Human health risk from consumption of aquatic species in arsenic-contaminated shallow urban lakes

Abstract

Arsenic (As) causes cancer and non-cancer health effects in humans. Previous research revealed As concentrations over 200 μg g^-1 in lake sediments in the south-central Puget Sound region affected by the former ASARCO copper smelter in Ruston, WA, and significant bioaccumulation of As in plankton in shallow lakes. Enhanced uptake occurs during summertime stratification and near-bottom anoxia when As is mobilized from sediments. Periodic mixing events in shallow lakes allow dissolved As to mix into oxygenated waters and littoral zones where biota reside. We quantify As concentrations and associated health risks in human-consumed tissues of sunfish [pumpkinseed (Lepomis gibbosus) and bluegill (Lepomis macrochirus)], crayfish [signal (Pacifastacus leniusculus) and red swamp (Procambarus clarkii)], and snails [Chinese mystery (Bellamya chinensis)] from lakes representing a gradient of As contamination and differing mixing regimes. In three shallow lakes with a range of arsenic in profundal sediments (20 to 206 μg As g^-1), mean arsenic concentrations ranged from 2.9 to 46.4 μg g^-1 in snails, 2.6 to 13.9 μg g^-1 in crayfish, and 0.07 to 0.61 μg g^-1 in sunfish. Comparatively, organisms in the deep, contaminated lake (208 μg g^-1 in profundal sediments) averaged 11.8 μg g^-1 in snails and 0.06 μg g^-1 in sunfish. Using inorganic As concentrations, we calculated that consuming aquatic species from the most As-contaminated shallow lake resulted in 4-10 times greater health risks compared to the deep lake with the same arsenic concentrations in profundal sediments. We show that dynamics in shallow, polymictic lakes can result in greater As bioavailability compared to deeper, seasonally stratified lakes. Arsenic in oxygenated waters and littoral sediments was more indicative of exposure to aquatic species than profundal sediments, and therefore we recommend that sampling methods focus on these shallow zones to better indicate the potential for uptake into organisms and human health risk.

Keywords: Crayfish; Fish; Littoral sediment; Polymictic; Snail; Trace metal.

Figure 1.

Location of five study lakes in the Puget Sound lowlands relative to the former ASARCO smelter (Commencement Bay/Nearshore Tideflats Superfund Site). Deposition zone predicted to have elevated arsenic in soils due to smelter emissions is indicated by the shaded area (Area-Wide Soil Contamination Task Force, 2003).

Figure 2.

(a) Dissolved oxygen concentrations (mg L⁻¹) and (b) dissolved arsenic concentrations (μg L⁻¹) in filtered water samples from the water column of four study lakes in June 2019 (closed symbols from shallow polymictic lakes, open symbols from the deep, seasonally stratified lake). Waters with dissolved oxygen concentrations above 1 mg O₂ L⁻¹ (dotted line; a.) are considered oxic. All dissolved arsenic measurements from Bonney Lake are below the LOD, and therefore reported as 0.125 μg L⁻¹.

Figure 3.

Mean arsenic concentrations in (a) Chinese mystery snail (Bellamya chinensis) whole tissues, (b) crayfish tail meat, and (c) fish (Lepomis sp.) fillet compared to littoral sediments of the study lakes (closed symbols from shallow polymictic lakes, open symbols from deep, seasonally stratified lakes). Error bars represent one standard deviation from the mean. Different letter labels denote significant difference (p < 0.05) between lakes.

Figure 4.

Percent concentration of the sum of inorganic (arsenate and arsenite) and organic (dimethylarsinic acid, monomethylarsonic acid, arsenobetaine, and arsenocholine) arsenic species in edible aquatic species tissues. For phytoplankton, the organic fraction is comprised of only dimethylarsinic acid, monomethylarsonic acid, and arsenosugar. Samples are from Killarney and Steel Lakes for each organism. Error bars represent one standard deviation from the mean.