Bioavailability, Toxicity
and Biotransformation of
Selenium in Midge (<i>Chironomus dilutus</i>) Larvae Exposed
via Water or Diet to Elemental Selenium Particles, Selenite, or Selenized
Algae
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Abstract
Elemental selenium (Se) is generally considered to be
biologically
inert due to its insolubility in water. It is a common form of Se
in sediment near uranium mining and milling operations in northern
Saskatchewan, Canada. Nanosized particles of many materials exhibit
different properties compared with their bulk phases, in some cases
posing health and ecological risks. Here we investigated the bioavailability
and toxicity of Se nanoparticles (SeNPs) using 10-day waterborne and
dietary exposures to larvae of <i>Chironomus dilutus</i>, a common benthic invertebrate. For comparison, larvae were also
exposed to waterborne dissolved selenite and to dietary selenomethionine
as selenized algae. Larval Se accumulation was evaluated using graphite
furnace atomic absorption spectroscopy or inductively coupled plasma
mass spectroscopy for total Se and X-ray absorption spectroscopy for
Se chemical speciation. Exposure to nanoparticulate Se resulted in
Se bioaccumulation, at high concentrations, inhibiting larval growth
in both waterborne and dietary exposures; larvae predominantly accumulated
selenomethionine-like species regardless of uptake route or form of
Se tested. Despite the observed Se accumulation, our findings suggest
there is little risk of direct SeNP toxicity to benthic invertebrates
in Se-contaminated sediments in northern Saskatchewan. Nevertheless,
elemental Se in sediments may be biologically available and may contribute
directly or indirectly to the risk of Se toxicity to egg-laying vertebrates
(fish and piscivorous birds) in Se-contaminated aquatic systems. It
thus may be necessary to include elemental Se as a source of potential
Se exposure in ecological risk assessments