基准剂量在镉接触环境流行病学研究中的应用

[目的]通过环境流行病学研究，估测环境镉接触引起肾功能不全的基准剂量。[方法]镉污染区居住的居民为接触组，非污染区居民为对照组。尿镉(UCd)为接触生物标记物；β微球蛋白(UBM)、尿N-乙酰-β-D-氨基葡萄糖苷酶(UNAG)、尿视黄醇结合蛋白(URBP)和尿白蛋白(UALB)为效应生物标记物，并均用尿肌酐校正。[结果]长期接触镉可引起肾脏的损害。本次调查β2微球蛋白、视黄醇结合蛋白、尿NAG酶和尿白蛋白重污染区显著高于对照区，与尿镉的增长呈明显的剂量效应关系。计算得基准剂量(BMD)，推出基准剂量的95％低限水平(LBMD)。镉所引起的各肾脏损伤指标的LBMD值是不同的，大小依次为尿NAG同功酶B(NAG-B)、NAG、UBM和UALB。[结论]镉引起的肾小球损害晚于肾小管损害；而NAGB的基准剂量值最低，证明NAGB是监测肾小管损害的相对敏感的指标。     

环境镉接触人群肾小管功能损害的研究

目的：探讨镉污染若干年后，镉接触人群的。肾小管功能损害。方法：测定居住在镉污染区20年以上的161名居民和非污染区42名居民的尿镉（UCa）、尿N-乙酰-β—D-氨基葡萄糖苷酶（UNAG）、尿β2-微球蛋白（LIB—MG）及尿视黄醇结合蛋白（URBP）水平。上述指标均用尿肌酐校正，并用几何均数进行比较。结果：镉污染区居民UCA、UNAG、UBMG、URBP水平及UNAG的异常率均显著高于对照组；UNAG、UBMG、URBP水平和异常率均与尿镉水平呈现出较强的一致性，尤以尿镉水平达10μg／gCr以上明显；各指标的变化以UNAG最明显。结论：镉能引起。肾小管的不可逆损伤：UNAG可作为镉接触人群肾小管功能损害的敏感指标：尿镉水平可反映体内镉负荷及肾功能损害程度。     

镉污染区居民肾功能损害的研究

目的探讨镉污染停止20余年后镉对接触人群的肾功能损害情况.方法于2001年,分别选择在张士灌区重、中、轻污染区及非污染区居住20 a以上的39、65、57及42名居民为调查对象,测定其尿镉(UCd)、尿N-乙酰-β-D-氨基葡萄糖苷酶(UNAG)、尿β2-微球蛋白(UBMG)、尿视黄醇结合蛋白(URBP)及尿白蛋白(UALB)水平,这些指标的水平均用尿肌酐校正,并用几何均数进行比较.结果与1992年相比,轻、中、重污染区及非污染区居民尿镉水平明显下降,但重、中、轻污染区居民的UCd、UNAG、UBMG、URBP水平及UNAG的异常率均高于非污染区居民(均P＜0.01);UNAG、UBMG、URBP、UALB水平和异常率均随尿镉水平的升高而增加,尤以尿镉水平达10μg/g Cr以上明显高于5μg/g Cr以下组.尿镉及肾损伤指标间均存在正相关(均P＜0.01).结论镉引起肾小管的不可逆损伤,严重者累及肾小球;尿镉水平可反映体内镉负荷及肾功能损害程度.     

