Comment on "An Observational Study on the Effectiveness of Point-of-Use Chlorination".

Dear Editor:

Household water treatment with sodium hypochlorite at the point-of-use has been widely shown to improve microbiological quality of stored household water (Quick et al., 1999; Quick et al., 2002) and reduce diarrheal disease in developing countries (Arnold, 2007).

The authors of "An Observational Study of the Effectiveness of Point-of-Use Chlorination" (JEH, April 2009) hypothesized the efficacy of point-of-use chlorination in controlled trials would vary from its effectiveness in households, and their study data led them to conclude human factors and uncontrolled water quality effects significantly decrease point-of-use chlorination effectiveness.

However, the authors' observational study used locally available commercial bleach of unknown sodium hypochlorite concentration. Previously published efficacy studies (including those referenced by the authors and others) were all conducted in populations with access to quality-controlled sodium hypochlorite products manufactured specifically for point-of-use water treatment.

Based on testing sodium hypochlorite concentration in 32 commercial bleaches from 12 developing countries, where the average error between advertised and measured concentration was 35% (range -45%-100%) (Lantange, in press), the Centers for Disease Control and Prevention (CDC) do not recommend using locally available commercially bleach for water treatment (CDC, 2008). As CDC concluded, "Due to disparities between advertised and actual sodium hypochlorite concentration, the use of commercial bleach for ongoing water treatment in developing countries is not recommended in the absence of ongoing quality control testing to confirm the concentration is appropriate for the dosage regimen recommended to the user."

The observational study authors also suggest physical and chemical water parameters influence disinfection efficacy. This is quite correct, and for this reason CDC has conducted chlorine dosage testing worldwide. Testing of 106 source waters from 13 countries found a 1.875 mg/L dosage was appropriate for protected sources or sources with <10 NTU turbidity, and a 3.75 mg/L dosage was appropriate for unprotected sources with >10 NTU (Lantange, 2008). Additional unpublished dosage data and targeted turbid source testing has confirmed these recommendations. In the observational study, the dosage regimen was 1 drop/liter, equivalent to ~2 mg/L dose (assuming 5% bleach and average drop size) (personal communication). The authors did not conduct source water testing, but noted "based on overall appearance" "chlorine was consumed by inorganic and organic compounds." This suggests turbidity in this study exceeded 10 NTU, and a 3.75 mg/L dosage (2 drops/liter) would have been appropriate.

Without quality control testing of the locally available bleach and an appropriate dosage regimen, it is not possible to discern whether the lack of chlorine residual and microbiologic improvement in study households' treated water was due to poor quality product, incorrect dosage, or user error. A more accurate conclusion based on the data presented would be, "Point-of-use chlorination promotion with an unregulated product and inappropriate dosage regimen without accompanying education is not effective at ensuring improvements in microbiological quality of household drinking water." This conclusion is consistent with published literature and over a decade of CDC experience in point-of-use chlorination.

The authors raise a valid point in distinguishing between laboratory efficacy and program effectiveness. However, products and dosage regimens known to effectively treat water must be distinguished from those known to inadequately treat water before conclusions about the effects of human factors can be drawn. Previous studies have documented correct chlorine residuals in 70% of households one year after one-time educational promotion of quality-controlled product by Kenyan nurses (Parker et al., 2006) and correct chlorine residual in 67% of households in a six-year-old program with quality-controlled products and consumer education in rural Haiti (Ritter, 2007). In each case, [greater than or equal to] 30% of households did not achieve residual chlorine target levels. Well-designed studies investigating how human factors affect programs using quality-controlled product promoted with educational materials and appropriate dosage regimens would be of great value to enhance program effectiveness.

Daniele Lantagne, PE

References

Arnold, B.F., & Colford, J.M., Jr. (2007). Treating water with chlorine at point-of-use to improve water quality and reduce child diarrhea in developing countries: a systematic review and meta-analysis. American Journal of Tropical Medicine and Hygiene, 76(2), 354-364.

Centers for Disease Control & Prevention. (2008). Safe Water for the Community: A Guide for Establishing a Community-Based Safe Water System Program. Retrieved July 15, 2009, from http://www. cdc.gov/healthywater/global/wash_programs.html

Lantagne, D. (2008). Sodium hypochlorite dosage for household and emergency water treatment. Journal of the American Water Works Association 100(8), 106-119.

Lantagne, D. (In press). Viability of commercially available bleach for water treatment in developing countries. American Journal of Public Health.

Parker, A.A., Stephenson, R., Riley, P.L., Ombeki, S., Komolleh, C., Sibley, L., & Quick, R. (2006). Sustained high levels of stored drinking water treatment and retention of hand-washing knowledge in rural Kenyan households following a clinic-based intervention. Epidemiology and Infection, 134(5), 1029-1036.

Quick, R.E., Kimura, A., Thevos, A., Tembo, M., Shamputa, I., Hutwagner, L., & Mintz, E. (2002). Diarrhea prevention through household-level water disinfection and safe storage in Zambia. American Journal of Tropical Medicine and Hygiene, 66(5), 584-589.

Quick, R.E., Venczel, L.V., Mintz, E.D., Soleto, L., Aparicio, J., Gironaz, M., Hutwagner, L., Greene, K., Bopp, C., Maloney, K., Chavez, D., Sobsey, M., & Tauxe, R.V. (1999). Diarrhoea prevention in Bolivia through point-of-use water treatment and safe storage: A promising new strategy. Epidemiology and Infection, 122(1), 83-90.

Ritter, M. (2007). Determinants of adoption of household water treatment in Haiti Jolivert Safe Water for Families (JSWF) Program. Atlanta: Emory University.