The consumption of American red crab from abandoned mining areas poses a risk to food safety due to the accumulation of high levels of metals

    El american red crab (Procambarus clarkii) has become one of the most widespread and problematic invasive alien species in the rivers of the Iberian Peninsula. On the other hand, its sport fishing for self-consumption as a seasonal product is deeply rooted in Spain, especially in rural areas. As a food product, red crab could be considered a healthy dish with a wide variety of nutritional benefits. However, tends to accumulate high levels of environmental pollutants, so its monitoring is essential to guarantee the food safety of its consumption, especially in aquatic ecosystems affected by the presence of abandoned mining waste that have never been rehabilitated or restored.

    A study developed by the Wildlife Toxicology Group of the Institute for Research in Hunting Resources (IREC – CSIC, UCLM, JCCM) has evaluated the public health risk associated with the consumption of American crabs from the Valdeazogues and Montoro rivers, in the province of Ciudad Real, specifically from the sections of these rivers that cross, respectively, the old Almadén Mining District, which was the world's leading producer of mercury (Hg) until the late XNUMXth century, and the former Alcudia Valley Mining District, the main producer of lead (Pb) in Spain until the end of the XNUMXth century.

    The levels of Hg in crabs from the Valdeazogues river and those of Pb in crabs from the Montoro river reflect the accumulation of mining contamination that persists in the sediments of these rivers. A 27% of crab tails from the Valdeazogues river and a 87% of those coming from the Montoro River far exceeded the maximum allowable levels established by the European Union for the consumption of crustacean meat. Even taking into account only the bioavailable fraction of these metals in crab tails (i.e., the proportion of ingested metals that is absorbed at the gastrointestinal level), which was approximately 28% for Hg and 34% for Pb. , the estimated risk ratios suggest that its use is not safe, especially for children. Cooking of the whole body of the crabs (tail muscle, shell and viscera from the cephalothoracic cavity) following a typical crayfish recipe revealed that the amount of metals that are extracted during the process, and that become part of the sauce is relatively small (approximately 9% for Hg and 2% for Pb). However, the high levels of Hg and Pb found in these crabs suggest that Its use as a condiment or cooking ingredient would not be recommended either..

    Fishing for American red crab in the Valdeazogues River is already restricted in most of the section that runs through the old Almadén Mining District. However, there is no type of signaling that informs and prevents risks to public health that could be derived from its consumption. For its part, red crab fishing in the Montoro River It does not have any type of restriction or recommendation associated with its consumption. The results of this work recommend the implementation of management measures and the development of environmental communication campaigns aimed at preventing food safety risks associated with the consumption of crabs from these mining districts. Likewise, they recommend investigating the consequences that the accumulation of high levels of potentially toxic metals such as Hg and Pb in the American red crab could have on the trophic chains of these ecosystems, since this invasive exotic species has become a a fundamental trophic resource for a multitude of native predators, such as the otter (Lutra lutra), whose conservation could be threatened by the biomagnification of mining contamination.

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    Reference:

    Rodríguez-Estival, J., Morales-Machuca, C., Pareja-Carrera, J., Ortiz-Santaliestra, ME, Mateo, R. 2019. Food safety risk assessment of metal pollution in crayfish from two historical mining areas: Accounting for bioavailability and cooking extractability. Ecotoxicology & Environmental Safety 185, 109682.