Calabrese E J, Stanek E J, Barnes R, Burmaster D E, Callahan B G, Heath J S, Paustenbach D, Abraham J, Gephart L A
Environmental Health Sciences Department, University of Massachusetts, Amherst 01003, USA.
Regul Toxicol Pharmacol. 1996 Dec;24(3):264-8. doi: 10.1006/rtph.1996.0139.
Despite considerable efforts to improve the design of soil ingestion studies, substantial variability in daily soil ingestion rates based on different tracer estimates exists in the same subjects. The present study assessed the hypothesis that one of the unexplored causes of this intertracer variation in soil ingestion estimation was related to differences in soil tracer concentration by particle size. The study analyzed the tracer concentration in soil for children in the Anaconda, Montana soil ingestion study for the particle size fraction less than 250 microm [corrected] in diameter. Soil ingestion estimates for these children were recalculated based on the new soil concentration values and compared to previous findings (E. J. Calabrese, E. J. Stanek, P. Pekow, and R. M. Barnes, submitted, 1996) when the soil concentrations were determined for soil particle size diameter of <2 mm. The results indicated that five tracers (Al, Si, Ti, Y, and Zr) did not have their soil concentrations changed by particle size. However, for three tracers (La, Ce, and Nd) the concentration increased by two- to fourfold with the smaller particle size. Recalculation of soil ingestion estimates indicates that the soil ingestion estimates of the five tracers not varying by particle size did not change while those of the remaining three tracers were decreased by approximately 60%. The revised calculations provide a substantial improvement in intertracer estimates of soil ingestion and suggest that the children ingested soil of small particle size. These findings are of significance since they (1) identify an important potential cause of intertracer variability in soil ingestion estimates, (2) establish a new criterion for soil tracer selection, and (3) develop a method for not only providing improved soil ingestion estimates but also determining the particle size of the ingested soil. These findings offer important potential applications for risk assessment practices at contaminated sites since soil ingestion is frequently the dominant route of estimated contaminant exposure in children.
尽管在改进土壤摄入研究设计方面付出了巨大努力，但同一受试者基于不同示踪剂估计的每日土壤摄入量仍存在很大差异。本研究评估了以下假设：土壤摄入估计中这种示踪剂间差异的一个未被探索的原因与不同粒径土壤示踪剂浓度的差异有关。该研究分析了蒙大拿州阿纳康达土壤摄入研究中儿童土壤中粒径小于250微米[已校正]的示踪剂浓度。根据新的土壤浓度值重新计算了这些儿童的土壤摄入量估计值，并与之前的研究结果（E. J. 卡拉布雷斯、E. J. 斯塔内克、P. 佩科夫和R. M. 巴恩斯，已提交，1996年）进行了比较，当时测定的土壤浓度是针对粒径小于2毫米的土壤颗粒。结果表明，五种示踪剂（铝、硅、钛、钇和锆）的土壤浓度没有因粒径而改变。然而，对于三种示踪剂（镧、铈和钕），浓度随着粒径变小增加了两到四倍。重新计算土壤摄入量估计值表明，五种粒径不变的示踪剂的土壤摄入量估计值没有变化，而其余三种示踪剂的估计值则下降了约60%。修订后的计算在示踪剂间土壤摄入量估计方面有了显著改进，并表明儿童摄入的是小粒径土壤。这些发现具有重要意义，因为它们（1）确定了土壤摄入估计中示踪剂间差异的一个重要潜在原因，（2）建立了土壤示踪剂选择的新标准，（3）开发了一种方法，不仅能提供改进后的土壤摄入量估计值，还能确定摄入土壤的粒径。这些发现为污染场地的风险评估实践提供了重要的潜在应用，因为土壤摄入通常是儿童估计污染物暴露的主要途径。
