Lake Victoria is Africa’s largest lake and, by surface area, is second only to Lake Superior in North America. Situated within Tanzania, Uganda and bordered by Kenya, the lake is rich in biodiversity. However, a report entitled ‘Freshwater Biodiversity in the Lake Victoria Basin’, published by the International Union for Conservation of Nature (IUCN) in 2018 found that of 234 native freshwater fish species in the Lake Victoria Basin, 86 are classified as threatened. The IUCN highlighted pollution as a danger to 90.2% of the lake’s native fish species.
In 2019, a team of Nation Media Group (NMG) journalists from Kenya and Uganda enlisted the help of scientists from the University of Nairobi and embarked upon a three-month investigation, conducted on site and in the laboratory. The multimedia team included Paul Wafula, a financial investigative reporter and Business Editor at the Daily Nation in Kenya, Sheila Sendeyo, Kevin Gitau and Robert Gichira (NTV – Kenya), Rita Kanya (NTV -Uganda) and Franklin Draku and Rachel Mabala (Daily Monitor – Uganda).
They travelled along the shores of the lake, on foot and by boat, collecting water samples, foiled at times by rain compromising water runoff. They braved leaky vessels, capricious tides, cantankerous hippos, security heavies and litigious lawyers in order to uncover what was causing the disappearance of various fish species and to independently verify allegations of pervasive pollution.
Much of the degradation was obvious to the naked eye. Plastic and non-biodegradable waste littered the shores. They found algal blooms and invasive water hyacinth – fed by high nitrogen concentrates from cage fish-farming industries and fertilisers – choking the lake and suffocating the fish. There were hidden toxins too.
The team collected 52 samples from river mouths and other locations on the lake, as well as effluent discharges from local factories, wastewater plants, paper mills and prisons. Analysis revealed that at least 13 poisons were contaminating the lake, endangering its aquatic fauna and posing a risk to human health. They found high concentrations of heavy metals such as lead, mercury, cadmium, chromium, zinc, iron and manganese, as well as fluoride and pesticides such as endosulfan, mirex and the banned pesticide DDT (Dichlorodiphenyltrichloroethane). Heavy metals were also present in the fish samples tested, although not all were at levels dangerous for human consumption. Bacterial indicators of human waste infested 92% of all the tested samples, transforming Darwin’s Dreampond into a wastewater settling pond of waterborne diseases.
The results of the investigation were publicised in a series with several print stories, a special magazine, and a TV documentary for NTV Kenya and NTV Uganda.
Rotting from the deep: The tragedy that is Lake Victoria, as well as Toxic Dump: The Poisons Killing Lake Victoria were published online on Nation.Africa on 17 February 2020.
It won Paul Wafula the Media Council of Kenya’s Environmental Reporting Award for 2020.
The team’s exposé of the silent putrefaction of Lake Victoria compelled governments to take action. Almost a dozen Kenyan companies were shut down. The National Environment Management Authority handed compliance notices to several others and hundreds more were put on a watch list. The Water Ministry formed a task team to work with regional governors in finding solutions and, for the first time, the ministry was allocated a budget to deal with pollution. A government programme to reclaim rivers is underway.
Featured image: Water sampling in Lake Victoria. Image: Supplied
Part 1: Rotting from the deep: The tragedy that is Lake Victoria
By PAUL WAFULA
River Kisat moves in surges, pricked from beneath by numerous inlets flowing into it from Kisumu City and its environs. Each inlet carries a different concoction of poison.
Kisat notoriously leaves a nauseating stink behind it that hangs over the air everywhere it passes. On a normal day, it is dark, thick and drags within it all manner of filth. It is a health hazard in motion.
No river in the Lake Victoria region carries the burden of a dilapidated and broken sewerage system than Kisat.
Grudgingly, it snakes through the populous Obunga slums, past Kisumu’s industrial area where fish processing factories, motor vehicle garages and other factories release effluent into it.
