Agriculture is the world's largest industry. It employs more than one billion people and generates over $1.3 trillion dollars worth of food annually, but some farm practices have serious negative impacts on the environment, which is why sustainable agricultural practices have been championed.
In essence, sustainable agriculture involves farming in a way to protect the environment, aid and expand natural resources, and make the best use of nonrenewable resources. But how does sustainable agriculture affect food safety, and thereby, public health? New research from Michigan State University published in the Nature journal NPJ-Science of Food finds both negative and positive impacts that need to be considered.
“When we think about sustainable agriculture, we're thinking primarily about what's good for the environment, and that's important,” said Felicia Wu, John A. Hannah Distinguished Professor and University Distinguished Professor, and an expert in food safety and security, and senior author on this paper with her postdoctoral research fellow Christian Scott. “However, we need to consider the the impacts on food safety and human health in the circular bioeconomy: one aspect of sustainable agriculture.
“The circular economy is a model of production and consumption that involves regenerating, reusing, refurbishing and recycling existing resources and materials,” Wu said. “In this way, the life cycle of products is extended and waste is reduced, but this shouldn’t come at a cost to public health. In the circular economy, a change in agricultural policy or practice that is focused on one aspect of the food system sector can have numerous unintended impacts in other areas - both for good and for bad.”
In her latest research, Scott and Wu looked at two sustainable agricultural practices that have unintended positive and negative impacts on food safety: alternative rice cultivation practices and no-till agriculture.
Alternative rice cultivation practices
For millennia, rice has been grown by planting rice seeds and flooding the rice paddy, which helps control weeds and requires fewer pesticides. The problem is that the land needs to be continually flooded, which is not environmentally friendly due to our global fresh water shortage. And there is another issue: arsenic.
Arsenic is naturally occurring in the earth's soils. When crop soil is wet, arsenic can be easily taken up into the crops, which creates a food safety issue. For thousands of years, arsenic has been known to be toxic; and in more recent years, naturally occurring arsenic levels in water and food have contributed to increased risk of cancers, cardiovascular diseases, and skin diseases. In the case of continually flooded rice, rice grains may contain arsenic if grown in areas where soilborne arsenic is high.
Wu said that the US Food and Drug Administration (FDA) will soon develop action levels based upon a 2021 Congressional report about baby foods - including infant rice cereal - pulled from grocery shelves containing occasional high levels of arsenic, cadmium, lead, and mercury.
But there is a solution to reducing arsenic in rice. The practice of alternate wetting and drying is a simple and inexpensive way of reducing water consumption in rice production substantially and reducing foodborne arsenic.
With this alternative method, the soil is not continually flooded but left to dry out between flooding anywhere from one to more than 10 days depending on a number of factors such as soil type, weather and crop growth stage. This allows farmers to cut down on water cost without sacrificing crop yield.
According to Wu, this is a win-win situation. “Alternate wetting and drying is a win-win for public health and the farmers,” Wu said. “The farmer spends less money, water is conserved, and the arsenic levels in the rice are brought down. Again, this is why sustainable ag also needs to take into account possible public health consequences. Sometimes, in benefit-cost analyses to adopt practices or policies, all secondary benefits and costs should be taken into account.”
No-till agriculture
The practice of no-till agriculture has several important economic, environmental and health benefits: it can preserve soil organic carbon, improve biodiversity, reduce soil erosion, reduce labor and agricultural input costs, and reduce particulate matter from tilling soil. However, this method means that crops residues are left in the field to decay and harbor fungi. The fungi may then produce mycotoxins, which are toxic and carcinogenic chemicals, in the following year's crops.
These mycotoxins cause a number of harmful health effects in humans and animals, as well as economic losses to farmers. Aflatoxin, the most toxic of the known mycotoxins, causes liver cancer in humans and other animals and has also been implicated in immune system dysfunction and growth impairment. The fungi that produce aflatoxin - and other mycotoxins - have been shown to overwinter in crop residue left in fields and increase mycotoxin risks in the next season.
“Given these concerns, a careful balance between ecological, health, and economic factors must be calculated by farmers in choosing a tillage system for their crops,” Wu said. “This is simultaneously a public health, agricultural science, and livelihood-economic calculation.”
If the agricultural products that farmers produce exceed the limits of consumable mycotoxins, they cannot be sold for human or animal consumption, due to regulations on allowable mycotoxin levels in over 100 nations worldwide. Further complicating the matter is that mycotoxins are expected to become a greater risk in the future due to climate change impacts.
“Because the end goal of agriculture is to feed humans, the food safety angle must be considered from a one-health approach that links in human health, animal health and the environment,” Wu said.