Foodland Supermarket spokeswoman Sheryl Toda has noted this effect of Oahu’s year-old ban on plastic bags: Customers are getting more exercise by doing an about-face and returning to the car to fetch the reusable totes they routinely forget.

“Many of our customers have developed the habit,” said Toda, “but I’ve seen some walk toward the store, look at our banner that says, ‘Got bags?’ and turn around and get it.”

Oahu became the final of Hawaii’s four counties to adopt varying forms of the ban, so Foodland already had been on the learning curve for a while. Its approach has been to sell reusable bags at 99 cents and $1.99, and credit shoppers with a nickel or frequent-flyer miles for each bag they supply themselves.

But this store chain does offer paper bags for free, joining the majority of the island’s businesses that issue single-use bags on demand — paper or the permitted thicker plastic.

The results of the ordinance, which the Honolulu City Council passed in 2012, are a bit ambiguous, with uncertainty over how much habits are changing and over whether plastic-bag waste is being reduced. As a result, groups advocating for a more complete ban are preparing to fight for amendments to close loopholes.

Figures compiled by the city indicate overall compliance. In March, the city Department of Environmental Services sent out some 9,500 data-seeking packets to retailers, and about 6,500 were returned. Department spokesman Markus Owens released the rounded tallies he said were issued by the refuse division.

Among the results:

>> Nearly one-quarter of those replying claim an exemption from the ban.

>> Of the roughly 2,600 that provide bags for customers, the largest sector, 38.5 percent, offer a combination of what’s allowed — paper, reusable and compostable bags.

>> About 1,125 businesses have been inspected for compliance, including major stores and farmers markets; non-compliance warning letters have been issued to a few, Owens said.

But regarding the environmental impacts of the law, evidence of lessening litter or other damaging effects of the filmy plastic bags is entirely anecdotal. Nobody knows whether there’s an appreciable change in the consumption of plastic.

Lori Kahikina, department director, said that though concrete data is lacking, various contacts in the community do report a reduction in litter.

“I’ve not seen the bags in the first place at the beach,” Kahikina said, “I didn’t realize it was such a problem. But I have heard some positive feedback.”

Environmental groups, however, are drawing the conclusion that any substitution of thicker plastic for thinner, and replacing plastic with substantial amounts of paper bags represents only a weak improvement.

Stuart Coleman, executive director of the Surfrider Foundation and one of the principal champions of the bag ban, said the current ordinance is “going against the whole spirit of the law.”

He and other activists in what’s been dubbed the Rise Above Plastics Coalition are going back to Honolulu Hale and hope to see a bill within months begin to move through City Council. Kahikina and others in the city administration said they would not oppose any amendment that emerges.

Coleman said he would favor allowing retailers to issue single-use paper bags and charge a fee. But the main intent of legislation being drafted would be to eliminate the thicker plastic that’s now an option for single-use bags given to customers.

Plastic bags of 2.25 mils in thickness were included in the definition of reusable bags; a mil is .001-inch thick.

Allowing that compromise was a mistake, said Kahi Pacarro, executive director of the nonprofit Sustainable Coastlines Hawaii.

Many store managers understood the mission to reduce fossil fuels used in the production of plastic, and the risk of bags being swept to sea and entangling marine life, Pacarro said.

“Sadly, some locally owned stores did not, and decided to circumvent the intent of the law by making thicker bags,” he said in an email response to the Honolulu Star-Advertiser. “We, along with many community members, are dismayed at the disregard to our aina and have vowed to do what we can to eliminate the continual use of these thicker, more dangerous plastic bags.”

Despite the limitations, Coleman said, Hawaii does have the distinction of being the first state that now has all counties on board with some kind of plastic bag ban.

California was actually the first to enact a statewide ban, in 2014, but that law was challenged by the plastics industry and bag manufacturers and put on hold until a referendum could take place. That will be on the ballot in November (see story above for a summary of how the ban-the-bag campaign is faring elsewhere).

There have been unintended consequences here, with reports from some retailers that some customers use their personal bags as a means for shoplifting items from the store.

Lauren Zirbel, executive director of the Hawaii Food Industry Association, confirmed that this goes on, adding that employing security to guard against this theft is generally more costly than the amount that’s lost.

She also cited reports of some shoppers reusing stained totes, causing a sanitation problem.

“That might be surprising to some people,” she said. “People are putting meat and fish in the reusable bag, and they’re not washing them and bringing them back to the store, causing their food to be contaminated.”

Zirbel is one of many in the retail industry who would prefer that a fee be charged for any bags supplied by the store. This would encourage shoppers to bring their own carriers, she said. It also would cover the store’s bills for providing the bags, Zirbel added, a cost now passed on to all customers in the form of higher merchandise prices.

Adrian Hong agrees with that. The president of Island Plastic Bags believes the change that’s needed is to allow stores to offer what bags they prefer, but to allow them to charge a fee. This has the effect of reducing the demand for single-use bags without curtailing customer — or retailer — choice about meeting that demand.

Relying wholly on reusable bags would be an error for any store doing business in the visitor industry, Hong said.

“Stores are afraid to do away with single-use bags, because they’re afraid to lose customers,” he said. “And the No. 1 industry is tourism, and you don’t pack your reusable bag with your swim trunks.”

Further, he said, a statewide plastic-bag ban seems likely to pass in California, a referendum proposal that would require any paper bags that are issued to be made of 40 percent recycled paper.

The demand from such a populous state for that paper, which is in limited supply, will drive up the cost of paper bags for Hawaii retailers, too, Hong said. He underscored this as a reason why store owners should have the choice.

Supporters of the ban can feel some hope that customers are catching on to the more environmentally friendly rules. Toda said that Foodland is now issuing almost three times as many rewards to customers for bringing in their own bags than was the case when the ordinance first took effect.

Ultimately, Coleman added, this movement delivers a win all around — to shop, shopper and Mother Nature. That argument helped sell the compromise measure to the industry to begin with, he said.

“We told them, ‘What would you rather see your logo on: a plastic bag on the side of the road, or in a ditch, or floating and ending up in the ocean; or a reusable bag people are taking to other stores, and to picnic?’” he recalled. “And they said, ‘Oh, yeah, this is about branding.’”