低剂量环境镉暴露人群肾功能状况与血浆转化生长因子-β1的关系

[目的]探讨低剂量环境镉暴露对肾功能和血浆转化生长因子-β1(TGF-β1)的影响,以及相互之间的关系。[方法]采用横断面研究,选择太原市有污染灌溉史且土壤镉含量为2.30 mg/kg的某自然村居民为暴露组,选择无污染灌溉史且与暴露组村落相距约32 km、土壤镉含量为0.22 mg/kg的某自然村居民为对照组。调查对象在当地的居住年限均大于5年。检测调查对象的血浆TGF-β1、尿镉、尿-N-乙酰-β-D-氨基葡萄糖苷酶(UNAG)、尿白蛋白(UALB)和尿肾损伤因子1(UKim-1)。分别用非参数检验、χ~2检验对肾损伤异常率进行比较,肾功能指标及血浆TGF-β1经对数转换后进行Pearson相关分析,影响因素采用多元线性回归分析。[结果]暴露组人群尿镉水平为1.06μg/g(以尿肌酐计,后同),高于对照组(0.71μg/g)(P0.001),男性、女性尿镉水平(1.08、1.01μg/g)均高于同性别对照组人群(0.73、0.70μg/g,均P0.05)。暴露组人群UNAG(17.40 U/g)、UALB(12.79 mg/g)均高于对照组(分别为14.80 U/g、11.70 mg/g)(均P0.05)。随着尿镉水平的升高,UNAG、UALB、UKim-1的异常率升高(χ_(趋势)~2分别为19.945、13.356、12.068,均P_(趋势)0.05)。暴露组血浆TGF-β1(13.38μg/L)高于对照组(10.11μg/L)(P0.001),但不同尿镉水平人群血浆TGF-β1的差异无统计学意义(P0.05)。Pearson相关分析结果显示:尿镉与UNAG、UALB、UKim-1和年龄均呈正相关关系(相关系数分别为0.14、0.22、0.10和0.19,均P0.05);血浆TGF-β1与尿镉无相关性,与UNAG呈正相关关系(相关系数为0.12,P0.05)。多元线性回归分析结果显示,尿镉对UNAG、UALB和UKim-1的变化影响较大(b'分别为0.22、0.25和0.15,均P0.05)。[结论]环境镉暴露可引起肾脏功能的损害。随着尿镉水平增加,肾功能异常率也明显增加;且血浆TGF-β1与UNAG呈正相关。本研究所调查地区研究对象镉暴露水平相对较低,尚未发现尿镉与血浆TGF-β1之间的关系。     

镉砷接触工人肾功能损伤研究

目的　探讨镉、砷对作业工人肾功能的联合作用。方法　以我国中南某厂镉、砷作业工人 114名为本研究的职业接触对象。以尿镉 (UCd)、尿砷 (UAs)作为接触标志物 ,尿 β2 微球蛋白(Uβ2 MG)、尿白蛋白 (UALB)、尿N 乙酰 β D 氨基葡萄糖苷酶 (UNAG)作为镉、砷致肾小管和肾小球损害的效应标志物。结果　UCd、UAs水平与Uβ2 MG、UALB、UNAG水平间均为正相关 ,具有明显的剂量-效应关系 (P <0 .0 5 ,P <0 .0 1)。结论　镉、砷对作业工人肾脏功能的联合作用主要表现为相加作用。     

基准剂量在镉接触人群骨效应研究中的应用

目的通过镉接触人群流行病学研究，估测环境镉接触引起人群骨质疏松的基准剂量。方法镉污染区居住的居民为接触组，非污染区居民为对照组。尿镉（UCd）、血镉（BCd）为接触生物标记物；代表骨质疏松的Z评分为效应生物标记物。结果污染区人群尿镉、血镉水平均明显高于对照地区（P〈0．05），且高污染医人群尿镉、血镉水平明显高于中污染区（P〈0．05）。与5μg/gCr组相比，各人群尿镉水平、血镉水平最高组的骨密度均明显降低，差异有统计学意义（P〈0．05）。人群随着体内镉接触水平的升高，骨质疏松的患病率均随之明显升高，有统计学意义（P〈0．05）并有线性关系（P〈0．05）。计算得到基准剂量（BMD），推出基准剂量的95％低限水平（BMDL）。镉所引起的骨质疏松指标的尿镉BMDL值高于镉致肾功能不全指标的BMDL值。结论高剂量镉能引起人群骨质疏松，但时间上晚于镉致肾功能不全的损害。基准剂量是一种值得应用的新方法。     

