Alberto Mantovani discusses the consequences of climate changes for human health and welfare, including the disruption of agricultural productions
Ongoing climate changes are a main challenge to global choices for sustainability and resilience. Climate changes are more complex than “warming”; besides specific features in different world areas, they entrain increased risks for extreme events, such as drought, forest fires and floods; in densely populated regions climate changes may synergize with atmospheric pollution. Consequences for human health and welfare may be severe and diverse, including the disruption of agricultural productions. In addition, some less evident, but nonetheless important, consequences for human exposure to toxic chemicals should not be overlooked.
Seafood and food safety
The bioaccumulation of methylmercury, a potent neurodevelopmental toxicant, in seafood is a main concern for food safety. According to the Europoean Environment Agency, increased ocean temperatures may result in increased mercury levels in marine animals. Also, increased release of mercury from its environmental “stores” may result from flooding, heavy rainfall, thawing of frozen soil (permafrost) and even forest fires (as wood contains amounts of mercury). In general, climate changes may alter the trapping/scavenging of high-concern pollutants into environmental comparts: rising temperature and snow melting can increase the availability of persistent endocrine disruptors (dioxins, PBDE etc.) for bioaccumulation in food webs. Farmed fish and seafood are increasingly important for food security worlwide: while fish is liable to toxicant bioaccumulation, it is also, and mainly, an important source of nutrients including omega-3 fatty acids. However, climate changes may impair this benefit-to-risk balance; for instance, alterations in the aquatic pH adversely affect the marine phytoplankton, the primary omega-3 synthesizer, hence the omega-3 availability in edible seafood. Using science-based guidance values for contaminants and nutrrients as protection goals, the fisheries and aquacultutre system needs innovation, e.g., novel fish farming methods and clever selection of es for human food.
Pesticide impacts
Climate changes do obviously impact on plant health and agricultural practices; they may also impact on the parameters for assessing the safety of pesticides.
Residues in treated plants as well as secondary contamination of food chains through the agricultural environment (eg. pastures) make-up the dietary exposure to pesticides. In the field, pesticides aretransformed into by-products, often to a large extent, by abiotic (temperature, etc.) and biotic (plant metabolism) factors; together with the parent substance by-products represent the residue burden. Toxicologically relevant residues have to be characterized; indeed some by-products pose greater toxicological concerns than the parent substance. For instance high temperature and humidity increase the formation of the endocrine-disrupting ethylene thiourea from the widely used dithiocarbamate fungicides. Several pesticides give rise to more than 40 by-products with different chemical structures: thus, high-concern residues may derive from a low-concern parent compound.
According to the European regulation, “very high concern” pesticides, including endocrine disruptors, should be used only if human exposure is “negligible”; however, the assessment of a “negligible” exposure must include the toxicologically relevant by-products from abiotic and biotic processes.
It is apparent that parameters used to model and predict the residue patterns can be significantly affected by climate changes, with important consequences; substances claimed to protect food security might be banned or restricted, and safer compounds and/or methods should be sought.
These few examples indicate how climate changes can impact on the web of relationships connecting environment, food security and food safety (the “One Health” conceptual framework), calling for timely and science-based strategies for resilience.
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