There are many widespread chemical contaminants in the environment, including toxic metals and metalloids (TMMs), which can enter the food chain, persist and bioaccumulate to levels that can pose a long-term risk to human health.

TMMs include non-essential trace elements such as arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb), and essential trace elements such as chromium (Cr), copper (Cu), iron (Fe) and zinc (Zn), which are of concern for their toxicological effects on humans and animals. Long-term exposure to TMMs can lead to a broad spectrum of potential adverse health effects, such as renal and hepatic diseases, central and peripheral nervous system and circulatory disorders, reproductive toxicity, genotoxicity, teratogenicity and carcinogenicity. Because of their occurrence, toxicity and potential for human exposure, As, Pb, Hg and Cd are also high on the priority list of pollutants.

TMMs are transferred from soil, air, feed and water to animals in high concentrations and then into food of animal origin, such as fishery products, meat and meat products. High levels of contamination and high dietary intake of these products can result in levels of human exposure to TMM that can lead to adverse health consequences.

The level of undesirable toxic elements in porcine skeletal muscle tissue is generally not considered to be a food safety concern. However, the same is not always true for edible internal organs, as most TMMs accumulate gradually, especially in the kidneys, liver, heart, lungs and brain. This factor may be important from a human health point of view as pork offal, and in particular liver, is widely consumed in many countries around the world, including European ones.

Data on TMM concentrations in pig meat and liver are available from different countries. The contamination levels are mostly measured in samples of lean pigs slaughtered at 5-6 months of age and weighing approximately 100 kg. Contamination levels in these samples were generally within the recommended safety limits. In contrast, little information is available on TMM contamination in Italian heavy pigs. Heavy pigs are typically fattened to 170 kg and slaughtered at 9 months of age.

In a new study, the degree of contamination of pig muscle and liver tissues from Italian heavy pigs with 12 TMMs (As, Al, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Sn, U and Zn) was assessed for the first time and used to assess dietary exposure of different age groups of the Italian population. The effect of consumption of pork and pork liver on the toxicological guidance values for each TMM has also been estimated to characterise the potential human health risk associated with dietary exposure to these food contaminants.

In both tissues, iron (Fe), zinc (Zn) and copper (Cu) were the most abundant elements, while uranium (U) was detected only in ultra-trace amounts. Arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), lead (Pb), uranium (U) and zinc (Zn) showed significantly higher concentrations in liver than in muscle (p ≤ 0.01), for example, Cd and Cu were present in 60 and 9 times higher concentrations in liver tissue, respectively. This suggested that heavier weight and higher age at the slaughter of heavy pigs may influence the accumulation of these elements in liver tissue. Nevertheless, the concentrations of all TMMs were low in all samples, such that the resulting estimated dietary intakes did not pose food safety concerns.

However, the analysis also showed that children at high intakes may be exposed to levels of Cd, Fe and Zn that can contribute to more than 24, 46 and 76% of the tolerable weekly intake of these elements through combined consumption of pork and pork liver, respectively. Since other foods from the whole diet are additional sources of exposure to Cd, Fe and Zn, it can be assumed that the tolerable weekly intake of these metals from the whole diet is greatly exceeded and therefore some food safety concerns arise for the younger population.

The results suggest that the transfer and accumulation of TMMs from feed to animal tissues should be reduced as much as possible. Integrated monitoring programmes should be enhanced to control the presence of contaminants in soil, feed, water, livestock and associated meat products, while the need for dietary intake should be assessed more frequently. In the context of risk management, action levels and target levels for TMMs could be established to immediately identify and minimise sources of contamination. Risk communication should include informing consumers to consume pork liver within reasonable limits and specific dietary advice should be given in particular for the most vulnerable categories of consumers, such as children, the elderly, pregnant and lactating women.