“By pairing the ‘Microwave Safe’ and ‘Freezer’ labels on product packaging, SC Johnson implies that this practice is safe,” the suit alleges.

A California woman initiated a class action lawsuit against SC Johnson in May, claiming that the company did not disclose the potential risks of microplastic leaching in its Ziploc brand plastic storage containers and bags. The suit alleges that SC Johnson made a “material omission” when it neglected to notify consumers that its products contain polyethylene and polypropylene, which have been shown to transfer microplastics into food.

In the civil complaint, the plaintiff claims that SC Johnson’s “Microwave Safe” and “Freezer” labels on its storage products mislead consumers to think that it’s safe to freeze and reheat food inside their containers. The lawsuit cites research showing that freezing or reheating food stored in polyethylene and polypropylene containers can accelerate microplastic leaching.

Furthermore, reheating food that has been previously frozen can worsen the “vulnerability to microwaving due to the weakened structure caused by freezing,” according to the suit. By pairing the “Microwave Safe” and “Freezer” labels on product packaging, SC Johnson implies that this practice is safe, the suit alleges.

Though the SC Johnson includes extensive instructions in its packaging on how to safely reheat foods in its Ziploc containers, these contain no warnings about the risks posed by heating the containers themselves. When exposed to high temperatures, polypropylene products can release microplastics at rates up to 16.2 million particles per liter, according to one study on plastic baby bottles.

Responding to the suit, a spokesperson for SC Johnson called the claims “without merit” and stated: “Plastic is in the food we eat, the water we drink, and the air we breathe, and it comes from many sources. That’s why we are strong advocates for plastic regulation, supporting a global plastics treaty, and sharing the latest scientific research.”

However, the plaintiff in this case is not alleging a specific harm caused by SC Johnson’s product, which would be difficult to prove, given the multiple sources of microplastics in the environment. Following the lead of other high-profile “forever chemical” and microplastics class actions, the plaintiff is only contending that SC Johnson failed to warn consumers about potential harms, a more straightforward claim.