2.3 Describe water use and users

(here specifically discussed with respect to cyantoxins)

Which share of the water is used for drinking-water, for irrigation, or for other uses? Is exposure to aerosols likely? Are there specific sensitive consumer groups such as children’s swimming classes, hospitals or dialysis units, who should receive targeted warnings in times of risk of elevated cyanotoxin occurrence?

· Hospitals and dialysis units [c1] ,

· Private supplies[c2] using surface water or shallow wells strongly influenced by surface water;

· Settings with formation of aerosol[c3] from surface water, e.g. irrigation, decorative fountains, in some settings water used for cooling (e.g. mining drills);

· Recreational use (including illegal use [c4] of sites such as drinking-water reservoirs)

è Document your list of water use and users, e.g. in the worksheet provided on the starting page of this decision support tool.

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[c1] Dialysis exposes people to approximately 120 L of water. The preliminary WHO Guideline value for Microcystin-LR is based on the assumption of oral consumption of 2 L of water per day. Thus, water for dialysis should contain at most 1/60 of the concentration accepted for drinking-water, i.e. < 0.04 µg/L. Furthermore, some experimental data indicate that through oral uptake only a fraction of the microcystin ingested will reach the blood stream, while dialysis will transfer microcystin directly into the circulatory system. Thus, tolerable concentrations in water for dialysis should be even lower than 0.04 µg/L

This concern is substantiated by the well documented case of deaths through exposure to cyanotoxins during dialysis (Jochimsen et al. 1997).

è Dialysis units should therefore recieve early warnings when blooms occur, even when cyanotoxin concentrations are well below guideline levels and effective removal through treatment is assumed.

[c2] e.g. farm dugouts; supplies for holiday houses. As far as possible, this inventory should include of illegal or not notified supplies è Warning them during bloom season may be adequate

[c3] Uptake as aerosol has been repeatedly discussed since Fitzgeorge (1994) demonstrated substantial microcystin uptake through nasal membranes. Anecdotal evidence indicates illness through exposure through aerosols and is plausible even if to date unpublished. è Warning these user groups when blooms occur may be appropriate.

Swimming is often practiced even where it is illegal, e.g. in drinking-water reservoirs. è Warning notices when blooms occur may be nonetheless appropriate to protect public health.