Multimodal characterisation of nanomaterials in the environment

Lead Research Organisation: Imperial College London
Department Name: Materials

Abstract

Engineered nanomaterials (ENMs) are found in many consumer products including cosmetics and personal hygiene goods. Nanomaterials are also found in additives for diesel fuels to improve fuel efficiency. These materials will come into contact with the environment, for example, if they are washed down the sink, or if they become airbourne, however we currently have no idea about whether they are hazardous or not and regulations are not in place to control their release or treatment. The life cycle of ENMs in the environment is not known and there exist large knowledge gaps in this field. The reason for this is that the concentrations and properties of ENMs in consumer products are largely unknown (or not indicated by companies). Very little is known about the behaviour or lifetime of ENMs in the water effluent and soils as it's extremely hard to monitor this behaviour, as we do not have the tools to detect these tiny materials in very complex environments. This project will apply new and sophisticated experimental characterization tools for predicting potential environmental risks associated with the use of selected consumer products incorporating ZnO, Ag, TiO2 and CeO2 ENMs. An overarching goal is to evaluate which are the critical charateristics of ENMs (size, chemistry etc.) which may cause damage to the environment through two of the most predominant environmental pathways - from the effluent of a waste water treatment plant to waters and also from sewage sludge to soils. This information will ultimately to provide guidance to regulators on policy and to industry about how to design "safe" classes of ENMs and mitigate against risk, while avoiding overregulation. Avoiding overregulation is vital, as we do not want to re-experience what happened e.g. at Fukushima, where 160,000 people were forced to relocated without need, since the risk presented to regulators and the government was too high. This has since resulted in 1,599 deaths, as the displaced residents are suffering from health problems, alcoholism and high rates of suicide.
Our team has an extensive track record in developing unique techniques to track these nanomaterials in complex environments and will apply their knowledge of this field to tackle this extremely pertinent concern. The projects experimental approaches include both physical science experiments and toxicological approaches, generating results to improve our limited understanding of the potential environmental hazards. The results generated from the project will also contribute to our very limited knowledge on various aspects of the fate, transport, bioavailability, and ecotoxicity of ENMs and will allow us to answer questions such as "can toxic doses of ENMs reach organisms or are these concentrations negligible at the point of exposure to the organism?", "if they are toxic, is it possible to re-engineer ENMs such that they do not present a risk", "do the nanomaterials dissolve or change their chemistry in the environment and ultimately detoxify and how does this vary between the different nanomaterials?", "which nanomaterials present the greatest risk and how do we minimise the environmental and health risks of these hazardous materials without overly precautionary regulations". This multifaceted strategy will make a major development in understanding the fate of ENMs in the environment to guide policy regulation whilst avoiding unnecessary overregulation, and ultimately guide the safe development of these materials for future commercial exploitation.

