Where does nitrate come from?
Nitrate is formed when nitrogen combines with oxygen in water. It occurs naturally in plants, including in many vegetables that we eat. It also comes from human-made sources, including fertilizers, animal feedlots, and sewage. Nitrate dissolves in water and can easily be carried by rainwater and melting snow until it reaches surface water or groundwater. When there are elevated levels of nitrate in a water source, that’s almost certainly because of human-made contaminants.
Why is excess nitrate bad for human health?
When we consume too much nitrate, that can make it harder for our blood to transport oxygen. In infants younger than six months, that can lead to a condition called methemoglobinemia (or "blue baby disease"), which can cause the skin to turn blueish-gray and may lead to serious illness or death.
Ongoing research has found that other health conditions are also linked to consuming high levels of nitrate. Peer-reviewed studies document increased risk of colon cancer, thyroid disease, and neural tube birth defects, like spina bifida and anencephaly, in populations with prolonged exposure to drinking water contaminated with nitrate. What is even more concerning is these health effects are observed when the nitrate levels in drinking water are lower than antiquated federal drinking water standards allow.
If plants need nitrogen to grow, why is excess nitrate bad for the environment?
Too many nutrients is a bad thing. When excess nitrate is present in waterways, it may overstimulate the growth of algae, creating what is known as an algal bloom. This not only encourages the formation of unsightly "scum" on the water, but can also have a myriad of negative effects on the environment. When the algae die and decompose in the water, the decomposition process consumes oxygen. This depletion of dissolved oxygen makes it harder for animals to survive in the water. The result is a dead zone, which in turn leads to fish kills and overall decreased plant and animal diversity