It accelerates with each slope as it races towards Lake Victoria. As if rushing for freedom, to escape further pain and destruction, it meanders through the final 4-kilometer journey of its existence, collecting raw sewage from toilets and back channels of estates and city buildings.
The weight of the sludge within it pushes it on from behind. It hurries further down, gushing beneath the last bridge on the busy Kisumu-Busia highway, not too far away from the Kisumu International Airport.
Shortly after the bridge, it becomes still and silent as it slithers through Nyanza Golf club, past a creaky wooden footpath, as if not to alert golfers that it was passing by, before it is embraced by the calmness of Lake Victoria.
As it meets the lake at its mouth, River Kisat forms a big brown bowl in the lake, the size of a basketball pitch. The filth in it separates it with the green oily waters infront of it. The final hurdle it has to confront is a green layer of an interwoven carpet of water hyacinth awaiting it. This is before it is completely swallowed by the lake and its miserable life forever put to an end.
It is impossible to imagine any waste from Kisumu that does not end up in Kisat.
Ironically, River Kisat also carries poison from the Kisumu Water and Sewerage Company (KIWASCO). Instead of cleaning waste from factories feeding into it, KIWASCO is part of the polluters sucking life out of the world’s second biggest fresh water lake.
As it pollutes the lake from one side, the water company is pumping the same water out of the lake, several meters away. This polluted water is what it struggles to treat and sell to hundreds of thousands of residents in the region.
KIWASCO represents just what is wrong with Lake Victoria.
Not very far away from River Kisat is Kodiaga Maximum Security Prison. Here, the prison does not even try to hide that Lake Victoria is its toilet for the 3000 inmates and remandees behind its rusty gates.
The prison unrepentantly emits raw sewage into River Saka in broad daylight. Downstream, before the contaminated water ends up into the lake, residents are fetching it for drinking and other household uses.
Kodiaga Prison’s wastewater lagoons do not work. Its sewer lines overflow during rainy seasons, and end into River Saka, which dutifully transports it to the lake.
The prison uses a sewer system built in the 1950s by the colonial government. It functioned until sometime in 2008 when it broke down. Ten years later, the government has never found enough money to build it another system.
These are not the only offenders that have led to the increasing expanse of the algal bloom in the Winam Gulf of Lake Victoria.
There is Maseno University, a university that prides itself as being the only one on the equator. But it does not have a wastewater treatment system. It allows its sewage from thousands of students to pour into open land, then to a nearby stream.
Its final destination? Lake Victoria.
Then there are agro-based industries, bottlers, breweries, and sugar manufactures releasing poorly treated effluent. All of the boast of state of the art treatment plants that have won numerous awards. But the truth on the ground is different. Most do not pre- treat their waste to the required standards before pumping it into the KIWASCO waste system.
Given their financial might and the need to support industries, KIWASCO’s warnings are routinely ignored. After some point, it gets overwhelmed, and decides to do the unimaginable. The water company is forced to release back into the lake, effluent heavy with Ammonia, pesticides, heavy metals and poorly treated sewage heavy with bacteria and disease other causing chemicals.
Afterwards, it sits back and hopes that the fresh water lake will somehow dilute it, and get the problem out of its hands.
But the lake has had enough. The poison is being handed down its throat at a rate that is faster than it can disperse, dilute, decompose, recycle or store in harmless form.
To understand the magnitude of the problem, you must travel the whole breadth and width of the lake.
Its greatest length from north to south is 337 km while its greatest breadth is 240 km. Its coastline exceeds 3,220 km.
In some of its worst areas, the lake vomits the debris of plastics and other non-biodegradable waste back onto the nearby banks. Fishermen know what is going on. More than 12 fish species have disappeared. They simply cannot survive the poison. Only the Nile Perch, which is adapted to surviving in heavily polluted waters, remains the easiest find on the lake.
This has set the up for the deadly fights with Uganda army, as they fight for their survival by fishing in their waters. Those who cannot endure the deadly fights anymore have retired. They now use their boats for sand harvesting, destroying the remaining beaches on the lake.
