Cryptosporidium and Giardia in tropical recreational marine waters contaminated with domestic sewage: estimation of bathing-associated disease risks.

Sewage is a major contributor to pollution problems involving human pathogens in tropical coastal areas. This study investigated the occurrence of intestinal protozoan parasites (Giardia and Cryptosporidium) in tropical recreational marine waters contaminated with sewage. The potential risks of Cryptosporidium and Giardia infection from recreational water exposure were estimated from the levels of viable (oo) cysts (DIC+, DAPI+, PI-) found in near-shore swimming areas using an exponential dose response model. A Monte Carlo uncertainty analysis was performed in order to determine the probability distribution of risks. Microbial indicators of recreational water quality (enterococci, Clostridium perfringens) and genetic markers of sewage pollution (human-specific Bacteroidales marker [HF183] and Clostridium coccoides) were simultaneously evaluated in order to estimate the extent of water quality deterioration associated with human wastes. The study revealed the potential risk of parasite infections via primary contact with tropical marine waters contaminated with sewage; higher risk estimates for Giardia than for Cryptosporidium were found. Mean risks estimated by Monte Carlo were below the U.S. EPA upper bound on recreational risk of 0.036 for cryptosporidiosis and giardiasis for both children and adults. However, 95th percentile estimates for giardiasis for children exceeded the 0.036 level. Environmental surveillance of microbial pathogens is crucial in order to control and eradicate the effects that increasing anthropogenic impacts have on marine ecosystems and human health.

Applying the mental models framework to carbon monoxide risk in northern Mexico.

OBJECTIVES: Low-income residents of northern Mexico rely on unvented heaters during the winter, a practice that puts them at elevated risk for carbon monoxide intoxication. The goal of this study is to develop a communication protocol for carbon monoxide intoxication risks among the primarily low socioeconomic status population of Ciudad Juárez, Chihuahua, Mexico. METHODS: The mental models risk communication approach was used to identify important gaps in public understanding. This approach consists of step-by-step assessment of information needs and effectiveness of risk communication efforts by using interviews and surveys. RESULTS: The mental models process uncovered a key technical misunderstanding, the subject population's belief that carbon monoxide can be seen or smelled, which may result in a risk-prone behavior: failure to use a carbon monoxide detector. A communication protocol was designed to address this and other knowledge gaps, and it produced significant improvements in subjects' knowledge in a pretest/posttest evaluation. CONCLUSIONS: The mental models process was successful in developing a communication instrument capable of improving knowledge in the subject population. Future research needs include assessing the extent to which this instrument succeeds in changing behavior and reducing the risk of carbon monoxide intoxication. Future interventional efforts may focus on encouraging people to use carbon monoxide detectors.

Applying the mental models framework to carbon monoxide risk in northern Mexico / Aplicación del enfoque de los modelos mentales al riesgo por monóxido de carbono en el norte de México

OBJECTIVES: Low-income residents of northern Mexico rely on unvented heaters during the winter, a practice that puts them at elevated risk for carbon monoxide intoxication. The goal of this study is to develop a communication protocol for carbon monoxide intoxication risks among the primarily low socioeconomic status population of Ciudad Juárez, Chihuahua, Mexico. METHODS: The mental models risk communication approach was used to identify important gaps in public understanding. This approach consists of step-by-step assessment of information needs and effectiveness of risk communication efforts by using interviews and surveys. RESULTS: The mental models process uncovered a key technical misunderstanding, the subject population's belief that carbon monoxide can be seen or smelled, which may result in a risk-prone behavior: failure to use a carbon monoxide detector. A communication protocol was designed to address this and other knowledge gaps, and it produced significant improvements in subjects' knowledge in a pretest/posttest evaluation. CONCLUSIONS: The mental models process was successful in developing a communication instrument capable of improving knowledge in the subject population. Future research needs include assessing the extent to which this instrument succeeds in changing behavior and reducing the risk of carbon monoxide intoxication. Future interventional efforts may focus on encouraging people to use carbon monoxide detectors.

OBJETIVOS: Los residentes de bajos ingresos del norte de México dependen durante el invierno de calefactores no ventilados, una práctica que los pone en mayor riesgo de intoxicación por monóxido de carbono. Se elaboró un protocolo de comunicación sobre los riesgos de intoxicación por monóxido de carbono en la población fundamentalmente de bajo nivel socioeconómico de Ciudad Juárez, Chihuahua, México. MÉTODOS: Se utilizó el enfoque de comunicación de riesgos de los modelos mentales para identificar importantes brechas en la comprensión pública. Este enfoque consiste en la evaluación paso a paso de las necesidades de información y la eficacia de los esfuerzos de comunicación de riesgos, mediante entrevistas y encuestas. RESULTADOS: El proceso basado en los modelos mentales descubrió un malentendido técnico clave: la población estudiada cree que el monóxido de carbono se puede ver u oler. Esto puede llevar a un comportamiento proclive al riesgo: no utilizar detectores de monóxido de carbono. Se diseñó un protocolo de comunicación para atender esta y otras brechas en el conocimiento que, según las evaluaciones previa y posterior, mejoró significativamente el nivel de conocimiento de las personas. CONCLUSIONES: El proceso basado en modelos mentales permitió desarrollar exitosamente un instrumento de comunicación capaz de mejorar el nivel de conocimiento en la población estudiada. Investigaciones futuras deben evaluar en qué grado este instrumento logra modificar el comportamiento y reducir el riesgo de intoxicación por monóxido de carbono. Nuevas intervenciones podrían centrarse en estimular el uso de detectores de monóxido de carbono.

