It’s all a question of balance. Defenders of the conventional plastic bags given out by retailers say the bags are a convenience for shoppers, especially those walking for some distance with their purchases. And the bags are often saved for other household uses.

But most of them are not used again, as evidenced by the recycling bins supermarkets have posted by their entrances. For every one that makes it into one of these bins, many more proliferate in dumpsters and dumps, or — worse — flutter about, sometimes ending up as threats to marine life when they land offshore.

So on balance, the ubiquitous throw-away plastic bag is a bad bargain, especially for any community that’s bounded on all sides by the ocean. Honolulu, which has a particular need to reduce the amount of this kind of litter, should proceed with the scheduled July 2015 implementation of its own ban on the items.

Honolulu City Councilman Breene Harimoto is seeking a needed refinement to the ordinance the Council passed back in 2012. Bill 38, introduced last week, would eliminate the exemption for "biodegradable" plastic bags — a good idea.

According to the bill’s statement of purpose, "recent studies indicate all types of plastic bags, regardless of the feedstock from which they are derived, may adversely affect the environment," decomposing into fragments of plastic that may harm insects, fish and animals that consume them.

In addition, the legislation notes that there is no reliable standard for what qualifies as a "biodegradable" bag, making enforcement of this provision impossible.

Hawaii’s other counties already have bans in effect, and they make no distinction between biodegradable or ordinary plastic bags (or "compostable," the term used in the Maui ordinance). Honolulu’s law should align with those across the state.

One element in Harimoto’s bill that should be amended: the six-month extension before implementation, which is not necessary. Harimoto said he "wrestled" with the extension idea but wanted to eliminate at least one argument in opposition: Retailers might have ordered biodegradable bags and this would allow them time to use their stock.

The fact is, Honolulu has waited long enough already, and retailers have more than a year to use any supplies they might have purchased.

Advocates for the plastic bag have pushed back against what is now a national trend toward bans, typically enacted at the municipal level. For example, the industry has argued that the cloth bags are often manufactured overseas, requiring more energy to transport than the largely domestically produced plastic bags.

In Hawaii, at least, this argument falls short. Everything — the reusable totes as well as the plastic bags — is an import. The concern about protecting the marine environment from fly-away plastic bags resonates much more strongly.

Other local governments have enacted the bans, and the reduction in the waste stream has been documented. In San Jose, Calif., for example, officials have conducted litter surveys following its 2012 ban and found a reduction of bag litter, down about 89 percent in the storm drain system, 60 percent in creeks and rivers, and almost that much in city streets and neighborhoods. Similar results have been registered in other cities.

Bag bans do work. It’s time to get started with Honolulu’s own initiative.