Do you know what’s really in your drinking water?

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A new study found evidence that drinking water may contain pharmaceutical contaminants. Getty Images

Emerging contaminant threats in the United States water supply — things like pharmaceuticals, antibiotics, and hormones — are garnering attention from public health experts and the federal government.

In recent research by the United States Geological Survey (USGS), a governmental organization that studies ecological hazards, these contaminants were found in a significant number of groundwater sources around the United States that are used for drinking water.

Among the contaminants discovered: bisphenol-A (or BPA) an endocrine-disrupting chemical frequently used in consumer plastics; methotrexate, an immunosuppressant and cancer treatment; and sulfamethoxazole, an antibiotic.

Samples also frequently included ubiquitous drugs like 1,7-dimethylxanthine (a metabolite of caffeine) and acetaminophen, an over-the-counter painkiller.

But, before you think of switching to bottled water, there’s more to the story than that, and likely no reason to worry — yet.

In what is described as the first large-scale study of the occurrence of hormones and pharmaceuticals in untreated groundwater aquifers, USGS researchers analyzed samples for 21 different hormones and 103 pharmaceuticals at 1,091 sites around the United States.

They found at least one hormone or pharmaceutical in 7 percent of the 844 aquifers at depths used for public water supply and 14 percent of 247 sites at aquifers used for domestic supply.

The sites tested represent about 60 percent of all the water pumped for drinking water supply across the country, providing water for about 80 million people.

Despite their findings, the overall message of the report is optimistic.

“Although we do occasionally see hormones and pharmaceuticals, really the occurrence of [them] in untreated groundwater used for drinking water supply across the U.S. is not widespread, and exposure to these compounds at concentrations that we detected is unlikely to have adverse effects on human health based on comparisons to available human health benchmarks,” Laura Bexfield, a hydrologist with the USGS and author of the research, told Healthline.

Just because these chemicals are found in the water supply doesn’t mean that they will necessarily make it into water from your tap. Experts can, at this point, only speculate about how much, if any, makes it through water treatment facilities.

They do note, however, that people who draw water from their own domestic wells are at a greater likelihood of exposure.

Even with the results of the USGS survey, there is a palpable anxiety about the public health implications of pharmaceuticals showing up in drinking water, but experts say we may not have any idea what the actual effects will be of chronic low-dose exposure to these drugs for years to come.

“There is obviously real concern about it, meaning that it is reasonable to anticipate that there are likely going to be health consequences from these kinds of contaminants,” said Dr. Ken Spaeth, chief of occupational and environmental medicine for Northwell Health System.

“How much of that translates at the tap is hard to say,” said Spaeth, who wasn’t affiliated with the research.

Experts and health officials are also grappling with how to accurately test for these contaminants.

Fortunately, strides are being made toward that development as well.

Researchers at West Chester University in Pennsylvania recently presented their evidence of a new method to test for several pharmaceutical contaminants in the water supply. The method is able to test for:

  • acetaminophen
  • codeine, an opioid painkiller
  • fluoxetine, an SSRI antidepressant known under the brand name Prozac
  • chlorpyrifos
  • sulfamethoxazole
  • thiabendazole.

They say that these tests are important for both ecologic and public health means.

Fish and other aquatic life are likely to have higher exposure to these contaminants. Recently, different drugs have begun showing up in the organisms that inhabit certain waters in the United States. Earlier this year, bay mussels in Washington’s Puget Sound tested positive for oxycodone, an opioid prescription analgesic.

“Aquatic organisms could be exposed to aqueous contaminants like pharmaceuticals throughout their entire lifetimes,” said Neha Sunger, PhD, an assistant professor of environmental health at West Chester University in Pennsylvania. “There is tremendous uncertainty regarding the mechanisms/modes of action of many of these compounds in aquatic organisms,” she said.

Pharmaceutical contamination in aquatic wildlife also potentially raises the risk for more human contact through direct consumption of these animals.

For now, however, there remains a tremendous gap in what we know about how much pharmaceutical contaminants are showing up in water and what the effects will be in the years to come.

Unfortunately, says Spaeth, the nature of public health causes it to lag behind emerging threats.

“Whether it’s asbestos or lead, it’s always full speed ahead with chemicals or products, even when we don’t know the full potential health consequences. Then later, when these health consequences become clearer, we wring our hands and say we really ought to do something about this,” he said.

Pharmaceutical and hormonal contaminants, including bisphenol-A, antibiotics, and opiates, are being detected in a significant portion of the United States groundwater supply for drinking water. It’s unknown what, if any, amount of these chemicals will make it through water treatment to the tap. Researchers say that the levels detected are unlikely to cause any harmful effects.

However, the results of potential long-term exposure to small amounts of pharmaceuticals is unknown, but worrisome.