Mill Valley, a town of nearly 15,000 four miles north of the Golden Gate Bridge in San Francisco, approved a ban on Aug. 3 that will go into effect Nov. 2.

The city becomes the 24th California town to ban the use of PS take-out food packaging. There also is one county-wide ban in Santa Cruz, and Marin County is expected to enact a county-wide PS ban later this year.

In addition, four California cities and one California county prohibit the use of PS packaging at municipal facilities.

The Mill Valley ban applies to containers, bowls, plates, trays, cartons, cups, forks, knives, spoons, straws, lids, bags, sacks, wrappings and other items designed for one-time use to transport or store prepared or takeout food.

It applies to all restaurants and retail food vendors and also applies to packaging for food that is left over from partially consumed meals prepared at restaurants or any other retail food vendor.

The new law also encourages city facilities and organizations or individuals renting city facilities to use durable food service items. If that is not a feasible option, such groups or individuals are “required to use biodegradable disposable food packaging” rather than non-biodegradable disposable food packaging, unless the biodegradable option costs 15 percent more than the non-biodegradable option.

Mill Valley defined biodegradable disposable food packaging as uncoated paper and cardboard, paper and cardboard that meet ASTM International standards for biodegradable coatings and liners, and bioplastics that meet ASTM standards for bioplastics.

The law also said that any bioplastics should be “clearly labeled, preferably with a color symbol” so people who collect and process bioplastics “can easily distinguish the ASTM standard compostable bioplastic from non-degradable plastic.”

Polystyrene ice chests and coolers were excluded from the ban.

Fewer than 5 percent of the cities in California have bans on PS take-out packaging and most of them are coastal communities.