大鼠体内镉负荷与尿金属硫蛋白关系的实验研究

[目的]分析大鼠尿金属硫蛋白(UMT)与体内镉负荷的关系,探讨UMT作为镉接触性生物标志物的可行性。[方法]24只SD大鼠分为4组,分别皮下注射给予0、0.5、1.0、2.0mgCd/kg体重CdCl27d。原子吸收分光光度法(AAS)测定肝脏、肾脏、胰脏、尿液、血液中镉的含量;比色法测定尿N-乙酰-β-D-氨基葡萄糖苷酶(UNAG)水平;酶联免疫吸附法(ELISA)检测UMT的含量。[结果]镉染毒大鼠血镉、尿镉、肝镉、肾镉、胰镉含量随染镉剂量的增加而明显增加,与对照组相比差异有统计学意义(P<0.05);各染镉组大鼠UNAG水平未见明显改变(P>0.05);UMT含量随着染镉剂量的增加而明显增加(P<0.05),并且与肝镉、肾镉、胰镉、血镉、尿镉含量呈明显正相关,相关系数分别为0.703、0.815、0.691、0.654、0.641(P<0.01)。[结论]UMT与体内镉负荷指标间存在较好的一致性,能反映机体镉负荷水平,可作为镉接触生物标志物。     

白银市某镉污染区人群尿镉基准剂量研究

目的估测环境镉接触致人群肾损伤的基准剂量(BMD),推出基准剂量的95%下限(BMDL),探讨镉的生物接触限值。方法选择甘肃省白银市某镉污染区居民为调查对象。以尿镉为人体镉负荷指标,以尿β2-微球蛋白和尿NAG酶为肾功能指标,应用BMD法对资料进行拟合与分析。结果随着体内镉接触水平的升高,Uβ2-MG和UNAG的异常发生率均明显升高,经趋势卡方检验,差异有统计学意义(P<0.01);选择Log-Logistic为最优模型计算尿镉BMD和BMDL,当以尿NAG为效应指标时,BMD/BMDL值为(6.46/5.21)μg/g·cr,以尿β2-MG为效应指标时,BMD/BMDL值为(3.16/2.26)μg/g·cr。结论在运用BMD法时应注意效应指标临界值的选取、剂量的设置以及最优模型的选择;建议以更为敏感的尿β2-MG为效应指标所计算的BMDL值为依据,适当降低尿镉的生物接触限值。     

应用基准剂量法探讨砷、镉接触人群肾功能损害危险性评价

目的研究砷接触人群肾功能损害情况,探讨镉在砷接触人群肾功能损害方面与砷的联合作用。方法以贵州省地方病办公室1991年3月确诊并经1997年3月和2001年3月临床复查的122例砷中毒患者为本次调查对象,无砷污染区居民123名作为对照。以尿砷、尿镉作为接触标志物,尿β2微球蛋白(Uβ2MG)、尿白蛋白、尿N乙酰βD氨基葡萄糖苷酶(UNAG)作为砷、镉致肾小管和肾小球损害的效应标志物。同时分别计算尿砷、尿镉的基准剂量(BMD)及其下限值(BMDL)。结果接触组的接触指标和效应指标均高于对照组,尿砷、尿镉水平与Uβ2MG、尿白蛋白、UNAG水平间均为正相关,具有明显的剂量效应关系;砷、镉联合毒性比单独砷或镉同等剂量下的毒性更大。尿砷的BMD和BMDL值(以肌酐含量计)分别为12191～17188μg/g和10211～14444μg/g;尿镉的BMD和BMDL值(以肌酐含量计)分别为105～148μg/g和088～124μg/g。结论砷、镉联合毒性剂量明显低于单一毒性剂量,镉可能增强了砷在长期砷接触人群中对肾脏的损伤作用;运用BMD方法计算砷接触人群肾功能损伤尿砷、尿镉的BMD和BMDL值,尿砷、尿镉的BMDL值分别为以肌酐含量计10211μg/g、088μg/g。     

