Climate change, including rising temperatures and changes in weather extremes, is expected to increase the exposure of food to certain pathogens and toxins [Likely, High Confidence]. This will increase the risk of negative health impacts [Likely, Medium Confidence], but actual incidence of foodborne illness will depend on the efficacy of practices that safeguard food in the United States [High Confidence].

This finding is from chapter 7 of The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment.

Process for developing key messages: The chapter was developed through technical discussions of relevant evidence and expert deliberation by the report authors at several workshops, teleconferences, and email exchanges. The authors considered inputs and comments submitted by the public, the National Academies of Sciences, and Federal agencies. For additional information on the overall report process, see Appendices 2 and 3. The author team also engaged in targeted consultations during multiple exchanges with contributing authors, who provided additional expertise on subsets of the Traceable Accounts associated with each Key Finding.

Because the impacts of climate change on food production, prices, and trade for the United States and globally have been widely examined elsewhere, including in the most recent report from the Intergovernmental Panel on Climate Change,fcd24eab-974a-46aa-8434-78b8cd3f0ef0 c04c5716-c318-4a4c-9774-ae61ce97d305 d0c735f3-4b2c-4dec-907c-09e81818b288 67bff3c8-bddd-4bbb-975d-bec307df5f72 3baf471f-751f-4d68-9227-4197fdbb6e5d c390e13f-8517-40a9-a236-ac4dede3a7a0 this chapter focuses only on the impacts of climate change on food safety, nutrition, and distribution in the context of human health in the United States. Many nutritional deficiencies and food-related illnesses are of critical importance globally, particularly those causing diarrheal epidemics or mycotoxin poisoning, and affect U.S. interests abroad; but the primary focus of this chapter is to address climate impacts on the food safety concerns most important in the United States. Thus, the literature cited in this chapter is specific to the United States or of demonstrated relevance to developed countries. The placement of health threats from seafood was determined based on pre- and post-ingestion risks: while ingestion of contaminated seafood is discussed in this chapter, details on the exposure pathways of water-related pathogens (for example, through recreational or drinking water) are discussed in Chapter 6: Water-Related Illness.

Description of evidence base: Multiple lines of research have shown that changes in weather extremes, such as increased extreme precipitation (leading to flooding and runoff events), can result in increased microbial and chemical contamination of crops and water in agricultural environments, with increases in human exposure.19d0c5a6-be45-4234-8d62-6d3eff596da5 696355ed-9253-428a-a2b5-ad114a79bdd3 01c49cdf-06bb-41ef-95be-37a8553295b7 During times of drought, plants become weaker and more susceptible to stress, which can result in mold growth and mycotoxin production if plants are held in warm, moist environments.1ca7e70d-66b3-42e1-9a68-31b976d2622f 40aee056-3c0d-407d-997f-e4f254962f81

While studies that link climate change to specific outbreaks of foodborne illness are limited, numerous studies have documented that many microbial foodborne illnesses increase with increasing ambient temperature.b6d4024a-eeca-4900-8198-d65b084285a2 02b85405-4cd5-4185-a14f-07e4fc6cc4e9 There is very strong evidence that certain bacteria grow more rapidly at higher temperatures and can increase the prevalence of pathogens and toxins in food.1ca7e70d-66b3-42e1-9a68-31b976d2622f 8bce78b9-816b-480d-a6bf-18ded7984f5b e573afb0-9fee-45a5-bbd6-e3abdf6e5bd8 Case studies have demonstrated that lack of refrigerated storage, particularly during very warm weather, leads to increases in microbial growth and higher exposure to pathogens.67bff3c8-bddd-4bbb-975d-bec307df5f72 b6d4024a-eeca-4900-8198-d65b084285a2 02b85405-4cd5-4185-a14f-07e4fc6cc4e9 0ad0a878-82e3-4980-ae61-7341036f50aa c912323b-ab87-4865-ab9f-5dc13a730e64

New information and remaining uncertainties: Concentrations of pathogens and toxins in food are expected to increase, resulting in an increase in the risk of human exposure to infectious foodborne pathogens and toxins. However, the number or severity of foodborne illnesses due to climate change is uncertain. Much of this uncertainty is due to having controls in place to protect public health. For example, contaminated crops are likely to be destroyed before consumption, and certain pathogens in food, like mycotoxins, are highly regulated in the United States. Consequently, the extent of exposure and foodborne illness will depend on regulatory, surveillance, monitoring, and communication systems, and on how, and to what extent, climate change alters these adaptive capacities. Furthermore, for certain pathogens, it is not yet clear whether the impact of climate change on a pathogen will be positive or negative. For example, climate change could lead to fewer cases of norovirus infection in the winter, but worsening health outcomes are also possible due to elevated transmission of norovirus during floods. Similarly drought can reduce water quality, increase runoff, and increase pathogen concentration, but can also decrease the survivability of certain foodborne pathogens.

Assessment of confidence based on evidence: There is high confidence that rising temperature and increases in flooding, runoff events, and drought will likely lead to increases in the occurrence and transport of pathogens in agricultural environments, which will increase the risk of food contamination and human exposure to pathogens and toxins. However, the actual prevalence of disease will depend on the response of regulatory systems and, for certain pathogens, the relative importance of multiple climate drivers with opposing impacts on exposure. Thus there is medium confidence that these impacts of climate change on exposure to pathogens and toxins will likely lead to negative health outcomes. There is a high confidence that the actual incidence of foodborne illness will depend on the efficacy of practices that safeguard food in the United States.

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