Nature Climate Change | Climate Feedback

AAAS 2011: Climate change poses challenge to food safety

Sid Perkins

WASHINGTON, DC – Climate change will pose a number of challenges to food safety in the coming decades, from boosting the rates of food- and water-borne illnesses to enabling the spread of pathogens, researchers reported Monday at the annual meeting of the American Association for the Advancement of Science.

Depending on the greenhouse gas emissions scenario, global average temperature is expected to rise between 1.1° and 6.8° Celsius by the end of the century. And warmer temperatures are known to increase rates of some diseases: According to a recent study of salmonellosis in Europe, frequency of the ailment rises about 12 percent for every 1°C that air temperature increases beyond a baseline of 6°C, said Cristina Tirado, an environmental scientist at the University of California, Los Angeles. The precise cause for this trend isn’t clear, said Ewen Todd, a bacteriologist at Michigan State University in East Lansing. It’s possible that warmer temperatures cause bacteria to grow more quickly, or people may prepare food differently in warmer weather (grilling outdoors vis-à-vis cooking in a kitchen, for example).

Climate change can increase disease risks in several ways, Tirado added. The concentration of methyl mercury in fish increases about 3.5 percent for every 1°C rise in water temperature. Warmer sea-surface temperatures can boost the frequency of harmful algal blooms, leading to an increased incidence of paralytic shellfish poisoning. Higher water temperatures also enable the spread of pathogens to higher latitudes: An outbreak of vibriosis on an Alaskan cruise ship in 2005, later linked to oysters that had been harvested near one of the ship’s ports of call, represents the spread of the disease-causing Vibrio parahaemolyticus to a locale more than 1,000 kilometers north of its previous known range. Dust storms, which are expected to increase in some regions due to climate change, could wreak their own havoc, because iron-rich mineral dust can drive a 10- to 1,000-fold increase in the growth rate of Vibrio bacteria.

Indirect effects of climate change abound as well. For instance, an increased frequency of intense storms and floods means that water purification systems could be overwhelmed more often, leading to a more-frequent incidence of waterborne diseases, says Sandra Hoffman of the U.S. Department of Agriculture’s Economic Research Service in Washington, D.C. Increased temperatures, particularly in the summer, may lead to longer and more-frequent electrical blackouts, during which food may be more susceptible to the growth of disease-causing agents. Climate-driven changes in the production, processing and transport of food could also boost the incidence of disease, she noted.

But some changes in behavior could trim the increased incidence of disease, Hoffman noted. If people begin to buy more of their foods locally rather than purchasing items transported long distances — either by conscious decision or in response to rising energy prices — the incidence of transport-related diseases may be reduced. One of the challenges to future food safety will be maintaining and improving disease surveillance, especially in developing nations, says Hoffman. While deaths attributable to food- and water-borne illnesses in industrialized nations are measured only in the hundreds each year, in developing nations the annual death tally for the same diseases is around 2.2 million.


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