San Francisco took a big step toward protecting marine ecosystems Tuesday, as the city’s Board of Supervisors passed legislation to ban Styrofoam products in food packaging.

The ban, which will mostly go into effect on Jan. 1, prohibits the product in packaging like ice chests, packing peanuts, food trays and dock floats, according to the San Francisco Chronicle.

Styrofoam, technically known as polystyrene foam, is a widely used, inexpensive resource for the packing industry, but it is also very harmful in marine ecosystems. It does not naturally decompose, so it can disrupt the food chain, stay in the ocean or clog up landfills for centuries.

More than 100 cities nationwide have some form of law in place restricting polystyrene use, including Washington D.C., but San Francisco’s ban is touted as the toughest anti-Styrofoam law yet.

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