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Over 400 tons of silver nanoparticles (AgNPs) are produced annually, 30% of which are used in medical applications due to their antibacterial properties. The widespread use of AgNPs has implications over the entire life cycle of medical products, from production to disposal, including but not limited to environmental releases of nanomaterials themselves. Here a cradle-to-grave life cycle assessment from nanoparticle synthesis to end-of-life incineration was performed for a commercially available nanosilver-enabled medical bandage. Emissions were linked to multiple categories of environmental impacts, making primary use of the TRACI 2.1 impact assessment method, with specific consideration of nanosilver releases relative to all other (non-nanosilver) emissions. Modeling results suggest that (1) environmental impacts of AgNP synthesis are dominated by upstream electricity production, with the exception of life cycle ecotoxicity where the largest contributor is mining wastes, (2) AgNPs are the largest contributor to impacts of the bandage for all impact categories considered despite low AgNP loading, and (3) impacts of bandage production are several times those bandage incineration, including nanosilver releases to the environment. These results can be used to prioritize research and policy measures in order to improve the overall ecotoxicity burdens of nanoenabled products under a life cycle framework.

Silver nanoparticles (AgNPs) can be produced through a variety of synthesis routes with differing mechanisms, inputs, yields, reaction conditions, and resulting size distributions. Recent work has focused on applying green chemistry and sustainable manufacturing principles to nanomaterial synthesis, with the goal of reducing life cycle energy use and environmental impacts. Life cycle assessment (LCA) is used here to analyze and compare the environmental impacts of AgNPs produced through seven different synthesis routes (cradle-to-gate). LCA reveals both direct and indirect or upstream impacts associated with AgNPs.Synthesis routes were chosen to represent current trends in nanoparticle synthesis and include physical, chemical and bio-based methods of production. Results show that, across synthesis routes, impacts associated with the upstream production of bulk silver itself were dominant for nearly every category of environmental impact, contributing to over 90% of life cycle burdens in some cases. Flame spray methods were shown to have the highest impacts while chemical reduction methods were generally preferred when AgNPs were compared on a mass basis. The bio-based chemical reduction route was found to have important tradeoffs in ozone depletion potential and ecotoxicity. Rescaling results by the size-dependent antimicrobial efficacy that reflects the actual function of AgNPs in most products provided a performancebased comparison and changed the rank order of preference in every impact category. Comparative results were also presented in the context of a nanosilver-doped wound dressing, showing that the overall environmental burdens of the product were highly sensitive to the synthesis route by which the AgNPs are produced.Environ. Sci.: Nano This journal is † Electronic supplementary information (ESI) available. See Nanoparticle synthesis has been found in several life cycle assessments (LCAs) of AgNP-containing products to be a large contributor of environmental impacts. Impacts are highly dependent on the synthesis route, yet several routes lack LCA data and/or results. Here we conduct and compare LCAs for all industrially important synthesis routes and identify critical inputs and synthesis steps, informing future process improvements. Impacts from the production of bulk silver were dominant for nearly every impact category, but with different patterns among routes. Results are presented on a mass basis as well as by antimicrobial efficiency, a novel approach. This work provides a transparent and general basis for the research community to model nano life cycle impacts in subsequent assessments of AgNP-enabled products.

Increasing use of silver nanoparticles (AgNPs) in consumer products as antimicrobial agents has prompted extensive research toward the evaluation of their potential release to the environment and subsequent ecotoxicity to aquatic organisms. It has also been shown that AgNPs can pose significant burdens to the environment from life cycle emissions associated with their production, but these impacts must be considered in the context of actual products that contain nanosilver. Here, a cradle-to-gate life cycle assessment for the production of 15 different AgNP-enabled consumer products was performed, coupled with release studies of those same products, thus providing a consistent analytical platform for investigation of potential nanosilver impacts across a range of product types and concentrations. Environmental burdens were assessed over multiple impact categories defined by the United States Environmental Protection Agency's Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI 2.1) method. Depending on the product composition and silver loading, the contribution of AgNP synthesis to the overall impacts was seen to vary over a wide range from 1% to 99%. Release studies found that solid polymeric samples lost more silver during wash compared to fibrous materials. Estimates of direct ecotoxicity impacts of AgNP releases from those products with the highest leaching rates resulted in lower impact levels compared to cradle-to-gate ecotoxicity from production for those products. Considering both cradle-to-gate production impacts and nanoparticle release studies, in conjunction with estimates of life cycle environmental and health benefits of nanoparticle incorporation, can inform sustainable nanoenabled product design.

Nano specific challenges of applying LCA towards nano-enabled agrochemicals to assess their environmental implications are identified in this perspective.

This study focused on nitrate leaching through soil during growth of romaine lettuce where 2-D graphite (CNPs) were combined with fertilizer and applied to soil to test the CNP effect on yield, nitrate leaching, and plant nutrient uptake.

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Engineered nanomaterials are finding application in a wide range of consumer electronics. In particular, carbon nanotubes (CNTs) are candidate materials for use in enhancing the performance of lithium-ion battery anode and cathodes. However, past studies indicate that some toxicological effects exist for CNTs, although full evaluation may yet take time. Appraisals of material flows of potential products containing CNTs are useful for early recognition of environmental problems, for investment planning in production and waste management infrastructures, and for government policy formulation. This material flow analysis (MFA) study uses a stock dynamics and logistic model to forecast the technology transition from conventional Li-ion batteries in portable computers to CNT Li-ion batteries and the subsequent waste generation of CNTs in obsolete laptop batteries. State-specific recycling rates for electronic waste are projected to determine the quantities of CNTs in laptop batteries destined for recycling, incineration, or landfilling. As markets for CNT-enabled electronics begin to expand, United States collection and recycling facilities may consider establishment of new processes or controls to reduce the potential for CNT emissions and exposures.