Global warming makes it easier for bacteria and other germs to contaminate the food supply, and this little-discussed danger of climate change teaches painful and sometimes life-threatening lessons to hundreds of millions of people every year. One of them is 75-year-old Sumitra Sutar from Haroli village in Maharashtra, India.
Five years ago, Sutar was eating leftovers and lentil curry, her staple for more than five decades. This time, she recently recalled, her diet caused her to vomit “at least 15 times a day.” Eventually, she learned the culprit was a food-borne bacteria that produces toxins that can cause vomiting, eye inflammation and respiratory infections. Global warming has made the world more welcoming to the growth of the pathogen Bacillus cereus in food stored after cooking. One study found that cooking rice at home is not enough to inactivate its spores.
Researchers and health workers are sounding the alarm: Food supplies are vulnerable to greater spoilage due to more frequent extreme heat, floods and droughts, increasing the risk of contamination and foodborne disease outbreaks. Experts say extreme heat can cause bacteria to multiply faster and accelerate food spoilage. Rising water levels from severe flooding can contaminate crops with sewage or other unnecessary waste, while higher humidity can promote the growth of salmonella on lettuce and other raw produce. The World Health Organization estimates that 600 million people become ill from foodborne diseases each year, resulting in 420,000 deaths. Children under five are particularly at risk, with 125,000 children dying each year from this largely preventable disease.
Many factors, including agricultural practices and global food supply chains, make such problems more common, and a growing body of research highlights that climate change also plays a significant role.
A review study published this year in eBiomedicine found that the threat of non-typhoid salmonella increases with each degree Celsius rise in temperature Campylobacter, a bacterium that often makes people sick by causing food poisoning, increased by 5%.
bacterial greenhouse
The village of Sutar has reported a severe rise in temperatures over the past decade, with summer highs reaching 43 degrees Celsius (109.4 degrees Fahrenheit). Padmashri Sutar, a community health care worker and Sumitra Sutar's daughter-in-law, said many people in the area have reported an increase in foodborne illnesses.
A review article published in “Climate Change” pointed out that rising temperatures and changing precipitation patterns have led to the proliferation of foodborne pathogens, including the most common: Salmonella, Escherichia coli (E. coli) and Campylobacter jejuni.
Ahmed Hamad, one of the report's authors and a lecturer in food hygiene and control at Benha University in Egypt, said: “Rising temperatures can promote the presence of Listeria, Campylobacter and Growth of bacteria such as salmonella.
A study in northwestern Mexico examined how environmental factors influence outbreaks of salmonella, the bacterium responsible for many foodborne illnesses around the world. Studies have found that the incidence of the disease is highest in areas with warmer temperatures (35 to 37 °C (95-98.6 F)) and annual rainfall greater than 1,000 mm (39.4 inches).
Another paper published this year in Applied and Environmental Microbiology found that climate change will increase the risk of foodborne illness caused by Salmonella enterica, noting that high humidity promotes the growth of Salmonella. This bacteria affects 1.2 million people in the United States each year.
Hudaa Neetoo, associate professor of microbiology and food safety at the University of Mauritius, warned that ready-to-eat products pose a higher risk of foodborne illness in extreme heat.
“During heat waves, the levels of pathogenic microorganisms in these products can increase significantly and reach levels sufficient to cause illness, as they do not require any final heat-killing step.”
In addition to heat waves, flooding can cause manure to flow from neighboring animal pastures into farmland, contaminating produce, including salads, vegetables and raw leafy greens, she said.
“Animal waste can contain human pathogens such as pathogenic E. coli, salmonella and campylobacter, and research has found that household washing alone is not sufficient to decontaminate produce and reduce microbial levels to safe levels,” she said.
She also warned that produce can be systematically contaminated with pathogens that enter crops through the roots and become internalized, making them difficult to remove.
Another direct impact of flooding is overflowing sewage systems, which “can contaminate crops and water sources with harmful pathogens such as salmonella, E. coli and norovirus. Flooding can also introduce pathogens into irrigation systems, increasing the risk of crop contamination,” Hamad explain.
Indirect effects of climate change may also lead to outbreaks of foodborne illness. A paper published in the Journal of Health Monitoring notes that as fresh water becomes increasingly scarce, treated wastewater may be used to irrigate crops, possibly carrying pathogens from animal or human feces. This increases the risk of contamination.
Martin Richter, head of the food safety department at the German Federal Institute for Risk Assessment, said: “When communities rely entirely on wastewater reuse, the first goal must be to treat the water to a safe level that does not pose a risk to consumers. “Sometimes, one serving of pathogen is enough to cause disease,” so wastewater must be treated thoroughly, he recommends prioritizing the use of fresh water for irrigating foods that are usually eaten raw, while using treated wastewater for irrigating crops that are usually cooked.
“Cooking food at 70 degrees Celsius for at least two minutes will destroy most pathogens that may be present on its surface,” he said.
More precautions needed
Padmashri Sutar, a community health care worker, said people in her village no longer use river water for cooking and rely entirely on groundwater.
“Many people in the village used to get sick after drinking river water, but now they have completely avoided it.”
She said many people need education about the link between climate change and foodborne illness.
“To make people aware of this, I give simple examples such as the increase in the frequency of food spoilage.”
She also urged people to clean water containers after flooding or heavy rain, and discussed how pathogens and bacteria are now more likely to contaminate vegetables and milk.
People who participated in awareness events now eat fewer leftovers.
“They prefer to cook fresh food now and only buy the required amount of vegetables,” she said.
Neetoo said health care workers need more long-term data on climate change and foodborne illness.
“Universities should conduct long-term monitoring studies and trend analysis to better predict the impacts of climate change on food systems.”
She also advocates researching new ways to decontaminate warehouses, containers and food affected by flooding.
Hamad called for increased monitoring and surveillance to detect potential outbreaks early. He added that infrastructure should be improved to ensure food processing and distribution systems are resilient to extreme weather events and that health infrastructure is robust, especially in flood-prone areas.
common misunderstandings
Experts stress the need to educate people about the role of climate change in foodborne illness.
“Many people view climate change as a purely environmental issue without recognizing its profound impacts on public health, including increasing the risk of foodborne illness,” Hamad said.
One prominent misconception is that cold weather kills all pathogens.
“Certain bacteria, such as Listeria, can still grow at low temperatures, posing risks even in colder climates,” he explains.
Sutar said people often interrupt her when she talks about the reasons behind the rise in foodborne illnesses. They reiterated a common belief that improper food handling is the sole cause behind these illnesses. She patiently explains how climate change is exacerbating the growth of pathogens in the environment and water sources.
“People are unwilling to accept that climate change can also cause foodborne illness,” Sutar said. She added that many people in her area do not report such illnesses because they do not take them seriously and think it is a Isolated cases do not deserve public attention. Meanwhile, many other people in the area also suffered from vomiting, fever, gastrointestinal problems and other symptoms after eating contaminated food.
Sutar said she has become a evangelist for spreading the climate and food supply message.
“I'm asking people to not only observe changing climate patterns, but also to think carefully about what's on their plate.”
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