Life on Earth would not exist without water. Plants and animals rely on fresh water daily, even more than some people may recognize. In fact, survival experts note that a human can survive without food for anywhere from eight to 21 days, but only three days to a week without adequate water. Even though water is such a crucial commodity, many waterways and drinking water sources are under attack. Substances people use everyday are turning up in rivers, oceans and lakes, affecting not only marine life, but people as well. It’s important to note that the United States has one of the safest public drinking supplies in the world, as does Canada. The U.S. Environmental Protection Agency regulates drinking water quality in public water systems, and strict concentration levels for pollutants and chemicals have long since been established. The daily responsibility of providing safe drinking water to the public in Canada rests with the provinces and territories, while municipalities oversee the operations of treatment facilities. However, contamination can occur in source water as well as in distribution systems even after water has been treated. Contaminants can include naturally occurring chemicals and minerals, as well as materials that are used in manufacturing, local land use and through sewer or wastewater releases. The following are just a few of the contaminants that can cause adverse conditions if present in water. • Arsenic: Arsenic can enter the water from natural deposits in the earth or from industrial agricultural pollution, advises the Centers for Disease Control and Prevention. This may be a concern for those who rely on well water. • Benzene: Federal drinking water surveys in the United States estimated that roughly 1.3 percent of groundwater systems contained benzene. Large concentrations of benzene can be troublesome because it is known to cause cancer. Benzene is found in crude oil and gasoline, but also can occur naturally in volcanic gases and smoke from forest fires. Chlorine: Chlorine in small amounts has been standard in U.S. drinking water treatment since 1904 and is in most Canadian drinking water. While chlorine can eradicate many pathogens, there is a downside. In the 1970s, scientists discovered that chlorine added to water can mix with organic matter and form trihalomethanes, one of which is chloroform, according to the water safety resource Water Benefits Health. THMs increase the production of free radicals that can be cancer-causing. • Giardia: This tiny parasite is found in soil or water that has been contaminated with feces from infected animals or people, advises the World Health Organization. Swallowing contaminated drinking water or recreational water at lakes or pools can cause gastrointestinal illness. • Improper pH: There are some proponents of consuming alkaline water to increase fat burning and neutralize acidic blood, as well as to act as an antioxidant. However, according to the Cleveland Clinic, elevating the pH too much toward the alkaline side can affect kidney function and also cause the skin to become dry, itchy and irritated. Water is needed to maintain health, but various contaminants may be lurking in water supplies. Testing water regularly can provide insight as to what might be hiding among those oxygen and hydrogen molecules.