Here is a list of things that are thicker than a typical plastic grocery bag: A strand of hair. A coat of paint. A human cornea.

High-density polyethylene is a miracle of materials science. Despite weighing less than 5 grams, one bag can hold 17 pounds, well over 1,000 times its own weight. At about a penny apiece, the bags are cheap enough for stores to give away and sturdy enough to carry home two gallons of milk in the evening and still be up to the task of scooping Cujo's poop the next morning.

Yet almost as soon as grocers started offering their customers the choice of "paper or plastic?" these modern marvels became a whipping boy for environmentalists, politicians, and other well-intentioned, ill-informed busybodies. Plastic bags for retail purchases are banned or taxed in more than 200 municipalities and a dozen countries, from San Francisco to South Africa, Bellingham to Bangladesh. Each region serves up its own custom blend of alarmist rhetoric; coastal areas blame the wispy totes for everything from asphyxiated sea turtles to melting glaciers, while inland banners decry the bags' role in urban landscape pollution and thoughtless consumerism.

But a closer look at the facts and figures reveals shaky science and the uncritical repetition of improbable statistics tossed about to shore up the case for a mostly aesthetic, symbolic act of conservation.

How did one of the most efficient, resource-saving inventions of the 20th century become an environmentalist bugaboo?

Research

Before 1800, if you bought or traded for an object, you were pretty much on your own to get it home. People carried baskets for the little stuff and wheeled carts for the bigger items, often toting scraps of canvas or other durable fabric to wrap messier or more fragile goods, such as meat or pastries. This was back when the germ theory of disease was yet to be broadly accepted, and there were not yet Laundromats on every street corner.

In the early 19th century, paper became cheap enough that merchants started using it to package their wares, tying off the bundles with string—a huge leap for both convenience and sanitation. The paper bag was invented in the 1850s, but it wasn't until the 1870s that a factory girl named Margaret Knight cobbled together a machine that cut, folded, and glued flat-bottomed paper receptacles. While the brown paper bag seems like the height of humdrum to modern eyes, Knight's machine was kind of a big deal: She won a bitter intellectual property fight to receive one of the first patents ever awarded to a woman, and was eventually decorated by Queen Victoria for her efforts. Over time, the paper bag got cheaper and stronger and sprouted handles, but it remained essentially unchanged, comfortably dominating the stuff-schlepping market for the next 100 years.

Meanwhile, German chemist Hans von Pechmann was messing around with methane and ether in a lab in 1898 when he happened to notice a waxy precipitate called polymethylene. Unfortunately, no one could puzzle out what to do with the goo, so another 30 years would pass before DuPont chemists stumbled upon a similar compound, polyethylene. This time, the British figured out they could use it to insulate radar cables, which is where the substance served its war duty. In 1953, Karl Ziegler of the Kaiser Wilhelm Institute (later re-christened the Max Planck Institute, for obvious reasons) and Erhard Holzkamp invented high-density polyethylene (HDPE) and soon after figured out how to use it to make pipes. Ziegler even snagged a Nobel Prize for the invention in 1963.

But Gustaf Thulin Sten is the real hero (or villain, depending on your point of view) of our tale. An employee of the Swedish company Celloplast, Sten was the person who had the inspiration to punch holes into the side of super-thin tubes of HDPE, thus creating the ubiquitous, filmy "T-shirt bags" we know and love (to ban) today.

In a 1993 book that claims to reveal the "hidden life of groceries and other secrets of the supermarket," journalist Vince Staten pinpoints the moment that the global takeover of the plastic bag became inevitable: a 1985 gathering of the New Materials and Profits in Grocery Sacks and Coextrusions Conference at a Holiday Inn in Somerset, New Jersey, at which a representative from Chem Systems announced that plastic bags were 11.5 percent cheaper than paper. Just like that, the world changed. Plastic bags were stocked in 10 percent of grocery stores in 1983, according to Plastics World magazine. By 1985 it was 75 percent. "Paper or plastic?" immediately became an everyday question, a punchline, and a source of angst.

Almost from the beginning, plastic bags were controversial. After several high-profile suffocation deaths of children, manufacturers worked together to create a public safety campaign, staving off regulation and reducing accidents. As grocers substituted plastic for paper to bolster their bottom lines, suburban shoppers, who preferred to line up flat-bottomed paper bags in the backs of their cars, complained, even as urban shoppers rejoiced at the ability to comfortably and reliably carry more than two bags at a time.