人血浆抗金属硫蛋白抗体与镉致肾损伤易感性的关系

目的研究人血浆抗金属硫蛋白扰体（anit-MT Ab）与职业镉接触所致肾功能损伤的关系。方法选择某镉冶炼厂男性作业工人为研究对象，进行接触评定和效应评定，以尿镉（UCd）、血镉（BCd）和职业镉摄入（TTCd）为接触指标，尿β2-微球蛋白（Uβ2-MG）、尿N-乙酰-β-D-氨基葡萄糖苷酶（UNAG）、尿白蛋白（UALB）作为镉敛肾损伤的效应标志物。酶联免疫吸附法（EHSA）检测血浆中anti-MT Ab滴度。结果职业镉接触组中UCd（3．16μg／g Cr）、血镉（9．28βg/L）、Uβ2-MC（81．17βg/g Cr）、UALB（7．03mg／gCr）水平明显高于对照组，随着职业镉接触水平升高，Uβ2-MG、UNAG和UALB含帚和异常发生率明显升高。对照组与接触组间anti-MT Ab滴度的差异无统计学意义（P〉0．05）。anti-MT Ab滴度并不随接触剂晕增加而增加，与血镉、UCd和TIEd间无明显联系（P〉0．05）。拄接触组中anti-MT Ab与UNAG和Uβ2-MG呈正相关，相关系数分别为0．302和0．218（P〈0．05）。相同机体镉负荷下，anti-MT Ab高滴度人群较低滴度人群更易出现肾小管损伤，比值比为4．200。结论职业性镉接触与肾功能损害间存在剂量一反应关系，而与血浆anti-MT Ab间无明显关联。镉接触人群中血浆anti-MT Ab高水平者更容易出现肾脏损伤。     

Environmental exposure to cadmium at a level insufficient to induce renal tubular dysfunction does not affect bone density among female Japanese farmers

Some recent research suggests that environmental exposure to cadmium, even at low levels, may increase the risk of osteoporosis, and that the bone demineralization is not just a secondary effect of renal dysfunction induced by high doses of cadmium as previously reported. To investigate the effect of exposure to cadmium at a level insufficient to induce kidney damage on bone mineral density (BMD) and bone metabolism, we conducted health examinations on 1380 female farmers from five districts in Japan who consumed rice contaminated by low-to-moderate levels of cadmium. We collected peripheral blood and urine samples and medical and nutritional information, and measured forearm BMD. Analysis of the data for subjects grouped by urinary cadmium level and age-related menstrual status suggested that cadmium accelerates both the increase of urinary calcium excretion around the time of menopause and the subsequent decrease in bone density after menopause. However, multivariate analyses showed no significant contribution of cadmium to bone density or urinary calcium excretion, indicating that the results mentioned above were confounded by other factors. These results indicate that environmental exposure to cadmium at levels insufficient to induce renal dysfunction does not increase the risk of osteoporosis, strongly supporting the established explanation for bone injury induced by cadmium as a secondary effect.     

The effects of low environmental cadmium exposure on bone density

Recent epidemiological data indicate that low environmental exposure to cadmium, as shown by cadmium body burden (Cd-U), is associated with renal dysfunction as well as an increased risk of cadmium-induced bone disorders. The present study was designed to assess the effects of low environmental cadmium exposure, at the level sufficient to induce kidney damage, on bone metabolism and mineral density (BMD). The project was conducted in the area contaminated with cadmium, nearby a zinc smelter located in the region of Poland where heavy industry prevails. The study population comprised 170 women (mean age=39.7; 18-70 years) and 100 men (mean age=31.9; 18-76 years). Urinary and blood cadmium and the markers of renal tubular dysfunction (β₂M-U RBP, NAG), glomerular dysfunction (Alb-U and β₂M-S) and bone metabolism markers (BAP-S, CTX-S) as well as forearm BMD, were measured. The results of this study based on simple dose-effect analysis showed the relationship between increasing cadmium concentrations and an increased excretion of renal dysfunction markers and decreasing bone density. However, the results of the multivariate analysis did not indicate the association between exposure to cadmium and decrease in bone density. They showed that the most important factors that have impact on bone density are body weight and age in the female subjects and body weight and calcium excretion in males. Our investigation revealed that the excretion of low molecular weight proteins occurred at a lower level of cadmium exposure than the possible loss of bone mass. It seems that renal tubular markers are the most sensitive and significant indicators of early health effects of cadmium intoxication in the general population. The correlation of urinary cadmium concentration with markers of kidney dysfunction was observed in the absence of significant correlations with bone effects. Our findings did not indicate any effects of environmental cadmium exposure on bone density.     

