finding 7.2 : chemical-contaminants-in-the-food-chain

Climate change will increase human exposure to chemical contaminants in food through several pathways [Likely, Medium Confidence]. Elevated sea surface temperatures will lead to greater accumulation of mercury in seafood [Likely, Medium Confidence], while increases in extreme weather events will introduce contaminants into the food chain [Likely, Medium Confidence]. Rising carbon dioxide concentrations and climate change will alter incidence and distribution of pests, parasites, and microbes [Very Likely, High Confidence], leading to increases in the use of pesticides and veterinary drugs [Likely, Medium 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: There are a number of established pathways by which climate change will intensify chemical contaminants within the food chain. Multiple studies have shown that increases in ocean temperatures are likely to increase the potential for mercury exposure, likely due to the increased uptake and concentration of mercury in fish and mammals at higher metabolic rates associated with warmer ambient temperatures.28025deb-e0a3-4b76-b1d4-770bc897aa71 67bf0866-1dd9-49ce-a909-848cc3f69a77 0677152e-5892-427e-967b-540e16d30628 90048433-9538-4100-a94f-3ecb8940519f Another pathway includes extreme weather events, which can move chemical contaminants such as lead into agricultural fields and pastures (as well as into drinking or recreational water sources—see Chapter 6: Water-Related Illness).3bfe667e-40cb-4dc3-9da4-75df2ab699ce 443c29a9-352d-4e29-b787-cbf549968901 d30a33b7-b186-4ef5-9629-da98ca21ee8b A final pathway is through rising minimum winter temperatures and longer growing seasons, which will very likely alter pest distribution and populations. A large body of literature shows that temperature, carbon dioxide (CO2) concentrations, and water availability are also likely to affect pest development, number of pest generations per year, changes in pest range, rate of infestation, and host plant and animal susceptibility.c04c5716-c318-4a4c-9774-ae61ce97d305 4b0cbc38-2722-418e-a982-5e04837291b0 bf92266b-c107-4d7c-9bbb-1e4a08fa0fc7 afc4d024-e3a0-436c-b037-28a2397bf4c7 1985bce4-5738-4ba6-ac9a-0d676d2ce4a3 Empirical models and an analysis of long-term in situ data indicate that rising temperatures will result in increased pest pressures.c11c6252-a26d-431f-b450-2d590921cdc7 722318af-75e4-4a36-a2bb-6ba291901c7a 4c6335ac-bf06-4a51-8d12-677ce9b21f55 These changes are expected to result in increased use of pesticides,c11c6252-a26d-431f-b450-2d590921cdc7 c37a868d-ab73-4775-988e-1ad89e14f20e which can lead to increased human exposure.32be7b58-9a19-4710-ad79-cea600732146

New information and remaining uncertainties: Each of the pathways described in the evidence base has variable levels of uncertainty associated with each step of the exposure pathway.c0419502-0517-447b-886f-ece5ec4cda6c For all these pathways, projecting the specific consequences on human health in the Unites States is challenging, due to the variability in type of pathogen or contaminant, time and duration of exposures, individual sensitivity (for example, genetic predisposition) and individual or institutional adaptive capacity. While increasing exposure to chemicals will exacerbate potential health risks, the nature of those risks will depend on the specific epidemiological links between exposure and human health as well as availability and access to health services. Resulting incidence of illness will depend on the genetic predisposition of the person exposed, type of contaminant, and extent of exposure over time.32be7b58-9a19-4710-ad79-cea600732146

Assessment of confidence based on evidence: Although it is likely that climate change will increase human exposure to chemical contaminants, the specific pathway(s) of exposure have varying levels of uncertainty associated with them and hence there is medium confidence regarding the overall extent of exposure. This chapter focuses on three such pathways. First, it is likely that elevated sea surface temperatures will result in increased bioaccumulation of mercury in seafood, but there is medium confidence regarding human illness because rates of accumulation and exposure vary according to the type of seafood ingested, and because of the role of varying individual sensitivity and individual or institutional adaptive capacity (particularly behavioral choices). Similarly, it is likely that extreme events will increase contaminants into agricultural soil and the food chain. However, there is medium confidence regarding exposure because the specific nature of the contaminant and the food source will vary, and because the extent of exposure will depend on risk management, communication of public health threats, and the effectiveness of regulatory, surveillance, and monitoring systems within the current food safety network. There is high confidence that it is very likely that rising CO2 and climate change will alter pest incidence and distribution. There is medium confidence that such changes in incidence and distribution are likely to increase chemical management and the use of veterinary drugs in livestock. However, in all these pathways, the specific consequences on human health in the Unites States are uncertain, due primarily to the variability in type of pathogen or contaminant, time and duration of exposures, individual sensitivity (for example, genetic predisposition), and individual or institutional adaptive capacity.

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