The booming environmental movement was initially flummoxed. Forest conservation was a big deal in the '80s, a point in favor of plastic. But fossil fuels were a no-no, so maybe paper was better? Both types of bags at the time were tough to recycle. The debate raged on, leaving eco-conscious shoppers unclear about the best course of action.

Reduce

In 2010, Guinness World Records named plastic bags the most ubiquitous consumer item in the world. But peak bag may already be upon us.

In 2007, San Francisco became the first U.S. city to prohibit plastic bags, citing concerns about water pollution and waste disposal. Chicago, Austin, Portland, and nearly all of Hawaii soon followed suit, chiming in with complaints about wastefulness, climate change, and more. Chinese officials banned plastic bags two months before hosting the 2008 Olympics, for the same reason they banned high-emissions vehicles and daytime pajama-wearing-such unsightly displays didn't match up with the image the People's Republic wanted to present to the world. In China, they call the floating sacks "white pollution." South Africans refer to bags snagged in bushes as their "national flower."

In Washington, D.C., concern about used plastic bags finding their way down storm drains, through the Anacostia River, and into the Chesapeake Bay was the primary justification for the capital city's 5-cent bag tax in 2010, under the slogan "Skip the Bag, Save the River." In 2006, the California Coastal Commission claimed that plastic bags make up 3.8 percent of beach litter, and a few years later the California Ocean Protection Council upped the ante to 8 percent of all coastal trash. Last year the Dallas City Council pinned 5 percent of the area's refuse on bags.

But the definitive American litter study—yep, such a thing exists—reports much lower figures. The 2009 Keep America Beautiful Survey, run by Steven Stein of Environmental Resources Planning, shows that all plastic bags, of which plastic retail bags are only a subset, are just 0.6 percent of visible litter nationwide. And those California data? They come from the International Coastal Commission (ICC), which the California Coastal Commission notes relies on information "collected by volunteers on one day each year, and is not a scientific assessment." (This insight, and many others in this story, is derived from a study produced last year by Julian Morris and Brian Seasholes for Reason Foundation, the nonprofit that publishes reason.) In D.C., a 2008 analysis prepared for the city's Department of the Environment by the Anacostia Watershed Society found that plastic bags were only the third-largest contributor to litter in the river, after food wrappers and bottles and cans.

Stein's study did find plastic bags in storm drains, but again, they made up only about 1 percent of the total litter.

Some plastic bags do find their way into the sea, of course. And one of the other concerns cited for the banning and regulation of plastic grocery bags is the safety of marine wildlife. The Blue Ocean Society for Marine Conservation is just one organization among many that claim that more than 1 million birds and 100,000 marine mammals and sea turtles die each year from eating or getting entangled in plastic.

Morris and Seasholes reconstructed an elaborate game of statistical telephone to source this figure back to a study funded by the Canadian government that tracked loss of marine animals in Newfoundland as a result of incidental catch and entanglement in fishing gear from 1981 to 1984. Importantly, this three-decade-old study had nothing to do with plastic bags at all.

Porpoises and sea turtles are undeniably charismatic megafauna—the pandas of the deep—and it's understandable that environmental groups would want to parade them around in a bid to drum up sympathy, almost certainly driven by the sincere belief that plastics put the beloved animals at grave risk. But in the end, there's little evidence that that's true. As David Santillo, a senior biologist with Greenpeace, told The Times of London, "It's very unlikely that many animals are killed by plastic bags. The evidence shows just the opposite. We are not going to solve the problem of waste by focusing on plastic bags. With larger mammals it's fishing gear that's the big problem. On a global basis plastic bags aren't an issue."

Reuse

But what about larger-scale impacts, such as climate change? Where do grocery bags stack up there? A 2011 study from the U.K.'s Environmental Agency attempted to quantify the emissions footprint both of plastic bags and of their substitutes. Holding the typical HDPE grocery bag up as the standard, researchers found that the common reusable non-woven polypropylene bag—the ubiquitous crinkly plastic tote, typically made with oil—had to be used at least 11 times to hold its own against an HDPE grocery bag. Cotton bags had to be used an amazing 131 times to do the same.

