Two hundred and ninety – the average number of plastic bags a Washington state resident uses each year.

More than 500 billion plastic bags are used in the world annually. Invented by a Swedish company in the 1960s and introduced to grocery store checkout lines in 1976, these ultra-thin plastic grocery bags have become a leading source of pollution worldwide.

Made from high-density polyethylene, a byproduct of oil and natural gas, these convenient, lightweight bags litter beaches, clog city sewers and harm marine life.

We pay nothing for plastic bags at the grocery store, but that doesn’t mean that they have no cost. People don’t purposely litter these bags, but many escape. Sometimes called “toxic tumbleweeds,” these aerodynamic bags enter our waterways through sewers or by air and find their way into Puget Sound.

In 2011, researchers from the University of Washington Tacoma’s Center for Urban Water found some form of plastic pollution in every sample taken from Puget Sound water and beach debris.

In 2012, the plastic bag was the fourth most common item found in the 10 million tons of trash picked up during the annual International Coastal Cleanup sponsored by Ocean Conservancy. Cigarette butts were the first item, followed by food wrappers/containers and plastic beverage bottles. The fifth most common items found were lids and caps.

The Marine Research Foundation estimates that 100,000 marine animals die each year because of plastic litter in the North Pacific Ocean. Plastic often appears like food to marine life. Turtles and whales mistake plastic bags for jellyfish, bottle caps for squid, and small plastic pieces for fish eggs. In West Seattle, a beached gray whale was found with 20 plastic bags in its stomach!

Eventually, this plastic debris finds its way into the Pacific Ocean, where it follows the prevailing currents and either washes up on a beach or ends up in the Great Pacific Garbage Patch floating between California and Hawaii.

Also known as the North Pacific Subtropical Gyre, this area of plastic-filled seawater measures at least twice the size of Texas. Worldwide, there are five ocean gyres (large systems of rotating ocean currents) all accumulating plastic debris.

According to WWF, most plastics do not biodegrade. Unless removed, it can take between 20 and 1000 years for plastic to break down into ever-smaller particles called micro-plastics. These micro-plastics are found everywhere in the oceans including inside plankton, the keystone of the marine food chain.

These micro-plastics act like sponges by accumulating toxins such as DDT and PCB. According to Environment Washington, these toxic concentrations are magnified by ten times at each step of the marine food chain. Puget Sound’s orcas and Chinook salmon are already at risk from PCB.

Many Washington communities have passed a ban on plastic bags with a 5-cent fee on paper bags to encourage people to bring their own reusable, washable shopping bags. Isn’t it time for Kirkland to join this movement?

Vivian Weber, Kirkland