The Nitrogen Effects From Cow Manure on Humans

People have been milking cows for thousands of years. Until the late 1800s, all milking was done by hand, and the size of dairy herds was limited by how many cows the available farm workforce could milk in a day. When small hand-milked herds were dispersed over the landscape and wandered in pastures and wild lands, the impact of nitrogen from manure on humans was minimal. Innovations in milking technology through the 19th century and the advent of commercial refrigeration in the 20th century allowed for vast increases in dairy herd size. Massive herds and confined feeding operations create millions of tons of nitrogen-rich manure in one concentrated area.

Dairy cows consume nitrogen in their feed. About one-third of the nitrogen they consume is released into the milk they produce. Excepting a tiny fraction absorbed by the body, the remaining two-thirds is excreted in urine and feces. The nitrogen in this dairy manure can pollute waterways through runoff, damaging human water supplies or fisheries; or it can be converted to ammonia, causing air pollution effects damaging to human health.


According to the Union of Concerned Scientists' 2008 Report "CAFOs Uncovered: The Untold Costs of Confined Animal Feeding Operations," there are nearly 10,000 CAFOs in the United States. Dairy CAFOs are operations with over 1,000 cows. Dairy farms of this size produce hundreds of thousands of tons of manure in a small area. Even if a CAFO dairy farm has sufficient acreage to spread manure adequately, that manure will first be gathered into holding ponds or tanks, where nitrogen from the manure is likely to escape in the form of water or air pollution.


There are two primary types of nitrogen effects on humans from dairy manure. The first is water pollution. Nitrogen-rich manure is likely to run off of farm operations in rain water and enter lakes and ponds. The second type of effect is air pollution. Through bacterial interactions, nitrogen in dairy manure is converted to airborne ammonia, which is dangerous for humans to breathe.


Excess nitrogen in waterways causes oxygen depletion which damages water quality which affects human recreational and commercial fisheries use. The nitrogen functions as a nutrient in the water, causing excessive algal growth. Decomposition of that excess growth draws dissolved oxygen from the water, which can lead to short-term fish kills or a gradual loss of oxygen-loving species like trout. According to a report of the Penn State College of Agricultural Sciences, components of cow feces and urine interact through the process of bacterial degradation, converting to ammonia.According to the U.S. Environmental Protection Agency (EPA) ,Ammonia impairs air quality in itself and also interacts with other substances in the atmosphere to create fine particulate matter responsible for haze and human respiratory problems. Improperly managed manure has caused acute and chronic water quality problems.While manure can contribute pollutants such as excessive amounts of nitrogen and phosophorus, organic matter, sediments, pathogens, heavy metals, hormones and antibiotics to the environment.

The best way to deal with this manure is to de-concentrate the animals and likewise de-concentrate their waste. Sustainable, pasture-based systems allow for the animals to distribute their waste in amounts that the soil can absorb, without using large quantities of water for washing or fuel to power trucks for transportation and spraying. By shopping at small, local sustainable farms and supporting pasture-based methods of waste management, we can all encourage change and promote healthier and more environmentally-friendly farming.