Antibiotics in water and the risk of drug-resistant bacteria
A JRC report brings together data on antibiotic levels in water, showing that small concentrations have found their way into a range of Europe's waterbodies. Because of the threat of new drug-resistant bugs evolving when these antibiotics come into contact with bacteria present in the water, scientists are gathering evidence to better understand the potential risk.
Their data confirms that the levels of antibiotic residues in drinking water are minute and do not represent a risk to human health. However, antibiotic residues can be found at higher levels in waste water, surface waters, agricultural runoff and water used for aquaculture (farms of fish, muscles, seaweed and other marine species).
The report is part of JRC efforts dedicated to investigating the implications of antibiotics in water. Scientists aim to determine the minimum concentration of antibiotics that could cause resistance in bacteria, so that future limits can be based on risk assessments that take into account this potential.
The report also highlights that the development and spread of antimicrobial resistance (AMR) (the phenomenon of bacteria resisting the effects of antibiotics) can be constrained if measures are taken to improve the effectiveness of wastewater treatment processes and to control the use of antibiotics in medicine and animal husbandry.
Resistant bacteria regularly evolve in places where antibiotics are commonly used - such as in hospitals where the MRSA 'superbug' (resistant to a wide range of antibiotics) is often found. On top of this, antibiotics don't simply disappear after they've done their job of fighting off a bug. They are excreted from the body and so there's also a risk of similar bugs proliferating in water in treatment plants, in manure and slurry, and in the environment if the concentration of antibiotics is high enough to select for their survival.
The prevalence of antibiotic use has led to growing concern over the spread of AMR. In Europe, about 25000 people die of infections from antimicrobial-resistant bacteria every year. It's also estimated that AMR costs the EU €1.5 bn per year in healthcare costs and productivity losses.
Which antibiotics? How are they monitored?
Looking at data on 45 antibiotics from 13 countries worldwide, the report's authors found sulfamethoxazole, trimethoprim and ciprofloxacin to be the three most frequently found in the water that flows out of waste water treatment plants. Most of the data came from Europe (79.2%) and, for the antibiotics detected, the concentrations ranged up to 1 µg/L (one millionth of a gram per litre).
These medicines are all commonly prescribed for urinary tract infections, while ciprofloxacin is also prescribed for ear and chest infections. Similar concentrations of antibiotics were also reported in surface waters, despite the fact that a reduction in their levels might reasonably have been expected due to the dilution of these substances as effluents run into rivers and lakes.
Ciprofloxacin is included alongside amoxicillin, erythromycin, azithromycin and clarithromycin on the Watch List monitoring programme under the EU's Water Framework Directive, which gathers data on substances that may pose a risk at EU level. The analytical methods used have to be able to detect concentrations as low as between 0.019 and 0.089 µg/L, corresponding to concentrations considered not to have direct effects on aquatic organisms such as algae, crustacean and fish.
The report notes that there has so far been little research into the use and effects of antibiotics in the aquaculture sector. In Europe, the use of antibiotics in all animal farming activities, including aquaculture, is regulated by specific legislation.
Aquaculture products (as well as any products from the animal farming systems) must not contain pharmacologically active substances above an established Maximum Residue Limit. Efficient monitoring at EU level relies on surveillance programmes implemented in the EU Member States, and relevant data are made available to the Commission.
Aquaculture is the fastest growing food-producing sector and it is estimated to account for approximately half of the total food supply coming from fish. While it is necessary to prevent bacterial diseases in aquaculture products, the use of vaccines could lessen the need for chemicals and antibiotics in this sector, on condition that vaccines against the most relevant diseases are registered and accessible in all EU member states.