The Kenyan government first built the Kisumu Port as part of the blue economy agenda it is pushing. Then went back to do an environmental impact study of what the project will do to the lake and its environment – a classic case of putting the cat before the horse. The environment can wait. Why the government was in so much hurry to slap the environment on its face, no one knows.
Somewhere inside the lake, there are other polluters. Currently, cage farming is the in thing. Cages are mushrooming on the lake day and night. There are at least 4000 cages on the lake owned by about 60 firms. Some of the feeds being sprinkled on the cages go to the bottom to further nitrify the lake and act as fertilizer for the invasive hyacinth. When it is in season, the hyacinth weed expands to cover about 1400 hectares every day.
Then there are rivers traveling far and wide from as far as the Mau, Kericho, Mount Elgon and Nandi escarpments in the Rift Valley, that finish their journey in Lake Victoria. Others pass through tea plantations and rice farms that use numerous chemicals. Just like Kisat, they do not always arrive clean.
For instance, the angry Nzoia River carries waste from the Rai Paper mills in Webuye. Then there is Kibos River, which endures the effluent from Kibos Sugar. Nyando River has the notorious Agro-Chemicals and Food Company, a repeat offender, to deal with.
Migori River carries all the mercury from the gold mines and offloads it into the Lake.
Here, impoverished gold miners wake up every day to go to the mines. Every day, without proper gear, they use mercury to ‘clean’ their gold find and the waste flows downstream into the lake.
Their hands tell the story of hardship as the deadly chemicals tear their muscles and cause fresh little wounds every day. The money they make far supersedes the pain. Besides, they have never seen anyone die of mercury poisoning. In fact, many miners swear that the deadly chemical cannot kill. There is no evidence.
The county governments in the region know where the problem is. From Migori to Kisumu and Busia, they know what impact the pollution is having on their population.
Instead, they have turned the hyacinth menace into a cashcow. A reason to make more proposals to international donors to attract billions of shillings in funding. Then retire back to the comfort of their air-conditioned offices and do halfhearted measures to end the menace. Some of the equipment bought by donors is rotting in yards. It is an open secret. The hyacinth is godsend. It eradication is a money minting venture.
In Uganda, the situation is no different. Given, the military deployed by President Yoweri Museveni has helped slow down the pollution. But when you visit the Nakivubo channel, which is a stone throw away from Uganda’s capital Kampala, you will come face to face with the ugly face of pollution.
After Nairobi River, the Nation shifted its gear to Lake Victoria, Africa’s biggest lake. It is also the second largest freshwater lake in the world, only beaten to the top spot by Lake Superior in North America.
At its best times, the giant lake, whose original name is Nam Lolwe, had more than 200 species of fish, of which the Tilapia is the most economically important. The lake’s basin covers 238,900 square km.
In this investigation, we found loads of insecticides, acaricides and herbicides that should never be found in drinking water according to the World Health Organisation (WHO). We also found pesticides that were banned in 2001 still flowing into the lake.
Last year, scientists shocked the world when they gave it 400 years to complete dry up and disappear. But that is not Nam Lolwe’s immediate problem.
For three months, we have travelled along its shores and what is left of its once beautiful beaches. From its border in Tanzania, around its curves and bays in Kenya, we followed it into Uganda’s capital Kampala and the industrial town of Jinja.
Accompanied by toxicology experts from the University of Nairobi, we also travelled to the source of the Nile, from where countries downstream from Ethiopia to Egypt draw their lifeline.
In our second part of the Toxic Flow series, we picked 54 samples at 28 locations on the lake, rivers and effluent discharges from factories in the region. We also bought fish samples imported from China and flew them to Nairobi, for testing.
Today, pollution has been linked with the increase in the prevalence of diseases like cancer and immunosuppression.
Communities around the lake also know what is ailing them.
For example, gold miners at Migori were aware that their activities introduce mercury as a pollutant. Industries including those making sugar, breweries and paper may be contributing the pollution.
The team evidenced polluted water passing through area areas that exposed the community. This included residential and recreational facilities including Nyanza Golf Club.
