Amazon.com was sued on Friday by consumers over its alleged sale of a wide variety of rice contaminated by arsenic and other "heavy metals".

The proposed class action in Seattle federal court covers 18 types of rice sold through Amazon, including from familiar brands such as Ben's Original and Amazon-owned Whole Foods' 365.

"Amazon sold these rice products with alarmingly high levels of heavy metals to an intended consumer audience that includes children, with no warning whatsoever about the dangers of heavy metals," the complaint said.

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The lawsuit followed a study last week by Healthy Babies, Bright Futures, a nonprofit that focuses on babies' exposure to toxic chemicals.

That study found arsenic in all 145 rice samples purchased nationwide, with 28 percent exceeding a US Food and Drug Administration limit for infant rice cereal.

It also found cadmium in all but one sample, and lead and mercury in more than one-third of tested samples.

Amazon, based in Seattle, had no immediate comment.

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Exposure to heavy metals has been associated with negative health effects such as nervous system problems, immune system suppression and kidney damage, and autism spectrum disorder and attention deficit hyperactivity disorder in young children.

The 18 rice products include two from Ben's Original and three with the 365 label.

Plaintiffs Ashley Wright and Merriman Blum said they would not have bought or would have paid less for Iberia Basmati 100 percent Aged Original rice, one of the products, if they knew the rice was contaminated or Amazon never tested it for heavy metals.

Friday's lawsuit seeks unspecified damages of at least $5 million for Amazon's alleged violations of Washington state consumer protection laws.

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Makers of baby food and dark chocolate have also faced many consumer lawsuits over the alleged presence of heavy metals.

The case is Wright et al v Amazon.com Inc, U.S. District Court, Western District of Washington, No. 25-00977.