Plastic litter pollution is a global contaminant of the marine environment. The most visible effects of litter, whether discarded offshore or derived from coastal sources, are the dangers to wildlife, hazards to navigation, and aesthetic degradation of coastlines. Garbage floating on the sea surface can also impede rescue efforts by confusing the search for wreckage associated with marine accidents and disasters.

While one might expect the very isolated beaches of Sable Island to be pristine, remarkable quantities of debris wash ashore. During the 1980s the island was used as a sampling station to monitor plastic pollution in the waters of the Scotian Shelf region. The study described trends in litter accumulation, identified types, relative proportions, and sources of plastic litter, and established a baseline for future comparisons. Plastic litter, measured by both number and weight was found washing ashore at a monthly rate of roughly 200 items/km, or 8 kg/km. Considering that Sable Island is 40 km in length, the study indicated that plastic litter was coming ashore on north beach at a rate of 8000 items per month. Recently there has been some change in the types of debris found on the island, however the amount of garbage coming ashore has not noticeably diminished since the 1980s.

Entanglement in net scraps, rope, strapping and other plastic items injures or kills marine animals, including species of commercial importance. Sickness or death may result from accidental ingestion of items such as plastic pellets and polyethylene bags. The amount of hazardous debris found on the beach is an indication of the quantity of debris that threatens marine life - seals, seabirds, sea turtles, and fish - in the surrounding waters. Entangled seals are often seen on the island. The majority are caught in fragments of trawl or gill net, and others in scraps of monofilament net and pieces of plastic strapping. Most of the entangled seals have deep wounds where the entangling material cuts through hide, blubber and flesh.

For many years garbage has been disposed of at sea by military, fishing, research and passenger vessels, both foreign and domestic. Significant progress was made in reducing the amount of shipboard waste dumped in the ocean by Canadian vessels, and many countries are working together through international agreements such as MARPOL to reduce garbage disposal at sea. However, trash that isn't thrown in the ocean, gets dumped somewhere else - and trash dumped on land can sometimes work its way out to sea via rivers, storm sewers and flooding. The impact of litter pollution in the marine environment is one aspect of a much larger environmental issue. In attempting to deal with the problem there must be an overall change in present attitudes that encourage inappropriate and wasteful use of materials, and result in abuse of resources and pollution of both land and water.