Water pollution in Mozambique

Mozambique is a developing country where the majority of the population still lacks access to safe drinking water, in spite of the fact that there is sufficient water to cover their needs. The primary source of water pollution is effluent from households, agriculture and industry, but the growing interest in exploiting natural gas, metals and other resources in the coastal areas of the country is also increasing the risk of polluted drinking water. In addition, it is thought that higher temperatures resulting from global climate changes can lead to an increase in the runoff of nutrients into surface water, which in turn intensifies the eutrophication of lakes and the blooming of cyanobacteria.

The blooming of cyanobacteria is a serious pollution problem because many species of these bacteria produce toxic components, so-called cyanotoxins. A higher incidence of cyanobacteria has been detected in drinking water reservoirs and both bacteria cells and dissolved toxins can be found in the drinking water. The largest group of cyanotoxins are called microcystins and increased attention is now being paid to these because they can have a negative effect on human health.

Chronic exposure to microcystins can cause serious health problems for animals and humans, for example damage to the liver. Humans are exposed to these toxins by drinking polluted water and also via direct skin contact and inhalation. An intense growth of toxin-producing bacteria in drinking water can also have detrimental effects on the environment and the economy. Microcystins therefore pose a serious problem for the population and the authorities. In order to reduce these problems, an effective management of the drinking water systems, which is capable of monitoring cyanobacterial blooms and their toxins, is required.

Olivia Pedro's doctoral research has helped to increase knowledge about the occurrence of microcystins and microcystin-producing cyanobacteria in freshwater used for drinking in Mozambique. She conducted her studies by taking samples from three different areas in southern Mozambique: the Pequenos Libombos dam, the Nhambavale lake and the Chòkwé irrigation canal. The first two are the main sources of drinking water for the population in Maputo and Chidenguel respectively, while the Chòkwé canal is principally used for irrigation. By means of various chemical and molecular methods, Pedro found concentrations of microcystins that were far higher than WHO's recommendations for the content of drinking water. She also discovered that there were seasonal variations in bacteria blooms and the production of toxins.

This PhD thesis is significant because it is the first to show that there is a connection in Mozambique between the season and the amount of cyanobacteria Microcystis and the concentration of microcystins in freshwater.