Despite intensive mining activities in Burkina Faso, little is known on the environmental impacts of metals and
metalloids potentially released from these activities. Water samples and 334 fish from 10 reservoirs were
taken in order to evaluate the extent of mercury (Hg), selenium (Se) and arsenic (As) contamination in aquatic
systems and their potential health risk for humans and wildlife, taking into account their antagonistic interactions.
Water and fish levels of these elements were relatively low and did not reveal an important impact of
gold mining activities. Water temperature and conductivity were the key factors associated with higher levels
of MeHg. Higher sulfate contentwas reported in sites with more particulate Hg, As and Se, suggesting anthropogenic
origin of metal(loid) inputs in water reservoirs. Metal(loid) concentrations in fish were low and ranged
from 0.002 to 0.607 μg/g wet weight (w.w.) for Hg, 0.023 to 0.672 for Se and 0.039 to 0.42 for As. These levels
are similar or slightly higher than those reported in many other studies from Africa. Nevertheless, more than
70% of piscivore fish exceeded the threshold for wildlife protection for MeHg. Further, a traditional risk analysis
performed ignoring Se antagonismindicated that these piscivores should be consumed by humans with caution.
However, when taking into account the antagonistic effect of Se on Hg toxicity, up to 99% of all fish could be
protected from Hg toxicity by their Se content. When considering both As/Se and Se/Hg antagonism, 83% instead
the 99% of fish should be considered safe for consumption. Fish Se and As concentrations did not pose potential
risk for both animals and humans. Overall, these reservoirs were relatively unaffected by As, Se and Hg contamination
despite the rising gold mining activities. Further, considering antagonistic effects of As, Se and Hg may
help refine consumption advisories.