Co-considering Selenium Concentrations Alters Mercury-Based Fish and Seafood Consumption Advice: A Data Compilation and Critical Assessment

There has been persistent interest in the mediating role
of the
micronutrient selenium (Se) in mercury (Hg) toxicity since the 1960s.
Despite many unresolved questions regarding Se–Hg interactions,
considerable research has been performed to document Se:Hg molar ratios
in aquatic animals as a basis for inferring the health risks associated
with their consumption. We compiled the co-reported Se and Hg data
for 386 shellfish, finfish, and aquatic mammals from 89 papers to
assess differences in consumption safety categorizations according
to health risk metrics that (a) consider Hg concentrations alone or
(b) co-consider Se and Hg concentrations. Species-specific mean Hg
concentrations for 23% of all data points in our database exceeded
the FAO/WHO maximum level, and 68% and 83% had estimated daily intake
per meal values for adults and children above the Joint FAO/WHO Expert
Committee on Food Additives Provisional Tolerable Daily Index. In
contrast, only 12% of data points would be categorized as unsafe for
consumption on the basis of their 1:1 Se:Hg molar ratios. Se-inclusive
risk metrics reversed safety categorizations for a majority of high-trophic
level species that are most likely to exceed Hg-based risk thresholds.
Adopting Se-inclusive risk metrics has potentially significant implications
for seafood consumer health and is likely premature.