Planned Impact

With increasing commercialisation and up-scaling of silver, zinc oxide, ceria and titania nanomaterials production, comes a concomitant need to understand occupational health, public safety and environmental implications of these materials. Due to the enormous number of permutations of nanoparticles shape, dimensions, composition, and surface chemistry, only a fundamental understanding of the critical processes will allow a realistic, practical assessment of the risks of wide range of possible products. The proposed work will impact on ENM development by establishing the relative environmental risk associated with different classes of ENMs. By establishing the potential of each classes of ENM for any environmental risks, suitable precautionary measures can be identified. At the moment, the uncertainty surrounding ENM safety is a major barrier to commercial development. By establishing a higher level of confidence about safe handling of these classes of ENM, this project will have a major economic impact. Nanoscale studies of the complex environment-nano interface lie at the heart of technical challenges. Despite numerous reports, there is no consensus regarding environmental toxicity enacted by these nanomaterials due to a lack of understanding of their lifecycle in the environment. This project will make a step-change in our understanding of the fate of these nanomaterials and their ultimate bioreactivity with organisms. The following groups will benefit:
a. ENM manufacturers and their customers: Businesses will be able to make informed decisions about which technologies to pursue. Alternatively, they will be able to select effective safety measures or potentially redesign their products to avoid any potential hazards.
b. Government, society and policy makers: The Environment Agency and the Department for the Environment, Food and Rural Affairs will benefit from insight to any hazards associated with these classes of ENMs to recommend on policy and regulations to ensure safe handling in the workplace and the environment. The health and safety executive has been working hard recently to provide appropriate and balanced advice to companies working in the area; the outputs of this project will help them to refine their advice. The Royal Commission on Environmental Pollution and Royal Society are actively involved with public engagement in the field of environmental and nanotoxicology and will also benefit from this research which will feed into reports, commissions and recommendations made by these and similar societies.
c. Society: Clearly, workers in the ENM and water industries need to be protected adequately from any potential risks whilst maximizing their productivity; only with a detailed understanding of ENM toxicology, can appropriate control measures be selected. More generally, the public will benefit from the safe development and commercialisation of ENM technologies.
d. Instrument manufacturers and service providers will benefit from the development of new in situ techniques for tracking nanomaterials in complex environments, allowing them to expand their markets.
e. Improved training for early career researchers: A significant impact of this grant will be generation of highly trained PDRAs people in advanced materials characterisation and environmental science. There is a lack of skilled people in these interdisciplinary areas.
f. Timescale for benefits to be realized: In the short-term any general conclusions about ENM safety are likely to have a relatively rapid impact on health and safety policy. In the longer term, these results may contribute to an understanding of the environmental significance, if any, of ENM structure.
 