Osteoporosis and renal dysfunction in a general population exposed to cadmium in China

Osteoporosis is a common metabolic disease characterized by low bone mass and microarchitectural deterioration of bone tissue. Many factors are involved in the occurrence of osteoporosis. Cadmium can cause both osteomalacia and osteoporosis and these effects have long been investigated through various epidemiological or experimental studies. The present study examines a possible relationship between cadmium nephropathy and its effects on the skeleton in populations living in a polluted area in southeast China. Monophoton absorptiometry was used to measure bone mineral density in the population and the Z score (the number of SD from the difference between the measured bone density of the individual and the group mean value for sex- and age-matched controls) was introduced to define osteoporosis (Z score < -2). Osteoporosis caused by cadmium exposure was demonstrated in this study on a general population environmentally exposed to cadmium in China. It was found that there were significant differences in the prevalence of osteoporosis among the different urinary cadmium groups (chi2 = 18.84, P = 0.0008). The linear trend test gave chi2 = 16.281, P = 0.00005. There was a dose-response relationship between cadmium exposure (urinary cadmium) and prevalence of osteoporosis. Of 31 subjects with osteoporosis, 23 subjects were suffering from renal dysfunction. The prevalence of renal dysfunction (74.19%) was significantly higher than that in those without osteoporosis (chi2 = 16.53, P < 0.001). Stratum analysis was performed to further assess the relationship between bone damage and renal impairment caused by cadmium. There was a significant difference between those with and without tubular damage (chi2 = 19.92, P = 0.000) but not in those with and without glomerular damage (chi2 = 0.08, P = 0.114). This showed that glomerular dysfunction plays a smaller role than tubular dysfunction in the causation of bone damage. It was found that the prevalence of osteoporosis increases with increasing values of parameters of tubular damage. Osteoporosis caused by cadmium is thus related to kidney dysfunction and especially to tubular damage and its severity but not to glomerular damage. The present study has thus demonstrated the combined adverse effects (osteoporosis and renal dysfunction) caused by environmental exposure to cadmium for the first time in Asia outside the endemic area in Japan.     

Urinary calcium as a biomarker of renal dysfunction in a general population exposed to cadmium

Urinary beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase have been recommended as sensitive indicators of renal dysfunction induced by cadmium. However, an increase in urinary calcium in early renal damage induced by cadmium has been reported both in humans and in animal experiments. To investigate the feasibility of using urinary calcium as a biomarker of renal dysfunction induced by cadmium, two areas were selected in this study, namely, a polluted area with a 3.71 mg/kg cadmium concentration in rice and a control area with a 0.07 mg/kg cadmium concentration. The total number of participants was 499, made up of 252 in the control group and 247 from the cadmium-polluted area. Urinary cadmium, urinary calcium, and zinc concentrations were measured by atomic absorption spectrometry, and beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase in urine were analyzed. The levels of urinary cadmium and urinary calcium in persons from the exposed area were significantly higher (P < 0.05) than those in the control area for both men and women, but there was no significant difference regarding urinary zinc between the two areas. A significant dose-response relationship between the prevalence of hypercalciuria and the excretion of urinary cadmium was observed, and a significantly increased prevalence of calciuria was found when excretion of urinary cadmium exceeded 2 micrograms/g creatinine. The findings were similar to those for excess urinary secretion of beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase. Because cadmium can affect Ca2+ uptake by tubular cells, with decreased renal Ca2+ reabsorption, calciuria may reflect tubular cell damage caused by cadmium. It was concluded that cadmium exposure can result in increased excretion of urinary calcium in a general population and that there is a significant dose-response relationship. Urinary calcium can therefore be used as a biomarker of renal dysfunction induced by cadmium.     

