Doctors should take into account the ‘downstream’ effects on the environment when they prescribe drugs, suggests a scientist at the US Environmental Protection Agency

Let’s talk about urine. We don’t usually give it much thought, but there’s a fair chance that yours contains traces of one of the 3,000 pharmaceuticals regularly prescribed in Europe and that the drug will end up contaminating the environment.

Around 80% of aquatic pharmaceutical pollution comes from domestic medicines (those that we take at home rather than in hospital), and while unused drugs that have been deliberately flushed down the toilet are a problem, the biggest source is excretion.

Drugs are designed to alter human physiology at low doses and so can make particularly potent contaminants. Recently, UK rivers were found to be harbouring bacteria with genes for antibiotic resistance as a result of waste water treatment. Antidepressants in sewage are known to disrupt the reproduction of molluscs and crustaceans. They have also been reported at trace levels in Polish tap water, though the risk (if any) to humans is unknown.

Waste products from the contraceptive pill skew sex ratios in fish, and the anti-inflammatory painkiller diclofenac has contributed to the deaths of millions of vultures. In 2013, the EU added diclofenac and the hormones 17α-ethinylestradiol and 17β-estradiol to an environmental pollutant “watch list”, meaning that their levels in surface water are now being monitored – though not yet controlled.

A paper published on Friday reports that at least one pharmaceutical contaminant – the anti-anxiety drug oxazepam – has a potentially beneficial effect, extending the lifespan of perch. However, the study was conducted under lab conditions rather than on fish exposed in the wild, and it’s not necessarily good news (unless you’re a perch) because we don’t know what the knock-on effects on the wider ecosystem could be.

Thus far, all attempts to control pharmaceutical pollution have been “end-of-pipe” approaches to filter out the chemicals at sewage treatment plants. But Christian Daughton of the US Environmental Protection Agency is proposing a new idea. Rather than focusing all our efforts on cleaning up aquatic pharmaceutical pollution, we should tackle the problem at source by practising what he calls eco-directed sustainable prescribing (EDSP).

This approach would require doctors to consider the environment as well as their patient when they prescribe a drug. Daughton proposes that doctors do two things. First, reduce the frequency and dosage of prescriptions. Second, consider how the drugs they prescribe are metabolised and excreted from the body. Whenever we take a drug, our body – mainly our liver – sees the unexpected arrival of this strange new molecule as a threat. So it pulls atoms off here and sticks new chemical groups on there in an attempt to inactivate it.

Some drugs are more extensively metabolised than others. A heavily metabolised drug is converted to an array of metabolic products that are usually (though not always) less active than the parent compound. But when a drug is poorly metabolised – perhaps because it is not very soluble, or if the patient doesn’t carry the gene for a particular variant of a liver enzyme – then the greater proportion of any dose passes out of our bodies unchanged, meaning that when it gets into the environment it is still in the active form.

Daughton suggests that doctors should try to use extensively metabolised drugs where possible, so that we excrete inactivated products with – in theory – minimal effect on aquatic life. We should think of patients and the environment as “a single, integral system”, he says.

Pharmaceutical pollution preoccupies environmental engineer Ole Pahl, who heads up Glasgow Caledonian University’s arm of the noPILLS research project, which aims to reduce pollution from pharmaceutical residues. What does he think of the idea? “The science behind excretion profiling is relatively straightforward, and it could be considered – alongside toxicity, bioaccumulation potential and environmental persistence,” he says. “But the social aspects, are, I feel, very complex.”

In what way? “There is a danger that patients might feel bad about taking ‘toxic’ medicine, and so don’t complete their course. Our research indicates that we have complex relationships with medicines … we need a much more refined public discussion about the impact medicine might have on the environment.”



Pharmaceuticals are undeniably effective, and often life-saving. But they’re also physical artefacts of contemporary medicine in which we invest personal meaning and significance. Do we need to adjust our attitude towards them?

“It’s often said that people expect pills from a doctor, and would be unhappy if they didn’t get any, but I’m not convinced that’s true,” says Karin Helwig, a member of Ole’s team. “My impression is that most people would prefer not to take any medicines when they don’t really need them.” Consider antibiotics: many conditions for which they are prescribed would resolve without them. Reducing these prescriptions would benefit the environment and help control the development of antimicrobial resistance.

Helwig also highlights the increasing use of antidepressants. “That’s something that’s being discussed in many contexts, but one thing is that many people get [them] while on waiting lists for talking therapies. If we can reduce the waiting lists we could reduce the pharmaceutical load.”

Having said that, Helwig is keen to stress that she doesn’t wish to tell hard-pressed medical staff how to do their jobs.

The upstream prevention of pharmaceutical pollution is not an entirely new idea. The Swedish “Wise List” project, designed to streamline the prescription of drugs in Stockholm, includes a requirement to consider the environmental effects of drugs. But as Daughton points out, his proposal would aim to reduce or prevent active drugs from getting into the environment in the first place.

It’s an attractive idea, but Daughton is the first to point out the limitations, not least the difficulty he encountered finding relevant pharmacokinetic data. It wasn’t hard to get hold of basic information about how the body metabolises drugs, because this has to be provided by manufacturers as part of the process of registration. However, the metabolism of some drugs is reversible. Our bodies may deactivate them, but as soon as we excrete them microbes convert them back to their active form.

And we all metabolise drugs differently, depending our genetic makeup, age, ethnicity, gender and even diet. So how could doctors be sure that a patient’s excretion profile for any given drug is the most environmentally friendly? That might be a matter for future research to develop personalised medicine.

For now, Daughton proposes what he calls a proxy measure of pollution risk: the Biopharmaceutics Drug Disposition Classification System, which classifies drugs by their intestinal permeability and solubility in water. He has found that Class IV drugs – those that are relatively less soluble and that don’t easily cross the intestine – are slightly more likely to be found in environmental waters than others. It’s early days, but as a first step perhaps prescribers should try to reduce the dosage of Class IV drugs, where possible?

In the past, the idea of controlling environmental contamination resulting from excretion has been considered a “non-starter”, says Daughton. For now, he would just be happy to get the medical profession and patients talking about ways to prevent – as well as clean up – pharmaceutical pollution. So should we, as the users of medicines, start considering our bodies as a source of pharmaceutical pollution?