An Observational Study on the Effectiveness of Point-of-Use Chlorination

Article excerpt

Introduction

Consumption of fecally contaminated water is a leading cause of death in rural regions of less-developed countries (Briscoe, 1986). According to the World Health Organization (WHO, 2004), 1.8 million people die each year from diarrheal diseases, 90% of which are under the age of five. Most of these deaths are in less-developed countries, especially in rural areas where there is limited access to safe water and adequate sanitation. In fact, WHO attributes 88% of diarrheal disease to consumption of unsafe water, lack of adequate sanitation, and poor hygiene. WHO further suggests that simple improvements in drinking water quality using point-of-use (POU) treatment, including chlorine, can lead to a reduction in diarrheal episodes by between 25% and 40% (WHO, 2004).

POU chlorination currently plays a major role in providing safe drinking water in many rural areas without piped distribution systems (Rangel, Lopez, Mejia, Mendoza, & Luby, 2003; Reller et al., 2003). While it is widely understood that chlorine can achieve a significant inactivation of most waterborne pathogens in controlled laboratory and controlled POU settings (Blaser, Smith, Wang, & Hoff, 1986; Whan, Grant, Ball, Scott, & Rowe, 2001), many variables may still influence the effectiveness of POU chlorination in the field, such as uncontrolled water quality parameters, behavioral factors associated with rural water treatment, and so on (Fernandez Gomez et al., 1993; Patel & Isaacson, 1989). These variables might contribute to reduced effectiveness of POU chlorination in practice, as compared to more controlled laboratory and intervention field settings, and are not typically included in rural drinking water studies.

Studies on POU drinking water treatment interventions are challenged by many aspects such as the complex transmission pathways of diarrheal disease, lack of consistency in field methods, and controversy over the best indicator to represent diarrheal pathogens (Gleeson & Gray, 1997; Young, Clesceri, & Kamhawy, 2005). Additionally, human factors and uncontrolled water quality parameters are not always included in POU studies.

Luby and co-authors conducted a study in Karachi, Pakistan, that compared drinking water quality in control households to intervention households that received a safe container and a diluted hypochlorite solution. They found a significant difference (2 [log.sub.10]) in thermotolerant coliform (TTC) concentration between these two groups of households (Luby et al., 2001). Sobsey and co-authors conducted a similar study in Bangladesh and Bolivia that also combined safe storage with chlorine use. Their study showed some reduction of indicator organisms as well as incidence of diarrhea when chlorine was used effectively (Sobsey Handzel, & Venczel, 2003). These intervention studies, however, exclude real-world chlorine-use variables such as chlorine storage time, concentration, and proper dosing, because participants are more likely to use chlorine properly after initial training or with assistance from the investigators than they are in actual nonresearch study situations. In nonresearch villages, chlorine training and assistance are not common components of household chlorine use.

In addition, human behavior is likely to change over time, making study length an important variable. In fact, Arnold and Colford (2007) found attenuation in the reduction of childhood diarrhea as study length increased. Most interventions are relatively short, while real-world chlorine use should be indefinite and consistent in order to be effective. Longer studies and observational studies are likely to be more accurate descriptions of real-world chlorine use.

Efficacy describes the potential of an intervention under ideal conditions, e.g., [log.sub.10] reduction of microorganisms with a proper chlorine dose and contact time. Effectiveness is a more general term that includes efficacy. …