How harmful are antibiotics to Swedish watercourses?

Antibiotics can be found in our watercourses close to sewage works, together with thousands of other chemical residues. The question is what effect these antibiotics have on the environment.

The levels of antibiotic residues in Swedish watercourses are usually extremely low, at no more than a few nanograms per litre. Antibiotic residues are present alongside other chemical residues from products such as detergents, hygiene products and pesticides.

“In these areas we are seeing changes to flora and fauna, but it tends to be hard to establish which pollutants are the main cause,” says the Department of Biological and Environmental Sciences’ Professor Lars Förlin. “When it comes to antibiotic residues, however, we suspect that this could be a contributory factor to the higher levels of antibiotic-resistant bacteria often found near sewage works.”

IT IS NOT ONLY antibiotics that can encourage the development of resistance. The same is also true of metals and certain pesticides, for example, which enter the environment via sources such as sewage works. Nor is it entirely certain that the bacteria acquire their resistance in the receiving water course – resistance may have arisen in the sewage works or beforehand.
“Antibiotics probably have fairly little effect on animals and plants in our watercourses. However, the question is whether areas where there are harmless antibiotic-resistant bacteria strains can act as potential sources for the spread of resistance genes to pathogenic bacteria. The risk of this actually happening may be small, but the possible consequences are so great that the risk must be taken seriously.”

It would therefore be best if discharges of substances from sewage works and other distribution sources were minimised.
“Technological solutions exist for sewage works to reduce discharges of chemical pollutants including antibiotics and to further reduce the quantities of bacteria discharged. One important reason why this is not done is that the solutions can be quite expensive.”

EVEN IF ANTIBIOTICS do not appear to be an obvious problem in Swedish watercourses, they may be problematic in other parts of the world.
“A few years ago, the Sahlgrenska Academy’s Professor Joakim Larsson showed that industries in India that manufacture antibiotics discharge extremely high levels of certain antibiotics, at levels that are millions of times higher than those seen in Swedish watercourses.”

Researchers found a very high proportion of multi-resistant bacteria in the studied watercourse sediments.
“Here, it must be noted that the main cause for the situation in these areas is a widespread failure to deal with industrial waste water in a safe manner.”