Reactive Nitrogen Fact Sheet

Nitrogen is literally all around us, including nearly 80 percent of each breath we take. Though it is the most plentiful element in the earth’s atmosphere, it’s unusable in its inert state and must be transformed into reactive nitrogen before plants and animals can use it to make protein, DNA, and other compounds essential for life. Yet changes to the nitrogen cycle, like the more well-known changes to the carbon cycle, are creating environmental havoc.

100 years ago, chemists invented a process to turn the inexhaustible resource of inert nitrogen gas in the atmosphere into reactive, biologically available nitrogen in the form of ammonia. A few decades later, the widespread use of synthetic nitrogen to fertilize croplands had boosted global food production and helped to catapult world population from 1.6 billion to six billion during the 20th century.

More than half of the synthetic fertilizer ever produced has been made since 1985. Production of reactive nitrogen for chemical fertilizer has jumped from 10 million metric tons in the late 1950s to just over 100 million metric tons in 2008.

While the US, Western Europe, and Asia suffer the consequences of the release of too much reactive nitrogen into the environment, other regions like Africa suffer from limited access to chemical fertilizer, resulting in poor crop yields and worsening malnutrition.

Higher crop yields – a mixed blessing

In the last 50 years, a dramatic increase in the use of chemical fertilizer and fossil fuels has been matched by an equally dramatic rise in nitrogen pollution. Reactive nitrogen helps grow food and biofuel crops. And almost all of it eventually escapes to the environment. While some ends up in the food we eat, most ends up in the atmosphere or in groundwater, freshwater, or ocean ecosystems, where it can cause a host of environmental and health problems.

Growing impacts on human health and the environment

A single molecule of reactive nitrogen can pack a wallop as it moves, or ‘cascades’ through the environment. It can worsen climate change, air and water pollution, coastal dead zones, and cause biodiversity loss.

Waterborne nitrogen

The runoff of reactive nitrogen into water supplies creates aquatic dead zones where life is much diminished. These so-called “dead zones” occur because algae flourish in the presence of reactive nitrogen; algal blooms in turn deplete oxygen supplies as the algae eventually die, sink, and decompose, starving shrimp and fish of needed oxygen. Chemical fertilizer runoff from the Mississippi River watershed is the chief cause of an 8,000 square-mile “dead zone” in the Gulf of Mexico.[1] Fish, shrimp and other shellfish that are the mainstay for commercial fishing operations along the Gulf cannot survive in the dead zone’s oxygen-deprived conditions. In addition to causing dead zones, nitrogen runoff poses a threat to human health. Drinking water with elevated nitrate levels may cause cancer.

Airborne nitrogen

Reactive nitrogen is present in the atmosphere in gaseous and particulate form. These compounds can cause a number of environmental problems, including:

• Ground-level ozone – When nitrogen oxides react with volatile organic compounds in the presence of sunlight, they form ground level ozone – or smog. Smog damages lung tissue and reduces lung function, especially among children, people who work or exercise outdoors and those with lung diseases like asthma. In addition, ozone can damage forests and reduces crop yields.
• Acid rain – Nitrogen oxides contribute to acid rain. Even ammonia, when deposited to ecosystems, will act as an acidifying agent.  Acid rain damages water supplies and fisheries, as well as cars, buildings and other structures.
• Air pollution – Nitrogen oxides react with ammonia, other compounds and moisture in the air to form particles such as ammonium nitrate. When these particles are breathed into the lungs, they affect breathing and respiratory systems, damage lung tissue and cause premature death.  Breathing particles can exacerbate respiratory ailments like emphysema and bronchitis and aggravate existing heart disease.
• Climate change – Nitrous oxide (N₂O) is a greenhouse gas 300 times more potent than carbon dioxide. Agriculture is responsible for about 80 percent of human-caused N₂O. Fertilized fields, livestock operations, wetlands and coastal ecosystems that receive anthropogenic reactive nitrogen all emit nitrous oxide to the atmosphere. Recent studies have shown that corn-ethanol production has aggravated, not lessened, global warming.[2]  Other minor human-caused sources of nitrous oxide emissions include vehicle emissions and fossil fuel combustion.

 US Environmental Impacts

• Coastal dead zones like those in the Gulf of Mexico threaten the Chesapeake Bay and Lake Erie, and are spreading rapidly worldwide. The number of known dead zones has risen steadily from 39 at the end of the 1960s to 405 in 2009.[3]
• Atmospheric deposition of nitrogen from fossil-fuel combustion is the largest single source of nitrogen pollution in much of the northeastern United States, leading to acid rain that contributes to the Chesapeake Bay dead zone.
• In the Mojave and Sonoran deserts of the southwestern U.S., non-native grasses like red brome thrive on atmospheric nitrogen pollution. The grasses provide dangerous fuel for wildfire and threaten native plant survival.[4]
• In California, invasive European grasses spurred by increased nitrogen emissions from auto exhaust are wiping out native wildflowers that don’t adapt to nitrogen-rich soil. [5]

Health Impacts

• Nitrogen oxides formed by fossil fuel combustion create ozone, otherwise known as smog. Tiny particles in smog damage lung tissue, increase the risk of cancer and cause heart disease. A recent 18-year study shows that long-term, low-level exposure to ozone can be lethal, increasing the yearly risk of death from respiratory diseases by 40% to 50% in heavily polluted cities like Los Angeles, California.[6]
• Health impacts from increased nitrogen pollution include the consequences of ozone pollution on asthma and respiratory function, and potentially increased allergies and asthma. High nitrate levels in drinking water elevate the risk of blue-baby syndrome and may also spell increased risk of cancer and other chronic diseases.[7]

Global Impacts

• In Asia, the growing use of coal and other fossil fuels results in the growing release of nitrogen oxides to the atmosphere. China is now the world’s top user of synthetic fertilizers, applying 41 million tons in 2004, an 8 million-ton jump in just ten years. The number of dead zones along the Chinese coastline now equals those in North America and Western Europe.[8]
• In Latin America, the release of nitrogen into water supplies from inadequate sewage treatment threatens public health, while more rural areas grapple with agricultural runoff and the impacts on freshwater supplies and air quality that follow.
• Africa faces crises resulting from nitrogen deficiencies, as population growth and agricultural demands exceed the land’s ability to provide. But even in Africa, there are highly localized areas that suffer sewage disposal problems or runoff from synthetic fertilizer.

Solutions

International Nitrogen Initiative (INI) scientists say that by targeting key points in the creation, transport and use of reactive nitrogen, its benefits can be enhanced and its problems reduced. These key ‘control’ points include decreasing emissions from fossil-fuel combustion, increasing nitrogen-uptake efficiency of crops, improving animal manure management strategies, and implementing advanced sewage treatment in selected regions.[9]

For more information, please see our

International Nitrogen Initiative Global Nitrogen Assessment