Rapport 1056 In vitro.pdf - Svenska EnergiAskor AB

VÄRMEFORSK
The bioaccessible fraction of antimony, arsenic, cadmium, chromium, copper, lead,
nickel and zinc in a selection of ashes showed a higher variation between the different
elements than between the different ashes. With the exception of arsenic in two of the
investigated ashes, the bioaccessible concentration was substantially less than the total
concentration of all elements in all ashes. The bioaccessible fraction of arsenic was high
both in fly ashes (>85%) and in bottom ashes (40-85%). The bioaccessible fraction of
lead was also relatively high and varied between 14 and 60% in the different ashes.
Cadmium also had a high bioaccessible fraction which varied between 50-75% in the
investigated ashes. The bioaccessible fraction of chromium was much smaller compared
to the bioaccessible fraction of the other elements, and was with two exceptions less
than 12%. The bioaccessible fraction of copper was relatively high and varied between
20 and 70% in the different ashes.
In this study, particle size fraction only had an effect on the bioaccessible fraction of
arsenic, chromium, and copper. For these elements, bioaccessibility was higher in the
smaller particle size fraction representing involuntary ingestion. Particle size fraction
also had an effect on the total concentration of cadmium, nickel, antimony and zinc,
with higher total concentrations in the smaller particle size fraction.
Total concentration only had an effect on the bioaccessible fraction of arsenic, copper
and lead, with higher bioaccessible fractions at lower total concentrations.
The type of ash had an influence on the bioaccessible fraction of arsenic, cadmium,
chromium and antimony, with a higher bioaccessible fraction of arsenic, chromium and
antimony in fly ashes compared to in bottom ashes, and a higher bioaccessible fraction
of cadmium in bottom ashes compared to in fly ashes. Type of ash also had an influence
on the total concentration of arsenic, chromium, copper, nickel and zinc. Whereas the
total concentration of arsenic, chromium and zinc was higher in fly ashes than in bottom
ashes, the total concentration of copper and nickel was higher in the bottom ashes
compared to in the fly ashes.
Thus, the bioaccessible fraction of arsenic in this study depended on particle size
fraction, total arsenic concentration and type of ash.
The literature study performed within the project revealed that very little is known
about oral bioavailability of metals in ashes. The results generated in the experimental
part of the project therefore contribute important information to this area of research.
However, caution should be used when interpreting the experimental results as the
study only included a small number of ashes. In addition, the in vitro model used for
analysis of the bioaccessible fraction is not validated with in vivo data for several of the
metals investigated.
Keywords: oral bioavailability, bioaccessibility, in vitro test, arsenic, metals, particle
size fraction
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