(UNESCO / Japan Young Researchers' fellowships programme)

Evaluating pollution by carcinogenic and mutagenic xenobiotics of aquatic ecosystems in Bamako and its surroundings

Summary of research carried out: 
Evaluating pollution by carcinogenic and mutagenic xenobiotics of aquatic ecosystems in Bamako and its surroundings

Anthropic activities in nature are giving rise to an accumulation of carcinogenic xenobiotics, genotoxics, oncogenes, teratogens, endocrine disruptors (reproductive problems), and so forth.

In general, the concentration of anthropogenic disruptors increases from link to lin. Special attention has been paid to the carcinogenic and mutagenic power of these chemical compounds in higher-level organisms, such as the fish and birds of the aquatic ecosystems of the Niger River in Bamako.

Our investigation focused on the impact of xenobiotics on the biotic elements of the aquatic ecosystems in Bamako and its surroundings.

We examined 157 samples from the liver and intestinal tissue of hydrobiotic organisms from the ecosystems under review.

The experiment (described by Ames, B.N. et al., 1975) made it possible to detect any special accumulation sites for organic pollutants, and their method of transfer, to conduct a comparative study of enzyme activity in biliary fraction; to identify sensitive animals and to evaluate the toxicity of the chemical compounds. The study yielded the index of lipophilic polluting agents responsible for a probable bioaccumulation in the final biological consumer, for example, human beings.

Among the 157 samples analysed we found a mutagenic effect or activity (shown in bold) in the tissues, intestine and liver of 121 of them, in 85% of the fish and 81% of the birds, or 77% in total. The fish showed mutagenic activity on at least one of the bacterial strains (TA-98, TA-100, TA-1535, TA-1637 and TA- 97). In contrast, 15 tissue, liver and intestine samples and 10 fish tissue samples tested negative on the Ames test on all bacterial strains. The biotest demonstrated significant mutagenic activity in migratory birds compared to that found in native populations.

Chemical analyses of 15 samples demonstrated the presence of xeniobiotics with concentrations ranging from 10 times (for biphenyl, fluorene, indol[I,2,3-cd+pyrene, …], 200 times (for DDT, benz[ox]pyrene …) to 1,000 times (for pyrene, phenol …) higher than that authorized for water. We found 30 substances of which 45% were mutagenes and 16% were carginogens.

Biochemical analyses of cytochrome P450 enzyme activity in the birds revealed that it was higher than the activity recorded in the fish. Despite that advantage, the birds tested also demonstrated a significant accumulation of organic pollutants that can cause cancer or mutation in those animals.

Biological and chemical analyses indicated a high pollution level in the Niger River. This river needs special monitoring.

The proper implementation of the recommendations will make it possible to reduce the concentration of the chemical compounds in the tissues of aquatic animals in the Niger River in Bamako and the comparatively high death rate of species found in the ecosystems under consideration.


4 February 2008

Translated from French by UNESCO