Water is by far the most ingested substance on the planet. Even with modern water-treatment facilities, water can be a significant source of dangerous contaminants, spreading acute and chronic diseases. Continual exposure to certain man-made chemicals can be highly insidious, causing damage over months or years with often serious and sometimes deadly effects. Chlorine, used for disinfection in many commercial and residential facilities, can react with organic matter to form cancer-causing trihalomethanes. Even naturally occurring contaminants can show up in drinking water with deadly consequences. According the Center for Disease Control and Prevention, E. coli bacteria is responsible for an estimated 73,000 cases of infection and 61 deaths per year in the United States. Lead is toxic when ingested and causes a wide variety of systemic and developmental problems in adults and children yet this metal can leach from old pipes and fixtures, making its way into drinking water. Many homes and offices built before 1988 may have lead-containing pipes and fixtures still in use. In the US, about 1,000,000 children under the age of six have an amount of lead in their blood that exceeds the level of concern. Pesticides have been discovered in every large watershed in the US. The dangerous synthetic chemicals used in pesticides have also been detected in an alarmingly high percentage of groundwater wells in the US.