Sodium dichloroisocyanurate (NaDCC) tablets as an alternative to sodium hypochlorite for the routine treatment of drinking water at the household level

Abstract

Household water treatment using sodium hypochlorite (NaOCl) has been recognized as a cost-effective means of reducing the heavy burden of diarrhea and other waterborne diseases, especially among populations without access to improved water supplies. Sodium dichloroisocyanurate (NaDCC), which is widely used in emergencies, is an alternative source of chlorine that may present certain advantages over NaOCl for household-based interventions in development settings. We summarize the basic chemistry and possible benefits of NaDCC, and review the available literature concerning its safety and regulatory treatment and microbiological effectiveness. We review the evidence concerning NaDCC in field studies, including microbiological performance and health outcomes. Finally, we examine studies and data to compare NaDCC with NaOCl in terms of compliance, acceptability, affordability and sustainability, and suggest areas for further research.

Section snippets

Background

Contaminated drinking water, along with inadequate supplies of water for personal hygiene and poor sanitation, are the main contributors to an estimated 4 billion cases of diarrhoea each year causing 2.2 million deaths, mostly among children under the age of five in developing countries (Kosek et al., 2003). Unsafe water is also an important contributor to other potentially waterborne diseases, including typhoid, hepatitis A and E, polio and cholera.

An estimated 1.1 billion people lack access

Basic chemistry and potential advantages of NaDCC over NaOCl

Chlorine has been used as a disinfectant for the treatment of drinking water for more than 100 years. It is by far the most commonly used means of disinfecting water, and its effectiveness as a microbicide has been widely assessed (AWWA, 2000). While most conventional systems in developed countries treat water with chlorine gas (delivered as a liquid in pressurized systems), other common alternatives include calcium hypochlorite, sodium hypochlorite, lithium hypochlorite and chloroisocyanurates

Toxicity and regulatory review

All chlorine products have some level of toxicity; this is what renders them such effective microbicides. When chlorinated water is ingested, however, the available chlorine is rapidly reduced by saliva and stomach fluid to harmless chloride ions salts (Kotiaho et al., 1992). This is true for all sources of chlorine, including both NaOCl and NaDCC. The unique characteristic of the isocyanurates is cyanuric acid, the carrier that allows the chlorine to be contained in a solid, stable and dry

Microbial effectiveness

As noted above, NaDCC is an alternative source of FAC (HOCl). Accordingly, the significant body of evidence on the antimicrobial action of chlorine is as relevant to NaDCC as it is to NaOCl and other sources of chlorine (White, 1998; Dychdala, 2001; CDC, 2005). While certain bacterial spores have shown greater resistance to NaDCC (Bloomfield and Arthur, 1992), thus at least suggesting the potential for differences in activity based on the chlorine donor, no differences have been reported in

Health impact

There is a growing body of evidence of the effectiveness of household-based interventions, including chlorination, against endemic diarrhoea (Clasen et al., 2006; Fewtrell et al., 2005). In most intervention trials, the disinfectant was a solution of NaOCl (liquid bleach) (Austin, 1993; Kirchhoff et al., 1985; Quick et al., 2002; Reller et al., 2003; Sobsey et al., 2003; Luby et al., 2004; Crump et al., 2005; Lule et al., 2005). In other trials, the disinfectant was calcium hypochlorite (

Compliance and acceptability

Like other health interventions, compliance with and the acceptability and affordability of household water treatment solutions are believed to be important factors in the uptake of the intervention, their wide-spread diffusion, and thus their long-term health impact. The consistent use of point-of-use water treatment has been shown to be an important factor in the prevention of endemic diarrhoea (Clasen et al., 2006). Acceptability and affordability are essential to their uptake and the

Affordability, scalability and sustainability

Part of the preference for NaDCC tablets expressed by the Tanzania focus groups was based on participants’ perceptions about affordability. This suggests an important aspect about household economics in low-income settings that is well known by consumer companies that sell to the so-called “bottom of the pyramid”: unit price minimization (Prahalad, 2005). Table 1 compares the retail price charged to consumers for 500 ml bottles of NaOCl currently paid by PSI for its WaterGuard campaign in

Conclusion and need for further research

Like other sources of hypochlorous acid, NaDCC has been shown to be an effective antimicrobial agent. The chemical composition and physical characteristics of NaDCC tablets, however, may offer certain advantages over NaOCl as a possible donor of free chlorine in the disinfection of water at the household level. The safety of the compound for the routine treatment of drinking water has now been satisfactorily addressed. There is also evidence that suggests that use of NaDCC tablets increases

Acknowledgements

The authors are grateful to Dr. Sally Bloomfield of the International Scientific Forum on Home Hygiene and Dr. Thomas Kuechler of Occidental Chemical Corporation for suggesting sources and for reading and commenting on this paper.

T. Clasen provides research services to Medentech, Ltd. which manufactures and sells Aquatabs™, a water treatment product whose active ingredient is NaDCC. P. Edmondson is the Technical Director of Medentech, Ltd.

References (55)

• S.F. Bloomfield et al.(1985)

The antibacterial properties of sodium hypochlorite and sodium dichloroisocyanurate as hospital disinfectants

J. Hosp. Infect.

• L. Fewtrell et al.(2005)

Water, sanitation, and hygiene interventions to reduce diarrhoea in less developed countries: a systematic review and meta-analysis

Lancet Infect. Dis.

• M.S. Nascimento et al.(2003)

Effects of different disinfection treatments on the natural microbiota of lettuce

J. Food Prot.

• Afroz Molla, M., 2005. Pilot study on the effect of an intervention using sodium dichloroisocyanurate (Aquatabs)...
• Austin, C.J., 1993. Chlorinating household water in The Gambia. In: Proceedings of the 19th WEDC Conference, Accra,...
• Committee report: disinfection at large and medium-sized systems(2000)

J. Am. Water Works Assoc.

• Baylac, P., Sere, O., Wanegue, C., Luigi, R., Polveche, Y., 1996. Comparaison du pouvoir désinfectant de la chloramine...
• S.F. Bloomfield

Chlorine and iodine formulations

• S.F. Bloomfield et al.(1992)

Interaction of Bacillus subtilis spores with sodium hypochlorite, sodium dichloroisocyanurate and chloramine-T

J. Appl. Bacteriol.

• S.F. Bloomfield et al.

The antibacterial properties of sodium dichloroisocyanurate and sodium hypochlorite formulations

J. Appl. Bacteriol.