Impacts of the Global Nitrogen Cycle on Humans

Nitrogen is the cornerstone of structures, such as amino acids, DNA and RNA, making it central to the existence of life. The global nitrogen cycle encompasses the journey of nitrogen throughout the spheres and its interactions with the environment; from air and water to soil and microbes to plants and animals to people. Humans make pronounced contributions to a nitrogen cycle that is now out of sync, and humans are experiencing the backlash, as air and water become contaminated.

Human Contribution to Nitrogen Cycle

• When scientists developed the laborious Haber process, it became possible to mimic nature and convert nitrogen into ammonia for use as soil fertilizers, most of which seep into groundwater. This process alone adds approximately 80 megatons of nitrogen to the global cycle every year. The main energy source for humans is still fossil fuels, which releases over 20 megatons of nitrogen compounds, such as nitrous oxide into the atmosphere as greenhouse gases.

Nitrogen in Water

• The drinking water standard set by the World Health Organization (WHO) for nitrogen compound nitrate of 45 mg per liter is generally exceeded; even in the U.S., up to 20 percent of groundwater is considered contaminated from fertilizers and livestock. Nitrates are potentially carcinogenic, and levels below the WHO standard are associated with cancers, such as non-Hodgkin's lymphoma, as well as bladder and ovarian cancers. Nitrates are linked to other reproductive illnesses, most notably methemoglobinemia or blue-baby syndrome, which is often misdiagnosed.

Nitrogen in Air

• Harmful nitrogen oxides lingering in the lower atmosphere contribute to the production of ozone, which lines the human lung, causing respiratory ailments, such as asthma and reactive airways disease (RAD). Breathing in reactive nitrogen is also blamed for several cardiopulmonary diseases, cancers and susceptibility to human rhinovirus infection. Regular high exposure could be fatal, as close to two million people from developing countries die every year from nitrogen-related air pollution.

Indirect Impact

• Nitrogen compounds in air and water translate to land and aquatic ecosystems. This has knock-on effects on human diseases, such as malaria and West Nile virus, as the mosquito life cycle is affected by nitrogen. Shellfish feeding on harmful algae that flourishes, due to excess nitrogen, leads to food poisoning and even neurological or paralytic disorders. Bacteria that causes the water-born disease, cholera, is also linked to increased nitrogen.