In 2007, for a brief moment, the "It bag" wasn't a $30,000 Hermes Birkin, it was a cotton tote designed by Anya Hindmarch that read: "I'm NOT A Plastic bag." Celebrities from Ivanka Trump to Keira Knightly were snapped toting the sold-out satchels for glossies like Life&Style and Grazia. While we can never know for sure, it seems wildly unlikely that Ivanka Trump has carried 131 loads of groceries in her life, much less in that particular bag.

What's more, those U.K. Environmental Agency figures assume the HDPE bag is not being reused. Nor do they account for the energy and materials needed to regularly wash the reusable bags in hot soapy water. Other alternatives did perform somewhat better in the global-warming matchup, including paper bags (which would have to be reused three times to match the single-use HDPE bag's footprint) and another type of reusable bag made of low-density polyethylene (four times).

About 65 percent of Americans report that they repurpose their grocery bags for garbage. By contrast, a survey by the marketing research firm Edelman Berland found that consumers reported forgetting their reusable bags on 40 percent of grocery trips and opted for plastic or paper instead. Prior to the movement to ban plastic bags, many American homes had a nook, cranny, or drawer that functioned as a kind of grocery-sack clown car. It seemed that whatever the size of the container, an infinite number of bags could be stuffed inside. My family called it the bag o' bags. As in: "Katherine! This mold experiment has gone on long enough! Go get me a bag from the bag o' bags so that I can throw it away," or "Karina, you better remember to get a bag from the bag o' bags for that wet swimsuit, unless you want the books in your backpack to get wet." If we wound up with an unmanageable surplus, we could just drop the bags at the recycling centers that used to sit in the parking lots of most suburban grocery stores.

Then there are the frequently unmeasured consumption consequences of the bans themselves. For example, in San Francisco, after the grocery/retail plastic bag ban went into effect in 2007, depriving customers of a source of free bags, sales of still legal, low-density polyethylene plastic bags shot up 400 percent.

Recycle

"It takes 12 million barrels of oil to produce the 100 billion plastic bags that are thrown away in the U.S. every year." Versions of this claim show up everywhere from New York Times editorials to Save the Bay pamphlets. But the origins of the figures are murky and the dramatic tone is misleading. Even if the number is accurate, it is almost a literal drop in the bucket: Americans consume a total of about 19 million barrels of oil a day. But as Morris and Seasholes point out, all that fretting about oil use "is surprising, not least because nearly all HDPE bags are produced from natural gas, not oil. Indeed, between 1981 and 2012, on average only 3.2% of polyethylene bags were made from oil. The reason is simple: it is far less expensive to produce ethylene, the feedstock for polyethylene, from natural gas (methane) than from oil." While the price of oil has recently declined, the assumption that plastic bags are made primarily from oil remains false.

In 2010, according to the U.S. Environmental Protection Agency, Americans threw away 690,000 tons of HDPE bags. Of those, approximately 30,000 tons were recycled. That means a total of 660,000 tons were discarded, mostly into landfills (approximately 82 percent of non-recovered municipal solid waste goes to landfill; 18 percent is incinerated). That same year, Americans also chucked almost exactly the same amount of "reusable" polypropylene bags (680,000 tons), of which zero were recovered. In other words, those polypropylene reusable bags actually constituted a slightly higher proportion of all bags going to landfills.

In April, NPR's Planet Money reported on the economics of plastic recycling, and noted that while recycled plastic from bags and sacks was once a profitable industry, times have changed. The prices of oil and gas have fallen, which means it is cheaper to just make new bags rather than undertake the laborious process of recycling the old ones. As Tom Outerbridge, who runs a Brooklyn recycling center called Sims, explained, "We can't afford to put a lot of time and money into trying to recycle it" if no one's buying the final product.

Reject

In March, The Washington Post reported on the surprising strength of the plastic bag industry in the face of regulatory onslaught.

In 2008, officials in the deep blue city of Seattle voted to impose a 20-cent fee on both plastic and paper single- use bags. "There's a competitive side to seeing who can come up with the most progressive legislation," city councilman and former local Sierra Club leader Mike O'Brien told The New York Times. But industry rallied before the implementation date, spending $1.4 million on a citywide ballot measure to repeal the fee. The referendum campaign was a success; Seattle voters rejected the surcharge, which would have been the most punitive in the nation, in 2009. Still, three years later, Seattle became the fourth city in Washington State to approve an outright plastic- bag ban, along with a 5-cent fee on paper bags.

