Drugging the Environment
Humans have spiked ecosystems with a flood of active pharmaceuticals. The drugs are feminizing male fish, confusing birds, and worrying scientists.
August 1, 2015|
Because of its high prescription rate—the U.S. alone dispensed 76.9 million metformin prescriptions in 2014—it’s not surprising that the drug is abundant in the environment. Metformin was present in every water sample Kümmerer’s team tested, including tap water, at concentrations exceeding environmental safety levels proposed by an international Rhine River Basin agency by 50 percent. When publishing the results in 2014, Kümmerer and his coauthors concluded that the drug is likely “distributed over a large fraction of the world’s potable water sources and oceans.”1
Ecologists have long recognized that pharmaceuticals, both unmetabolized drugs like metformin and others that break down into various metabolites, are polluting the environment, but researchers have traditionally focused on just two classes: antibiotics and endocrine-disrupting compounds such as the birth control hormone estradiol. Antibiotics in the environment promote antibiotic resistance in a range of bacterial species, and endocrine disruptors are known to affect development and reproduction in animals.
Metformin was not thought to have either of those effects on animals. But in lab experiments conducted earlier this year, Klaper’s team discovered that male minnows exposed to metformin at concentrations comparable to those of wastewater treatment plants produce proteins typically found only in female fish, develop feminized gonads, weigh less, and have fewer offspring.3 The antidiabetic is now one of a growing list of drugs that researchers are realizing pose major ecological problems.
“All [pharmaceuticals], by design, are meant to elicit a biological response,” says the US Geological Survey’sDana Kolpin, chief of the organization’s Emerging Contaminants Project. “We need to know what the environmental consequences are.”
Like so-called “legacy” pollutants that have been banned in many countries, including polychlorinated biphenyls (PCBs) and DDT, pharmaceuticals can persist for years, even decades. Pharmaceuticals are designed to maintain their strength and quality on the long route from manufacturer to pharmacy to medicine cabinet, and even sometimes inside the human body. That same stability, unfortunately, prevents many pharmaceuticals from degrading in the environment.
And within that chemical concoction, drugs interact with one another, with bacteria, and with basic environmental elements such as water. Chemical and biological reactions can result in a host of transformation products—new chemicals with new properties. Some bacteria break down metformin, for example, yielding a metabolite called guanylurea, which is also bioactive and stable in the environment. Similarly, the antidepressant enlafaxine (trade name Effexor) degrades into desvenlafaxine (Pristiq), another antidepressant. Such metabolites can sometimes be more toxic than their parent compounds.
“Degradation expands that universe of potential chemicals exponentially,” says Kolpin.
Fish don’t want birth control, but scientists say they get it from your pill
Your birth control pill is affecting more than just your body.
Flushed down toilets, poured down sinks and excreted in urine, a chemical component in the pill wafts into sewage systems and ends up in various waterways where it collects in fairly heavy doses. That's where fish soak it up.
A recent survey by the U.S. Geological Survey found that fish exposed to a synthetic hormone called 17a-ethinylestradiol, or EE2, produced offspring that struggled to fertilize eggs. The grandchildren of the originally exposed fish suffered a 30 percent decrease in their fertilization rate. The authors mulled the impact of what they discovered and decided it wasn't good.