Regional characteristics of cadmium intake in adult residents from the 4th and 5th Chinese Total Diet Study

Low-level, chronic ingestion of lead and cadmium: The unspoken danger for at-risk populations

The long-term effects of low-level, chronic exposure to lead and cadmium through ingestion are often overlooked, despite the urgency surrounding the clinical onset and worsening of certain pathologies caused by these metals. This work reviews current legislation, global ingestion levels, and blood levels in the general population to emphasize the need for reactivity towards this exposure, especially in at-risk populations, including patients with early-stage renal and chronic kidney disease. Global data indicates persistent chronic ingestion of lead and cadmium, with no decreasing trend in recent years, and a daily consumption of tens of micrograms worldwide. Moreover, the average blood lead and cadmium levels in the general population are concerning in many countries with some significantly exceeding healthy limits, particularly for children. Technologies developed to cleanse soil and prevent heavy metal contamination in food are not yet applicable on a global scale and remain financially inaccessible for many communities. Addressing this chronic ingestion at the human level may prove more beneficial in delaying the onset of associated clinical pathologies or preventing them all together.

Is Environmental Cadmium Exposure Causally Related to Diabetes and Obesity?

Cadmium (Cd) is a pervasive toxic metal, present in most food types, cigarette smoke, and air. Most cells in the body will assimilate Cd, as its charge and ionic radius are similar to the essential metals, iron, zinc, and calcium (Fe, Zn, and Ca). Cd preferentially accumulates in the proximal tubular epithelium of the kidney, and is excreted in urine when these cells die. Thus, excretion of Cd reflects renal accumulation (body burden) and the current toxicity of Cd. The kidney is the only organ other than liver that produces and releases glucose into the circulation. Also, the kidney is responsible for filtration and the re-absorption of glucose. Cd is the least recognized diabetogenic substance although research performed in the 1980s demonstrated the diabetogenic effects of chronic oral Cd administration in neonatal rats. Approximately 10% of the global population are now living with diabetes and over 80% of these are overweight or obese. This association has fueled an intense search for any exogenous chemicals and lifestyle factors that could induce excessive weight gain. However, whilst epidemiological studies have clearly linked diabetes to Cd exposure, this appears to be independent of adiposity. This review highlights Cd exposure sources and levels associated with diabetes type 2 and the mechanisms by which Cd disrupts glucose metabolism. Special emphasis is on roles of the liver and kidney, and cellular stress responses and defenses, involving heme oxygenase-1 and -2 (HO-1 and HO-2). From heme degradation, both HO-1 and HO-2 release Fe, carbon monoxide, and a precursor substrate for producing a potent antioxidant, bilirubin. HO-2 appears to have also anti-diabetic and anti-obese actions. In old age, HO-2 deficient mice display a symptomatic spectrum of human diabetes, including hyperglycemia, insulin resistance, increased fat deposition, and hypertension.

N-methyl-d-aspartate receptor 1 activation mediates cadmium-induced epithelial-mesenchymal transition in proximal tubular cells

Cadmium (Cd) is a commonly found environmental pollutant and is known to damage multiple organs with kidneys being the most common one. N-methyl-d-aspartate receptor 1 (NMDAR1) is a ligand-gated ion channel that is highly permeable to calcium ion (Ca2+). Because Cd2+ and Ca2+ have structural and physicochemical similarities, whether and how Cd could interfere NMDAR1 function to cause renal epithelial cells dysfunction remains unknown. In this study, we investigated the role of NMDAR1 in Cd-induced renal damage and found that Cd treatment upregulated NMDAR1 expression and promoted epithelial-mesenchymal transition (EMT) in mouse kidneys in vivo and human proximal tubular epithelial HK-2 cells in vitro, which were accompanied with activation of the inositol-requiring enzyme 1 (IRE-1α) / spliced X box binding protein-1 (XBP-1s) pathway, an indicative of endoplasmic reticulum (ER) stress. Mechanistically, NMDAR1 upregulation by Cd promoted Ca2+ channel opening and Ca2+ influx, resulting in ER stress and subsequently EMT in HK-2 cells. Inhibition of NMDAR1 by pharmacological antagonist MK-801 significantly attenuated Cd-induced Ca2+ influx, ER stress, and EMT. Pretreatment with the IRE-1α/XBP-1s pathway inhibitor STF-083010 also restored the epithelial phenotype of Cd-treated HK-2 cells. Therefore, our findings suggest that NMDAR1 activation mediates Cd-induced EMT in proximal epithelial cells likely through the IRE-1α/XBP-1s pathway, supporting the idea that NMDAR1 could be a potential therapeutic target for Cd-induced renal damage.

