Beware of mercury poisoning in fish
Published On January 23, 2018 » 1635 Views» By Evans Musenya Manda » Features
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By DANIEL SIKAZWE – In the cacophony of a bustling market in Lusaka’s Central Business District, several fish traders are busy wadding off a buzz of flies circling round their fresh breams.
The fish comes from a diversity of sources, including Zambia’s natural water bodies and fish farms.
This writer stops by to ask a few of the fish traders whether they have heard about the possibility of the fish they are selling having the potential to pass on to humans the most dangerous diseases on earth commonly known as Minamata disease.
Minamata disease is caused by mercury poisoning through human consumption of fish mostly.
“Va mercury siniviziba. Ife tima order chabe nsomba. Kapena mufunseko ba mu Shoprite. Kapena ni field yamene bamasebenzelako (This mercury staff, I know nothing about it. I simply order my fish from fishermen. Ask those in Shoprite. Maybe that’s the field they work in),” said Joseph Tembo who has been selling fish for more than five years in the market.
Another fish trader, Mary Kalaluka, who has been in fish trading since 1993, has an excuse for not knowing about the possibility of the presence of mercury in fish.
“I really don’t know what mercury is. I wouldn’t even know because I have not studied science. I didn’t go far in school,” Ms Kalaluka said.
Her competitor on the neighbouring stand, Mercy tells the writer of this story: “I have been in the fish business for more than 10 years. I know about a metal called mercury but I have never heard that it can be found in fish”.
If you have been to a dentist and have required a tooth fill-in to relieve your pain, the amalgam used has some mercury content in it.
Juliet Chisenga Boma, a tutor at the Zambia Dental School in Lusaka, says mercury is used in the tooth amalgam because “…it is a very strong metal that can help the dental patient with chewing”.
She said dentists take care to ensure that the combination of metals in the amalgam does not come into contact with the gums and other parts of the mouth.
The amalgam, which contains 65 per cent silver, 29 per cent tin, 6-13 per cent copper, two per cent Zinc, with the rest comprising mercury, has been used and remains in use in Zambia in dental surgeries despite a growing opposition to its use in the northern hemisphere and generally in the scientific world.
Boma says, “The amalgam is imported and at the moment, there are no standards set for mercury content in the amalgam in Zambia’’.
The Zambia Bureau of Standards (ZABS), despite having specifications for mercury contamination in industrial effluent and products like wheat flour, opaque beer, cosmetic creams, lotions and gels, milk replacers and dairy, does not yet have standards set for fish and dental amalgams.
A visit to the ZABS laboratory revealed that the last testing done by the organisation to detect the amounts of mercury in local fish was done in 2013 for two commercial clients of the organisation.
But even then, the results could not be relied upon because they were not done using the most accurate instrument called the Hydride.
However, ZABS Director of Technical Standards Margaret Lwenje Lungu noted that despite the absence of standards on fish and amalgams due to lack of credible research done in Zambia recently, the organisation depends on international standards set by bodies like the World Health Organisation (WHO) and Codex.
Mercury is a silver-white metal that is in liquid form at room temperature.
It is easily distinguishable from all other metals by its liquidity at even the lowest temperatures occurring in moderate climates.
In its purest form, mercury is a smooth, silvery-white mobile liquid with a metallic luster.
It is the metal sometimes called quicksilver.
It is the mobile liquid we see in thermometers.
It is an important component in amalgams used by dentists.
The metal is also present in some fungicides, hearing aids and watch batteries, paints, mercurial drugs, antiquated cathartics, and ointments.
It is widely used in the manufacture of lighting fixtures such as fluorescent, metal halide, and mercury vapour lamps; dental amalgams; mining and reprocessing of gold; batteries; and paint.
The presence of mercury is considered contamination in the cells of living organisms because scientists agree that there is no known beneficial use of mercury in our bodies.
Mercury in our bodies puts us at the risk of dying from coronary heart disease, myocardial infarction and a documented rapid progression of carotid atherosclerosis.
Mercury can undergo rapid transformation in the water based food chains before it reaches us in more dangerous forms.
