They are in soaps, cosmetics, shampoos, even toothpaste. Tiny pieces of plastic — most no bigger than a pencil dot — called “microbeads” are designed to do everything from help exfoliate skin to whiten teeth.

But they are pouring by the billions into oceans, rivers and bodies of water like San Francisco Bay, scientists say, contaminating the environment and wildlife as people rinse and wash, sending the microbeads down drains and through sewage treatment plants, which aren’t designed to filter them.

On Monday, state lawmakers in Sacramento are scheduled to vote on the nation’s strictest ban on microbeads, prohibiting them in all personal care products starting Jan. 1, 2020.

“It’s almost like confetti, like small grains of plastic sand,” said Mark Murray, executive director of Californians Against Waste, an environmental group supporting the ban.

“We shouldn’t be adding these plastics to our environment. We’re just pouring them into the oceans.”

The bill, AB 888, by Assemblyman Richard Bloom, D-Santa Monica, is virtually identical to a similar bill that Bloom wrote last year. That measure, AB 1699, passed the California Assembly easily last May, and then died in the state Senate amid industry opposition when Republicans came out broadly against it and Democrats wavered.

This year, the chemical and cosmetics industry has so far kept a lower profile. But lobbyists working with the Personal Care Products Council and the California Manufacturers & Technology Association have been pushing for an exemption to allow biodegradable plastics to remain legal.

Earlier this year, the industry won that loophole when lawmakers in New Jersey and Colorado banned microbeads but allowed biodegradable plastic. The governor of Illinois signed a law last year with the same guidelines.

Lisa Powers, a spokeswoman for the Personal Care Products Council, a Washington, D.C., group that represents companies that manufacture cosmetics, sunscreen, toothpaste and other items, did not respond Sunday when asked for the industry’s position on California’s bill.

Last year, the council opposed the bill, as did the California Chamber of Commerce, Grocery Manufacturers Association and other industry groups.

“Plastic microbeads are used in cosmetic and personal care products because of their safe and effective exfoliating properties,” the Personal Care Products Council said in a statement last summer. “However, many personal care products companies have voluntarily committed to discontinue formulating with plastic microbeads in cleansing products in favor of other viable alternatives despite the uncertainty associated with the science.

“We urge policymakers to work with all sectors of the business community as they seek to eliminate plastic waste in our waterways and to identify effective and realistic solutions.”

Supporters of the California ban say there are already lots of products for sale with natural alternatives, such as apricot shells and cocoa beans, and that they do not want to allow biodegradable plastics. Those plastics simply break into tiny pieces and are not consumed by microorganisms and decomposed as part of the natural food chain, particularly in cold ocean waters, they note. Also, there are no scientific standards in the other state laws to specifically define what “biodegradable” means.

“We are loathe to include an exemption for a plastic product that we can’t define,” said Bloom. “We are hoping that California will model a better approach that can be adopted by other states.”

Tiny bits of plastic have been found in high concentrations in the Great Lakes, the Los Angeles River and the Pacific Ocean where, according to some studies, they outnumber plankton. Scientists say the plastic also absorbs contaminants such as pesticides and PCBs, which then are accumulated in fish when they eat the bits, mistaking them for fish eggs, plankton and other natural materials. People who eat the affected fish also can be exposed to the chemicals.

In January, scientists skimmed the water surface over nine large areas of San Francisco Bay. They found between 14,000 and 440,000 plastic particles, including microbeads, per square kilometer — an area of about 250 football fields, said Rebecca Sutton, a senior scientist with the San Francisco Estuary Institute, a research organization based in Richmond.

“It’s a persistent substance, and organisms like fish are trying to ingest it,” Sutton said. “And you’ve got chemical contaminant issues. This is a preventable type of pollution, and it’s certainly not something we could encourage to have in the bay.”

Supporters of the bill include the California Association of Sanitation Agencies, Sierra Club California, the cities of Palo Alto and San Francisco, the East Bay Municipal Utility District, Breast Cancer Fund and the Surfrider Foundation.

Last August, Crest announced that although microbeads have been found safe by the FDA, the company would be phasing them out of its toothpastes by March, 2016. Responding to consumer concerns, Johnson & Johnson also said it will be removing microbeads from its products by 2017.

Bloom said consumers who don’t want to buy products containing microbeads should look on the labels for ingredients like polyethylene and polypropylene.

“It’s exactly like food,” he said. “We have to be more conscientious about reading labels. These products are listed. The more educated people are about what’s in their products, the healthier we will be.”

Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN.