Researchers have reported that chlorine, a chemical used in the majority of wastewater treatment plants, may not be fully preventing pharmaceutical substances from entering the nation’s water supplies. Not only that, but chlorine treatment may also lead to the formation of new antibiotics and contribute to antibiotic resistance.

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The presence of antibiotics in the environment can encourage antibiotic resistance.

The research will be presented at the 249th National Meeting & Exposition of the American Chemical Society, a meeting featuring almost 11,000 presentations on a wide range of different scientific topics. The findings suggest a re-evaluation of how wastewater is treated is required.

“Treated wastewater is one of the major sources of pharmaceuticals and antibiotics in the environment,” says Olya Keen, PhD. “Wastewater treatment facilities were not designed to remove these drugs. The molecules are typically very stable and do not easily get biodegraded. Instead, most just pass through the treatment facility and into the aquatic environment.”

Chlorine is a disinfectant with a long history of effective water treatment. The US Environmental Protection Agency (EPA) describe it as reliable and effective against a wide spectrum of pathogenic organisms, and more cost-effective than other forms of disinfectant.

There are also a number of disadvantages that come with using chlorine, however, such as its toxicity and the effect that it has on certain forms of matter in wastewater, potentially creating more hazardous substances.

The new study adds another disadvantage to the EPA’s list, suggesting that chlorine may be failing to eliminate pharmaceuticals from wastewater, with potentially serious repercussions for the environment. “Pharmaceuticals that get out into the environment can harm aquatic life, making them react slowly in the wild and disrupting their hormone systems,” states Keen.

But there may be an even more dangerous consequence of treating wastewater with chlorine. The researchers found that exposing doxycycline – a common pharmaceutical pollutant found in wastewater – to chlorine increased the antibiotic properties of their samples.

“Surprisingly, we found that the products formed in the lab sample were even stronger antibiotics than doxycycline, the parent and starting compound,” says Keen. She adds that the compounds formed could potentially be previously unidentified antibiotics.

Increased exposure to antibiotics in the environment, even at low levels, can result in the development of antibiotic-resistant microbes, leading to an overall weakening of the capacity of antibiotics to fight bacterial infections.

Antibiotic resistance is a major public health concern at present. The Centers for Disease Control and Prevention (CDC) state that each year in the US, at least 2 million people develop bacterial infections from antibiotic-resistant bacteria. At least 23,000 people die each year as a result of these infections.

Keen suggests that the best solution to the problem presented in the research would be to reduce the amount of pharmaceuticals that reach treatment plants altogether. At present, the disposal of pharmaceuticals is not regulated.

By placing a greater emphasis on collecting and incinerating old and unused pharmaceuticals, the amount that would be disposed of in drains or with regular garbage would be decreased, subsequently reducing the risk of harmful environmental exposures.

The findings also have implications for drinking water treatment systems which also frequently use chlorine as a disinfectant. Chlorine must remain in the piping system of treatment facilities for several hours, Keen explains, which affords plenty of time for the disinfectant to interact with any pharmaceuticals that may be present and potentially develop new antibiotic compounds.

Funding for the research was provided by the University of North Carolina at Charlotte and the National Science Foundation.

Recently, Medical News Today reported on a study that raised concerns about whether current water treatment facilities can adequately remove engineered nanoparticles from the water supply.