Changes in our genetic makeup, (the core determining principle of our individual and group design as human beings) can result from our exposure to mercury.
A person with Minamata disease experiences tremours and has impaired hearing and speech. When such a person attempts to write using a ball point pen, it is impossible to keep the pen steady on the paper.
The person can also not walk steadily.
The patient will produce excessive saliva and will sweat profusely.
In more advanced cases of the disease, the person will have cerebral palsy, blindness, deafness, microsephally and loss of speech, and motor coordination and mental disturbances.
United Nations (UN) Secretary General Antonio Guterres tells the story of the first time Minamata disease came to the attention of the world – in his foreword to the Minamata Convention, the main international treaty designed to manage and eradicate mercury and its compounds.
“In 1956, two sisters, aged two and five, were diagnosed in Minamata Bay, Japan, with the crippling, untreatable and stigmatizing effects of mercury poisoning.
“In the decades that followed, their story would be retold many times, becoming synonymous with the tens of thousands of adults, children and unborn infants to suffer from what is known as Minamata disease,” Mr Guterres said.
The disease affects human beings and other living creatures where there are concentrations of mercury in water bodies like rivers, lakes, oceans and wells.
Minamata is the name of a bay area in south-western Kyushu, Japan.
The place is well-known for providing the world with earliest large scale knowledge of the impact of mercury and its compounds through human consumption of fish and shellfish in water bodies like oceans, rivers, lakes and ponds.
This is in spite of the fact that scientists had been aware of the effects of inorganic mercury contamination on human health as early as 1865 when two men working in a European chemical factory were reported to have suffered mercury poisoning.
Minamata is fresh on the mind of the author of this story when Andrew Zulu, a Lusaka City Market fish trader who has been plying his trade since 1980 argues that his fish, bought from fishermen who working in the Kafue River, cannot have mercury.
He asserts that, “Maybe the fish that comes from bigger rivers like the Zambezi can have mercury. This is because Kafue does not have much fish compared to the bigger rivers,” he says.
According to him, Kafue River, for its size, has too many diversions of its water to farms and gardens so if there is any mercury, it goes to those places and there can never be any swallowed by the fish.
When this writer shows Andrew a map of  the areas through which the Kafue River  flows on its way to the Zambezi, Andrew reluctantly agrees with the writer that it’s possible his fish could contain mercury or mercury compounds.
This is because the Kafue River flows through some of the busiest parts of the country where there are mining activities, oil processing factories, wet flue cleaning systems and affluent households that use products that contain mercury.
Besides that, mercury can also get into the river through run-off and leachate from mercury contaminated soils.
Andrew later took leave from the conversation because two customers were now waiting to buy his fish.
Preliminary studies conducted by the Zambia Environmental Management Agency (ZEMA) – the successor to the Environmental Council of Zambia, indicate that there are deposits of mercury in the Kafue River largely due to mining activities in the Copperbelt Province.
ZEMA Principal Inspector and Head of Pesticides and Toxic Substances Department Christopher Kanema said mercury in Zambia is released into the environment through various anthropogenic or human activities.
These include gold mining, open air burning of waste management, fuel refining, use of cosmetics that contain mercury compounds, as well as metal production and processing.
With regards to the Kafue River, ZEMA is sure of the presence of mercury in this important water source, but the agency cannot ascertain at this point whether there is already contamination of the fish in the river.
“I wouldn’t say that the presence of mercury in the Kafue River is alarming. The thing is, there is an indication, just an indication that our fresh waters are at risk of being exposed to mercury and so the study brought out that aspect, that there is presence of mercury which means that the Government, through relevant agencies, needs to up strategies for monitoring and managing as well as getting rid of mercury and mercury compounds,” Mr Kanema said.
An international, multilateral agreement to save humans, other living organisms and the environment from the deadly impact of mercury and mercury compounds has been in place since 2013.
And Zambia is a signatory to the convention.
Activities are already in place to ensure the implementations of the recommendations of the Minamata Convention in Zambia.
The Minamata Convention, a culmination of several years of conversations between governments, civil society organisations, science and environment experts, as well as multilateral organizations, was signed near Minamata Bay in Japan in 2013.

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