Renal effects evolution in a Chinese population after reduction of cadmium exposure in rice

Cadmium is a well-known nephrotoxic agent with extremely long biological half-time of 10-30 years in human. To investigate the evolution of cadmium-induced renal effects in the population, a number of 148 residents who lived in cadmium-polluted area were followed-up for 3 years after the reduction of cadmium exposure in rice. Urinary cadmium (UCd), β₂-microglobulin (B2M) and albumin (ALB) were analyzed in 1995 and 1998, respectively. The results demonstrated that the changes of renal effects of residents depended on the levels of UCd before inflow of cadmium to human body declined. In cases where UCd were less than 10 μg/g creatinine in 1995, evidence was found indicating significant decreases in proteinuria (i.e., B2M and ALB) 3 years later, whereas, in cases where the excretion of UCd exceeded 10 μg/g creatinine in 1995, progression was observed. The study of dose-response relationships between UCd and B2M or ALB also showed that the cadmium-induced renal dysfunction might be reversible if UCd concentration was low-level before exposure decreasing, otherwise it might be irreversible or aggravated.     

Investigation of the relationship between low environmental exposure to metals and bone mineral density,bone resorption and renal function

Environmental exposure to metals has been linked to adverse health outcomes. Exposure to cadmium has been associated with decreased bone density, an increased risk of osteoporotic fracture and possible renal dysfunction. Older women are a group at risk of renal and bone density impacts and exposure to metals may be an important risk factor for these health outcomes. This study was a cross sectional study of 77 women aged 50 years and above examining the relationship between metals exposure and renal and bone health. Urinary and blood metals concentrations, plasma creatinine, iron, ferritin and transferrin were measured in these subjects. Bone biomarkers assessed included the pyridinium crosslinks, pyridinoline and deoxypyridinoline measured by ELISA. Renal function was assessed using eGFR and KIM-1. Whole body, hip and lumbar spine bone mineral density was assessed using DEXA. Blood and urinary metals concentrations were generally low in the subjects, with a median urinary cadmium concentration of 0.26 μg/g creatinine (range <0.065–1.03 μg/g). Urinary cadmium was found to be a significant predictor of bone mineral density at whole body, lumber spine, total hip and femoral neck, with increasing urinary Cd concentrations associated with decreased bone density. Urinary cadmium and aluminium concentrations were positively correlated with bone resorption whilst blood zinc and mercury concentrations were negatively correlated. Urinary aluminium was positively correlated with KIM-1 concentrations, a marker of early kidney damage, however blood zinc concentrations were significantly negatively correlated with this biomarker. This study provides additional support for low cadmium exposure being of concern for the health of older women. Further investigation into the role of exposure to other metals on bone and renal health is warranted.     

Cadmium and lead in blood in relation to low bone mineral density and tubular proteinuria

Long-term exposure to cadmium may cause kidney and bone damage. Urinary cadmium is commonly used as the dose estimate for the body burden of cadmium. However, elevated levels of cadmium in the urine may reflect not only high levels of cadmium dose but also renal dysfunction. In this study we used blood cadmium as the dose estimate. In addition, we analyzed blood lead. We examined 479 men and 542 women, ages 16-81 years, who were environmentally or occupationally exposed to cadmium and lead. We used urinary protein alpha 1-microglobulin as a marker for tubular proteinuria and measured forearm bone mineral density using dual-energy X-ray absorptiometry. The relationship between blood cadmium and tubular proteinuria was strong, even when we excluded occupationally exposed participants. The subgroup with the highest blood cadmium levels had a 4-fold risk of tubular proteinuria compared to the subgroup with the lowest blood cadmium levels. In the older age group (age > 60), the risk of low bone mineral density (z-score < -1) for the subgroup with the highest blood cadmium levels was almost 3-fold compared to the group with lowest blood cadmium levels. We found no similar associations for lead. The observed effects may be caused by higher cadmium exposure in the past. This study strengthens previous evidence that cadmium exposure may affect both bone mineral density and kidney function.