Overuse of synthetic fertilizer has released excessive amounts of nitrogen into the atmosphere, causing imbalance in biological lifecycles, according to a 1998 study published in Science Magazine. Synthetic nitrogen and pesticide chemicals have been released into the atmosphere at increasing rates since their widespread use began after WWII. In the U.S. 80 million people are exposed to levels of air pollution that are a health risk, according to the World Resources Institute. Synthetic fertilizer is the leading source of atmospheric nitrates(please see Reference #2).
How Nitrogen Works
Nitrogen is a basic building block of all life. It is the most abundant element in the atmosphere but it cannot be used by plants until it is transformed (fixed) into ammonium or nitrate compounds. Nature transforms nitrogen into fixed nitrogen through certain bacteria and algae. The natural bacterial microorganisms in soil transform natural nitrogen into usable nitrogen in a normal nitrogen cycle. Synthetic fertilizer distorts the normal nitrogen cycle.
Effects of Excessive Nitrogen
Synthetic fertilizer is the major source of fixed nitrogen released into the global atmosphere, according to Peter Vitousek's Human Alteration of the Global Nitrogen Cycle. The World Resources Institute has determined that coastal rivers in the northern U.S. and Europe receive 20 times the amount of fixed nitrogen than is natural. Excessive fixed nitrogen in the biological cycles of life produce a range of negative effects from soil infertility to learning disabilities in children.
Soil Fertility Impact
Synthetic fertilizers rely on nitrogen, potassium and phosphorus to produce plant growth. Excess nitrogen is the most damaging pollutant of the three because plants cannot absorb as much as they are given in synthetic form. Excess nitrogen leaches into the soil, waterways and air. Plant health and human health depends on balanced nutrients. Nitrogen overload throws this balance off and leads to a decline in soil fertility.
Effects of Pesticides
"By their very nature, most pesticides create some risk of harm," according to the Environmental Protection Agency report on pesticides. Some chemicals in pesticides may cause cancer and some disrupt hormone function. Children are more vulnerable to negative effects from these chemicals than adults. The EPA recommends considering how much health risk there is in a particular pesticide and how much exposure there will be, before using it.
The excessive use of synthetic fertilizers and pesticides is mitigated by the practices of sustainable agriculture and home organic gardening. These systems rely on the "stewardship of natural and human resources" to grow food, according to the University of California at Davis's Sustainable Agriculture Research and Education Program. Organic gardeners work with natural biological processes rather than using synthetic products to boost productivity. Compost has been found to transform excessive chemicals in soil, returning it to natural mineral balance.