The burden of chronic kidney disease associated with dietary exposure to cadmium in China, 2020

Cadmium (Cd) exposure increases the risk of chronic kidney disease (CKD). But the contribution of dietary Cd intake, the primary exposure route of Cd in humans, to the CKD burden remains to be evaluated in China. Concentrations of Cd in foods and population glomerular filtration rate (GFR) were retrieved from studies published between January 2000 and February 2023 in China. Daily food consumption in adults aged ≥35 years old was obtained from two nationwide Chinese surveys. Dietary Cd intake and its contribution rate among total Cd exposure from diet, inhalation, smoking and water were evaluated. Urinary Cd (UCd) was estimated using the toxicokinetic (TK) model based on dietary Cd intake. The effect of Cd on kidney function has been quantified with the previously published dose-response relationship between UCd and GFR. The incidence and disability-adjusted life years (DALYs) of CKD attributable to dietary Cd intake were derived considering the contribution rate of dietary Cd intake at the national and provincial levels. The national average dietary Cd intake was 0.6891 μg/kg bw/day, contributing 63.69% of total Cd exposure. The Cd exposure through foods resulted in 2.34 (95% uncertainty interval, UI: 1.54-3.40) stage 4 CKD and 0.37 (95% UI: 0.20-0.59) stage 5 CKD cases per 100,000 persons/year in mainland China, 2020. The corresponding DALYs loss associated with stage 4 and stage 5 CKD due to dietary Cd intake were 5.14 (95% UI: 3.24-7.67) and 4.78 (95% UI: 2.32-8.30) per 100,000 persons/year, together accounting for 2% of total DALYs of CKD. Greater dietary Cd intake and corresponding burden of late-stage CKD were observed in Southern areas than in Northern areas. Diet remains the primary exposure to Cd in Chinese adults. Efforts to reduce dietary Cd exposure would positively impact public health, especially in Southern provinces with high Cd exposure.

Quantitative analysis of the minimum days of dietary survey to estimate dietary pesticide exposure: Implications for dietary pesticide sampling strategy

Populations are exposed to pesticides through diet on a daily basis. However, there is no research guiding how to evaluate dietary pesticide exposure, and researchers used 1-day, 3-days, 7-days or even longer dietary survey to evaluate without any consensus. It is important for dietary pesticide evaluation to identify the minimum survey days. To increase knowledge of this, a data combination was applied between a two-wave consecutive repeated-measures study in Baoding City and the Fifth China Total Diet Study. Further policy consistency on pesticides were evaluated to explain its credibility. We computed the sensitivity and specificity to evaluate how well different days of dietary survey classify participants with high exposure, and calculated the minimum days required to estimate the participant-specific mean at different acceptable error range. With 1 day of dietary survey, the classification sensitivity was low (<0.6) for total HCH, endosulfan, chlordane, cyhalothrin, allethrin, and prallethrin; that for the other pesticides was high sensitivity (≥0.6). Sensitivity increased as the number of days increased, and the maximum marginal sensitivity increase (≥0.039) occurred from 1 to 2 days for all pesticides except phenothrin, whose maximum marginal sensitivity increase (0.042) occurred from 2 to 3 days. The specificity increased gradually from 0.8 to 0.9 from 1 to 7 days. Under the acceptable error range of 0.5%, 3-28 days were required for participant-specific mean estimation and 1-7 days were required when acceptable error range was shrunk in 1%. Only 1 day was enough if 5% error range was acceptable. In conclusion, 3 days in the study period was cost-effective to distinguish high exposure group, and it rose to 7 when estimating participant-specific mean from a conservative perspective. This study can serve as a reference to determine the minimum survey days for epidemiological studies employing dietary surveys.

