At a Glance

Boston's ban on plastic carryout bags took effect Friday.For now, it applies only to stores that are 20,000 square feet or larger.About 350 cities, counties and states have banned or taxed plastic bag use.

Boston has joined the growing list of cities that have banned single-use plastic bags.

Boston's ban took effect Friday for stores that are 20,000 square feet or larger. The ban only applies to "checkout bags," the , according to the city's website.

Retailers can still offer three types of bags: recyclable paper bags, compostable plastic bags or reusable bags. However, they must charge at least 5 cents for each bag.

The rules will apply to shops that are 10,000 square feet or more beginning in April 2018. By next summer, all stores in the city will need to comply with the rules.

Nearly 350 cities, counties and states have , according to Forbes.

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Shoppers in Boston are being encouraged to bring their own reusable bags, and some stores Boston.com reported.

The Boston City Council overwhelmingly approved the ban in November 2017. The have "significant adverse impacts on the environment and their light weight makes them particularly susceptible to air currents that land them in the streets, gutters, abandoned lots and trees throughout the city."

Another problem with plastic bags is that they don't decompose. They degrade into smaller particles. Scientists estimate that there are 5.25 trillion particles of plastic — weighing 269,000 tons — according to 5Gyres.

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California voters approved a statewide ban on single-use plastic bags in 2016. Hawaii's most populous counties have banned non-biodegradable plastic bags at checkout, creating according to the National Conference of State Legislatures.

Among the cities that have banned them are Seattle, Los Angeles and Austin, Texas. Washington D.C. and New York City implemented bag fees.

Chicago enacted a ban but dumped it after retailers began offering slightly according to the Sun-Times. The city replaced the ban with a 7-cent fee on all carryout bags.

At least 10 states have approved legislation that prevents local governments from enacting bans or fees on plastics.

The plastics industry and some grocers argue that if plastic bags are banned, shoppers will just use more paper, which could be worse for the environment.