RESPONSE

Editor:

 

Dr. Kravitz agrees with us that water delivered to peoples' homes ought to be free of total coliforms. Our finding that drinking water in rural Trinidad was contaminated in 55% of homes receiving pipeborne water and in 88% of homes receiving truckborne water must have alarmed Dr. Kravitz as much as it did us.

For water from untreated water supplies, we agree with Dr. Kravitz that fecal contamination is a sensible bacterial indicator of drinking water quality. This is why we displayed the percentages of samples contaminated with fecal coliforms and E. coli, in addition to total coliforms. Also, we went a step further and determined the frequency of virulence markers in the E. coli isolates, thereby elucidating the health risk to consumers of the water that less-specific methods had found to be contaminated.

Dr. Kravitz has objected to our application, in our discussion of our results, of the United States Environmental Protection Agency (EPA) standard of zero total coliforms. This may reflect the vast differences between his research setting in low-income Lesotho and the situation in middle-income Trinidad and Tobago, where the 1999 per capita GNP figures were, respectively, US$ 550 and US$ 4 390 (1). In Dr. Kravitz's experience of developing countries, "where people may not understand concepts of pathogenicity, most rural water systems rely on surface sources or shallow wells." We reported in our Trinidad study that only 19 of the 167 households (11.4%) drank water obtained directly from surface sources or wells. The vast majority of households consumed water from treated water supplies. Therefore, in Trinidad and Tobago the EPA standard of zero coliforms is not an "untenable, unrealistic, or unnecessary goal," as suggested by Dr. Kravitz. Even for the minority of households in Trinidad that consume untreated water, the goal of zero coliforms is neither unrealistic nor unnecessary. Literacy rates in Trinidad and Tobago approach 100% and most households consuming untreated water could certainly be taught simple, low-cost methods of eliminating coliforms from their drinking water (2).

The infant mortality rate in the English-speaking Caribbean is more than double the rate in North America. A substantial portion of this excess mortality is due to intestinal infectious diseases, which are also a leading cause of death in children 1-4 years of age (3). Another compelling reason why the purity of the water supply is vital to Trinidad and Tobago is that the country has a thriving tourism component that could be adversely affected by outbreaks of communicable diseases.

Dr. Kravitz is concerned that setting stringent, "unreasonable" drinking water standards in developing countries may paralyze remedial efforts. Knowing that many of our samples were heavily contaminated with fecal coliforms, we categorized the samples as being "very poor" if fecal coliforms exceeded 20 per 100 mL. Even by this very conservative definition, the percentage of households with very poor drinking water quality ranged from 9% to 34%, depending on the town (Figure 2 in our article).

The information provided in that figure provides baseline data from which local authorities in Trinidad and Tobago can set medium-term targets for the progressive improvement of water supplies, as recommended by World Health Organization (WHO) guidelines (4). In recommending that developing countries set medium-term targets, however, the guidelines have not suggested that coliform-free water is a goal that is "untenable" or "unnecessary" for developing countries. Indeed, the WHO guidelines state that although the values for bacteriological quality were developed for large water-supply systems, they are also applicable to community supplies (4). Medium-term targets are simply a means of determining whether the country is making progress towards providing a safe water supply.

Compared with Lesotho, Trinidad and Tobago has relatively well-developed infrastructure, a very literate population, a dependence on tourism, and substantial financial resources. It is not unreasonable for residents and tourists alike to expect stringent drinking water standards and high quality drinking water that does not pose a significant threat to their health.

 

REFERENCES

1. World Bank. Country data [Internet site]. World Bank. Available from: http://www.worldbank.org/data/countrydata/countrydata.html. Accessed 23 February 2001.

2. Reiff FM, Roses M, Venezel L, Quick R, Witt VM. Low-cost water for the world: a practical interim solution. J Public Health Policy 1996;17(4):389-408.

3. Holder Y, Lewis MJ. Epidemiological overview of morbidity and mortality. In: Pan American Health Organization. Health conditions in the Caribbean. Washington, D.C.: PAHO; 1997. pp. 31-32. (Scientific Publication No. 561).

4. Guidelines for drinking-water quality. Volume 3: surveillance and control of community water supplies. 2nd ed. Geneva: World Health Organization; 1997.

 

A. A. Adesiyun
University of the West Indies
Faculty of Medical Sciences
School of Veterinary Medicine
St. Augustine, Trinidad and Tobago

 

L. McDougall
Caribbean Epidemiology Center
Port-of-Spain, Trinidad and Tobago

Organización Panamericana de la Salud Washington - Washington - United States
E-mail: contacto_rpsp@paho.org