We purposely collected 54 samples of water, sediments and some aquatic animals in two phases. We collected these samples at 28 different points along the Lake Victoria basin starting at Migori, Kuja, Homa Bay, Kendu Bay, Sondu, Dunga, Kisat, Kibos, Usoma, Kodiaga and Nyando River.
We went back for a second phase of sampling this time covering Jinja in Uganda, Nzoia River at Pan-paper and Marenga beach.
The sampling points picked represent the major anthropogenic activities along the Lake such as industrial, markets and agricultural.
We recorded GPS coordinates of every sampling point using a hand held smart phone. At every sampling point, the water samples were aseptically obtained in two pre-sterilized water-sampling containers for microbial quality. We also had an extra sample in another plastic container for physiochemical analysis.
We collected water at various depths including at the lake surface and mid-lake depth, while sediments were obtained at the shallow rivers’ mouth and the deep lake.
We then transported the samples in cool boxes to a deep freezer for storage before analysis. We flew some of the time sensitive samples to Nairobi to beat the testing window.
At every sampling point, the pH and temperature of the river and lake water were obtained in situ. The microbial water quality was analysed within six hours of sampling and results recorded.
Physiochemical analysis was carried out at the university lab after all the samples were obtained. Sediments and fish, where available, were also sampled and analysed chemicals.
Now, the results are out. East Africa’s most important lake is silently rotting from the deep.
The 13 deadly poisons killing Lake Victoria
By PAUL WAFULA
There are at least 13 deadly poisons inside Lake Victoria that are killing life in the lake and are affecting fish and other aquatic animals, a Nation Investigation has found.
A three month Investigation, Rotting from the Deep, can now reveal why Africa’s biggest fresh water lake is dying a slow death that has seen more than a dozen fish species disappear.
We selected 28 sampling points for this study. These locations were identified due to proximity to contamination through waste discharge or levels of human activities.
The sample locations include Migori River mouth, Kuja River mouth, Homa Bay, River Awach, Kendu Bay, Sondu River, Dunga beach, Kisat River at the golf club, Usoma beach, Nyando River and near Kisumu resort.
We also collected samples at Marenga beach, River Saka at Kodiaga prison, River Nzoia near Panpaper effluent discharge point and waste from Jaggery at Webuye. Other samples were picked at various factory effluent discharge points including those from Kibos Sugar and Kisumu Water and Sewerage Company (KIWASCO).
We traveled to Uganda and also sampled Nakivubo channel that carries the waste from Kampala into Lake Victoria. In Uganda we picked more samples at Gabba area near Kampala, at Masese beach and in Jinja at the source of the Nile. On the lake, we sampled various places included the lake deep, lake surface and near the shores.
From these locations, we collected a total of 54 samples of water, fish and sediments.
What we found in the water
Our study showed that the contamination is spreading from the shores heading towards the middle.
From these poisons, we found at least eight metals in various concentrations, with the most toxic being 75 times more poisonous than the recommended levels.
The metals found at most of our 28 sampling points include Lead, Mercury, Cadmium, Chromium, Zinc, Iron, Manganese and Fluoride.
Lead was widely distributed especially in Migori, Kendu bay, Effluent flowing through Nyanza golf club, Kodiaga prison discharge point, Nyando River, Jinja waters, fish from Masese beach in Uganda and Marenga beach in Kenya.
Lead causes decreased mental, nervous system and physical development in children. In adults, it causes high blood pressure, kidney damage and reduced fertility. We also found lead in excessive quantities in the fish imported from China that was being sold freely in Kisumu City and its adjacent towns.
Mercury was widely distributed especially in water samples from Migori, Kendu bay and Kisat River. According to the results of our study, Mercury can cause toxicity to the nervous system, immune system, intestines and can cause Kidney damage
We also found DDT (Dichlorodiphenyltrichloroethane), a banned pesticide that has adverse effects on humans and aquatic animals. Other pesticides we detected include endosulfan and mirex.
