Abstract
In Spain, certain population-based studies have shown high blood mercury (Hg) levels due to the high consumption of fish. Some studies have stated that one of the most consumed fish in Spain is canned tuna. Different Spanish organisms consider that it is safe to consume canned tuna as it supposedly has a low mercury content, particularly in so-called light tuna. However, in Spain light tuna is mainly yellowfin and bigeye tuna, while in other countries it is mainly skipjack tuna. This study analyzed 36 cans of the most popular brands in Spain and examined the influence of the type of tuna, packaging medium (olive oil, sunflower seed oil, water or marinade), different brands, prices and expiration dates. Mercury concentrations (mg/kg) were measured by atomic absorption spectrometry and thermal decomposition amalgamation. The medians observed were (mg/kg): light tuna: 0.314; IQR: 0.205 - 0.594, white tuna: 0.338; IQR: 0.276 - 0.558, skipjack: 0.311; IQR: 0.299 - 0.322, frigate tuna: 0.219; IQR 0.182 - 0.257 and mackerel: 0.042; IQR 0.029 - 0.074. We found statistically significant differences between white tuna, light tuna and mackerel (p = 0.004); light tuna and mackerel (p = 0.002) and white tuna and mackerel (p = 0.006). However, we found no differences between white tuna and light tuna, or among packaging medium, brands, prices or expiration dates. The limit of 0.500 mg/kg of mercury in canned tuna was exceeded by the following percentages of the cans: 33.3% of light tuna, 16.7% of white tuna, and 0% of Skipjack, frigate tuna and mackerel. The mercury content of the cans of Spanish light tuna that were analyzed was variable and high. The results of this study indicate that stricter regulation of Hg in canned tuna is necessary. Until then, it is safer to recommend that vulnerable populations such as children and pregnant women consume canned mackerel, which has a markedly lower mercury content.
Highlights
Methylmercury (MeHg) is a widespread and toxic form of high blood mercury (Hg) that results from the conversion of inorganic Hg to a methylated form by aquatic microorgan-isms and can bioaccumulate in the aquatic food web
We found statistically significant differences between white tuna, light tuna and mackerel (p = 0.004); light tuna and mackerel (p = 0.002) and white tuna and mackerel (p = 0.006)
Among the different types of canned tuna, light tuna is generally thought to contain the lowest concentrations of mercury
Summary
Methylmercury (MeHg) is a widespread and toxic form of Hg that results from the conversion of inorganic Hg to a methylated form by aquatic microorgan-isms and can bioaccumulate in the aquatic food web. Methylmercury (MeHg) is a widespread and toxic form of Hg that results from the conversion of inorganic Hg to a methylated form by aquatic microorgan-. Methylmercury accounts for more than 90% of total mercury content in fish and is attached to the thiol group of the cysteine residues in fish protein, and is not eliminated by cleaning or cooking the fish. Dietary intake of MeHg through ingestion of contaminated fish is a public health concern, primarily due to its neurodevelopmental toxicity in fetuses and children. Transplacental exposure is dangerous, as the fetal brain is very sensitive. A growing body of evidence suggests that MeHg exposure may lead to an increased risk of adverse cardiovascular impact in exposed adult populations [2,3]
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