U.S. Environmental Protection Agency, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA.
U.S. Environmental Protection Agency, Mid-Continent Ecology Division, 6201 Congdon Blvd., Duluth, MN 55804, USA.
Aquat Toxicol. 2019 May;210:227-241. doi: 10.1016/j.aquatox.2019.03.001. Epub 2019 Mar 5.
The effects on juvenile rainbow trout survival, growth, food consumption, and food conversion efficiency from dietborne exposures to inorganic arsenic (arsenite, arsenate) and to the organoarsenicals monomethylarsonate (MMA), dimethylarsinate (DMA), and arsenobetaine (AsB) were investigated in two experiments: (1) a 28-d exposure using live diets of oligochaete worms separately exposed via water to these five arsenic compounds and (2) a 56-d exposure using pellet diets prepared from commercial fish food to which arsenite, MMA, or DMA were added. In the live diet experiment, the degree to which worms could be contaminated with the organoarsenicals was limited by toxicity to the worms and other experimental constraints, so that their toxicity relative to inorganic arsenic could not be fully established, but AsB was concluded to have low toxicity, consistent with published results for mammals. For the pellet diet experiment, MMA and DMA were found to be at least an order of magnitude less toxic than inorganic As on the basis of concentration in the diet, as well as much less toxic on the basis of accumulation in the fish. The need to consider speciation in aquatic risk assessments for arsenic was further demonstrated by tissue analyses of three macroinvertebrate species from a mining-impacted stream, which showed large variations in both total arsenic and the relative amounts of inorganic and organic arsenic. Additionally, although effects of arsenic on trout appear to be well correlated with inorganic arsenic, worms were found to be more sensitive to waterborne DMA than to inorganic arsenic, showing that low toxicity of organoarsenicals cannot be assumed for all aquatic organisms. Various difficulties in evaluating and applying studies on dietborne exposures and fish growth are also discussed.
本研究通过两项实验，调查了无机砷（砷酸盐、亚砷酸盐）和有机砷化合物一甲基砷酸（MMA）、二甲基砷酸（DMA）和砷甜菜碱（AsB）经饮食暴露对幼年虹鳟鱼生存、生长、食物消耗和食物转化率的影响：（1）为期 28 天的暴露实验，利用通过水暴露分别使寡毛类蠕虫摄入这五种砷化合物的活体饮食；（2）为期 56 天的暴露实验，利用在商业鱼饲料中添加砷酸盐、MMA 或 DMA 制备的颗粒饲料。在活体饮食实验中，由于蠕虫对有机砷的毒性以及其他实验限制，蠕虫受到污染的程度有限，因此无法充分确定其相对无机砷的毒性，但根据哺乳动物的研究结果推断，AsB 的毒性较低。对于颗粒饮食实验，根据饮食中的浓度以及鱼类中的积累量，MMA 和 DMA 的毒性比无机 As 至少低一个数量级，毒性也小得多。组织分析表明，受采矿影响的溪流中的三种大型无脊椎动物物种中总砷和无机砷与有机砷的相对含量差异很大，进一步证明了在水生砷风险评估中需要考虑形态。此外，尽管砷对鳟鱼的影响似乎与无机砷密切相关，但发现水中 DMA 对鳟鱼的毒性比无机砷更大，这表明不能假设所有水生生物的有机砷毒性都较低。本研究还讨论了评估和应用饮食暴露和鱼类生长研究中存在的各种困难。
