Unraveling the threshold and interaction effects of environmental variables on cadmium contamination in rice grains.

Understanding Cd contamination in the soil-rice ecosystem and the underlying its threshold and interaction effects is crucial for controlling Cd pollution and ensuring food safety. Although the quantitative relationships between Cd and environmental variables have been extensively studied, the threshold and interaction effects of multi-source environmental variables remain largely unexplored. This study employs a combination of random forest analysis and a human health risk model to investigate the effects of variables on Cd levels in rice grains, with the goal of quantifying their contributions and elucidating their relationships. The results indicated that the 15 selected variables collectively explained 47.36 % of the variation in Cd content, with the top three variables being soil pH, distance from industrial park, and soil Zn. The majority of variables exhibited threshold effects on Cd levels in rice grains. By visualizing the interaction between Soil pH, distance from industrial park, and soil Zn with Cd levels in rice, we demonstrate the threshold effects of them on Cd level in rice grains, thereby providing further insight into the variation observed. Furthermore, oral intake of rice has been identified as the primary route of human exposure, significantly contributing to overall exposure pathways. Understanding these interactions is crucial for gaining insights into the underlying processes driving Cd pollution and fostering sustainable development within the industry. Our findings underscore the crucial need to consider multiple environmental variables and their interactions when managing heavy metals (HMs) contamination and mitigating health risks.