Occupational and environmental hazard assessments for the isolation, purification and toxicity testing of cyanobacterial toxins

Over 40 species in some 20 cyanobacterial genera can produce a range of structurally and functionally diverse toxins, known as cyanotoxins. Freshwater and marine cyanobacteria, encompassing both planktonic and benthic forms, can produce potent toxins, some of which have been well characterised in terms of their toxic effects and some of which are less well-understood [1]. The known cyanotoxins can exert their toxic effects through a variety of mechanisms (depending on the particular toxin): some are potent neurotoxins that can cause respiratory dysfunction and death through paralysis of respiratory muscles, e.g. saxitoxins, anatoxin-a, anatoxin-a(S). Some affect the liver and other organs, e.g. microcystins, nodularin, cylindrospermopsin, and some exert acute irritant effects on the skin and mucous membranes, e.g. debromoaplysiatoxin, lyngbyatoxin A. Some cyanotoxins are potent tumour promoters, e.g. debromoaplysiatoxin, lyngbyatoxin A, microcystins, nodularin. Long-term, low-dose exposures to microcystins and/or cylindrospermopsin in drinking water are suspected (but so far unproven) risk factors for the development of some types of cancer. Cyanobacteria are rich sources of novel bioactive compounds, many of which are poorly researched with respect to toxicity [2].Several cyanotoxins have been chemically synthesised, e.g. anatoxin-a [3-5], cylindrospermopsins [6,7], saxitoxins [8,9], lyngbyatoxin A [10,11], aplysiatoxins [12], and one of the microcystins and some microcystin structural components [13,14]. However, the processes involved in synthesis of cyanotoxins like cylindrospermopsin and microcystins are complex and multiple steps are required, so those particular molecules are unlikely to be synthesised on a commercial scale in the near future. Therefore the most efficient methods for obtaining research-enabling quantities of many cyanotoxins in the short to medium turn will be to bulk-harvest cyanobacteria from natural waterbodies or to grow laboratory isolat