Description 1. From survey data provided by the BGS, potential sample locations were identified in England and Wales which had elevated levels of cerium, silver, titanium and zinc. Sample locations were cross-referenced with historical maps/data that showed mining operations in the area, as it was assumed that these areas would be most profitable due to the working of minerals producing sub-micron sized particulates arising from contamination. A sampling program was undertaken, and ~40 sediment samples were collected. These samples have been fractionated (< 0.035 mm) and will be analysed by XRF for metal content. Further environmental sampling programmes have been undertaken/planned to investigate other potential sources of environmental nanomaterials (ENM) pollution - including collecting PM10 sample reels (taken using a BAM1020 analyser) and road sweeping samples from Bath Council for CeO2 ENM pollution, landfill leachates for various ENM pollutants, and waters from an open air swimming pool for TiO2 and ZnO ENM pollution associated with sunscreens. Environmental samples will be assessed in the FENAC laboratory, Birmingham. The proposed analysis will involve field-flow fractionation to separate out the nanoparticulate fraction. The resulting fraction will be analysed by ICP-MS for element specific nanoparticle concentration before further investigation by high resolution spectromicroscopic techniques at Bristol/Imperial. We have detected Zn in soil samples taken from children's playgrounds.
2.Commercial Ag NPs (20 nm) were incubated in R. subcapitata (green) algae under controlled conditions (T, illumination (white and UV)) and the structure of the AgNP- exposed algae was compared to that of the control algae (no AgNPs). Key findings include: 1. The Ag NPs had transformed to a sulfide when they came in contact with the algae; 2. Some Ag NPs came in contact with the cell wall of the algae, and there is evidence of dissolution; 3. The subcellular structure distribution of the algae was significantly modified as a consequence of exposure to the Ag NPs. Commercial TiO2 NPs (~20 nm) and CeO2 ENMs (~9 nm) have also been incubated in R. subcapitata algae under the indicated conditions. These NPs contacted the cell wall of the algae so, could impair functions that occur at the cell/media interface. Working with the SuperSTEM Daresbury, we have shown first evidence that CeO2NPs can enter these Algae; we are currently analysing whether the Ce3+/4+ ratio changes inside/outside the Algae. We have used cryo-X-ray microtomography beam line (B24) to confirm 3D inclusion of the NPs inside the Algae and have shown significant structural damage to the algae exposed to AgNPs (paper in progress).
3. A conceptual model of the pathways of ENMs from products consumed in households to the environment through the WWT is being developed to estimate concentrations of selected ENMs (CeO2, ZnO, TiO2 and Ag) in the environment. The model uses catchment site-specific data for the Prediction of Environmental Concentrations. Samples of influent water, sludge and biomass have been collected from Cambridge WWTP. A sampling campaign has been designed to understand the role of WWT leading to environmental contamination through the two main paths (directly in water from effluent and in soils through sewage sludge application). The selection of the sampling locations, timings and frequency has been determined based on plant operating parameters. 4. We have shown that ZnO engineered nanomaterials transform in simulated and real environmental media: We have successfully applied transmission X-ray microscopy (TXM) to study the speciation of ZnO ENMs in: i) influent water collected from Cambridge WWTP and ii) humic acid solution acidified to simulate a simplified primary sludge environment. X-ray absorption spectroscopy (XAS) spectra show ZnO ENM aggregation and surface transformations consistent with sulphide and phosphate species after 4 h in influent water, while ZnS and Zn3(PO4)2 are the major components remaining after humic acid incubation. Complementary, chemical mapping has been carried out on sludge samples at Diamond Light Source. Commercial ZnO ENMs (80-200 nm) were spiked into real primary sludge samples for two different times. ZnO was only found as a minor species after 4 h in real sludge samples, consistent with dissolution experiments showing that the ZnO NPs dissolve in these media releasing Zn2+ ions. A paper on the work has been submitted. One other paper on the real sludges will follow.
4.Four laboratory-scale anaerobic digesters have been set up and are ready for testing at Imperial. We have shown that none of four ENMs impact on anaerobic digester (AD) performance. The Ag NPs transform to less soluble/inert Ag2S NPs within the AD sludge and we are not able to find any ZnO NPs remaining within the AD sludges suggesting that they have dissolved.
5. Bioreactivity of AgNPs: A novel suite of photobioreactors have been set up in a REftec temperature controlled growth room for determination of toxicity of ENMs on algae with options for quantification of impacts in both planktonic and benthic modes. The facility allows for quantification of UV impacts in addition to visible light. A selection of media has been trialed to optimise quantification of impacts of ENM's whilst avoiding confounding issues of pH and precipitation of test ions, following dissolution of NP's. A field site has been identified for undertaking measurements of ENM's of river- grown periphytic biofilms. Preliminary data on the bioreactivity of AgNPs (20 nm) on the ISO standard species Raphidocelis subcapitata has been measured. No significant toxicity was recorded for concentrations of AgNPs in the range 0.5 to 500 µg l-1 (Figure 1), measured after a 24 hour exposure period, but thereafter, a rapid decline in photosynthetic performance was measured with a circa. Using very high resolution electron microscopy techniques, we have shown that the AgNPs are not internalised by the algae but instead are captured by a layer of extracellular protein which appears to be protective.
6. Impacts of four ENM's were quantified on river periphytic biofilm communities, using outdoor mesocosms, deployed June-July, 2018 at the FBA field-station, Dorset. Field-grown biofilms were exposed to one of two concentrations, designated LOW and HIGH selected to represent environmentally relevant and worse-case scenario concentrations respectively. Analyses are ongoing, but preliminary findings indicate significant negative impacts to a number of fluorescence-based indicators of photosynthetic functioning including the maximum electron transport rate (ETRm) after a 24 hr period of exposure, when compared with control biofilms, for nanoceria, titania and ZnO NPs (Fig. 2). Findings for the periphytic community responses for TiO2 compare favourably with results obtained for one of our laboratory-based single-species toxicity tests with the diatom Nitzschia palea, supporting our recommendation that the latter species could be used for standard toxicity testing methods to evaluate impacts of NP's to organisms that play a dominant role in the functioning of freshwater riverine ecosystems.
Exploitation Route Our research will be taken forward using the following academic and non-academic routes:
1) Society: A particle impactor has been purchased (California Instruments) to assess nanoscale pollutants in ambient air. The impactor draws air through three chambers, each housing a SEM stub. After a set period (determined by experimentation), the SEM stubs will be assessed using SEM with EDX. The impactor will be placed in various locations in the South West. This will allow us to assess whether air is a potential pathway for ENMs (such as the diesel additive CeO2) to reach human receptors. As part of this work, a collaboration with the Meteorological Research Institute, Japan Meteorological Agency - world experts in airborne nanoparticle capture and characterisation is being arranged.
2) Society and academia: In June 2017, the Bristol contingent of the team will make a second research visit to the Meteorological Research Institute (MRI) in Tsukuba, Japan to exchange samples, research ideas and best practice in relation to the capture and analysis of aerosol ENMs (CeO2, FeOx) from vehicle pollution. This marks the start of a collaboration with Prof Yashuioto Igarashi, the MRI lead expert on airborne nanopollution.
3) We presented the results of our work at the UK nanomaterials regulators meeting in November 2017 and set up a new collaboration with the CEH. We are going to exchange samples and work with them to understand transformations of our nanomaterials in soils.
Sectors Chemicals,Energy,Environment,Healthcare,Government, Democracy and Justice,Pharmaceuticals and Medical Biotechnology,Transport

