Hund-Rinke Kerstin, Simon Markus
Fraunhofer-Institut für Molekularbiologie und Angewandte Oekologie, Schmallenberg, Germany.
Environ Sci Pollut Res Int. 2006 Jul;13(4):225-32. doi: 10.1065/espr2006.06.311.
Due to their large potential for manifold applications, the use of nanoparticles is of increasing importance. As large amounts of nanoparticles may reach the environment voluntarily or by accident, attention should be paid on the potential impacts on the environment. First studies on potential environmental effects of photocatalytic TiO2 nanoparticles have been performed on the basis of widely accepted, standardized test systems which originally had been developed for the characterization of chemicals. The methods were adapted to the special requirements of testing photocatalytic nanoparticles.
Suspensions of two different nanoparticles were illuminated to induce their photocatalytic activity. For testing, the growth inhibition test with the green alga Desmodesmus subspicatus and the immobilization test with the daphnid Daphnia magna were selected and performed following the relevant guidelines (algae: ISO 8692, OECD 201, DIN 38412-33; daphnids: ISO 6341, OECD 202, DIN 38412-30). The guidelines were adapted to meet the special requirements for testing photocatalytic nanoparticles.
The results indicate that it is principally possible to determine the ecotoxicity of nanoparticles. It was shown that nanoparticles may have ecotoxicological effects which depend on the nature of the particles. Both products tested differ in their toxicity. Product 1 shows a clear concentration-effect curve in the test with algae (EC50: 44 mg/L). It could be proven that the observed toxicity was not caused by accompanying contaminants, since the toxic effect was comparable for the cleaned and the commercially available product. For product 2, no toxic effects were determined (maximum concentration: 50 mg/L). In the tests with daphnids, toxicity was observed for both products, although the concentration effect-curves were less pronounced. The two products differed in their toxicity; moreover, there was a difference in the toxicity of illuminated and non-illuminated products.
Both products differ in size and crystalline form, so that these parameters are assumed to contribute to the different toxicities. The concentration-effect curves for daphnids, which are less-pronounced than the curves obtained for algae, may be due to the different test organisms and/or the differing test designs. The increased toxicity of pre-illuminated particles in the tests with daphnids demonstrates that the photocatalytic activity of nanoparticles lasts for a period of time.
The following conclusions can be drawn from the test results: (I) It is principally possible to determine the ecotoxicity of (photocatalytic) nanoparticles. Therefore, they can be assessed using methods comparable to the procedures applied for assessing soluble chemicals. (II) Nanoparticles may exert ecotoxicological effects, which depend on the specific nanoparticle. (III) Comparable to traditional chemicals, the ecotoxicity depends on the test organisms and their physiology. (IV) The photocatalytic activity of nanoparticles lasts for a relevant period of time. Therefore, pre-illumination may be sufficient to detect a photocatalytic activity even by using test organisms which are not suitable for application in the pre-illumination-phase.
First results are presented which indicate that the topic 'ecotoxicity and environmental effects of nanoparticles' should not be neglected. In testing photocatalytic nanoparticles, there are still many topics that need clarification or improvement, such as the cause for an observed toxicity, the improvement of the test design, the elaboration of a test battery and an assessment strategy. On the basis of optimized test systems, it will be possible to test nanoparticles systematically. If a potential risk by specific photocatalytic particles is known, a risk-benefit analysis can be performed and, if required, risk reducing measures can be taken.
由于纳米颗粒在多种应用中具有巨大潜力，其使用变得越来越重要。由于大量纳米颗粒可能会主动或意外进入环境，因此应关注其对环境的潜在影响。关于光催化二氧化钛纳米颗粒潜在环境影响的初步研究是在广泛接受的标准化测试系统基础上进行的，这些系统最初是为化学品表征而开发的。这些方法已根据测试光催化纳米颗粒的特殊要求进行了调整。
对两种不同纳米颗粒的悬浮液进行光照以诱导其光催化活性。为进行测试，选择了绿藻斜生栅藻生长抑制试验和大型溞固定试验，并按照相关指南进行（藻类：ISO 8692、经合组织201、DIN 38412 - 33；大型溞：ISO 6341、经合组织202、DIN 38412 - 30）。这些指南已进行调整以满足测试光催化纳米颗粒的特殊要求。
结果表明，原则上可以确定纳米颗粒的生态毒性。结果显示，纳米颗粒可能具有生态毒理学效应，这取决于颗粒的性质。所测试的两种产品毒性不同。产品1在藻类测试中显示出明显的浓度 - 效应曲线（半数有效浓度：44毫克/升）。可以证明，观察到的毒性不是由伴随的污染物引起的，因为清洁后的产品和市售产品的毒性效应相当。对于产品2，未确定有毒效应（最大浓度：50毫克/升）。在大型溞测试中，两种产品均观察到毒性，尽管浓度效应曲线不太明显。这两种产品毒性不同；此外，光照和未光照产品的毒性也存在差异。
两种产品在尺寸和晶体形式上存在差异，因此假定这些参数导致了不同的毒性。大型溞的浓度效应曲线不如藻类的曲线明显，这可能是由于测试生物不同和/或测试设计不同。在大型溞测试中，预光照颗粒毒性增加表明纳米颗粒的光催化活性会持续一段时间。
从测试结果可以得出以下结论：（I）原则上可以确定（光催化）纳米颗粒的生态毒性。因此，可以使用与评估可溶性化学品所采用程序类似的方法对其进行评估。（II）纳米颗粒可能产生生态毒理学效应，这取决于特定的纳米颗粒。（III）与传统化学品类似，生态毒性取决于测试生物及其生理状况。（IV）纳米颗粒的光催化活性会持续一段相关时间。因此，即使使用不适合在预光照阶段应用的测试生物，预光照也可能足以检测到光催化活性。
首次展示的结果表明，“纳米颗粒的生态毒性和环境影响”这一主题不应被忽视。在测试光催化纳米颗粒时，仍有许多主题需要澄清或改进，例如观察到的毒性原因、测试设计的改进、测试组合的制定以及评估策略。基于优化的测试系统，将能够系统地测试纳米颗粒。如果已知特定光催化颗粒存在潜在风险，则可以进行风险 - 效益分析，并在需要时采取风险降低措施。
