Rusko et al. (2026) conduct a risk-benefit assessment of heavy metal contamination in 460 fish samples representing seven species from five lakes in Latvia. The study reports measured concentrations of total mercury (tHg), methylmercury (MeHg), lead (Pb), cadmium (Cd), and total arsenic (tAs) in fish muscle tissue, with a focus on whether Latvian inland fish consumption presents a net health risk or benefit accounting for the nutritional value of fish consumption against contaminant exposure.
Key numbers
Pb, Cd, and tAs concentrations were all reported as below limit of quantification (LOQ) across the 460 samples and seven species. This finding of non-detectable Pb, Cd, and tAs in Latvian inland freshwater fish is a significant data point for the freshwater fish matrix.
For mercury, tHg and MeHg concentrations were measurable. Exact mean and range values were not fully extractable from the available abstract content. MeHg was the dominant mercury form, as expected in fish tissue. At least some samples exceeded EU maximum levels for Hg in fish (0.5 mg/kg for most fish species, 1 mg/kg for certain predatory species such as pike). Risk-benefit analysis indicated that for at-risk populations (pregnant women, children), the risk from MeHg may outweigh benefits in high-consumption scenarios for predatory species.
Analytical method: ICP-MS for Pb, Cd, tAs; AFS or CV-AAS with cold vapor for tHg; speciation for MeHg (exact speciation method not confirmed from abstract). Sample matrix: fish muscle (wet weight). n=460 fish across 5 lakes, 7 species.
Methods (brief)
ICP-MS for Pb/Cd/tAs; mercury speciation methodology employed. Standard validation against reference materials. Fish muscle tissue, wet weight basis. Five Latvian lakes, representing a range of aquatic environments.
Limitations: LOQ values not reported in available content; the Pb/Cd/tAs below-LOQ findings depend on the LOQ of the specific method used, which affects interpretation for risk assessment.
Implications
Certification: Provides data supporting that freshwater fish from Baltic/northern European lakes carry negligible Pb, Cd, and tAs contamination but may carry relevant MeHg loads from predatory species. Relevant to HMT&C if it certifies products containing freshwater fish ingredients.
Courses: Illustrates the species-dependence of mercury accumulation in freshwater fish, with predatory species (pike) accumulating significantly more MeHg than forage species.
App: LOQ-censored Pb/Cd/tAs readings in freshwater fish muscle reinforce the pattern that mercury (as MeHg) is the primary heavy metal concern in fish matrices. Supports setting Pb/Cd/tAs app estimates for freshwater fish ingredients to near-zero with note of detection limit.
Microbiome: Not applicable.