Cyanobacterial toxins: removal during drinking water treatment, and human risk assessment.

Abstract

Cyanobacteria (blue-green algae) produce toxins that may present a hazard for drinking water safety. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s), cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer, to neurotoxicity. The occurrence of cyanobacteria and their toxins in water bodies used for the production of drinking water poses a technical challenge for water utility managers. With respect to their removal in water treatment procedures, of the more than 60 microcystin congeners, microcystin-LR (L, L-leucine; R, L-arginine) is the best studied cyanobacterial toxin, whereas information for the other toxins is largely lacking. In response to the growing concern about nonlethal acute and chronic effects of microcystins, the World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 pg/L drinking water. This will lead to further efforts by water suppliers to develop effective treatment procedures to remove these toxins. Of the water treatment procedures discussed in this review, chlorination, possibly micro-/ultrafiltration, but especially ozonation are the most effective in destroying cyanobacteria and in removing microcystins. However, these treatments may not be sufficient during bloom situations or when a high organic load is present, and toxin levels should therefore be monitored during the water treatment process. In order to perform an adequate human risk assessment of microcystin exposure via drinking water, the issue of water treatment byproducts will have to be addressed in the future.

Water quality assessment: surface water sources used for drinking and irrigation in Zaria, Nigeria are a public health hazard

“…Worldwide, 37% of people not using improved source of drinking water live in subSaharan Africa (WHO/UNICEF 2010). Such water sources are vulnerable to contamination with faecal pathogens, which pose serious public health risks linked to excessive nutrient levels and the presence of enteric pathogens in drinking and irrigation waters (Shuval 1990;Hitzfeld et al 2000;Pruss et al 2002). Nonpoint sources of such contamination include domestic and wild animal defecation, malfunctioning sewage and septic systems, stormwater drainage and urban runoff, while point sources include as industrial effluents and municipal wastewater treatment plants (Kistemann et al 2002;Albek 2003;Okoh et al 2007;Igbinosa and Okoh 2009;Odjadjare and Okoh 2010).…”

Assessing the toxicity of ingested Taihu Lake water on mice via hepatic histopathology and matrix metalloproteinase expression

“…Microcystins are a family of hepatotoxic cyanotoxins consisting of over 80 structural variants ), among which microcystin-LR (MC-LR) has received most concerns because of its high toxicity and frequency occurring in water blooms (Hitzfeld et al 2000). MC-LR is a kind of hepatotropic endotoxin which contains bioactivity and one structure of cyclic heptapeptide (Park et al 2001).…”

Protective effect of melatonin against nodularin-induced oxidative stress in mouse liver

“…The hepatotoxicity of cyanobacterial toxins has been well examined (Ueno et al 1996, Ding et al 1999, Hitzfeld et al 2000. However, the mechanism of the hepatotoxicity of nodularin and the methods of the protection against them have not been fully elucidated.…”