Evaluation of neighborhood treatment systems for potable water supply.

Piped water is available in Ciudad Juarez, Chihuahua, Mexico, but residual disinfectant is not reliably found in the public drinking water supply. Lack of confidence in the public supply leads many residents to rely on bottled water. To provide consistent disinfection, two health clinics were equipped with ultraviolet disinfection systems, and neighboring households were encouraged to obtain their drinking water from the treatment systems. Use of the treated water declined from 62% of self-selected study participants at the time of the first visit to 40% at the second visit. During the first visit, diarrhea prevalence was similar among households using treated water and other water sources yet diarrhea prevalence was higher among households using the treated water during the second visit. Microbiological quality of the treated water in the homes was not demonstrably superior to that of other sources.

Carbon monoxide exposure in households in Ciudad Juárez, México.

This study assessed exposure to carbon monoxide from gas and wood heater emissions in a sample of 64 households in peri-urban residential areas in Ciudad Juárez, Chihuahua, México. Indoor and outdoor carbon monoxide concentrations and temperatures were monitored for a continuous period of 1 week at 1 and 6-min intervals, respectively. The moving average carbon monoxide concentrations were compared to the World Health Organization (WHO) standards for carbon monoxide. Sixty-seven percent of households with gas heaters and 60% of households with wood heaters exceeded a health-based standard at some point during the monitoring. The difference between indoor and outdoor temperatures was modestly correlated with average carbon monoxide exposure (r=0.35, p-value <0.01). Heater type may be a stronger determinant of exposure, as households with a particular heater model (the El Sol FM-210) were significantly more likely to be among the more highly exposed households (odds ratio of 4.8, p-value of 0.02). A variety of health effects were pooled and found at elevated frequency in the households that exceeded the 8-h standard of 9ppm (odds ratio=5.1, p-value=0.031). These results highlight the need for further efforts to identify and mitigate potentially hazardous carbon monoxide exposures, particularly in moderate-income countries with cooler climates.

Evaluating in-home water purification methods for communities in Texas on the border with Mexico / Evaluación de métodos domésticos de purificación de agua para comunidades de Texas fronterizas con México

This study evaluated user preferences among three alternative in-home water treatment technologies suitable for households relying on trucked water in El Paso County, Texas, which is on the border with Mexico. The three technologies were: chlorination of household storage tanks, small-scale batch chlorination, and point-of-use ultraviolet disinfection. Fifteen households used each of the three technologies in succession for roughly four weeks each during April through June of 2004. Data were collected on treated water quality, and a face-valid survey was administered orally to assess user satisfaction with the technologies on a variety of attributes. Treatment with a counter-top ultraviolet disinfection system received statistically significantly higher ratings for taste and odor and likelihood of future use than the other two approaches. Ultraviolet disinfection and small-scale batch chlorination both received significantly higher ratings for ease of use than did storage tank chlorination. Over-chlorination was a common problem with both batch chlorination and storage tank chlorination. Water quality in the households using trucked water is now higher than was reported by a previous study, suggesting that water quality has improved over time.

Este estudio evaluó las preferencias de los consumidores de tres tecnologías domésticas para el tratamiento del agua, apropiadas para viviendas del condado de El Paso, Texas, situado en la frontera con México, que dependen del agua transportada en camiones. Las tres tecnologías fueron cloración de los tanques domésticos de almacenamiento, cloración de pequeños lotes de agua y desinfección mediante luz ultravioleta en el punto de dispensación. Quince viviendas utilizaron sucesivamente cada una de las tres tecnologías durante aproximadamente cuatro semanas entre abril y junio de 2004. Se registraron los datos sobre la calidad del agua tratada y se realizó una encuesta oral aceptada por los expertos para medir el grado de satisfacción de los usuarios con relación a diversos atributos de esas tecnologías. El tratamiento con el sistema de desinfección mediante luz ultravioleta instalado sobre la barra de la cocina tuvo una mejor valoración según el gusto y el olor del agua y una mayor probabilidad de uso futuro que los otros dos métodos. La desinfección mediante luz ultravioleta y la cloración de pequeños lotes recibieron mayor puntuación por su facilidad de uso con respecto a la cloración de los tanques de almacenamiento. La cloración excesiva fue un problema frecuente, tanto en la cloración de pequeños lotes como de los tanques de almacenamiento. La calidad del agua en las viviendas que utilizan agua transportada en camiones es ahora superior que la encontrada en estudios anteriores, lo que parece indicar que la calidad del agua ha mejorado.

Evaluating in-home water purification methods for communities in Texas on the border with Mexico.

This study evaluated user preferences among three alternative in-home water treatment technologies suitable for households relying on trucked water in El Paso County, Texas, which is on the border with Mexico. The three technologies were: chlorination of household storage tanks, small-scale batch chlorination, and point-of-use ultraviolet disinfection. Fifteen households used each of the three technologies in succession for roughly four weeks each during April through June of 2004. Data were collected on treated water quality, and a face-valid survey was administered orally to assess user satisfaction with the technologies on a variety of attributes. Treatment with a counter-top ultraviolet disinfection system received statistically significantly higher ratings for taste and odor and likelihood of future use than the other two approaches. Ultraviolet disinfection and small-scale batch chlorination both received significantly higher ratings for ease of use than did storage tank chlorination. Over-chlorination was a common problem with both batch chlorination and storage tank chlorination. Water quality in the households using trucked water is now higher than was reported by a previous study, suggesting that water quality has improved over time.