Also known as 'mermaid tears', nurdles are the pre-production pellet form of plastics. They are typically manufactured by large chemical companies from petroleum-based non-renewable resources. There is a growing bioplastics industry emerging but it has issues of its own, mainly that current versions of bioplastics do not biodegrade in the ocean.
Nurdles are typically shipped to plastic product manufacturers in rail cars or by truck. Some nurdles may be lost during transfer or spilled accidentally from damaged containers. Unless spilled nurdles are cleaned up they will be swept through the watershed by rain or dry-weather runoff to the nearest lake, bay or ocean.
The main issue with nurdles is that they can be mistaken for food by animals (fish, birds, marine mammals, sea turtles) and consumed. Nurdles have a striking resemblance to fish eggs. Another concern with release of nurdles (and other plastic materials) into the marine environment is that plastic particles may highly concentrate and transport synthetic organic compounds (e.g. persistent organic pollutants, POPs) commonly present in the environment and ambient sea water on their surface through adsorption. These pollutants can then potentially bioaccumulate up the food chain.