While manufactured nano-materials (MNM) can enter the environment from several sources and pathways (See Figure), use and disposal estimates of Tier 1 MNMs (Ag, TiO2, ZnO) suggest that their major point of entry will be to terrestrial ecosystems after being removed as solids from wastewater. It has been consistently shown that between 80 and 99% of Ag and TiO2 MNM-mass introduced to the WWTP are retained in the BS (14, 16-20). In the US and UK, the majority of BS is disposed of by land application (50-60%), followed by incineration (~15-20%), and disposal in landfills (~15-20%) (21, 22). There is concern that once the MNMs have been added to agricultural or managed lands and accumulate in the soil over time, they could pose long-term negative effects on soil fertility and microbial activity. Furthermore, there is concern that some MNMs may move into the food chain, percolate through soil to groundwater, or be carried in runoff into aquatic systems.