This strategy considers several domains represented by specific tools ranging from relatively simple in the lower tiers to more complex and specific in the higher tiers. The framework aim is to structure information collection and generation for cost efficient risk assessment, compliant with 3R animal use testing principles , which should also be pursued by means of grouping ENMs. A strategy for grouping ENMs based on releases, uses, physicochemical properties, bio accumulation, bio availability, and effects for both human and ecological risk assessment is currently in development across a number of EU research projects such as MARINA, NANoREG, SUN, and GUIDEnano. These efforts have been challenged by the complexity of ENM identity and interactions, but this approach is necessary, as the costs for safety assessment on a case by case basis would be exorbitant.Therefore, a vision on ENM grouping is needed, which should apply in a regulatory context.Applying grouping in regulatory risk assessments should enable read across, that is, filling a data gap by using information on one ENM, or a nonENM, for another substance in the same group.This strategy should be flexible enough to address different assessment goals depending on the user’s needs, considering all data already available as a starting point, contingent upon data quality evaluation and selecting the most appropriate tools to fill existing data gaps. Such a strategy should ideally be exposure driven, starting with identifying the most relevant exposure scenarios in the ENM life cycle, and evaluating completeness and quality of the available data from a risk assessment perspective. This facilitates careful prioritization of ENMs to optimize testing efforts and can inform more realistic ecotoxicological investigations.
Doing so can allow one to screen out irrelevant exposure routes, eliminate unnecessary testing,danish trolley and support prioritization of exposure scenarios. Exposure assessment should begin with an analysis of plausible exposure scenarios; where none is expected, further testing may be precluded for the applicable use patterns and volumes.Researchers and regulators need to understand actual exposures at biological receptors. This exposure driven approach can also provide important information on realistic environmental conditions to affect test designs for improved interpretation of laboratory toxicology studies. Such practices can ensue in the interim, while research continues to discover best hazard assessment practices. Experimental ENM toxicity assessments, using ecologically relevant receptors and across linked biological levels of organization, should inform developing and parametrizing dynamic process based models. Such models should respond to future scenarios and predict impacts. ENM characteristics, exposure conditions, and ENM transformation, dose, and body burden should be used in interpreting biological and computational findings for assessing ENM risks. ENM test results should be bench marked to results for appropriate controls to establish relative hazard . This applies to pinnacle concerns in ecological fate assessment of bio accumulation, bio magnification, and bio persistence.How to develop, interpret, and use pertinent information in ENM environmental risk assessment is a larger issue that should become part of an extended dialogue among regulators, industry, civil society organizations, researchers, and other societal members so that the fundamental research will inform decision making. Collaborative decisions are recommended for focusing ENM ecotoxicology toward relevant scenarios, including testing the most relevant materials throughout ENM life cycles and employing appropriate hazard assessment approaches, toward meaningful ecological risk assessment.
The overarching question motivating this critical review was: how can we ensure that hazard assessment in ENM ecotoxicology is as environmentally relevant as possible? The answer requires considering how ecotoxicity tests are performed, what constitutes pertinent concentration and test conditions for ENMs , the main biotic and abiotic attributes of the environment, how ecologically oriented hazard assessment is undertaken , and how the resulting information should be interpreted. Answering this question yielded three primary insights. First, environmental relevance is informed by a logical consideration of what exposures might occur, to which receptors, and to what outcomes. The consideration should begin with a plausible release and exposure scenario , and use best available knowledge and technologies to develop the full assessment approach. Concerns regarding ENM concentrations used in hazard assessments are paramount, but are not the only concerns. ENM concentrations should be selected to assess potential effects, but overly high concentrations that fundamentally change media conditions should be avoided. Still, concentrations ranging above and below predicted ENM average concentrations must be assessed for understanding potential organismal effects, underlying mechanisms and their concentration dependencies, and for informing process based dynamic biological effects models. In addition to the nanomaterial, the conventional material should be tested. ENM distributions and fates in broad environmental compartments do not equate to concentrations and forms near, or effective at, actual biological receptors.Therefore, research results on ENM effects should not be disregarded on the limited basis of environmentally relevant exposure concentrations when the study conditions were predicated on a broader hypothesis.
