Schilderman P A, Moonen E J, Kempkers P, Kleinjans J C
Department of Health Risk Analysis and Toxicology, Maastricht University, The Netherlands.
Environ Health Perspect. 1997 Feb;105(2):234-8. doi: 10.1289/ehp.97105234.
During the last few decades, the industrial production and use of Cd resulted in the release of significant quantities of Cd into the environment. Concern about health risks of human exposure to this toxic metal, which may be contained in soil and other environmental compartments, has increased significantly in recent years. Soil ingestion is a potentially important pathway of exposure to soil-absorbed environmental contaminants, especially for young children exhibiting hand-to-mouth behavior. Health risk assessments are usually based on unchanged bioavailability of soil-absorbed pollutants, e.g., heavy metals, neglecting interactions of metals with the soil matrix, which may lead to relatively lower bioavailability. This study was conducted to determine the bioavailability of Cd absorbed to soil in rats. Eight-week-old male Lewis rats were given either a soil polluted with CdCl2 (150 micrograms Cd/rat) dissolved in 5% gun acacia or an equal amount of Cd as CdCl2 dissolved in saline. Control rats were gavaged with isotonic saline. Cd concentrations in liver, kidney, brain, heart, and blood, as well as Cd content of urine and feces were analyzed using graphite furnace atomic absorption spectrometry. Tissue Cd concentrations in soil-treated animals were significantly lower than the tissue concentrations in the Cd-saline group; in the liver and kidneys of the Cd-saline and Cd-soil groups, 4 and 2.7% respectively, of the original doses were recovered. Relative bioavailability, calculated on the basis of blood Cd levels for the Cd-soil group as compared to the Cd-saline group, appeared to be 43%. No differences in the excretion pattern of Cd into feces were observed between the Cd-saline and Cd-soil groups. After 6 days, over 91% of the original dose was recovered in the feces of both Cd-treated groups. Cd excretion via urine was very low, but in the Cd-soil group a significant increase in urinary Cd was observed as compared to the control group. However, the amount of Cd excreted into urine of the Cd-soil group during the experimental period corresponded to only 0.01% of the original dose. In the Cd-saline group, no additional Cd was excreted into urine as compared to the control group. These results indicate that the soil matrix significantly reduced the absorption of Cd in the gastrointestinal tract. Consequently, exposure assessment models, assuming an unaffected bioavailability of soil-absorbed Cd, overestimate the internal dose and thereby overestimate health risks associated with direct ingestion of soil particles.
在过去几十年中，镉的工业生产和使用导致大量镉释放到环境中。近年来，人们对人类接触这种有毒金属（可能存在于土壤和其他环境介质中）所带来的健康风险的关注度显著增加。土壤摄入是接触土壤吸附的环境污染物的一个潜在重要途径，对于有手口行为的幼儿来说尤其如此。健康风险评估通常基于土壤吸附污染物（如重金属）不变的生物有效性，而忽略了金属与土壤基质的相互作用，这可能导致生物有效性相对较低。本研究旨在确定大鼠体内土壤吸附镉的生物有效性。给8周龄雄性Lewis大鼠分别喂食溶解于5%阿拉伯胶中的CdCl₂污染土壤（每只大鼠含150微克镉）或等量溶解于生理盐水中的CdCl₂形式的镉。对照大鼠灌喂等渗盐水。使用石墨炉原子吸收光谱法分析肝脏、肾脏、大脑、心脏和血液中的镉浓度，以及尿液和粪便中的镉含量。土壤处理组动物的组织镉浓度显著低于镉盐水组的组织浓度；在镉盐水组和镉土壤组的肝脏和肾脏中，分别回收了原始剂量的4%和2.7%。根据镉土壤组与镉盐水组血液镉水平计算得出的相对生物有效性似乎为43%。镉盐水组和镉土壤组之间在镉排泄到粪便的模式上未观察到差异。6天后，两个镉处理组的粪便中均回收了超过91%的原始剂量。通过尿液排泄的镉非常少，但与对照组相比，镉土壤组的尿镉显著增加。然而，在实验期间，镉土壤组排泄到尿液中的镉量仅相当于原始剂量的0.01%。在镉盐水组中，与对照组相比，没有额外的镉排泄到尿液中。这些结果表明，土壤基质显著降低了胃肠道中镉的吸收。因此，假设土壤吸附镉的生物有效性不受影响的暴露评估模型高估了内部剂量，从而高估了与直接摄入土壤颗粒相关的健康风险。
