Foodborne Diseases and Nutrition
Impacts on Risk
The U.S. Climate Change Science Program (CCSP) reported a likely increase in the spread of several foodborne pathogens due to climate change, depending on the pathogens’ survival, persistence, habitat range, and transmission in a changing environment. Drought has been shown to encourage crop pests such as aphids, locusts, and whiteflies, as well as the spread of the mold Aspergillus flavus flavus that produces aflatoxin, a substance that may contribute to the development of liver cancer in people who eat contaminated corn and nuts. Agronomists are also concerned that climate change-based increases in a variety of blasts, rusts, blights, and rots will further devastate already stressed crops, and thereby exacerbate malnutrition, poverty, and the need for human migration. The spread of agricultural pests and weeds may lead to the need for greater use of some toxic chemical herbicides, fungicides, and insecticides, resulting in potential immediate hazards to farm workers and their families, as well as longer-term hazards to consumers, particularly children. The safety of agricultural crops and fisheries also may be threatened through contamination with metals, chemicals, and other toxicants that may be released into the environment as a result of extreme weather events, particularly flooding, drought, and wildfires, due to climate change. Global changes in ocean currents and water mass distribution, along with changes in Arctic ice cover, length of melt season, hydrology, and precipitation patterns, will alter contaminant and pathogen pathways. Contaminants include a wide range of chemicals and metals such as PCBs, PAHs, mercury, and cadmium; pharmaceuticals such as synthetic hormones, statins, and antibiotics; widely used industrial chemicals such as fire retardants, stain repellants, and non-stick coatings; and pesticides and herbicides for agricultural use and vector control for public health protection. The health effects of human exposure to these environmental agents via complex land and ocean food webs are not well documented or understood, but evidence from animal studies is showing that such compounds accumulate in foods at concentrations that may affect fetal development, immune function, and other biological processes. These agents often occur together and may act synergistically, producing potentially greater harm than a single agent.
Recent findings demonstrate that pathogens that can pose disease risks to humans occur widely in marine organisms and may be affected by climate change. In one specific example, the CCSP noted the strong association between sea surface temperature and proliferation of many Vibrio bacteria species that occur naturally in the environment (including those that cause cholera), and suggested that rising temperatures would likely lead to increased occurrence of illness associated with Vibrio bacteria in the United States, especially seafood-borne disease associated with V. vulnificusv and V. parahaemolyticus. Rising temperatures and impacts on other environmental parameters such as ocean acidification may also lead to more virulent strains of existing pathogens and changes in their distribution, or the emergence of new pathogens. Increased risks from animal-borne disease pathogens could be especially acute in human populations that are highly dependant on marine-based diets for subsistence and who live where environmental effects resulting from climate change are pronounced (for example in certain native populations in Alaska). Increased acidity of water associated with climate change may alter environmental conditions leading to greater proliferation of microbes of a public health concern. This is a significant concern in molluscan shellfish, because ocean acidification may affect formation of their carbonate shells and immune responses, making them more vulnerable to microbial infection. The combined impact of potential contaminant-induced immune suppression and expanding ranges of disease-causing pathogens and biotoxins on food supply could be significant.