These class of pesticides can cause cancer, mouth ulceration, dysphagia and abdominal pain among other diseases if ingested.
DDT was outlawed in Britain in 1986 and banned as a pesticide worldwide under the Stockholm Convention in 2001 after it was discovered to be dangerous to wildlife and the environment.
Some of the ten rivers that drain into the lake are also dumping into the lake toxins that cause deadly diseases.
We also found bacteria in almost every location we tested that can cause all manner of water born diseases if ingested.
Out of 25 water samples, 23 had dangerous bacterial growth that can cause all manner of water born diseases.
The 23 had total coliforms at counts above what is allowable by the National Environment Management Authority (NEMA).
The contamination represents 92 percent of all the samples and it means that almost the entire lake is polluted by human waste, making the lake a one big toilet for the region.
The only safe samples were from River Kuja and the factory effluent at Nyanza golf club, having had no bacterial growth.
The results showed that 15 water samples (60 percent) had both Escherichia coli (E. coli) and total coliforms. Escherichia is a type of bacteria that lives in intestines. It is also found in the gut of some animals.
Most types of this bacteria are harmless and even help keep your digestive tract healthy.
However, some strains can cause diarrhea if you eat contaminated food or drink fouled water.
Ten (45 percent) samples obtained at Kuja River, Homa Bay deep and surface lake, River Awach surface and deep, Kendu Bay surface and deep, Sondu River and factory effluent at Nyanza golf club, as well as the one from the Jaggery factory at Webuye had no Escherichia coli contamination.
Nine heavy metals were analysed in all the 25 water samples out of which at least seven heavy metals were detected from different samples at levels above the recommended for drinking water.
The physiochemical properties of the same water were tested and most of the water samples had high levels of organic waste evident by the high Chemical oxygen demand (COD) and Biochemical oxygen demand (BOD) levels in 90 percent and 30 percent of the samples respectively.
COD is a measure of the capacity of water to consume oxygen during the decomposition of organic matter. On its part, BOD refers to the amount of dissolved oxygen that aerobic organisms need in order to break down organic material in water over time.
What we found in fish
We also tested the fish samples and sediments for the presence of heavy metals.
All the fish samples tested had at least seven different types of heavy metals.
These metals occurred at different concentrations and frequencies and they include lead, cadmium, chromium, zinc, iron, copper and manganese.
The good news is that some of the heavy metals were detected at levels that are safe for consumption. But not all.
Fish samples collected at Marenga beach in Kenya, Masese and Gabba area in Uganda as well as China fish we bought in Kisumu from a supplier that had lead at levels far above the recommended residue levels of 0.1ppm. This made them unfit for human consumption.
Lead is a dangerous poison and it can cause cancer if ingested in excess. Lead poisoning can also cause anaemia, general body weakness, kidney and brain damage. It can also cause immediate death in excessive quantities.
However, why lead is feared as a poison is because it can damage almost every body system from the heart, bones, kidneys, teeth, intestines, reproductive organs, nervous and immune systems. It can also damage mental and physical development in children.
The same fish samples had relatively high levels of zinc though below the Maximum residue level (MRL). MRL refers to the highest level of residue tolerated in food.
One fish sample obtained at Dunga beach had mercury at 0.03 mg/Kg (ppm), making it unfit for human consumption.
The tolerable intake for methyl mercury which is the form of mercury found in fish as established by World Health Organisation (WHO) is at 1.6 per Kg. This happens to be high if consumed by individuals of 10Kg body weight and below.
All the four fish samples at these locations had lead detected at levels above CODEX (FAO/WHO) permitted maximum residue levels.
Sediments, on the other hand had seven heavy metals detected with none having mercury. There are no guidelines available for concentrations in sediment. Excess mercury can harm the brain, heart, kidneys, lungs, and immune system.
It also damages the Gastrointestinal Tract also known as GIT that entails the digestive tract, alimentary canal and digestion tract. This messes up the entire human system that takes in food, digests it to extract and absorb energy and nutrients, and expels the remaining waste as feces.