In addition to tethering ENM ecotoxicology to exposure initiation scenarios , the concept of employing tiered approaches in hazard and risk assessment resonated . Multistage approaches to ENM hazard assessment are advocated.A highly developed tiered approach for health and safety testing of nanotechnologies has been published and strategies for tiered risk assessment and grouping are underway.Staging ENM ecotoxicology efforts, such that potential interactive impacts at all levels of biological organization are evaluated, could simultaneously inform risk assessment and predictive process based effects model development. As some ENMs can cause biological impacts from ENM properties or characteristics,ENM ecotoxicology should be oriented to logical exposure initiation scenarios based on ENM life cycles, via testing tiers . Finally,vertical aeroponic tower garden coordination is recommended among multiple disciplines in ENM environmental analysis, fate and transport modeling, and hazard assessment, toward rapidly advancing research using tiered approaches around realistic exposure scenarios.Scholars have published extensively on the multifunctional benefits of urban agriculture including: promoting urban sustainability, reducing air and water pollution, building social cohesion, promoting community health and nutrition, teaching food literacy, and creating radical economic spaces for resistance to the capitalist political economy and structural inequities embedded in the “neoliberal city” . Despite growing evidence of these diverse health, education, and environmental benefits of urban agriculture, these vibrant spaces of civic engagement remain undervalued by city policy makers and planners in the United States. Thriving urban farms and gardens are under constant threat of conversion to housing or other competing, higher value land uses due to rising land values, and other city priorities. This land use challenge and threat to urban farm land tenure is especially characteristic of U.S. cities like San Francisco, one of the most expensive land and housing markets in the country. Under the current urban agriculture paradigm in the U.S., food justice scholars and advocates either try to quantify and highlight the multiple benefits of UA or pursue a critical theoretical approach, arguing that urban agriculture can yield unfavorable results if pursued without an equity lens, especially in cities with intense development pressures and gentrification concerns . A productivist focus is problematic, because, while urban agriculture can be an important component of community food security, its other social and ecological benefits are just as, and sometimes more, significant . In this article, we suggest that the current debates around “urban agriculture” in the U.S. often lead to an unhelpful comparison with rural farms regarding yield, productivity, economic viability, and ability to feed urban populations, most notably in the policy arena.
Defined in these ways, the radical, transformative potential of urban food production spaces and their preservation often gets lost or pushed to the side in city planning decisions in metropolitan regions such as the San Francisco Bay Area, where the threat of displacement is ubiquitous given high levels of economic inequality and extreme lack of affordable land. In order to facilitate what scholars such as Anderson et al. 2018a refers to as the “agroecological transition,” already underway in many urban food ecosystems around the globe , we argue that applying an agroecological approach to inquiry and research into the diversity of sites, goals, and ways in which food is produced in cities can help enumerate the synergistic effects of urban food producers. This in turn encourages the realization of the transformative potential of urban farming, and an articulation of its value meriting protected space in urban regions. Urban agroecology is an evolving concept that includes the social ecological and political dimensions as well as the science of ecologically sustainable food production . UAE provides a more holistic framework than urban agriculture to assess how well urban food initiatives produce food and promote environmental literacy, community engagement, and ecosystem services. This paper presents a case study of 35 urban farms in San Francisco’s East Bay in which we investigated key questions related to mission, production , labor, financing, land tenure, and educational programming. Our results reveal a rich and diverse East Bay agroecosystem engaged in varying capacities to fundamentally transform the use of urban space and the regional food system by engaging the public in efforts to stabilize, improve, and sustainably scale urban food production and distribution. Yet, as in other cities across the country, urban farms face numerous threats to their existence, including land tenure, labor costs, development pressure, and other factors that threaten wider adoption of agroecological principles. We begin by comparing the concepts of UA and UAE in scholarship and practice, bringing in relevant literature and intellectual histories of each term and clarifying how we apply the term “agroecology” to our analysis. We pay particular attention to the important nonecological factors that the literature has identified as vital to agroecology, but seldomly documents . We then present findings from a survey of 35 diverse urban farm operations in the East Bay. We discuss the results, showing how an agroecological method of inquiry amplifies important aspects of urban food production spaces and identifies gaps in national urban agriculture policy circles. We conclude by positing unique characteristics of urban agroecology in need of further studies and action to create equitable, resilient and protected urban food systems.Agricultural policy in the United States is primarily concerned with yield, markets, monetary exchange, and rural development. The United States Department of Agriculture defines agricultural activities as those taking place on farms. Farms are defined as “any place from which $1,000 or more of agricultural products were produced and sold, or normally would have been sold, during the year” . Urban agriculture has been proliferating across the country in the last decade on both public and private lands, as both for profit and nonprofit entities, with diverse goals, missions and practices largely centered on food justice priorities and re localizing the food system. Yet U.S. agriculture policy has been struggling to keep up. In 2016, the USDA published an Urban Agriculture Toolkit, which aims to provide aspiring farmers with the resources to start an urban farm including an overview of the startup costs, strategies for accessing land and capital, assessing soil quality and water availability, production and marketing, and safety and security . The 2018 U.S. Farm Bill provides a definition of urban agriculture to include the practices of aquaponics, hydroponics, vertical farming, and other indoor or controlled environment agriculture systems primarily geared towards commercial sales. In both the Toolkit and Farm Bill, non profit, subsistence, and educational urban farming enterprises are not well integrated or included in the conceptualization of UA. While there are many definitions of urban agriculture in the literature from the simplest definition of “producing food in cities” to longer descriptions of UA such as that of the American Planning Association that incorporate school, rooftop and community gardens “with a purpose extending beyond home consumption and education,” the focus of many UA definitions used in policy arenas continues to center around the production and sale of urban produced foods. Accordingly, food systems scholars have recognized that “Urban agriculture, [as defined], is like agriculture in general”, devoid of the many political, educational, and food justice dimensions that are prioritized by many U.S. urban farming efforts. Thus the social political nature of farming, food production, and food sovereignty are not invoked by formal UA policy in the U.S. Many goals and activities common in urban food production, including education, nonmonetary forms of exchange, and gardening for subsistence are obscured by the productivist definitions and can be thus neglected in policy discussions.