Elevated Concentrations of Metal(loids) in Seaweed and the Concomitant Exposure to Humans

Overview

Khandaker and colleagues measured 17 elements in cultivated Malaysian Eucheuma cottoni seaweed from Langkawi, Semporna, and Kota Belud. The study reports dry-weight concentrations in microgram per gram and estimates dietary intake, noncarcinogenic hazard, and carcinogenic risk for an assumed East Asian adult seaweed consumer. The paper labels chromium as hexavalent chromium (Cr-VI) and arsenic as arsenic (As) (III), but the analytical method was ICP-OES rather than a chromatographic speciation method.

Key numbers

Fresh seaweed samples were collected from Kota Belud and Semporna in March 2018 and from Pulau Dangli, Langkawi in September 2018. The authors collected 4 kg of fresh whole seaweed from each location, with samples obtained from at least four sublocations at each farming site. Table 3 reports location group sizes of LKW n = 3, SPN n = 3, and KBL n = 2.

Table 3 reports metal concentrations in microgram per gram as mean ± relative standard deviation (RSD), with range in parentheses:

Table 2 reports LoD values in µg/kg: lead (Pb) 11.31, cadmium (Cd) 2.15, aluminum (Al) 3.08, Mn 1.20, Cu 1.89, Zn 0.89, Fe 1.01, As 14.51, nickel (Ni) 1.97, chromium (Cr) 4.66, Ag 0.35, and Si 37.94.

Table 1 reports CRM 7405-a recovery checks for HMT-relevant analytes: Pb certified 0.43 ± 0.03 mg/kg, recovered 0.45 ± 0.04, recovery 104.7%; Cd certified 0.79 ± 0.02, recovered 0.75 ± 0.03, recovery 94.9%; Al certified 147 ± 7, recovered 141 ± 6, recovery 95.9%; As certified 35.8 ± 0.9, recovered 35.26 ± 0.88, recovery 98.5%; Ni certified 2.2 ± 0.1, recovered 2.3 ± 0.08, recovery 104.6%; Cr certified 3.4 ± 0.1, recovered 3.29 ± 0.09, recovery 96.8%.

Table 4 estimates daily intake in Microgram Per Kilogram/kg/Day for an assumed East Asian adult consuming Malaysian seaweed at 10 g/adult/day. The paper’s equation 2 cites a default adult body weight of 70 kg, but the East Asian risk assessment uses 65 kg as the nominal body weight; back-calculating Table 4 values from Table 3 concentrations confirms the published intakes were computed with 65 kg. Mean daily intakes were Pb 1.2, Cd 0.3, As 0.7, Ni 1.5, Cr-VI 4.0, Al 6.3, and Ag 0.03.

Table 5 reports noncarcinogenic and carcinogenic risk estimates for the same assumed intake scenario: Pb HQ 0.203 and LTCR 6.08 × 10−4; Cd HQ 0.171 and LTCR 4.89 × 10−3; As HQ 1.547 and LTCR 5.22 × 10−2; Ni HQ 0.053 and LTCR 1.34 × 10−1; Cr-VI HQ 0.912 and LTCR 1.03 × 10−1. The summed hazard index is 4.38, and the summed lifetime carcinogenic risk is 2.94 × 10−1.

Methods (brief)

Fresh Eucheuma cottoni seaweed was collected from three Malaysian farming locations, washed, cut, dried at 70 °C to constant dry weight, blended, and sieved through a 25 µm mesh. For each analysis, 0.5 g dw was digested with 10 mL HNO3 and 3 mL HCl on a hot plate at 100 °C for 2 h, filtered through Whatman No. 41 paper, diluted with 10 mL deionized water, and analyzed by ICP-OES (Optima 5300DV, PerkinElmer). Calibration used Agilent multi-element standard solution 2A in 5% HNO3; validation used NIST SRM 1400 and NMIJ CRM 7405-a. The authors state each sample was analyzed in duplicate.

Update history

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