Schoof R A, Nielsen J B
PTI Environmental Services, Bellevue, Washington 98007, USA.
Risk Anal. 1997 Oct;17(5):545-55. doi: 10.1111/j.1539-6924.1997.tb00896.x.
The risks associated with environmental exposures to inorganic mercury are typically assessed based on toxicity studies conducted with the soluble salt, mercuric chloride (HgCl2). Evidence indicates, however, that inorganic mercury is present in soil as a variety of compounds and that oral absorption of inorganic mercury decreases with a decrease in the solubility of the mercury compound being studied. Thus, while HgCl2 is approximately 15-20% bioavailable, the bioavailability of cinnabar (HgS) may be 30- to 60-fold less. The solubility and, hence, bioavailability of inorganic mercury in soil is expected to be substantially less than that of HgCl2 due to the presence of less soluble compounds and their interactions with soil constituents. Quantification of this difference in bioavailability is important in assessing potential risks associated with exposure to mercury-containing soil. A review of available studies supports the expectation that mercury bioavailability in soils will be reduced. This paper reviews methods for assessing soil metal absorption with consideration of the characteristics of the oral absorption of elemental and inorganic mercury that should be evaluated in designing additional studies. Because of the very slow elimination of mercury in some species, it is recommended that a repeated-dose study be conducted. Such a study would yield an estimate of relative bioavailability based on a comparison of tissue mercury concentrations in animals ingesting soil with those of animals receiving HgCl2. The dose, age, gender, and species of animal selected are not expected to affect relative bioavailability estimates; however, it is recommended that studies be conducted in two animal species. Rats should be used because they have been used in many studies of mercury absorption and toxicity. A species of large animals such as monkeys, swine, or dogs should also be used to provide confirmation in a species with greater similarities to humans in gastrointestinal physiology and anatomy. Other critical factors in designing these studies, such as selection and characterization of soil samples, are also addressed.
与环境接触无机汞相关的风险通常基于对可溶性盐氯化汞（HgCl2）进行的毒性研究来评估。然而，有证据表明，无机汞在土壤中以多种化合物形式存在，并且所研究的汞化合物溶解度降低时，无机汞的口服吸收率也会降低。因此，虽然HgCl2的生物利用率约为15%-20%，但朱砂（HgS）的生物利用率可能要低30至60倍。由于存在溶解度较低的化合物及其与土壤成分的相互作用，预计土壤中无机汞的溶解度以及生物利用率将大大低于HgCl2。量化这种生物利用率差异对于评估与接触含汞土壤相关的潜在风险很重要。对现有研究的综述支持了土壤中汞生物利用率将会降低的预期。本文回顾了评估土壤金属吸收的方法，同时考虑了在设计更多研究时应评估的元素汞和无机汞口服吸收的特性。由于某些物种中汞的消除非常缓慢，建议进行重复剂量研究。这样的研究将通过比较摄入土壤的动物与接受HgCl2的动物的组织汞浓度来得出相对生物利用率的估计值。所选动物的剂量、年龄、性别和物种预计不会影响相对生物利用率估计值；然而，建议在两种动物物种中进行研究。应使用大鼠，因为它们已被用于许多汞吸收和毒性研究。还应使用一种大型动物物种，如猴子、猪或狗，以便在胃肠道生理和解剖结构与人类更相似的物种中进行验证。本文还讨论了设计这些研究中的其他关键因素，如土壤样品的选择和特性描述。
