CYANOBACTERIA IN FRESHWATER: INFLUENCE IN LIVER MORBIDITY IN EXPOSED ALENTEJO'S POPULATION BETWEEN 2000 AND 2010

Taking nutrients from the water column, phytoplankton can present high levels of growth and blooms arise if growth rates reach densities over 2.000 cells/ml. Cyanobacteria (prokaryotic, photosynthetic microorganism) is one group of this community and can produce toxins responsible for human injury after acute or systematic exposition. The main goal of this work is to correlate cyanobacteria blooms in Alentejo reservoirs and liver morbidity (cancer disease) in human exposed population, through direct or indirect water consumption. In Portugal seven reservoirs used to produce drinkable water located in Alentejo region were selected and studied between 2000 and 2008. Reservoirs were characterized in physical and chemical aspects, as well as phytoplantonic communities, through identification and counting of main present groups along the study period. In expressive blooms circumstances, liver toxin producers were founded, namely Microcystis aeruginosa, Aphanizomenon sppand Oscillatoria, and liver condition indicators showed highest levels in exposed populations. Liver cancer incidence was also more expressive in the exposed population, compared to nonexposed population. It was concluded that cyanotoxins systematic exposition promotes liver morbidity in the exposed population, attested by high levels of liver enzymes, cancer disease incidence and relative and attributable risks values, compared to non-exposed population's values.