Heavy metals (HM) can be accumulated along the food chain; their presence in food is a global concern for human health because some of them are toxic even at low concentrations. Unprocessed or minimally processed foods are good sources of different nutrients, so their safety and quality composition should be guaranteed in the most natural form that is obtained for human consumption. The objective of this scoping review (ScR) is to summarize the existing evidence about the presence of HM content (arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), methylmercury (MeHg), and aluminum (Al)) in unprocessed or minimally processed foods for human consumption worldwide during the period of 2011–2020. As a second objective, we identified reported HM values in food with respect to Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) International Food Standards for Maximum Limits (MLs) for contaminants in food. This ScR was conducted in accordance with the Joanna Briggs Institute (JBI) methodology and PRISMA Extension for Scoping Reviews (PRISMA-ScR); advance searches were performed in PubMed, ScienceDirect and FAO AGRIS (Agricultural Science and Technology Information) databases by two reviewers who independently performed literature searches with specific eligibility criteria. We classified individual foods in food groups and subgroups according to the Global Individual Information Food Consumption Data Tool (FAO/WHO GIFT). We homologated all the reported HM units to parts per million (ppm) to determine the weighted mean HM concentration per country and food group/subgroup of the articles included. Then, we compared HM concentration findings with FAO/WHO MLs. Finally, we used a Geographic Information System (GIS) to present our findings. Using our search strategy, we included 152 articles. Asia was the continent with the highest number of publications (n = 79, 51.3%), with China being the country with the largest number of studies (n = 34). Fish and shellfish (n = 58), followed by vegetables (n = 39) and cereals (n = 38), were the food groups studied the most. Fish (n = 42), rice (n = 33), and leafy (n = 28) and fruiting vegetables (n = 29) were the most studied food subgroups. With respect to the HM of interest, Cd was the most analyzed, followed by Pb, As, Hg and Al. Finally, we found that many of the HM concentrations reported exceeded the FAO/OMS MLs established for Cd, Pb and As globally in all food groups, mainly in vegetables, followed by the roots and tubers, and cereals food groups. Our study highlights the presence of HM in the most natural forms of food around the world, in concentrations that, in fact, exceed the MLs, which affects food safety and could represent a human health risk. In countries with regulations on these topics, a monitoring system is recommended to evaluate and monitor compliance with national standards. For countries without a regulation system, it is recommended to adopt international guidelines, such as those of FAO, and implement a monitoring system that supervises national compliance. In both cases, the information must be disseminated to the population to create social awareness. This is especially important to protect the population from the consumption of internal production and for the international markets of the globalized world.

Globally, there is growing concern over the presence of lead (Pb) in foods because it is a heavy metal with several toxic effects on human health. However, monitoring studies have not been conducted in Mexico. In this study, we estimated the concentrations of Pb in the most consumed foods and identified those that exceeded the maximum limits (MLs) for Pb in foods established by the International Standards. Based on the Mexican National Health and Nutrition Survey, 103 foods and beverages were selected and purchased in Mexico City retail stores and markets. Samples were analyzed twice using atomic absorption spectrophotometry. Values above the limit of quantification (0.0025 mg/kg) were considered to be detected. The percentage of detected values was 18%. The highest concentration was found in infant rice cereal (1.005 mg/kg), whole wheat bread (0.447 mg/kg), pre-cooked rice (0.276 mg/kg), black pepper (0.239 mg/kg), and turmeric (0.176 mg/kg). Among the foods with detected Pb, the levels in infant rice cereal, whole wheat bread, pre-cooked rice, and soy infant formula exceeded the MLs. The food groups with the highest percentages of exceeded MLs were baby foods (18%) and cereals (11%). Monitoring the concentration of contaminants in foods is essential for implementing food safety policies and protecting consumer health.

Cadmium (Cd) is a toxic heavy metal widely distributed in foodstuffs. In Mexico, few studies have evaluated Cd content in foods. This study aimed to determine Cd concentrations in foodstuffs that are highly consumed and bought in Mexico City to identify foods exceeding the Maximum Level (ML) and to assess the health risks of theoretical Cd intake from a diet following the Mexican Dietary Guidelines. A total of 143 foodstuffs were analyzed by atomic absorption spectrophotometry. Theoretical Cd intake was estimated in portions per week and compared with the Cd Tolerable Weekly Intake (TWI = 2.5 μg/kg per body weight). A total of 68.5% of the foodstuffs had detectable Cd concentrations. Higher concentrations were found in oyster mushrooms (0.575 mg/kg), romaine lettuce (0.335 mg/kg), and cocoa powder (0.289 mg/kg). Food groups with higher mean concentrations were vegetables (0.084 mg/kg) and snacks, sweets, and desserts (0.049 mg/kg). Ancho chili and romaine lettuce exceed the ML. The theoretical Cd intake estimation was 1.80, 2.05, and 3.82 μg/kg per body weight for adults, adolescents, and school-age children, respectively. This theoretical Cd intake represents a health risk only for school children exceeding the TWI by 53.2%. Our study confirms the presence and risk of Cd in Mexican foodstuffs and highlights the importance of monitoring programs.

The aim of this study was to synthesize the global evidence of heavy metal (HM) concentrations in baby foods and infant formulas. The toxic HMs lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) have been detected in baby foods and infant formulas, raising health concerns. Advanced searches were performed. Baby foods were classified into 7 groups according to their primary ingredient. Infant formulas were classified as: Stage 1 (12–36 months), and specialty. Median concentrations and interquartile ranges were calculated for each classification. The percentage of items by category exceeding the International Maximum Levels (MLs) was obtained. Seventy-five studies were included in the scoping review, which in total examined 580 baby foods and 251 infant formulas. Pb, Cd, and As were detected in over 60% of baby foods. The highest Pb median was found in rice mixes and fish mixes (0.008 mg/kg each), with >20% of their items exceeding the Pb ML. The highest Cd median was found in cereals (0.013 mg/kg) and mixes of various foods (0.008 mg/kg), with >17% of their items exceeding the Cd ML. For As, the highest median was found in mixed fish (0.165 mg/kg) and rice mixes (0.048 mg/kg), with 89% and 30% of items exceeding the As ML, respectively. For infant formulas, Pb, Cd, and As were detected in >60% of items. The highest Pb median concentrations were found in stages 1 and 2 (0.015 mg/kg each), with >60% of their items exceeding the Pb MLs. For As, without-stage (0.052 mg/kg) had the highest median, with >71% of items exceeding the As ML. Fifteen studies reported the health risks related to intake of various foods: significant risks were identified for infants ≥6 months for rice products, and ≤12 months stage 1 and 2 formulas. This review highlights widespread HM presence in baby foods and infant formulas. Exceedances of the ML were particularly notable in rice products for infants >6 months and infant formulas for babies ≤12 months of age.