It is normal for tap and bottled water, among other types of drinking water, to contain some amount of contaminants. In the US, the Environmental Protection Agency or EPA has set strict standards for around 90 various types of contaminants that can be present in drinking water. This page has a compilation of the most common water pollutants, which have been categorized below to give a more detailed information on some particular contaminants and how they affect your health.
E coli and Fecal Coliform
When E coli and Fecal Coliform bacteria are present in water, this is an indication that water may contain human / animal wastes that make it contaminated. Microbes in such wastes can cause cramps, diarrhea, headaches, nausea or other short-term symptoms.
The parasite known as cryptosporidium gains access to lakes and rivers by means of sewage and animal wastes. This microbe comes with an outer shell that lets it live outside the body for a long time, letting it tolerate most chlorine disinfectants. It causes a mild gastrointestinal disease called cryptosporidiosis. The disease can become severe or even fatal, though, for those who have very weak immune systems. Both EPA and CDC have an advice regarding Cryptosporidium for people who have compromised immune systems.
Giardia lamblia, like cryptosporidium, is a parasite that enters lakes and rivers by way of sewage and animal wastes. It causes gastrointestinal illnesses such as cramps, diarrhea and vomiting. It can also survive for a long time outside the body. It is hard to treat using basic chlorine disinfectants.
Though coliform bacteria are widespread in the environment, they are usually not harmful. However, their presence in drinking water is often caused by problems with the water distributing pipes or treatment system. This shows that water might be contaminated with disease causing germs.
Turbidity does not affect health in any way. It can interfere with disinfection, though, since the particles can work as protection for bacteria and virus, providing a medium for microbes to grow. Turbidity may show the presence of organisms that cause diseases. These include bacteria, parasites and viruses that can bring about symptoms like cramps, diarrhea, nausea and headaches.
Some minerals are radioactive and could emit some form of radiation called alpha radiation. People who drink water that contains alpha emitters exceeding EPA's standard for several years are more prone to acquiring cancer.
Beta / photon emitters
Some minerals that are radioactive emit some forms of radiation referred to as photons and beta radiation. When people drink water that contains beta and photon emitters beyond EPA's standard for several years, they become more prone to getting cancer.
Combined Radium 226/228
The acceptable amount of radium in drinking water is extremely small. People that drink water that contains radium 226/228 more than EPA's standard for so many years have a higher risk of acquiring cancer.
When radon gas dissolves, it can build up in underground water sources like wells, as well as the air inside your home. Breathing this gas can bring about lung cancer. You are more prone to developing cancer when you drink water that contains radon. Air borne radon is more harmful than radon in water.