Nitrates / Nitrites
Nitrates and nitrites are simple chemical compounds made up of nitrogen and oxygen atoms. These chemicals are variations of salt, but they're nothing you'd want to put on your dinner. In large enough amounts, nitrates and nitrites can disrupt blood's ability to carry oxygen throughout the body.
Of the two, nitrates are especially dangerous to humans. According to case studies performed by the Agency for Toxic Substances & Disease Registry, nitrate toxicity is a preventable cause of the blood disease, methemoglobinemia. When combined with other other proteins found in some foods and medicine, it forms nitrosamine, a cancer-causing carcinogen.
Rural areas are at greater risk of exposure from the runoff of nitrate-based fertilizers entering well water. If consumed, the body converts the nitrates into nitrites, which then reduce the amount of oxygen that can be carried by the blood. Infants under the age of 4 that drink contaminated well water are at extra risk of nitrate toxicity. Symptoms of nitrate toxicity in infants are often referred as a blue baby disease.
Long-term exposure can result in spleen hemorrhaging, excessive urine formation, and worst of all: death.
Your water can easily be tested for both nitrates and nitrites with the use of the WaterSafe All-In-One Home Drinking Water Test Kit. Most refrigerator water filters aren't capable of removing nitrates or nitrites, so it's often recommended using a reverse-osmosis water filtration system, especially for those who use well water.