Are we taking medication without knowing it?

The global consumption of medicines has been on the rise in the last decade. Between 2000 and 2019, in OECD countries, the use of cholesterol-lowering drugs almost quadrupled, antidepressants and antidiabetics doubled, and antihypertensives increased by 65%.

In Spain alone, some 817 million prescription-only drug packs were sold in the first nine months of 2022.

Part of the drug or active ingredient that we take with drugs is excreted by our body in the urine or faeces, either unchanged or as metabolites. These drugs and their metabolites end up in treatment plants which, because they are not designed to treat this type of compound, cannot completely remove them.

As a result, a significant amount of medicines gets into surface water through sewage discharges every day. These drugs can travel long distances from rivers to groundwater and agricultural soils, where they can be taken up by crops and enter the food chain.

Unregulated pollutants

Improvements in detection equipment and the development of more powerful analytical methods have given us the ability to detect in surface water and other environmental matrices what was an invisible and complex world a few years ago.

The presence of drug residues in water resources is not yet regulated. However, the European Union (EU) has established “watch lists” (implementation of decisions 2015/495, 2018/840, 2020/1161 and 2022/1307) to collect monitoring data for substances that are suspected to pose a significant risk for the aquatic environment, and through it for humans.

Several drugs appear on these lists, such as the antibiotic sulfamethoxazole, the antidepressant venlafaxine, and the oral antidiabetic drug metformin.

Impact on ecosystems

Drugs are biologically active molecules designed to have a pharmacological effect on living organisms. Therefore, it is not surprising that chronic exposure of aquatic organisms to drug residues can have a negative impact on their health.

The 2019 OECD report includes some of these effects observed in the laboratory:

• Analgesics can cause genotoxicity and neurotoxicity in molluscs and endocrine disruption in frogs.

• Antiepileptic drugs cause growth retardation in fish and reproductive toxicity in invertebrates.

• Antipsychotics cause behavioral disturbances in fish.

• Oral antidiabetic drugs potentially affect the endocrine system of fish.

• Hormones cause changes in the reproductive system of fish and frogs.

Thanks to data from both scientific and technical studies of its appearance, persistence and toxicity, the EU has recently published a proposal proposing the regulation of the concentration of certain antibiotics, analgesics and hormones in surface waters, as well as the antiepileptic carbamazepine and the antibiotic sulfamethoxazole in groundwater. waters.

From sewage treatment plants to our table

One of the main sources of drugs in the environment is wastewater treatment plant effluents, where these molecules appear in low concentrations – ranging from nanograms per liter to micrograms per liter – but constant.

Once released into surface waters, they may be subject to processes that occur naturally in the environment. For example, photodegradation, biodegradation or dilution. These natural attenuation processes are responsible for reducing its concentration or toxicity. The magnitude of these processes depends, among other things, on their physicochemical properties.

Unfortunately, some preparations are often persistent, resisting natural attenuation, and travel long distances to reach agricultural soils.

In 2016, a global literature review of studies measuring environmental concentrations of persistent pharmaceutical pollutants (including antibiotics, analgesics, lipid-lowering drugs, estrogens, etc.) identified a total of 631 different compounds or their environmental transformation products from 71 countries.

Surface water is one of the most used water resources in agriculture. When drug residues are found in it, which are the result of, among other things, human consumption, there is a risk to food safety due to their possible entry into agricultural plants that fall on our table, such as cereals, vegetables, fruits, etc. . .

Detecting drugs in irrigation water

The results of our work published in journals Environmental science in general And Ecological Internationalshow that 42 out of 50 drugs tested are found in water used to irrigate corn in agricultural areas south of the Community of Madrid.

Metformin, an oral antidiabetic drug included in the 2022 watch list, stands out among them in terms of concentration (up to 13 μg / l). These data are associated with its high consumption and the fact that almost the entire dose received is drunk. excreted in urine and feces.

Natural attenuation processes in the soil are very effective in reducing the concentration of most drugs by more than 60%. However, the antiepileptic carbamazepine and the antibiotic sulfamethoxazole are persistent and therefore susceptible to release into groundwater. The persistence of these compounds is one of the reasons for their inclusion in the proposed EU regulation.

Our studies show that most of the investigated preparations are stored in the roots. Only a small amount (0.02%) accumulates on the cob of corn, which poses little risk to food safety when it is consumed. However, it must be borne in mind that our diet includes many plant products that can accumulate more substances and which, in addition, are consumed raw.

Where to go?

One of the biggest challenges in assessing the risk associated with the presence of drugs in food is the availability of reliable concentration data and therefore field studies and powerful analytical methods.

Medicines are found in water along with a large number and variety of substances such as trace elements, pesticides, biocides, chemical additives and nanoplastics, which can have a synergistic negative effect. Accounting for the complex mixture of substances dissolved in water as a result of human activities is both important and challenging for risk assessment.

Data on the presence of drugs in the environment is not encouraging. There are possible key options for mitigating this problem by acting in various drug manufacturing sectors and at the level of waste management and wastewater treatment. In addition, it is important to encourage the prudent use of medicines.

Raffaella Meffe, Researcher at the Soil and Water Quality Group, IMDEA WATER and Ana de Santiago Martin, Researcher, Soil and Water Quality Group, IMDEA WATER

This article was originally published on The Conversation. Read the original.