The health effects of eating too much corn and corn products has sparked much debate in recent years. But corn is killing us in unseen, complicated ways in addition to damaging the environment, according to new research in Nature Sustainability. The study finds that air pollution from corn production in the U.S. causes 4,300 premature deaths every year.
Ammonia emissions from fertilizer use is the biggest driver of corn’s air quality impact, the research shows. And the top five corn-producing states—Iowa, Illinois, Nebraska, Minnesota and Indiana—are responsible for more than half of this premature mortality. Greenhouse gas emissions from corn farming, meanwhile, result in climate change damages of $4.2 billion.
The use of fertilizers, pesticides, and fuel make farming a major contributor to poor air and water quality and to climate change. And in the U.S., corn is a dominant crop that is used for animal feed, ethanol, and for human consumption. About 96 million acres of land are devoted to corn production, mainly in the Heartland states.
Researchers led by Jason Hill, a bioproducts and biosystems engineering professor at the University of Minnesota, wanted to analyze the emissions from corn agriculture. The team specifically looked at pollutants that contribute to the formation of PM2.5, tiny airborne particles that are smaller than 2.5 nanometers in diameter and are associated with cardiovascular and respiratory diseases, diabetes and cancer.
Dust and burning fuel lead directly to PM2.5, while chemical pollutants like ammonia, sulfur oxides, nitrogen oxides all help form the particulates. The researchers created a life-cycle model to calculate emissions responsible for PM2.5 from every step in the corn supply chain: fertilizer production, electricity use, transportation, and on-field corn production. They fed the model with county-level data on corn yield and resource use to map the emissions. Then they estimated increases in atmospheric PM2.5 due to these emissions, and incorporated air movement patterns and census data to analyze its population exposure and its health and economic effects. They estimated life-cycle greenhouse gas emissions as well.
Corn produced in the eastern states like Indiana, Michigan and Ohio had dramatically higher health damages per ton of corn. That’s because the farms are near densely populated urban areas; have lower yields; and use more animal manure as fertilizer, which gives more ammonia emissions than synthetic fertilizers.
Ammonia emissions from fertilizer use account for 71 percent of pollution-linked deaths. And the numbers don’t paint the full picture, the researchers say, because they do not consider what happens to the corn after it is produced. Almost 90 percent of corn produced in the US is used to make animal feed or ethanol, both of which further contribute to PM2.5 and greenhouse gases.
What can be done? The team says that changing fertilizer type and application method could bring benefits, as can practices such as switching to crops requiring less fertilizer and changing corn-growing location. They also suggest that farmers be offered incentives to switch to crops that demand less fertilizer.
Source: Jason Hill et al. Air-quality-related health damages of maize. Nature Sustainability, 2019.
Photo: Thanasis Anastasiou, flickr creative commons