Pesticides lurk in South Africa’s water
The toxins are found in water and the soil and these harm humans and the environment
National legislation should be implemented to phase out or ban highly hazardous pesticides immediately to lessen further harm to the environment and people.
This is according to Debbie Muir, a specialist programme manager at the department of forestry, fisheries and the environment, who was speaking at the recent Unpoison Our Water webinar.
Mark Heywood, of Maverick Citizen, and Anna Shevel, the coordinator of the civil society movement Unpoison, facilitated the discussion with water experts on topics that included pesticide and agrochemical contamination as well as antimicrobial chemicals and medication in sewage.
The risks posed by highly hazardous pesticides on biodiversity and ecosystem services are “unacceptable”, said Muir, adding that they pose significant risks to human health and the environment in developing countries and have been identified as a global risk.
Pesticide exposure and environmental threats reduce acceptable and clean water service delivery to the public and the environment “Pesticide contamination in water can lead to a reduction in species richness in aquatic mesocosms and systems and decreases in species diversity in aquatic ecosystems,” she said.
South Africa has developed a highly hazardous pesticides database. “We have moved from 124 highly hazardous pesticides at the end of last year to 186 highly hazardous pesticides currently.”
Of these, 102 are environmentally toxic. “In other words, they either have an impact on the environment, whether it’s water or bees or bio-accumulation in soil,” Muir said, noting that 90% of these were agricultural pesticides.
Atrazine and acrolein rank among the main agricultural water pollutants. “Atrazine is used mainly in the wheat and [maize] production areas while acrolein is a favourite pesticide used by the department of water and sanitation for the control of algae, fungi and submerged aquatic weeds in their canals.
“And this is where the alarm bells should be going off because those canals are carrying your drinking water to you and they are using acrolein in those canals to treat algae before they put it through the water purification plants and it comes out of your tap.”
Both Atrazine and acrolein are acutely toxic to aquatic organisms, and accumulate in fish. “When you’re looking at rivers and dams with a link to communities, which are doing subsistence farming, for instance, it also becomes bio-accumulation through the fish into the human body, which is a problem.
“Atrazine is bio-accumulative, highly toxic, persistent in soil, leaches and is a groundwater contaminant, but here’s the scary thing: it’s a possible human carcinogen; it’s an endocrine disruptor, it’s a reproductive and developmental toxin; it’s a neurotoxicant; it can cause renal failure and coma; it’s an irritant; it is a bad pesticide.”
Atrazine also accumulates in whatever it’s sprayed on and its residues are “in the food you eat. It is in your corn, it is in your maize, it is in your mealie pap; it is in your wheat — in your bread, there will be residues of atrazine,” she said.
Because it doesn’t break down in groundwater, it’s the country’s biggest groundwater contaminant. “There has been huge increases in childhood cancers in the Northern Cape and in the arid areas where the communities subsist off groundwater and huge increases in cases of ADHD [Attention-deficit/hyperactivity disorder] and all of this is linked to atrazine in the groundwater of the arid areas in this country, and that is just what we know so far.”
Muir said pesticides, including DDT and chlordane, have been detected in the eggs of birds such as African darters and weed cormorants. “Those are examples where
we’ve seen decline in reproductive fecundities and mortalities ... and there’s a risk of those species becoming vulnerable.”
There are behavioural changes in animals and developmental and reproductive changes over time. “An example of this is that the pesticides used in the Hluhluwe–imfolozi Park to control Chromolaena [an invasive shrub], which are persistent in the sand along the Hluhluwe River, have increased the temperature of the sand.
“And by doing that, they have changed the alignment of the sexes of the crocodiles being born, so there are now more males being born than females in the Hluhluwe-imfolozi Park, which is a concern because the impact on the behaviour and the competition with regards to mating and the crocodile populations has been taking a knock.”
Bettina Genthe, an environmental health researcher who has more than 35 years’ experience in the field of environmental health and water quality, said pollution is a multipathway process. “Water from farms runs off land to rivers, and water from rivers is used to irrigate crops, used for recreational activities and as a source for drinking water.”
She was shocked by a 2016 study on human exposure to wastewaterderived pharmaceuticals in fresh produce, which focused on carbamazepine, an anti-epileptic drug, which is ubiquitously detected in reclaimed wastewater, highly persistent in soil and taken up by crops.
The researchers from the Hebrew University of Jerusalem and Hadassah Medical Centre demonstrated in a randomised controlled trial that healthy individuals consuming reclaimed wastewaterirrigated produce excreted carbamazepine and its metabolites in their urine, while those who consumed freshwater-irrigated produce excreted undetectable or significantly lower levels of carbamazepine.
“The wastewater has some of the carbamazepine in it because the treatment works aren’t made to reduce it,” said Genthe. “That is used to irrigate our foods, we eat the food then people’s urine was tested who ate that food and they found carbamazepine in it.”
There are more than 700 pesticide active ingredients registered for use in South Africa and they contain many different materials, including active and inert ingredients, as well as contaminants and impurities. The active ingredient is usually the only component of the formulation listed on the pesticide label — and the only compound tested, she said.
Genthe cited a 2015 study by the Water Research Commission that investigated the contamination of water resources by agricultural chemicals and the effect on environmental health.
The pesticides’ risk to human health levels were found to be fairly low, with negligible risk associated with the consumption or use of water from the study areas. “Yet there are some warning signals. The study revealed relatively high concentrations of particularly atrazine, terbuthylazine and simazine [all endocrine disruptors] in maize and sugarcane areas.”
Inaction on endocrine disruption comes at a cost: “We’re talking hundreds of millions of euros per annum that can be attributed to endocrine disruption from environmental exposure, just for the males,” she said. “This includes testicular cancer, infertility because of low semen quality, hypospadias and cryptorchidism. “For the females, we’re talking billions … of euros per annum.”
There are thousands of contaminants in the environment with possible health effects. Water is an important exposure route for most of these compounds and the health costs are astronomical, she said. While treatment to remove these compounds is critical, “unfortunately not all can be removed”, and it’s expensive.
On chemical pollution, Leslie Petrik, who leads the Environmental and Nano Sciences research group at the University of the Western Cape, said: “And I’ve got studies from South Africa too showing our drinking water contains these chemicals. And this is because we’re waging chemical warfare at home. Everything that happens to us these days is being countered with a chemical, and we’re also the recipient of many pesticides from other countries.”
Banned pesticides from the European Union are ending up in countries like South Africa. “We’re importing a huge amount of these chemical pollutants.”
On the disadvantages of conventional wastewater treatment technologies, Petrik said this is because of their limited capability to completely removal solids, toxic sludges, and microbes or complex intermediates.
“So we can see that sewage is a significant source of chemical and microbial pollution and that many of these compounds escape through the wastewater treatment plants.”
None of the processes at a typical wastewater treatment plant or potable water plant are designed specifically to remove these compounds. “The recalcitrance of persistent pollutants requires new strategies for their removal,” Petrik said.