The effects of chemical fertilizers are not widely spoken about. This is partially because they are largely untested. We understand there is a risk of groundwater contamination and the environmental issues that brings, but we're still not entirely sure what it means for our own health.
To really understand this issue, we need to understand what chemical fertilizes actually do.
Fertilizer is any substance used to add nutrients to the soil to promote soil fertility and increase plant growth. Notice how nothing in there mentions the actual soil health; that's because not all fertilizers are made the same and not all are healthy for the soil.
Soil health relies on a balance of macronutrients and micronutrients, as well as microbial health. It's vastly more complicated then simply adding nitrogen, phosphorus and potassium (NPK) to the ground and calling it a day.
Why doesn't this work? Because science doesn't always get it right. In the past scientists once thought food only consisted of macronutrients, but have since discovered micornutrients, antioxidants and so on. The same goes for soil health: scientists have focused almost exclusively on NPK since their "discovery" in the mid-1800s. It's this reductionist science that has us assuming we understand the chemisty of Nature and soil and thinking we can solve it with a quick application of chemical fertilizers.
Unfortunately, as unsustainable farming and gardening practices continue our soil is stripped of its health and we depend on amendments even greater. This leads to some pretty negative effects of chemical fertilizers.
The biggest issue facing the use of chemical fertilizers is groundwater contamination. Nitorgen fertilizers break down into nitrates and travel easily through the soil. Because it is water-soluble and can remain in groundwater for decades, the addition of more nitrogen over the years has an accumulative effect.
At the University of Wisconsin, Madison, they discovered the effects of chemical fertilizers are compounded when mixed with a single pesticide. They discovered altered immune, endocrine and nervous system functions in mice, as well as influence on childen's and fetus's developing neurological, endocrine and immune systems. These influences "portend change in ability to learn and in patterns of aggression."73
One popular fertilizer, urea, produces ammonia emanation, contributes to acid rain, groundwater contamination and ozone depletion due to release of nitrous oxide by denitrification process. With it's increased use and projections of future use, this problem may increase several fold in the coming decades.105
Groundwater contamination has been linked to gastric cancer, goitre, birth malformations, and hypertension107; testicular cancer108 and stomach cancer.109
Excessive air- and water-borne nitrogen from fertilizers may cause respiratory ailments, cardiac disease, and several cancers, as well as can "inhibit crop growth, increase allergenic pollen production, and potentially affect the dynamics of several vector-borne diseases, including West Nile virus, malaria, and cholera."110
Perhaps one of the scariest effects of chemical fertilizers is something called methemoglobinemia. In infants it is alternatively known as Blue Baby Syndrome. The risk most often occurs when infants are given formula reconstituted with nitrate contaminated water. The condition causes a decrease in oxygen in the blood and results in a blue-grey skin color, causes lethargy and/or irritability and can lead to coma or death.111 I've been unable to find whether the same risk exists for breastfeeding babies whose mothers drank contaminated water.
Nitrogen groundwater contamination also contributes to marine "dead zones". The increase in the water-soluble nitrates creates an influx of plant-life, which eats up oxygen and starves out fish and crustaceans. This has an impact not only on the aquatic ecosystem, but on local societies who depend on food sourced from those areas. 106
And then there is the highly questionable use of raw sewer sludge as a fertilizer. Yes, you heard me right. In some countries, raw, uncomposted and untreated human waste is applied directly to crops and soil, a practice known as "night soil" since it's typically applied at night. The risk of disease is obvious and high112, 113 and this practice should never be confused with "humanure", a long, highly involved process of decomposing human waste into a safe resource.
Knowing and understanding the effects of chemical fertilizers doesn't do us much good without action on our part. Knowing how to protect our health is what counts.
Stay informed, get involved and make a difference in our health.
Understanding the effects of chemical fertilizers can have a profound impact on our environment and our health. But it's not all you can do! Be sure to keep moving forward with other Big Strides.
When you're ready for a few more steps:
Whatever step you take, remember to have fun!
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