People flush medicines, cosmetics, and hygiene products down the toilet or throw them in the trash every day. The waste ends up in water treatment plants and landfills and then makes its way into water supplies around the world.
But what happens after that?
New research examined the ways that common pharmaceuticals and personal care products degrade when they enter water systems. The researchers found that in some cases, the chemical by-products were more toxic to humans than the original products were.
Degradation products “are completely different chemical species, so they can have different toxic effects than their parent compounds,” said lead researcher Gayan Rubasinghege, an assistant professor of chemistry at the New Mexico Institute of Mining and Technology in Socorro.
“Sometimes they could be more toxic; sometimes they could be less toxic,” he said. “To get a complete picture of these pharmaceuticals and personal care products in the environment [and] their impact on the aquatic life or human health, we need to look at all of those things. Only then can we decide whether they are actually hazardous or not.”
Rubasinghege will present this work on 11 December at AGU’s Fall Meeting 2019.
Dissolved and Degraded, but Not Gone
“We have been producing more and more of these pharmaceuticals and personal care products to support the needs of a growing population,” Rubasinghege said. “When we say pharmaceuticals, we are talking about hundreds of different chemicals that are being produced and used every day,” including medicines, cosmetics, shampoos and soaps, and different types of plastics.
Scientists have quantified in a number of places just how much of our pharmaceutical waste ends up in water systems. The reported concentrations are often relatively low, “so people feel like, ‘Oh, it’s not so much. There shouldn’t be much impact on human health or impact on the aquatic life,’” Rubasinghege said.
However, “these are chemicals,” he added, “so they’re not going to last as they are in the environment. They’re going to change. They’re going to transform into something else.” Sunlight, microbes, and soil catalyze chemical reactions that turn the original compounds into new ones.
In laboratory tests, Rubasinghege’s team observed this degradation by dissolving ibuprofen in water and exposing it to sediments and simulated sunlight. “Within 5 or 10 days, 1,000 times of what has been reported [in the environment] completely disappeared or transformed into something else,” he said.
“We saw the same thing with amoxicillin,” he added. “We saw the same thing with clofibric acid, which is used to reduce plasma cholesterol. And we are working on diclofenac now, which is a nonsteroidal anti-inflammatory drug.”
The team then tested the effects of the sunlight-degraded ibuprofen on human liver and kidney cells. “In both the cases, we saw that a couple of degradation products from ibuprofen [are] 5–8 times more toxic compared [with] ibuprofen” at the same concentration, Rubasinghege said. The team also observed some toxic effects on a species of human gut bacteria (Lactobacillus acidophilus) and on an aquatic bioluminescent bacteria (Vibrio fischeri), but less so for the degradation products than for ibuprofen itself.
The bottom line is, even if reported concentrations of a pharmaceutical in our water are low, a lot more of that drug might have entered the water system originally and quickly transformed into something else, Rubasinghege said.
Unknown Degradation Paths and Impacts
“Ibuprofen is one of the most consumed pharmaceuticals around the world. It, and probably its transformation products, is found in considerable amounts in wastewater effluents,” said Adeyemi Adeleye, a civil and environmental engineer at University of California, Irvine who was not involved with this research.
“This study emphasizes the need to consider the by-products formed in the environment when assessing the risks of pharmaceuticals and other chemicals,” he said. “My hope is that the study will encourage other researchers in the field to expand their focus beyond the primary chemicals” and include the toxic effects of secondary chemicals too.
Rubasinghege’s group ultimately plans to put together a database of the most abundant pharmaceuticals and personal care products that enter the environment, how those compounds transform, and at what concentrations the degradation products are toxic to humans.
“We’re not saying that the drinking water is not safe,” he said. But people should take these results as an “eye-opener” that the reported pharmaceutical concentrations in our water are not the end of the story.
“Let’s do more studies about these degradation products,” Rubasinghege said. “Let’s do more studies to understand the complete picture of these compounds out there. Because the [environmental] impact of these could surface maybe in about 5 years, maybe in about 10 years. But if we understand it now and take actions now, we can avoid it in the future.”
—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer