The toxicity of ibuprofen and perfluorooctanoic
acid (PFOA) was evaluated individually and in binary
combination on two photosynthetic organisms, the green
alga
Pseudokirchneriella subcapitata, representative of
aquatic environments, and the monocotyledonous
Sorghum
bicolor
, for terrestrial ecosystems. Both non-target organisms
showed different sensitivities to pollutants. The alga
was more affected than the plant to each compound
assayed, whether separately or mixed in EC
50 proportion,
and PFOA was more toxic to both bioindicators. An analysis
of toxic chemical interactions covering the whole
range of effect levels was conducted using the Combination
Index method and indicated that synergism could be
expected at low effect levels in higher plants, while for
algae this type of interaction predominated at higher effect
levels. Ecological risk assessment was performed by calculating
the Hazard Quotient as the ratio between the
measured environmental concentration and the predicted
no-effect concentration, using our EC
50 data derived from
the mixture of pollutants. Acute hazard was found in the
terrestrial compartment (soil or sediments). In the light of
the data reported, we conclude that risk evaluation should
include toxicological information on compound interactions
that exert a toxic effect on non-target organisms.
