Species Sensitivity Distributions for Engineered Nanomaterials

Engineered nanomaterials
(ENMs) are a relatively new strain of
materials for which little is understood about their impacts. A species
sensitivity distribution (SSDs) is a cumulative probability distribution
of a chemical’s toxicity measurements obtained from single-species
bioassays of various species that can be used to estimate the ecotoxicological
impacts of a chemical. The recent increase in the availability of
acute toxicity data for ENMs enabled the construction of 10 ENM-specific
SSDs, with which we analyzed (1) the range of toxic concentrations,
(2) whether ENMs cause greater hazard to an ecosystem than the ionic
or bulk form, and (3) the key parameters that affect variability in
toxicity. The resulting estimates for hazardous concentrations at
which 5% of species will be harmed ranged from <1 ug/L for PVP-coated
n-Ag to >3.5 mg/L for CNTs. The results indicated that size, formulation,
and the presence of a coating can alter toxicity, and thereby corresponding
SSDs. Few statistical differences were observed between SSDs of an
ENM and its ionic counterpart. However, we did find a significant
correlation between the solubility of ENMs and corresponding SSD.
Uncertainty in SSD values can be reduced through greater consideration
of ENM characteristics and physiochemical transformations in the environment.

工程化纳米材料（Engineered Nanomaterials, ENMs）是一类相对新兴的材料，目前学界对其生态影响的认知仍较为有限。物种敏感度分布（Species Sensitivity Distribution, SSDs）是基于多种物种的单物种生物测定所得的化学品毒性测试数据构建的累积概率分布，可用于评估化学品的生态毒理学影响。近年来，工程化纳米材料急性毒性数据的可获得性不断提升，借此我们构建了10种专属工程化纳米材料的物种敏感度分布，并围绕三个维度展开分析：（1）毒性浓度的分布区间；（2）相较于离子态或本体形态，工程化纳米材料是否会对生态系统造成更高危害；（3）影响毒性变异的关键参数。本次研究得出的“5%物种将受到危害的有害浓度”估算值跨度较大：聚乙烯吡咯烷酮包被的纳米银（PVP-coated n-Ag）的该值低于1 μg/L，而碳纳米管（CNTs）则高于3.5 mg/L。研究结果表明，尺寸、配方以及包被层的存在均可改变材料毒性，进而影响对应的物种敏感度分布。工程化纳米材料与其离子对应物的物种敏感度分布几乎无统计学差异，但我们确实发现工程化纳米材料的溶解度与其对应的物种敏感度分布间存在显著相关性。若在研究中更多考虑工程化纳米材料的自身特性与环境中的物理化学转化过程，可有效降低物种敏感度分布数值的不确定性。