highest-risk species, exceeding both Thailand’s national As standard (2 mg/kg) at 8.51 mg/kg and the Codex Hg standard (0.5 mg/kg) at 0.55 mg/kg FW (mercury in cooked form). Lead was below LOQ in all 15 species. Risk assessment using national food consumption survey data found a high arsenic margin of exposure concern for young children (0–5.9 years) consuming high-arsenic marine fish and striped snake-head fish; a high mercury HQ risk was identified for marine fish under high-consumption or high-mercury scenarios.

Key numbers

All concentrations in mg/kg fresh weight (FW), mean ± SD, n=3 markets.

ND = not detected (<LOD 0.0009 mg/kg for Cd; 0.0007 mg/kg for As); <LOQ: As and Cd = 0.006 mg/kg FW; Hg and Pb = 0.012 mg/kg FW.

Standard exceedances: Grouper tAs 8.51 mg/kg exceeds Thailand’s national As limit of 2 mg/kg; grouper tHg 0.55 mg/kg FW (post-yield-factor cooked estimate) exceeds Codex Hg limit of 0.5 mg/kg but is below Thailand’s notification level of 0.5 mg/kg for the raw sample (0.38 mg/kg raw < 0.5 mg/kg). Longtail tuna tAs 1.92 mg/kg FW is near but just below the 2 mg/kg national standard.

Methods (brief)

ICP-MS-MS (Agilent 8800 triple-quadrupole) after microwave acid digestion with HNO3/H2O2; AOAC 2015.01. Internal standard: Au + Lu. CRMs: NIST SRM 1566b (oyster tissue) and NMIJ 7402-a (codfish tissue). Recoveries: As 90 ± 5%, Cd 100 ± 5%, Hg 111 ± 4%, Pb 110 ± 4%. LOD: As 0.0007, Cd 0.0009, Hg 0.0011, Pb 0.0011 mg/kg FW. LOQ: As 0.0063, Cd 0.0062, Hg 0.0124, Pb 0.0123 mg/kg FW. All arsenic is total arsenic; no HPLC speciation was performed. For risk assessment, the authors applied published %iAs fractions by fish food group (ranging from 2.5% for Indo-Pacific mackerel to 23.6% for striped snake-head fish) as a secondary calculation; direct iAs measurements were not made.

Implications

Certification: Grouper from Thai markets showed tAs 8.51 mg/kg FW and tHg 0.38 mg/kg FW raw, the highest values in this dataset. All other freshwater species were substantially cleaner; lead was below LOQ in all 15 species.

Courses: Illustrates the species-level variation in marine vs freshwater fish metal burdens in Southeast Asia; grouper and large predatory marine species carry disproportionate arsenic and mercury loads.

App: Total arsenic in marine fish (Bangkok markets) ranges from <LOQ to 8.51 mg/kg FW; tHg ranges from <LOQ to 0.38 mg/kg FW raw. Cd is low to trace in all species (<0.04 mg/kg). Pb universally <LOQ.

Wiki pages updated on ingest

• Mercury
• Arsenic
• Freshwater Fish
• marine-fish
• Seafood

Update history

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