Microplastics are defined as smaller than 5 milimeters in diameter. But these tiny particles accumulate in the sea, can enter the food chain, and are even found in the air. Personal care products containing microplastics, such as toothpaste, represent one of the most common intentional uses of microplastics in our daily lives.

Some cosmetic products can contain as much plastic added as the amount of plastic in which they are packaged, experts indicate. Exfoliating daily washes very often use of microplastics, often termed "micro-beads," which then get flushed into the household wastewater stream.

Via wastewater, microplastics reach the oceans, where they move enter the food chain through feeding zooplankton. In 2017, researchers found that 25 percent of marine fish tested in markets in Indonesia and California had plastic and textile fibers in their guts. Research is still lacking as to whether consuming microplastics through fish harms humans.

Several studies published in 2017 showed that microplastics have also been found in sea salt from the United States, Europe and China. It's not surprising, considering how plastic debris represent between 60 to 80 percent of the total marine waste, and that up to 12 million tons of plastic waste ends up in the ocean every year.

Beside microplastics in seafood like fish, shrimp and mussels, scientists point to other foods, such as honey. In the recently adopted European Union plastics strategy, honey was mentioned as one of the food products containing microplastics — to motivate a push toward a ban.

Aside from micro-beads in hygiene products, synthetic textiles also release a vast amount of tiny plastic fibers into wastewater. Researchers found that a typical 6-kilogram (13-pound) washing load of acrylic-fabric items (like fluffy blankets) generates more than 700,000 individual fibers. Synthetic fabrics account for around a third of ocean microplastics.

Vehicles tires are also a main source releasing microplastics into the environment. Tires are made of synthetic polymers mixed with rubber, which grinds down when used. This generates microplastics that are either blown around by the wind or washed away by rain. Norwegian and Swedish researchers agree that a large proporation of particles found in the sea come from car tires.

Microplastics have also been found in tap water. In an analysis of tap water samples from countries around the world, more than 80 percent were contaminated with some amount of plastic fibers. If synthetic fibers are in tap water, they are also likely to be in a number of other basic foodstuffs, like bread.

And yes, if tap water contains microplastics, beer could very well also be contaminated. A 2014 study found plastic particles in a total of 24 German beers - but variability in the results was high, and further research would needed for verification, the German Environment Agency has pointed out. In any case, cheers for now.