In Dallas, a coalition of plastic bag manufacturers are challenging a 5-cent markup that the city has imposed on single-use bags. Hilex Poly (now Novolex), Superbag Operating, the Inteplast Group, and Advance Polybag argue that the fee is illegal under an obscure Dallas law that states: "A local government or other political subdivision may not adopt an ordinance, rule or regulation to: prohibit or restrict, for solid waste management purposes, the sale or use of a container or package in a manner not authorized by state law; [or] assess a fee or deposit on the sale or use of a container or package."

In Georgia, the state Senate got a little meta, passing a ban on bag bans last session, which would have pre-emptively prevented restrictions. While the bill failed in the House, it may prove to be a model for other state pre-emptions around the country.

Ground Zero of the plastic wars, unsurprisingly, is California. Last year, Democratic Gov. Jerry Brown signed a statewide ban against plastic grocery bags that was scheduled to take effect this July 1. But the implementation has been stalled, thanks to 800,000 signatories to a petition circulated by the American Progressive Bag Alliance, a new group funded by plastics manufacturers. Voters will now have to ratify the ban on their 2016 ballots for it to go into effect. "This is a cynical ploy by out-of-state interests desperate to delay a ban already adopted in more than 100 communities across California," a spokesperson for Brown told the Associated Press.

Of course, if there's some banning going on, you can always rely on Congress to muscle in on the action. Rep. James P. Moran (D–Va.) has repeatedly introduced a bill to create a national 5-cent tax on all disposable plastic or paper bags supplied by stores to customers. The bill typically dies quietly in committee, but perhaps Moran was hoping that, as Gandhi famously didn't say: "First they ignore you, then they laugh at you, then they attack you, then you win."

Regurgitate

As I write this, a load of reusable grocery bags is tumbling around in my dryer. In the course of researching this article, I got so thoroughly grossed out by the malevolent horror lurking in my pantry that I had to stop writing and start washing.

I may love plastic bags, but I'm not immune to cultural and economic pressure, so when I remember to, I tote my reusable bags to the store like a good little yuppie. But this ostensibly modern act brings me back to conditions a little too reminiscent of the sub-hygienic reality faced by my great-great-grandmother, with her blood-and-crumb-covered reusable canvas wrapper.

If you're like most people, here's what you have probably done at least once: Put a leaky package of chicken in your cloth or plastic tote. Then go home, empty the bag, crumple it up, and toss it in the trunk of your car to fester. A week later, you go shopping again and throw some veggies you're planning to eat raw into the same bag. Cue diarrhea.

A 2011 survey published in the journal Food Protection Trends found coliform bacteria in fully half of the reusable shopping bags tested in a random survey of shoppers in Arizona and California. The same 2014 Edelman Berland study that found consumers frequently forgot their bags also unearthed the fact that only 18 percent of shoppers reported cleaning their bags "once a week or more." An article in the Journal of Infectious Diseases traced a 2010 outbreak of norovirus to nine members of an Oregon soccer team who had touched or eaten food stored in a contaminated reusable bag.

Your cute reusable tote decorated with whimsical watercolors of eggplants may actually be causing those stomach cramps.

Reconsider

Set your mind back to 1999, before our current wave of bag crackdowns, but well after the "plastic" answer to "paper or plastic?" began giving environmentalists the tremors. In that year's Oscar-winning American Beauty, an ambitious young filmmaker within the dull confines of suburbia captures an iconic image of a plastic sack—that product of banal late-capitalist excess—twirling artistically in the wind. "And this bag was just dancing with me," he says dreamily. "Like a little kid begging me to play with it. For 15 minutes. That's the day I realized that there was this entire life behind things, and this incredibly benevolent force that wanted me to know there was no reason to be afraid, ever."

Though it was meant as irony, there was an essential (if accidental) truth behind the speech. The technology behind plastic grocery bags is so useful it won a Nobel Prize. Employing an unimaginably small amount of base material, manufacturers can create tools of surprising strength and durability. Far from being the environmental threat activists make them out to be, plastic bags are not particularly to blame for clogged sewers, choked rivers, asphyxiated sea animals, or global warming. Instead, they are likely our best bet for carrying all of our junk in a responsible manner.

Don't believe the haters. Plastic bags are good for you.