Assessing heavy metal risks in liquid milk: Dietary exposure and carcinogenicity in China

China, as the world's second-largest market for dairy products, places significant importance on the safety of such products. In recent years, incidents related to the safety of dairy products have occurred frequently, posing substantial threats to public health and societal stability. The indiscriminate discharge of industrial sewage not only causes environmental pollution, but also may result in the presence of heavy metals in raw milk, thus raising concerns about food safety. This paper establishes a risk assessment model for heavy metal contamination in liquid milk, using dietary exposure assessment and simulation risk assessment. The assessment covers heavy metal contamination in soils and pastures across most provinces in China, excluding Taiwan, Tibet, Macau, and Hong Kong. Employing methods such as the pollution index, spatial cluster analysis, distribution fitting, and carcinogenic risk assessment, the study reveals that the overall pollution levels of heavy metals in the soil of Yunnan Province and Jiangxi Province are particularly severe, and the bioaccumulation effect made heavy metal pollution more pronounced in the forage samples of Yunnan Province. Furthermore, based on transfer factors, residents' daily dietary intake, and local economic levels, the study evaluates the carcinogenic risk and target total risk index of heavy metals in raw milk. The findings highlight that the risk of carcinogenicity and noncarcinogenicity is higher in the [3, 6) age group compared with other age groups, underlining the urgent need for improved regulation and monitoring to protect public health, especially for vulnerable populations. The study underscores that heavy metal contamination forms a complete "soil-feed-milk" risk chain. It highlights the need to establish a region-specific regulatory framework, focusing on the characteristics of pollution. In additional, dietary interventions for susceptible groups, such as children, should be strengthened to mitigate the long-term health effects of environmental pollution.