Plastic pollution is recognized as an emerging harm to natural resources and ecosystems that generates a range of economic impacts. Plastic production has increased substantially over the past fifty years, resulting in mismanaged plastic waste and increased marine debris. Microplastics and macroplastics have been documented in coastal environments around the world, and more recently, nanoplastics have been found in human tissues, drinking water, consumer products, and many foods. Environmental exposure to plastic particles has been clearly documented, and ongoing research seeks to describe the pathways by which plastic particles move in the environment and the harms caused by exposure to plastics. Given the ubiquity of plastic waste, states and municipalities face the added costs of identifying, mitigating, and remediating macro- and microplastics pollution. Examples of damages include added costs associated with waste management (e.g., source control and wastewater treatment), added costs to ensure public health (e.g., increased testing and removal of microplastics from drinking water), environmental harms to habitats and biota (e.g., harms to biota due to ingestion, entanglement in plastic marine debris), and economic impacts (e.g., lost tax revenue and lost recreation and tourism revenue/value). Based on established environmental damage assessment practices, we build on the best available science by integrating information on the sources and effects of plastics in models that calculate the costs of addressing the historical, current, and future impacts of microplastic and macroplastic pollution. In this talk, we will describe categories of environmental harm and methods for calculating damages and present a Gulf-specific case study for assessing potential damages from plastic pollution.