When results for the pesticides came, we detected 21 different types of pesticides comprising of organochlorines, organophosphates and pyrethroids in the water samples.
Most of which are used as insecticides, acaricides and herbicides and according to WHO 2006 guidelines, they are not supposed to be found in drinking water, so no guidelines are available. Somehow, in Kenya, these deadly pollutants have found themselves in water.
What we found in sediment
In sediments, 25 different pesticides were detected at varying concentrations and frequency.
Though no guidelines are available for this type of sample some pesticides like permethrin was detected at high concentrations of 12.5 ppm from sediment obtained at River Sondu.
We also detected 33 different pesticides in fish samples obtained from the Lake Victoria basin. Only pesticides were detected in safe levels.
Some of those detected included trifluralin at MRL of 0.001ppm and was detected at 0.01ppm from Sondu and Homa bay, marathion at MRL of 0.005 ppm detected at 0.005ppm from Homa bay, biphenyl at MRL of 0.01 detected at 0.07 ppm from Homa bay, phorate at MRL of 0.01 ppm detected at 0.04 and 0.03 ppm from Dunga and Usoma beach respectively.
Hexachlorobenzene at MRL of 0.01 ppm was detected at 0.09 ppm from Homa bay, while pyrazophos was detected at 0.021, 0.025, 0.026 and 0.07 ppm at Dunga, Sondu, Kendu bay and China fish respectively against MRL of 0.01ppm.
Acrinathrin at MRL of 0.01 ppm from fish obtained at Masese and chlorfenvinphos at 0.01 ppm from Marenga beach.
Out of the 28 sampling points comprising the Lake and its catchment rivers as well as discharge points and the Nile, River Awach had the highest number (67 percent) of heavy metals detected at levels above the recommended KS levels.
These were mercury, lead, cadmium, chromium, iron and manganese.
The second most contaminated was River Kisat that was sampled at the Nyanza golf club, with 5/9 (56 percent) heavy metals including mercury, lead, cadmium, chromium and iron.
This level of contamination could be attributed to among others the effluent discharged to the river at latitude -0.08317, longitude 34.75237 from KIWASCO treatment site.
River Migori at its mouth as well as the discharge at Kendu bay had each four out nine (44 percent) of the heavy metals detected above the recommended levels. These were mercury, lead, cadmium and chromium as well as cadmium, zinc, iron and manganese respectively.
Mercury detected at River Migori could be as a result of the gold mines that discharge to the river.
“Observations made during sample collection showed a lot of negligence in handling of mercury by the gold miners as they use it to process gold. High level of self-exposure with the toxic chemical and its vapor as well as environmental and water contamination is rampart in this area,” the report reads.
The discharges at Homabay and Kisumu beach had the least number of heavy metals, including cadmium and lead respectively at 1 out of 9 (11 percent) metals detected above KS recommendations.
In all the water samples tested in the first phase of sampling cadmium was found in 18 out of 20 (90 percent) samples above the recommended levels, second was lead at 13/20 (65 percent), then chromium 11/20 (55 percent), while mercury and manganese were at 4/20 (20 percent).
In the second phase of sampling all the five water samples had more than 44 percent heavy metals contamination, lowest being form Nile at Jinja.
Seven metals were shown to be occurring at levels above the Kenya Standard recommended levels for drinking water in more than 60 percent of the samples. These were lead, copper, chromium, zinc, iron, manganese and fluoride.
On physical properties, Lake Water at Homabay was the worst, failing in half of all the eight parameters of being compliant with the Kenyan Standards.
These were BOD, COD, nitrate and ammonia, an indication of organic waste discharge. Coming second were Lake Water at Kendu bay, River Sondu mouth and Lake Water at Kisumu beach with 38 percent noncompliance.
Pesticides are unlikely to occur in drinking water, according to WHO guidelines and there are therefore no recommended residue levels available for most of the pesticides.
In this study up to 21 different pesticides including organochlorines, organophosphates and pyrethroids were detected at different concentrations and frequencies in the water samples.