 
Description The PI presented work on the environmental impacts of engineered nanomaterials at the Huxley Summit, at the Royal Institution in December, 2019 to a panel of scientists and the public.
First Year Of Impact 2018
Sector Environment
Impact Types Societal

 
Description Assessing the risks of 2D nanomaterials in the environment
Amount £50,000 (GBP)
Organisation Lloyd's Register 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2017 
End 09/2021
 
Description STFC Batteries Early Career Award
Amount £1,900 (GBP)
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 12/2016 
End 06/2017
 
Description Anglian Water 
Organisation Anglian Water Services
Country United Kingdom 
Sector Private 
PI Contribution We will perform state of the art characterisation of nanomaterials in environmental media from taken from different stages of a waste water treatment plant.
Collaborator Contribution Anglian Water will provide us with water, sludge, and soils sample from different stages of treatment and different sites in the waste water treatment plants from identified nanomaterials hotspots.
Impact None yet.
Start Year 2006
 
Description British Geographical Socieity 
Organisation British Geological Survey
Country United Kingdom 
Sector Public 
PI Contribution We have found expertise within the BGS and are now having input from them in relation to identifying a number of possible pollution hotspot sites.
Collaborator Contribution Two hydrochemists at the BGS have agreed to sit on our steering committee.
Impact None
Start Year 2016
 
Description Characterisation of engineered nanoparticle impacted sewage waters 
Organisation University of Birmingham
Country United Kingdom 
Sector Academic/University 
PI Contribution The objective of the research project is to quantify the lifetime and to characterise the physiochemical characteristics of engineered nanomaterials (ENMs) as they reach the environment through wastewater treatment plants (WWTP), specifically as they partition between 1) water, wastewater, sludge and soil and 2) effluent and freshwater. The ENMs of interest are CeO2, ZnO, TiO2 and Ag. We have applied for time at the FENAC facility in Birmingham to perform field flow fractionation (FFF) to isolate the nano-scale (~100 nm) portion of the samples of engineered nanomaterials in soils and sediments. We will also perform single particle ICP-MS to detect the particles within these media. We will provide the facility with samples and scientific questions.
Collaborator Contribution They will supply instrumentation (FFF) and single particle ICP-MS facilities.
Impact We have been awarded the grant by NERC and are planning our first set of experiments.
Start Year 2017
 
Description An invited talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Angela Goode gave an invited talk on correlative in situ microscopy of nanomaterials in environmental media at the organic-inorganic interfaces meeting held by the Royal Microscopical society.The talk has sparked discussions with instrument manufacturers about buying new a new in situ TEM holder for our facility to develop our research on this topic.
Year(s) Of Engagement Activity 2018
 
Description Seminar Invited 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact The PI gave a talk on correlated imaging of nanomaterials in complex environments. I have set up a collaboration with an expert in in situ TEM which arose from this meeting.
Year(s) Of Engagement Activity 2018
 
Description Talk on Multimodal characterisation of nanomaterials in the environment Prof. Tom Scott, Bristol 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Prof. Tom Scott gave a presentation on our project to the MRI, Japan in October 2017.
Year(s) Of Engagement Activity 2016