New research discovers high levels of caffeine in surprising areas of ocean, rivers

All that coffee you drink has to go somewhere, and once it leaves your toilet, it’s running into oceans and rivers.

Particularly in the Pacific Northwest, that’s led to a dramatic and noticeable spike in the caffeine levels of of the bodies of water — to a point where researchers are concerned that it could harm fish and other wildlife.

Elise Granek, an assistant professor of environmental science at Portland State University, says there are no known natural sources of caffeine in the Pacific Northwest. 

“When we see caffeine in rivers or lakes or the ocean, our understanding is that the source is human waste. And that human waste may be from coffee, it may be from energy drinks, from pharmaceuticals, etc.,” she said.

Granek’s study looked at both areas that are seemingly at high risk of pollution, coast lines near cities and water treatment plants, as well as relatively unpopulated areas at low risk of pollution.

County-intuitively, the researchers found greater levels of caffeine in low risk areas.

“Although wastewater treatment plants in the U.S. are reported to only have about a 60-70 percent efficiency rate at removing caffeine, that’s probably enough to remove most of the caffeine and the remainder is diluted out,” Granek said.

In contrast, in low population areas, there is no central sewer system. Instead, homes and businesses dispose of their own waste, usually through a septic system. Regulations are much more lax with regards to how septic systems must work.

To be sure, Granek’s study didn’t find levels of caffeine in ocean and river water that will replace your morning coffee. In fact, the highest levels found in the ocean were 45 nanograms per liter and in a nearby river were 150 nanograms per liter.

“We’re talking about a very small amount,” she said.

But in laboratory testing, Granek’s team discovered that’s enough caffeine to have an adverse effect on inter-tidal mussels.

“Fifty nanograms was the lowest dose we looked at in terms of effects on mussels. And, that was enough of a dose to cause mussels to generate stress proteins,” she said. “There have been some reports that caffeine may affect reproduction. When organisms are stressed, they produce stress proteins to protect their cells. And, if an organism is under prolonged stress, then that organism may have to shift energy they would normally spend on growth and reproduction.”

Probably more important than the caffeine, though, Granek says, is what else is in the water with caffeine. Because the caffeine comes from wastewater, there’s also likely pharmaceuticals, household cleaners and a “suite of other contaminants” that are flowing into oceans and rivers not just in the Pacific Northwest, but across the country.

“People that are eating intertidal mussels, for example, if there’s high levels of caffeine at those sites, we are interested in finding out what other contaminants may be accompanying that caffeine at those sites, and whether any of them are contaminants of concern for human health,” she said.

Granek said its too soon to say with certainty that septic systems are the source of these contaminants, but it is likely. Once they can confirm it, however, Granek hopes to provide information that policymakers could use to change the regulations behind how effective septic systems must be.

“our ultimate goal is to provide information that will inform management and policymaking to reduce the level of contaminants that are entering marine systems,” she said.