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February 01, 2013

Study Names Cameroon as Hotspot for Mercury Contamination

by Ntaryike Divine Jr.

Soaring costs of meat, currently selling at US$6 per kg across Cameroon, have forced up to 20 million consumers to rely on low-priced fish for balanced diets.

But a scientific probe has unveiled bad news for those who depend on the relatively cheaper protein source. Its findings reveal that fish caught in Cameroonian waters contain extremely high concentrations of mercury, a chemical element and metal harmful to human health. 

The survey, titled Global Mercury Hotspots was conducted between May and June last year.  It’s findings were just recently made public.  The study measured the amount of ingested mercury in a sample population on the outskirts of Cameroon’s largest city and industrial hub, Douala. 

According to the findings, residents of the city are highly exposed to contamination by the metal.

Medics say humans are often exposed to its most poisonous form, methylmercury,  by consuming fish living in polluted waters.  Ingestion of the contaminated food can destroy the human immune and nervous systems, and damage developing embryos. 

The research was jointly manned by experts from the Biodiversity Research Institute, the International POP Elimination Network and the Center for Research and Education for Development. 

Nineteen trial subjects from two predominant fishing communities just outside of Douala – Youpwe and Takele - offered hair samples for analysis. Dr Gilbert Kuepouo, Coordinator at the Center for Research and Education for Development says results of the analyses conducted at a laboratory in the northeastern US state of Maine revealed disturbing methylmercury traces in the trial subjects.

He says 17 of the hair samples showed worrying mercury contamination levels way above WHO limits of one microgram of mercury per kilogram of human body mass.  Kuepouo says they found concentrations ranging from 2.8 to 3.8 micrograms per kilogram [or parts per million].  He adds that even more disturbing were two others who displayed exceedingly elevated levels surpassing 540 micrograms

Mercury occurs naturally in geological deposits, volcanoes, and also as an introduced contaminant in the environment from metal processing, gold mining, coal incineration and hospital waste.  It is easily carried over vast distances in the atmosphere by wind and then deposited on land and water sources.

Some of the mercury that falls from the air onto water sources is converted by marine bacteria into methylmercury.   Fish devour the microscopic animals called zooplanktons, who have consumed the substance.  At each stage in the aquatic food chain, the concentration of methylmercury,  which is much more easily absorbed than is excreted, is magnified.

Dr Jude Attah, the co-author of the report, says "Our conclusion is that the main source of contamination is fish, though there are other sources like some skin-lightening lotions, clay and artificial teeth workshops. The Wouri estuary where most of the fishing off Douala is done is highly polluted with mercury from the various industries around."

The researchers have recommended urgent measures to reduce mercury emissions in Douala, where more and more people depend on fish for proteins.

They are urging governments in the region to immediately enact legislation to encourage mercury-polluting industries to obtain equipment to clean up contaminated environment.  They also want a limit on imports of raw materials containing mercury and the inspection of industrial and hospital garbage before disposal. 

Since 2009, the United Nations Environment Program, UNEP has been pushing for a negotiated global pact to progressively phase out and eventually eliminate mercury emissions worldwide.  The initiative is due to be completed this year.  It will likely include a legally binding treaty which will stand as a basis for national laws and help to reduce emissions worldwide.

Listen to report on mercury contamination in Cameroon