Cadmium (Cd) exposure in humans primarily occurs through dietary intake, with conventional one-compartment toxicokinetic (TK) models linking dietary Cd intake to urinary Cd (UCd) levels, predominantly in Western populations with low background exposure. However, the applicability of this model to regions with high dietary Cd intake, particularly from rice consumption, remains uncertain. In this study, we conducted a comprehensive population-based survey involving 686 individuals from a typical Cd-polluted area and 296 from a non-polluted area in China, where rice serves as the staple food in both regions. Additionally, we selected 34 individuals from the polluted area for a 27-month intervention, during which home-grown high-Cd rice was replaced with low-Cd rice available in the market. We closely monitored temporal changes in Cd concentration and stable isotope signatures in urine samples. The adults in the polluted area had much higher dietary Cd intakes (mean 58.5 mu g kg-1 body weight month-1) and UCd (geometric mean 6.1 mu g g-1 creatinine) than those in the non-polluted area. There was a robust dose-response relationship (R2 = 0.67, n = 982) between UCd and beta 2-microglobulin, a biomarker of renal tubular impairment. The intervention reveals that a considerable proportion of Cd rapidly exuded after recent dietary intake, contradicting the conventional TK model. The modified TK model incorporating the direct blood-urine allocation greatly improved the association between dietary Cd intake and UCd. These results underscore the potential for high dietary Cd intake through rice in China to cause dose-dependent kidney damage. The modified TK model offers a reliable framework to estimate Cd-related thresholds and associated health risks for populations reliant on rice-based diets.

Honeycomb coal ash was selected as phosphorus adsorbent to explore the influence of different factors on phosphorus adsorption performance for phosphorus containing wastewater. The structural, physical and chemical properties of coal ash were determined by SEM, BET and XRF analysis methods. The response surface methodology (RSM) was applied for experimental design of phosphorus adsorbent. The effect of five independent variables including initial concentration of phosphorus, coal ash dosage, coal ash particle size, adsorption time and pH on the phosphorus removal efficiency (R (%)) was studied in the ranges of 5-7 mg/L, 6-10 g, 180-220 mesh, 20-30 min and 6.12-6.92 respectively. 46 runs of experiments were designed by the Design-Expert software. The optimum conditions for initial concentration of phosphorus, coal ash dosage, coal ash particle size, adsorption time and pH were found as 6.34 mg/L, 8.17 g, 207.97 mesh, 23.33 min and 6.64, respectively. At these conditions, removal efficiency and desirability function were found to be 96% and 1.000, respectively. The results of kinetic model reveals that the adsorption process conforms to Pseudo-first-order kinetics Equation (R2 =0.9991). The briquette ash has a good application prospect for the actual treatment of phosphorus containing wastewater, which provides a certain treatment strategy for the restoration of damaged water environment.