The World health organization pesticide evaluation scheme (WHOPES) program approves pesticides for direct application to drinking water for control of insects vectors transmitting disease.
Guideline values are therefore available for a few pesticides as maximum levels in drinking water namely; chlorpyrifos (0.03ppm), DDT and its metabolites (0.001ppm), permethrin (0.30ppm) and pyriproxyfen (0.30ppm). Amongst these only pyriproxyfen has been approved by WHO for addition to water for public heath purpose.
Some of the pesticides found in the samples analyzed from the Lake Victoria basin and its catchment rivers are of known toxicity to both humans and aquatic life.
Some of the pesticides found contaminating water samples include Fenitrothion an organophosphate used as insecticide is toxic to aquatic life, chlorofenvinphos affects the respiratory system in humans, cyhalothrin has been shown to cause irritation of the mucous membrane, bifenthrin is very harmful to aquatic life and has been classified as a possible human carcinogen.
Oxyfluoren which is used to kill broad leaf and grassy weeds is a possible carcinogen. A few of the pesticides detected in the water and other samples have been globally banned due to their toxicity and environmental persistence.
These include DDT, which is highly persistent in the environment, its very soluble in water, affects reproduction in humans and has been classified as a possible human carcinogen. Endosulfan was globally banned in 2012, is an insecticide and a known neurotoxic and causes birth defects, it has the ability to bio-accumulate.
Another banned pesticide detected was mirex, which is also a bio accumulator and persists in the environment as a persistent organic pollutant thus affecting aquatic life. It’s carcinogenic and an endocrine disruptor.
In the first phase, River Kodiaga had the highest number of detectable pesticides with 10/21 (48 percent), these were benfluralin, linuron, chlorofenvinphos, cyhalothrin, azinphos, oxyfluoren, methoxychlor, DDT, DDE and endosulfan. DDT was detected at 3.49 ppm, which was the most concentrated pesticide detected from water in this study.
River Kisat had the second highest number of pesticides with 9/21 (43 percent) detected which included, linuron, bifenthrin, acrinathrin, deltamethrin, cypermethrin, chlorpyrifos, DDT, endosulfan and mirex. Linuron was the most frequent pesticide in the water samples that was detected in 5/20 (75 percent) samples. Phorate and cyhalothrin were both the second most frequent occurring in water at 8/20 (40 percent).
The second set of samples had slightly higher level of contamination with Pan-paper effluent having 56 percent of the pesticides detected, this was followed by water from Marenga beach and that from Jinja had the lowest.
Twenty-Five different types of pesticides were detected in sediments at varying concentrations and frequencies in the study area.
Sediments from an industrial effluent sampled at Nyanza golf club, that form River Kisat and another from River Sondu had the highest number of pesticides at nine out of the 25 detected from each.
The pesticides found were resmethrin, benfluralin, tefluthrin, bifenthrin, cyhalothrin, pyrazophos, trifluralin, deltamethrin, biphenyl, hexachlorobenzene and permethrin which was the most concentrated in all the sediments at 12.5 ppm.
Deltamethrin was detected in all the 16 (100 percent) sediments, while biphenyl was in 13/16 (81 percent) of the samples, followed by bifenthrin and hexachlorabenzene that were both found in 12/16 (75 percent) of the samples, ethalfluralin was found in (56 percent) while others were below that, the least being detected in only one sediment sample.
On fish samples, we detected a total of 19 different pesticides contaminating the fish from Lake Victoria and its catchment basin at an average concentration of 0.095ppm. The highest pesticide was phenothrin at 1.47 ppm. However, there are no guidelines on what levels can be tolerated in food or be harmful to the body.
Hexachlorobenzene was detected at the highest concentration of 0.09 ppm, which in nine times more than the recommended 0.01 ppm – Maximum residue level (MRL).
The most frequent pesticide detected in fish was pyridaphenthion at 80 percent prevalence while linuron, pyrazophos and cypermethrin were each detected in three out of the five fish samples tested. This translates to a prevalence of 60 percent in the samples tested.