World Health Organization and International Guidelines for toxin control, Harmful Algal Boom management, and response planning.

Abstract

Drinking water guidelines are designed to protect public health and the safety of drinking water supplies by suggesting safe levels for constituents that are known to be hazardous to health. The World Health Organization (WHO) Guidelines for Drinking Water Quality (WHO 1996; 2004) represent a scientific consensus on the health risks presented by microbes and chemicals in drinking water and are often used to derive guideline values for individual countries, states or regions. The guideline values are to be used in the development of risk management strategies and are associated with guidance on monitoring and management practices. Although no human deaths due to the consumption of cyanotoxins have been recorded, cyanobacteria and their toxins remain a significant issue for the WHO, since extended exposure may cause gastroenteritis, among other more serious health impacts (NHMRC/NRMMC 2011). In addition, cyanotoxins are suspected to have resulted in fatalities when introduced into the human body through routes other than ingestion, such as through the use of toxin-containing water for renal dialysis (Jochimsen et al. 1998). Motivated by growing concern over the presence of cyanotoxins in drinking water, the WHO published an addendum to its Guidelines for Drinking Water Quality in 1998, which included a guideline value for microcystin-LR (MCLR), an acutely toxic cyanotoxin (WHO, 1998). The health-based guideline value for total (i.e., free plus cell-bound) concentration of MCLR was set at 1 μg/L; however, the WHO emphasizes that the guideline value is only provisional, since it only pertains to MCLR, and since the toxicity data for other cyanotoxins are still being collected (WHO, 2004). According to the WHO, not enough data exist to allow guideline values for other cyanotoxins to be developed (WHO 2004). Concern over drinking water contamination by cyanotoxins has also grown among national regulatory bodies, due to the increasing impact of anthropogenic activity on water resources, as well as the improvement of analytical methods identifying and measuring cyanotoxins. For example, Australian drinking water authorities have set a guideline value of 1.3 μg/L for microcystins, expressed as MCLR. New Zealand has developed maximum allowable values (MAVs) for several cyanotoxins, including anatoxin and anatoxin-A, cylindrospermopsin, microcystins, nodularin, and saxitoxins. The US Environmental Protection Agency, on the other hand, has yet to set any firm, enforceable maximum contaminant levels (MCLs) for cyanobacterial toxins, and has only added cyanobacteria and their toxins to its candidate contaminant list (CCL), which prioritizes contaminants for setting MCLs. In Canada, a maximum acceptable concentration (MAC) of 1.5 μg/L has been developed for cyanobacterial toxins, expressed as MCLR. Canada’s guideline was derived using tolerable daily intake (TDI) values, determined using no-observed adverse effect levels (NOAEL), which are based on human or animal toxicity studies. Brazil has developed guidelines for three cyanobacterial toxins (microcystins, saxitoxins, and cylindrospermopsin), with guideline values being set as 1.0 μg/L, 3.0" μg/L, and 15" μg/L, respectively. Several other countries, however, still rely on the WHO provisional guideline of 1"μg/L MCLR. A comprehensive summary of international guideline values for cyanobacterial toxins from various countries worldwide are summarized in Table 8.1.