What is a contaminant?
A contaminant is defined by the Safe Drinking Water Act (SDWA) as any physical, chemical, biological, or radiological substance or matter in water (U.S. Senate, 2002; 40 CFR 141.2). This broad definition of contaminant includes every substance that may be found dissolved or suspended in watereverything but the water molecule itself. The presence of a contaminant in water does not necessarily mean that there is a human-health concern. Whether a particular contaminant in water is potentially harmful to human health depends on its toxicity and concentration in drinking water. In fact, many contaminants are beneficial at certain concentrations. For example, many naturally occurring inorganic contaminants are required in small amounts for normal physiologic function, even though higher amounts may cause adverse health effects. On the other hand, man-made organic contaminants, such as pesticides, are not required by humans and may or may not have adverse effects on people, depending on conce
