Most of the problems associated with plastic bags are negative externalities of consumption.

A large plastic bag externality is how to dispose of them once they are used. Plastic bags can be recycled into other plastic bags; however, this is rarely the case Most plastic bags are not recycled instead they wind up in landfills, in the ocean, or even as litter.

The plastic bags that end up in landfills take up valuable landfill space. A typical landfill costs more than twenty million dollars to build and millions more per year in order to maintain. Nearly all of this money comes from taxpayers. Eventually the landfills will leak and can cause immense environmental damage. There will be large costs associated with cleaning up these messes in the future. Plastics in general makes up between 14 and 28% by volume of waste in general. Around the world over 200,000 plastic bags are dumped in landfills every hour (PlanetArk.com).Plastic bags in general take anywhere from 20 to 1,000 years to breakdown in the environment. This is a very long period of time; however, eventually they would breakdown and disappear. Once in a landfill though, they never breakdown. Modern landfills are designed so that nothing in them breakdowns. This means that as space becomes more of a premium something eventually will need to be done with the bags. There is a huge cost to this. All of these factors cost taxpayers billions of dollars over the years.

The plastic bags that are not put in the wastebasket end up as litter. Litter is a huge burden on society. Plastic bags cover the streets, clog drains and gutters, and are even linked to disease. Litter costs a lot of money to clean up. Possibly the largest and most problematic externality caused by plastic bag consumption is environmental damage. The environmental damage caused by plastic bags is enormous. Plastic makes up 80% of the volume of litter on roads, parks, and beaches and makes up 90% of floating litter in the ocean (BEC). In every square mile of ocean there are over 46,000 pieces of plastic. This puts an enormous strain on the environment. The little pieces of plastic act as a sort of sponge for chemicals. They soak up a million fold greater concentrations of such deadly compounds as PCBs and DDE (a breakdown product of the notorious insecticide DDT), than the surrounding seawater (Reusablebags.com). Marine life then eats these pieces and dies. It is estimated that over a 100,000 different birds, seals and whales die every year (Reusablebags.com). After the animal dies its carcass decomposes and the plastic is free to roam the ocean and kill again.

When plastic bags find their way into the ocean they kill endangered turtles. Turtles that confuse them for jellyfish, their primary food source, ingest plastic bags. The turtles then suffocate. Plastic bags wrap themselves around living coral and quickly kill them. This has become a huge problem for Australia, whose Great Barrier Reef is being threatened by little white bags of death. Plastic bags trap seals and sea lions, prevent whales from digesting and kill birds by the thousands.

source : http://www.plasticbageconomics.com/index.php

MERVYN