|dc.description.abstract||Over the past 40 years, world production of plastic resins increased 25-fold creating a global waste stream comprised of 60-80% plastics. Microplastics, plastic particles less than 5mm in size, are receiving increased attention as a potentially detrimental environmental contaminant. Primary sources of microplastic pollution include plastic pellets and powders produced by manufacturers for industrial sale that enter the waterway via spills, improper dumping or facility accidents and microbeads used as abrasives or exfoliant in commercial products. Secondary sources of microplastic pollution are fibers and fragments from the deterioration of larger plastics. Synthetic fibers enter our waterway as micro-sized fibers shed from laundry in our household sewage effluent that urban wastewater treatment centers are unable to capture. Microplastics have been found throughout our oceans, but little has been done to quantify them in our freshwater systems. This study examines the Snake River for the presence of microplastics. By looking at an entire river system, we hope to identify hot spots and sources of microplastic pollution, such as wastewater treatment facilities or recreational areas. Grab samples (average volume of 1.8 liters) and volume reduced samples with a 100-micron mesh plankton net (average volume of 3,328 L) were collected throughout the summer of 2016 approximately every 50 river miles along the Snake River out to the Pacific Ocean. In this presentation, the results from the grab samples collected at all 28 sites will be revealed. Of the 23 grab samples visually inspected to date, 16 contained putative microplastics.