Pharmaceutical and cosmetic silica nanoparticles: towards an understanding of their structure, fate and behaviour in aquatic systems

工程氧化物纳米颗粒广泛用于化妆品和个人护理产品（例如防晒霜、牙膏、护肤霜）和局部应用的药物配方（例如局部和透皮应用的药膏），并经常被排放到废水中。这项小额资助研究了典型的家用化妆品和药物配方中二氧化硅纳米粒子对废水的负荷，废水化学处理（絮凝和沉淀）去除二氧化硅纳米粒子的效率，以及二氧化硅纳米粒子在天然水中的稳定性、结构和行为。本研究选择二氧化硅纳米颗粒，因为这些类型的氧化物纳米颗粒在所研究的配方中广泛使用。先前的研究表明，对水生生物来说，离散的纳米颗粒和小聚集体可能比大聚集体更具生物可利用性/毒性，纳米颗粒的絮凝和沉降可能减轻生态毒性并减少纳米颗粒在水生系统中的分散。因此，本研究提供了一系列的实验室实验来测量SiO2纳米颗粒在一系列水生化学条件下的分散-聚集行为，从而评估SiO2纳米颗粒在化学水处理和排放到地表水时是否可能聚集和沉积。我们的假设是：(1)化妆品（防晒霜、牙膏）和药品（局部应用的面霜）为废水提供了SiO2纳米颗粒的重要来源。(2)化学水处理（絮凝沉淀）去除SiO2纳米颗粒的效果有限。因此，有可能通过处理过的废水将氧化物纳米颗粒排放到地表水中。(3)二氧化硅纳米颗粒在水生环境中的稳定性、运输和命运（与团聚体大小、结构和沉降速度有关）受到以下因素的影响：(a)水性基质化学（pH值、离子强度和组成），(b)与天然有机物的相互作用，以及(c)与水生沉积物的相互作用。

Engineered oxide nanoparticles are widely used in cosmetics and personal care products (e.g. sunscreens, toothpastes, skin creams) and in topically-applied pharmaceutical formulations (e.g. creams for local and transdermal application) and are routinely released into wastewaters. This Small Grant examines the loadings of SiO2 nanoparticles to wastewaters from typical domestic use of cosmetic and pharmaceutical formulations, the efficiency of removal of SiO2 nanoparticles by wastewater chemical treatment (flocculation and sedimentation) and stability, structure and behaviour of SiO2 nanoparticles in natural waters. SiO2 nanoparticles were selected for this study as these types of oxide nanoparticles are widely used in the formulations under study. Previous research indicates that discrete nanoparticles and small aggregates are likely to be more bioavailable/toxic to aquatic organisms than larger aggregates and that flocculation and sedimentation of nanoparticles are likely to mitigate ecotoxicity and reduce dispersion of nanoparticles within aquatic systems. Therefore, this study provides a series of laboratory experiments to measure the dispersion-aggregation behaviour of SiO2 nanoparticles under a range of aquatic chemical conditions, thereby assessing whether SiO2 nanoparticles are likely to agglomerate and sediment out during chemical water treatment and when discharged into surface waters. Our hypotheses are: (1) Cosmetics (sunscreens, toothpaste) and pharmaceuticals (topically applied creams) provide a significant source of SiO2 nanoparticles to wastewaters. (2) Chemical water treatment (flocculation and sedimentation) is limited in its effectiveness in removing SiO2 nanoparticles. There is therefore potential for discharge of oxide nanoparticles via treated effluent into surface waters (3) The stability, transport and fate of SiO2 nanoparticles in aquatic environments (in relation to aggregate size, structure and rates of sedimentation), are influenced by: (a) aqueous matrix chemistry (pH, ionic strength and composition), (b) interactions with natural organic matter and (c) interactions with aquatic sediments.