Cáncer gástrico en Costa Rica: ¿existe o no relación con la cloración del agua para consumo humano? / Gastric cancer in Costa Rica: is there or not related to the chlorination of water for human consumption?

RESUMEN

El cáncer gástrico, CG, es el tumor maligno con mayor mortalidad en hombres en Costa Rica. En el caso de las mujeres ocupa el segundo lugar, después del cáncer de mama. Desde el punto de vista histológico, el CG se divide en dos tipos el primero es el "difuso" y su etiología ha sido relacionada con factores genéticos. El segundo tipo es el "intestinal", vinculado con la exposición a cancerígenos ambientales como sustancias químicas tóxicas, altitud geográfica, edad, etc. En este sentido, algunos investigadores han estudiado las posibles relaciones de factores epidemiológicos y ecológicos, como las características físico-químicas de las aguas para consumo humano, ACH, los suelos, los plaguicidas usados en los cultivos, y la ingesta de cancerígenos en la leche como el Pteridium aquilinum, helecho macho. Con respecto al ACH, a partir de 1974, se ha relacionado la cloración del agua con la formación de subproductos de la desinfección como el cloroformo y el bromoformo, llamados trihalometanos, con potencial cancerígeno para favorecer la incidencia de CG en la población. Estos hechos, aunados al sensacionalismo periodístico han provocado inseguridad e incertidumbre entre la población consumidora de aguas sometidas a cloración...

ABSTRACT

Gastric cancer (GC) is the leading cause of cancer-related mortality in Costa Rican males. After breast cancer, it is the second highest cause of cancermortality in women in Costa Rica. From a histological point-of-view, GC is divided into two types the first isthe “diffuse” type and it has been related etiologically to genetic factors; the second type is the “intestinal”type and it has been linked to such environmental carcinogenic factors as toxic chemical substances, geographic altitude and age. Along these lines, someresearchers have studied possible relationships bettween epidemiological and ecological factors such as, for example, physico-chemical traits of water for human consumption (ACH), soils, pesticide use as well ascarcinogen intake in milk such as Pteridium aquilinum (the so-called male fern). Regarding ACH, since 1974,water chlorination has been causally linked to formation of byproducts of disinfection like chloroform and bromoform, so-called trihalomethanes, which have a propensity for causing a higher incidence of GC in the population. These facts, along with media hype, have provoked uncertainty and doubts regarding the safety of chlorinated water among the public. With this background in mind, an exploratory-ecological epidemiological study was carried out with the explicit purpose of analyzing if there is or if there isn´t a statistically significant link between the incidence of GC and the consumptionof chlorinated water in Costa Rica. The analysis used the GC-mortality results in 458 districts during the years1999 to 2002 and the data obtained from the National Water Laboratory on the type of water (chlorinatedor not), the number of years of disinfection and the source of the water (underground, surface or mixed).For the statistical analysis, a Standardized Mortality Index (IME) and the Pearson correlation coefficient...