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What climate change means for fungi and food safety

By Angel Medina-Vaya

Global warming is creating conditions perfect for the growth of mycotoxins in foods. What does this mean for Southeast Asia, one of the world’s major food production regions?

We live in a world of fungus. This includes ones like yeasts, mushrooms and antibiotic producers that we benefit from and many others like athlete’s foot and moulds in plants and foods that we don’t benefit from.

Climate change, and the warmer and more humid conditions it brings, is predicted to accelerate the growth and diversity of fungi in the environment. This will mean much greater threats to health particularly from foods susceptible to carrying mycotoxins, which are toxic substances produced by fungal moulds.

Over the last five decades, it’s been shown that cereals, nuts, spices, dried fruits, coffee, cocoa, fruit juices, grapes and red wine may all contain mycotoxins under warm and humid conditions—the kinds of conditions that are typical of Southeast Asia especially.

Because of the severity of the health risks involved, we need to start thinking much more about fungi and the impact of climate change. Many of the mycotoxins that enter human and animal food chains are ‘hidden’ and aren’t killed off by heat or other kinds of food processing. For instance aflatoxins, especially aflatoxin B1, can damage DNA and cause liver cancer in humans and animals. 

Other mycotoxins have a range of health effects including kidney damage, gastrointestinal impacts, reproductive disorders or suppression of the immune system. The most recent serious outbreak reported is of schoolchildren in rural Kenya who had consumed mouldy maize, resulting in about 150 fatalities and up to 500 children being hospitalised because of acute exposure to aflatoxins.

A report from the World Health Organization in February 2016, Mycotoxin Control in Middle and Low-Income Countries, warned that the issue of mycotoxins in the food chain had been ignored for too long and needed a coordinated international response. Aflatoxins have been regularly identified as affecting crops of maize and peanuts in India and Thailand, as well among coconuts in the Philippines, Sri Lanka and other countries in Asia Pacific. 

What’s climate change got to do with it?

Pests and fungal diseases are on the march (at an estimated rate of 6km per year from the equator outwards to the poles) and that’s a result of some of the key characteristics associated with climate change: higher temperatures at times of year when crops are being harvested, stored and transported; higher levels of rainfall and more humidity, a damper atmosphere, which encourages all types of fungal growth; and crop stress caused by drought conditions.

In the new milder climate conditions there are therefore risks of mycotoxin contamination increasing in regions which have been relied upon as the ‘bread baskets’ for food production. Increased contamination levels may occur of existing mycotoxins, or emigration of other mycotoxins may occur to new regions where they were not previously prevalent.

A key issue in the Asia-Pacific region is the impact of mycotoxins on cereal grains. Harvesting periods tend to coincide with the start of the rainy season, when drying crops in the sun is less likely. Damp grains combined with humid conditions are perfect for mycotoxin growth. For this reason, the aflatoxins level in Asian cereal grains exceeds the permitted limits for export to Europe. Cases of aflatoxin poisoning and liver cancer among humans are concentrated in Asian countries—such as India, Indonesia, the Philippines, Taiwan and Thailand—where more people rely on maize in their diet. 

Our recent studies at Cranfield University have looked at the role of one of the most fundamental factors behind climate change, the impact of increased levels of CO2. They have shown how higher CO2 levels combine with higher temperatures to further increase the likelihood of growth of mycotoxins—more of the dangerous aflatoxin B1 will be produced on maize-based substrates or maize grain in future. This will have profound implications in terms of mycotoxin contamination of cereals. 

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