July 29 (Reuters) - Amazon.com ( AMZN ) urged a federal

judge to dismiss a proposed class action over its alleged sale

of rice tainted by arsenic and other "heavy metals," denying the

accusation it fraudulently concealed contamination.

In a filing late on Friday in Seattle federal court, Amazon ( AMZN )

said the presence of heavy metals in rice was a "decades-old,

well-known issue" that was easy to discover, and the plaintiffs

did not claim there were more metals than regulators allowed.

Amazon ( AMZN ) also said Section 230 of the federal Communications

Decency Act shields online platforms from liability over content

from third parties, such as rice sellers.

Lawyers for the plaintiffs did not immediately respond on

Tuesday to requests for comment.

The lawsuit on May 23 covered 18 types of rice sold

through Amazon ( AMZN ), including from brands such as Ben's Original and

Amazon ( AMZN )-owned Whole Foods' 365.

Plaintiffs Ashley Wright and Merriman Blum said they would

not have bought or would have paid less for their Iberia basmati

rice, one of the products, had they known it was contaminated or

Amazon ( AMZN ) never tested it for heavy metals.

Exposure to heavy metals has been associated with nervous

system problems, immune system suppression and kidney damage. It

has also been associated with autism spectrum disorder and

attention deficit hyperactivity disorder in young children.

The lawsuit followed a study by the nonprofit Healthy

Babies, Bright Futures, which found arsenic in all 145 rice

samples purchased nationwide, cadmium in all but one sample, and

lead and mercury in more than one-third of tested samples.

The case is Wright et al v Amazon.com Inc ( AMZN ), U.S. District

Court, Western District of Washington, No. 25-00977.