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Drugs in our seawater

Pharmaceuticals, including antibiotics and anti-inflammatories, are accumulating in False Bay

False Bay receives so much persistent pollution from Cape Town that antibiotics and anti-inflammatory drugs are in the seawater, and accumulating up the food chain.

This has implications for antibiotic resistance, which the World Health Organisation states is one of the biggest threats to global health, food security, and development today. Antibiotic resistance occurs due to bacteria being exposed to non-lethal doses of the antibiotic drugs. As a result, antibiotic medication becomes ineffective in treating infections and diseases such as pneumonia and tuberculosis.

The antibiotic Sulfamethoxazole is present in False Bay’s waves, as well as in the sediment, seaweed, and marine invertebrates such as mussels, limpets, sea snails, sea urchins, and starfish. High levels of Diclofenac- an anti-inflammatory drug sold over the counter as Voltaren – are also present.

This is made known in the recent publication of findings made by scientists Cecilia Y. Ojemaye and Leslie Petrik from the University of the Western Cape’s Chemistry Department.

Ojemaye and Petrik took samples of seawater, sediment, seaweed, and marine invertebrates from eight sites in False Bay – from Miller’s Point on the south western side, to Rooi Els on the south eastern side – in 2018. The sites were chosen for being near wastewater treatment works which treat industrial, medical, and domestic wastewater and sewage before releasing it into the sea.

Besides Sulfamethoxazole and Diclofenac, Ojemaye and Petrik tested for six other pharmaceutical and personal care products (PPCPs), which are known as persistent chemical compounds as they fail to break down in the environment.

Their paper is titled Pharmaceuticals and Personal Care Products in the Marine Environment Around False Bay, Cape Town, South Africa: Occurrence and Risk-Assessment Study. It was published on 30 March this year in the scientific journal Environmental Toxicology and Chemistry.

The scientists found that two chemical compounds they tested for – triclosan and caffeine – could not be detected, but six other persistent chemical compounds were found in all samples.

These were:

  • Diclofenac, a non-steroidal anti-inflammatory;
  • Sulfamethoxazole, an anti-biotic;
  • Acetaminophen, used for pain relief;
  • Lamivudine, an antiretroviral;
  • Phenytoin, an anticonvulsant;
  • Carbamazepine, an anticonvulsant.

Diclofenac was found in the highest concentrations, second only to Sulfamethoxazole which was the most concentrated chemical compound in sea water samples from Strand and Rooi Els.

The reason these chemical compounds were chosen is because they are listed as the most prescribed drugs in South Africa’s public health sector, and studies on waste water being treated for reuse as drinking water, have shown they are present in the effluent released into the bay from wastewater treatment works.

Source of contamination

These persistent chemical compounds, which the scientists note, have become “a major issue” in water bodies around the world “because of their daily use by millions of people” do not form part of the pollutants the City monitors in wastewater effluent. The City, along with all other municipalities in South Africa, test the effluent released from wastewater treatment works for bacteria such as e.coli, and excess nutrients such as ammonia and nitrogen. The treatment for, and monitoring of, persistent chemical compounds is not required by national wastewater management minimum standards.

As it is, the vast majority of wastewater treatment works in South Africa fail to meet even the minimum effluent quality standards, including many managed by the City of Cape Town, seven of which the study notes release effluent into False Bay.

“The concentration of PPCPs found in seawater are an indication of possible sewage pollution of this marine environment with these compounds because most sewage-treatment plants are not designed to remove these PPCPs from their effluent,” state the authors.

The effluent being released into the ocean from City wastewater treatment works, such as this flow at Strandfontein from the Cape Flats wastewater treatment works, is shown to contain persistent pharmaceutical compounds which are accumulating in seaweed, shellfish, and fish in False Bay. Photo Steve Kretzmannbinary comment

Health risks and ecological impact

This study shows that although concentrations of pharmaceutical compounds such as Diclofenac and Sulfamethoxazole in seawater are low, they are persistent and become more concentrated up the food chain. In a process known as bio-accumulation, the organisms absorb these compounds continually present in their environment faster than they are able to break them down and excrete them.

As an example, the concentration of Diclofenac in False Bay seawater, was 3.70 – 4.18 nanograms per litre (ng/L). In seaweed it was 101.50 – 309.11 nanograms per gram (ng/g), and 67.67 – 780.26 ng/g in marine invertebrates. A previous study by Ojemaye and Petrik on the prevalence of these pharmaceuticals in fish, found Diclofenac in some False Bay fish to be as high as 1812 ng/g.

Alongside Diclofenac, Sulfamethoxazole and other drugs which are not fully metabolised before being excreted, are numerous other chemical compounds found in shampoos, soaps, and other personal care products. Many of these, the study notes, “are of toxicological concern” and “the potential environmental risk caused by these compounds should not be underestimated”.

“When it comes to consuming seaweed, shellfish, or fish, it’s a bit like standing in the chemist and taking a bit of every tablet in the shop.”

“When it comes to consuming seaweed, shellfish, or fish, it’s a bit like standing in the chemist and taking a bit of every tablet in the shop,” said Petrik when talking to Mother City News about the findings.

Sulfamethoxazole, present in the seawater at concentrations up to almost to 5ng/L in places, and also in edible seaweeds analysed, “could result in the development of antibiotic resistance by humans and other marine organisms”.

The authors note that seaweed has been eaten and used in animal feed in various parts of the world for centuries, and is currently mooted an alternative source of proteins as the global population grows and food scarcity increases.

They cite other studies on “the growing evidence of the health and nutritional importance of the consumption of seaweeds. But “high levels” of chemical compounds such as Diclofenac found in seaweeds show that the “health impact of using contaminated seaweeds for food and medicinal purposes should be considered”.

“The risks associated with exposure to these compounds among others include increased cancer risk, decreased fertility, and effects on the immune system,” state the authors.

City response

City mayco member for spatial planning and environment, Marian Nieuwoudt, said the City is “aware of the growing concern surrounding the presence of PPCPs in marine and coastal ecosystems”.

However, Nieuwoudt said effluent from sewage treatment plants was not the only source of contamination in False Bay. She said the City is conducting its own study in order to “not only better understand the presence of CECs (chemicals of emerging concern), but ultimately to also understand the multiple pathways that lead to the presence of pharmaceutical compounds in coastal waters”.

Among the other sources of pollution the City was studying were urban run-off that includes agricultural, commercial, and domestic sources of pollution flowing into stormwater systems, and the illegal or improper connection of household or commercial waste water into the stormwater system, which ultimately disperses into the ocean.

She noted the presence of PPCPs in False Bay was a concern, but was also a global problem

“indicative of our ever expanding ecological footprint based on our almost limitless resource consumption and consequent multiple waste streams that arise from such consumption”.

The technology to remove perennial chemical compounds such as those found in PPCPs from sewage and waste water at the volumes produced by the city, did not yet exist, said Nieuwoudt.