During a Thursday afternoon session at the 2022 Institute for the Advancement of Food and Nutrition Sciences’ (IAFNS’) Annual Meeting and Science Symposium, Felicia Wu, Ph.D., discussed her recently published study about the rising prevalence of aflatoxin in U.S. corn production due to the effects of climate change. Dr. Wu is a Distinguished Professor of Food Safety, Toxicology, and Risk Assessment at Michigan State University.
According to Dr. Wu, aflatoxin is a type of mycotoxin that is produced by the fungi Aspergillus flavus, and A. flavus thrives and produces aflatoxin in warm, dry climates. “The populations that are most vulnerable [to aflatoxin] are people who live in warm climates where tree nuts, corn, and spices are staple foods,” Dr. Wu said. “…currently, the regions most affected are sub-Saharan Africa, Southeast Asia, Central America, and the U.S. South.”
Aflatoxin poses a public health risk due to its association with liver cancer, and aflatoxin is “the most potent, naturally occurring human carcinogen,” according to Dr. Wu. Approximately 100,000 cases of liver cancer are caused by aflatoxin per year, and acute aflatoxicosis can occur at high doses, which has a 40 percent mortality rate. Additionally, aflatoxin can cause issues in childhood development and immune system dysfunction.
Dr. Wu explained that, because the U.S. Food and Drug Administration (FDA) regulates aflatoxin, it poses more of an economic risk than a food safety risk in the U.S.—for now. However, she warns that the effects of near-term climate change create uncertainty around the level of risk that aflatoxin will pose to U.S. food safety in the future.
Dr. Wu continued by describing how A. flavus infects corn and produces aflatoxin through two primary methods, which are both affected by climate change. First, during the “silking” phase of corn growth, A. flavus can enter corn through its silk and proceed to produce aflatoxin. Later in corn’s growth cycle, during the “denting” phase when its kernels fill with starch, A. flavus can infect corn through fractures that may occur in the surface of kernels. A. flavus can thrive and produce large quantities of aflatoxin in a starch-filled kernel.
Dr. Wu’s study aimed to develop and validate a model of aflatoxin risk as a function of temperature, rainfall, and grower practices in U.S. corn production. Based on data from farmers’ crop insurance claims between 2011 and 2020, Dr. Wu and her team projected that aflatoxin will pose an increased food safety risk to U.S. corn between 2031 and 2040. “Anecdotally, we have already seen that three particularly hot and dry summers in the Midwest—2005, 2006, and 2012—caused aflatoxin to spread to the Corn Belt,” she added.
A. flavus thrives at temperatures from 32–38 degrees Celsius (approximately 90–100 degrees Fahrenheit) and is impeded by moisture. Dr. Wu’s predictive model showed that, as climate change begins to alter temperatures and rainfall patterns, optimal times and geographic areas for planting corn will begin to shift. While some corn-producing areas, such as Texas, will see a decrease in aflatoxin prevalence, the U.S. Midwest—the Corn Belt—will see a rise. Specifically, aflatoxin problems will be most intense in Kansas and Missouri, and to a lesser extent in Iowa, Illinois, and Nebraska. Regarding Texas, Dr. Wu said, “… [reduced aflatoxin in Texas] is not good, because that means it may be too hot for the corn to survive, which poses food security concerns.”
Dr. Wu provided suggestions for what can be done to mitigate the risk of aflatoxin from corn. She advocated for biotechnology solutions, such as CRISPR gene editing, to produce resilient breeds of corn. She also spoke to the role of water in mitigating aflatoxin risk, stating that irrigation and planting in moister locations are increasingly unreliable tactics as the water table continues to sink. “The water table will become a precious resource,” Dr. Wu said. She also mentioned that planting the correct corn hybrid in the appropriate agricultural location can help reduce aflatoxin risk, but added, “… what is going to become the new Corn Belt? Is it going to be ever-shifting north?”
Aside from adhering to good agricultural practices (GAPs) such as proper planting and irrigation, improved post-harvest processes can be useful. Dr. Wu suggested keeping food as cool and dry as possible, and not storing crops for excessively long times. “Anything that can reduce stress for the corn plant will reduce the risk of any kind of infection, including aflatoxin infection,” Dr. Wu said. “This is something we need to start paying attention to now, because of the large impact it will have on U.S. and global food security.”
After Dr. Wu’s presentation, an attendee enquired about the role of pesticides in an aflatoxin risk management plan. Dr. Wu responded that, unlike some other mycotoxins, A. flavus does not respond well to fungicides. Regardless, Dr. Wu stated that it is not beneficial to overuse fungicides, and there are predictive models that the agrifood sector can use to assess whether it would make sense to apply a fungicide based on crop, temperatures, geographic location, and other factors.
Another attendee asked about the effect that short, dramatically heavy rainfall periods—a symptom of climate change—might have on aflatoxin prevalence. Dr. Wu answered that, while heavy rains will not cause an issue during corn’s silking phase, it can be especially dangerous right before harvest, during the denting phase. “When there are heavy rains in September, if there are any A. flavus growing in corn, it will absolutely bloom and produce a huge amount of aflatoxin,” Dr. Wu said.
The IAFNS 2022 Annual Meeting and Science Symposium took place on June 21, 2022–June 23, 2022, both virtually and in-person in Washington D.C.