Editing IPCC:AR6/SRCCL/Chapter-5 (section)

==== 5.2.4.1 Impacts on food safety and human health ====

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Climate change can influence food safety through changing the population dynamics of contaminating organisms due to, for example, changes in temperature and precipitation patterns, humidity, increased frequency and intensity of extreme weather events, and changes in contaminant transport pathways. Changes in food and farming systems, for example, intensification to maintain supply under climate change, may also increase vulnerabilities as the climate changes (Tirado et al. 2010 <sup>[[#fn:r411|411]]</sup> ).

Climate-related changes in the biology of contaminating organisms include changing the activity of mycotoxin-producing fungi, changing the activity of microorganisms in aquatic food chains that cause disease (e.g., dinoflagellates, bacteria like ''Vibrio'' ), and increasingly heavy rainfall and floods causing contamination of pastures with enteric microbes (like ''Salmonella'' ) that can enter the human food chain. Degradation and spoilage of products in storage and transport can also be affected by changing humidity and temperature outside of cold chains, notably from microbial decay but also from potential changes in the population dynamics of stored product pests (e.g., mites, beetles, moths) (Moses et al. 2015 <sup>[[#fn:r412|412]]</sup> ).

Mycotoxin-producing fungi occur in specific conditions of temperature and humidity, so climate change will affect their range, increasing risks in some areas (such as mid-temperate latitudes) and reducing them in others (e.g., the tropics) (Paterson and Lima 2010 <sup>[[#fn:r413|413]]</sup> ). There is ''robust evidence'' from process-based models of particular species ( ''Aspergillus'' /Aflatoxin B1, ''Fusarium'' /deoxynivalenol), which include projections of future climate that show that aflatoxin contamination of maize in Southern Europe will increase significantly (Battilani et al. 2016 <sup>[[#fn:r414|414]]</sup> ), and deoxynivalenol contamination of wheat in Northwestern Europe will increase by up to three times current levels (van der Fels-Klerx et al. 2012b, a) <sup>[[#fn:r1429|1429]]</sup>

Whilst downscaled climate models make any specific projection for a given geography uncertain (Van der Fels-Klerx et al. 2013) <sup>[[#fn:r1430|1430]]</sup> , experimental evidence on the small scale suggests that the combination of rising CO <sub>2</sub> levels, affecting physiological processes in photosynthetic organisms, and temperature changes, can be significantly greater than temperature alone (Medina et al. 2014 <sup>[[#fn:r415|415]]</sup> ). Risks related to aflatoxins are likely to change, but detailed projections are difficult because they depend on local conditions (Vaughan et al. 2016 <sup>[[#fn:r416|416]]</sup> ).

Foodborne pathogens in the terrestrial environment typically come from enteric contamination (from humans or animals), and can be spread by wind (blowing contaminated soil) or flooding – the incidence of both of which are likely to increase with climate change (Hellberg and Chu 2016 <sup>[[#fn:r417|417]]</sup> ). Furthermore, water stored for irrigation, which may be increased in some regions as an adaptation strategy, can become an important route for the spread of pathogens (as well as other pollutants). Contaminated water and diarrheal diseases are acute threats to food security (Bond et al. 2018 <sup>[[#fn:r418|418]]</sup> ). Whilst there is little direct evidence (in terms of modelled projections) the results of a range of reviews, as well as expert groups, suggest that risks from foodborne pathogens are likely to increase through multiple mechanisms (Tirado et al. 2010 <sup>[[#fn:r419|419]]</sup> ; van der Spiegel et al. 2012 <sup>[[#fn:r420|420]]</sup> ; Liu et al. 2013 <sup>[[#fn:r421|421]]</sup> ; Kirezieva et al. 2015 <sup>[[#fn:r422|422]]</sup> ; Hellberg and Chu 2016 <sup>[[#fn:r423|423]]</sup> ).

An additional route to climate change impacts on human health can arise from the changing biology of plants altering human exposure levels. This may include climate changing how crops sequester heavy metals (Rajkumar et al. 2013 <sup>[[#fn:r424|424]]</sup> ), or how they respond to changing pest pressure (e.g., cassava produces hydrogen cyanide as a defence against herbivore attack).

All of these factors will lead to regional differences regarding food safety impacts (Paterson and Lima 2011 <sup>[[#fn:r425|425]]</sup> ). For instance, in Europe it is expected that most important food safety-related impacts will be mycotoxins formed on plant products in the field or during storage; residues of pesticides in plant products affected by changes in pest pressure; trace elements and/or heavy metals in plant products depending on changes in abundance and availability in soils; polycyclic aromatic hydrocarbons in foods following changes in long-range atmospheric transport and deposition; and presence of pathogenic bacteria in foods following more frequent extreme weather, such as flooding and heat waves (Miraglia et al. 2009 <sup>[[#fn:r426|426]]</sup> ).

In summary, there is ''medium evidence,'' with ''high agreement'' that food utilisation via changes in food safety (and potentially food access from food loss) will be impacted by climate change, mostly by increasing risks, but there is ''low confidence'' , exactly how they may change for any given place.

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