Estimation of health risks associated with dietary cadmium exposure

In much of the world, currently employed upper limits of tolerable intake and acceptable excretion of cadmium (Cd) (ECd/Ecr) are 0.83 µg/kg body weight/day and 5.24 µg/g creatinine, respectively. These figures were derived from a risk assessment model that interpreted β2-microglobulin (β2MG) excretion > 300 μg/g creatinine as a "critical" endpoint. However, current evidence suggests that Cd accumulation reduces glomerular filtration rate at values of ECd/Ecr much lower than 5.24 µg/g creatinine. Low ECd/Ecr has also been associated with increased risks of kidney disease, type 2 diabetes, osteoporosis, cancer, and other disorders. These associations have cast considerable doubt on conventional guidelines. The goals of this paper are to evaluate whether these guidelines are low enough to minimize associated health risks reliably, and indeed whether permissible intake of a cumulative toxin like Cd is a valid concept. We highlight sources and levels of Cd in the human diet and review absorption, distribution, kidney accumulation, and excretion of the metal. We present evidence for the following propositions: excreted Cd emanates from injured tubular epithelial cells of the kidney; Cd excretion is a manifestation of current tissue injury; reduction of present and future exposure to environmental Cd cannot mitigate injury in progress; and Cd excretion is optimally expressed as a function of creatinine clearance rather than creatinine excretion. We comprehensively review the adverse health effects of Cd and urine and blood Cd levels at which adverse effects have been observed. The cumulative nature of Cd toxicity and the susceptibility of multiple organs to toxicity at low body burdens raise serious doubt that guidelines concerning permissible intake of Cd can be meaningful.

Chain modeling for the biogeochemical nexus of cadmium in soil-rice-human health system

This paper presents a novel chain model named soil-food-human (SFH) for clarifying the biogeochemical cascades among the triple challenges of cadmium contamination, food safety, and related public health effect. The model was developed based on the integration of spatial distribution pattern of soil environment and the biogeochemical process of cadmium in soil-rice-human health, and it was validated through a case study. In soil environment terms, SFH predicted the spatial distribution of soil properties with an average prediction accuracy of 82.28%. In food production terms, the SFH can identify the safe production zones for planting rice and unsafe area for adjusting croppingsystems with a relative error of 39.41%. In food consumption terms, SFH mapped the high-resolution map of cadmium exposure dose, which gives a new solution to assess the food safety risks for self-sufficient populations. For the health effect of rice cadmium exposure, SFH simulated the spatiotemporal pattern of urinary cadmium based on toxicokinetic which revealed the health effect of rice cadmium exposure. The chain model provides a new insight in understanding the biogeochemical cascades between food production, food safety, and public health, making it possible to develop a comprehensive strategy to tackle cadmium pollution in soil-rice-human health system.

Occurrence, accumulation, and health risks of heavy metals in Chinese market baskets

Residual levels and accumulation characteristics of six hazardous heavy metal elements (As, Cd, Hg, Tl, Pb, and U) and seven essential heavy metal elements (Cr, Mn, Fe, Ni, Cu, Zn, and Se) were investigated in 17 kinds of frequently consumed foodstuffs collected from 33 cities distributed in five regions of China. The concentrations of the detected metals were lower than the maximum limits promulgated by the Chinese government except Pb and inorganic As (iAs). Foods of aquatic origin and terrestrial plant origin exhibited high potentials to accumulate heavy metals, especially algae and shellfish. The calculated hazard index (HI) of heavy metal exposure via consumption of foodstuffs were 2.93-5.01 for adults in the five surveyed region, implying the co-exposure of heavy metals via food consumption would lead to potential non-carcinogenic risks. iAs was the predominant contributor to HI values with the average contribution of 40.5% in all five regions. Consumption of terrestrial plant origin foods contributed 76.9% of HI values induced by heavy metal exposure. The calculated target cancer risks of iAs in the five regions were 5 × 10^-4-1 × 10^-3, all exceeding the acceptable level of 10^-4, indicating it is necessary and urgent to reduce the contamination of iAs in foodstuffs on the Chinese markets.

