The oceans and rivers are so polluted with tiny bits of plastic that eating fish might pose a growing health risk, researchers warn.

The known hazards of heavy metals and chemicals in fish already well known, including mercury, cadmium, and lead. But now there is a new reason to reconsider your fish intake: microplastics, which can bring exposure to Bisphenol-A (BPA) and phthalates.  

Researchers say some 8 million tons of plastic are dumped into the oceans annually. One research paper published in June found the average American now ingests a staggering 74,000 microplastic particles annually. 

Scientists are only just beginning to study the impact of microplastics on human health. It is still not clear, for example, whether plastic ingestion poses an additional cancer risk in humans. 

Many seafood lovers had assumed that after gutting, filleting, and cooking, fish would be safe. But Dr. Michael Greger of NutritionFacts.org cites a March 2017 study of fish caught in the Persian Gulf that concluded otherwise. 

The problem seems to be microplastics do not stay the gut of a fish, and leak out into surrounding tissue. The same effect has been found in animals. 

The study reported: "Microplastics with a wide variety of colors, shapes, and sizes were detected in all investigated fish muscle samples."

One reason microplastics in fish are a special concern: Chemical and metal concentrations in fish tend to increase as contaminants travel up the food chain from small fish like herring to apex predators such as swordfish or tuna.

Greger states plastic pollution in waterways might pose a threat to human health.

"It's evident we're exposed to microplastic pollutants in seafood, which may create a food safety risk," he writes.

So, what does it matter if people routinely ingest minuscule particles of plastic in fish? So far, no one is sure. But with about 8 million metric tons of plastic being dumped into the ocean every year, nobody thinks it is good.

Some researchers, noting the worldwide increase in tumors in wildlife, and even speculate environmental plastics might be the cause.

"The particles may release absorbed pollutants like PCBs," Greger said, "and also release plastics chemical additives like BPA, which collectively may cause hormone disruption, cancer risk, and DNA damage."

The FDA has not yet established acceptable levels of ingestion of microplastics.

Perhaps the most worrisome fact to keep in mind going forward, according to Consumer Reports, is "plastic production is expected to more than quadruple between 2015 and 2050, which means the amount of plastic contamination in the environment will rise along with it."

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