Consequences of surface coatings and soil ageing on the toxicity of cadmium telluride quantum dots to the earthworm Eisenia fetida

Kristi Tatsi; Thomas H Hutchinson; Richard D Handy

doi:10.1016/j.ecoenv.2020.110813

Consequences of surface coatings and soil ageing on the toxicity of cadmium telluride quantum dots to the earthworm Eisenia fetida

Ecotoxicol Environ Saf. 2020 Sep 15:201:110813. doi: 10.1016/j.ecoenv.2020.110813. Epub 2020 Jun 13.

Authors

Kristi Tatsi¹, Thomas H Hutchinson², Richard D Handy³

Affiliations

¹ School of Biological Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK.
² School of Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK.
³ School of Biological Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK; Visiting Professor, Department of Nutrition, Cihan University-Erbil, Kurdistan Region, Iraq. Electronic address: r.handy@plymouth.ac.uk.

PMID: 32544745
DOI: 10.1016/j.ecoenv.2020.110813

Abstract

The bioaccumulation potential and toxic effects of engineered nanomaterials (ENMs) to earthworms are poorly understood. Two studies were conducted following OECD TG 222 on Eisenia fetida to assess the effects of CdTe QDs with different coatings and soil ageing respectively. Earthworms were exposed to carboxylate (COOH), ammonium (NH₄⁺), or polyethylene glycol (PEG) coated CdTe QDs, or a micron scale (bulk) CdTe material, at nominal concentrations of 50, 500 and 2000 mg CdTe QD kg^-1 dry weight (dw) for 28 days in Lufa 2.2 soil. In the fresh soil study, earthworms accumulated similar amounts of Cd and Te in the CdTe-bulk exposures, while the accumulation of Cd was higher than Te during the exposures to CdTe QDs. However, neither the total Cd, nor Te concentrations in the earthworms, were easily explained by the extractable metal fractions in the soil or particle dissolution. There were no effects on survival, but some retardation of growth was observed at the higher doses. Inhibition of Na^+_/K⁺-ATPase activity with disturbances to tissue electrolytes, as well as tissue Cu and Mn were observed, but without depletion of total glutathione in the fresh soil experiment. Additionally, juvenile production was the most sensitive endpoint, with estimated nominal EC₅₀ of values >2000, 108, 65, 96 mg CdTe kg^-1 for bulk, PEG-, COOH- and NH₄⁺-coated CdTe QDs, respectively. In the aged soil study, the accumulation of Cd and Te was higher than in the fresh soil study in all CdTe QD exposures. Survival of the adult worms was reduced in the top CdTe-COOH and -NH₄⁺ QD exposures by 55 ± 5 and 60 ± 25%, respectively; and with decreases in growth. The nominal EC₅₀ values for juvenile production in the aged soil were 165, 88, 78 and 63 mg CdTe kg^-1 for bulk, PEG-, COOH- and NH₄⁺-coated CdTe QDs, respectively. In conclusion, exposure to nanoscale CdTe QDs, regardless of coating, caused more severe toxic effects that the CdTe bulk material and the toxicity increased after soil ageing. There were some coating-mediated effects, likely due to differences in the metal content and behaviour of the materials.

Keywords: Bioaccumulation potential; Growth; Nanoparticles; Reproductive success; Survival; Toxic metals.

MeSH terms

Animals
Bioaccumulation
Cadmium Compounds / chemistry
Cadmium Compounds / metabolism
Cadmium Compounds / toxicity*
Models, Theoretical
Oligochaeta / drug effects*
Oligochaeta / metabolism
Particle Size
Quantum Dots / chemistry
Quantum Dots / metabolism
Quantum Dots / toxicity*
Reproduction / drug effects
Soil / chemistry*
Soil Pollutants / chemistry
Soil Pollutants / metabolism
Soil Pollutants / toxicity*
Surface Properties
Tellurium / chemistry
Tellurium / metabolism
Tellurium / toxicity*
Time Factors

Substances

Cadmium Compounds
Soil
Soil Pollutants
Tellurium
cadmium telluride