The burden of coronary heart disease and stroke attributable to dietary cadmium exposure in Chinese adults, 2017

Cadmium (Cd) is a metal with a long biological half-life that could cause health issues, such as coronary heart disease (CHD), stroke, and other cardiovascular diseases (CVD). Recent studies showed an ascending trend in the dietary Cd intake in the Chinese population. The contribution of dietary Cd intake to CHD and stroke burden, on the other hand, remains to be established. To calculate the disease burden for CHD and stroke attributable to dietary Cd, we estimated dietary Cd intake by associating the Cd concentration in food with consumption frequency. The toxicokinetic (TK) model and dietary Cd consumption were used to simulate urinary cadmium (U-Cd) concentrations. The population attributable fraction (PAF) can be derived for the computation of the attributable disease burden expressed as Disability-Adjusted Life Years (DALYs) in provinces, genders, and age groups by combining the relative risk (RR) with the population distribution of U-Cd. The mean of dietary Cd consumption and the geometric mean of U-Cd in the Chinese adult population are 0.684 μg/kg bw/day and 0.88 μg/g creatinine. The CHD burden attributable to dietary Cd was 3.26 million DALYs, with a 9.69% proportion of the total CHD burden. The DALYs for stroke attributable to Cd in food was approximately 3.64 million, accounting for 8.22% of the overall stroke burden. Furthermore, the attributable disease burden of CHD and stroke are higher in the south, women, and middle-aged and older adults. Our study suggested that foodborne Cd exposure contributes a considerable proportion of the CHD and stroke burden. More attention is needed to control Cd in food in order to reduce the burden of CHD and stroke in the Chinese population.

Cadmium and Lead Exposure, Nephrotoxicity, and Mortality

The present review aims to provide an update on health risks associated with the low-to-moderate levels of environmental cadmium (Cd) and lead (Pb) to which most populations are exposed. Epidemiological studies examining the adverse effects of coexposure to Cd and Pb have shown that Pb may enhance the nephrotoxicity of Cd and vice versa. Herein, the existing tolerable intake levels of Cd and Pb are discussed together with the conventional urinary Cd threshold limit of 5.24 μg/g creatinine. Dietary sources of Cd and Pb and the intake levels reported for average consumers in the U.S., Spain, Korea, Germany and China are summarized. The utility of urine, whole blood, plasma/serum, and erythrocytes to quantify exposure levels of Cd and Pb are discussed. Epidemiological studies that linked one of these measurements to risks of chronic kidney disease (CKD) and mortality from common ailments are reviewed. A Cd intake level of 23.2 μg/day, which is less than half the safe intake stated by the guidelines, may increase the risk of CKD by 73%, and urinary Cd levels one-tenth of the threshold limit, defined by excessive ß₂-microglobulin excretion, were associated with increased risk of CKD, mortality from heart disease, cancer of any site and Alzheimer's disease. These findings indicate that the current tolerable intake of Cd and the conventional urinary Cd threshold limit do not provide adequate health protection. Any excessive Cd excretion is probably indicative of tubular injury. In light of the evolving realization of the interaction between Cd and Pb, actions to minimize environmental exposure to these toxic metals are imperative.

Exposure Assessment of Cadmium in Female Farmers in Cadmium-Polluted Areas in Northern Japan

Akita prefecture is located in the northern part of Japan and has many cadmium-polluted areas. We herein performed an exposure assessment of cadmium in 712 and 432 female farmers in two adjacent cadmium-polluted areas (A and B, respectively), who underwent local health examinations from 2001-2004. We measured cadmium concentrations in 100 food items collected from local markets in 2003. We then multiplied the intake of each food item by its cadmium concentration in each subject to assess cadmium intake from food and summed cadmium intake from all food items to obtain the total cadmium intake. Median cadmium intake levels in areas A and B were 55.7 and 47.8 µg/day, respectively, which were both higher than that of the general population and were attributed to local agricultural products, particularly rice. We also calculated weekly cadmium intake per body weight and compared it to the previous provisional tolerable weekly intake reported by the Joint FAO (Food and Agriculture Organization)/WHO (World Health Organization) expert committee on food additives or current tolerable weekly intake in Japan of 7 µg/kg BW/week. Medians in areas A and B were 7.2 and 6.0 µg/kg BW/week, respectively. Similar estimated values were also obtained by the Monte Carlo simulation. These results demonstrated that the cadmium exposure levels among the farmers were high enough to be approximately the tolerable weekly intake.