POISONED CHALICE: TOXIN ACCUMULATION IN CROPS IN THE ERA OF CLIMATE CHANGE
Contamination pathways–implications for crops, animals, and people
Worldwide, over 80 plant species are known to cause poisoning from accumulation of nitrates.10
amounts of aflatoxins.16 Under normal
growing condition, plants convert nitrate into amino acids and protein. Drought conditions slow or prevent the conversion, causing nitrate to accumulate indefinitely to the level that becomes toxic to animals.11
Common crop plants most
susceptible to nitrate accumulation are barley, maize, millet, millet, maize, sorghum, soybean, sudangrass, and wheat.12 When cattle, sheep, and goats consume large quantities of high nitrate plants, their ruminant digestive processes cannot break down the nitrate fast enough to avoid poisoning. Acute nitrate poisoning in animals can lead to miscarriage, asphyxiation, and death. Nitrate poisoning in livestock can ruin the livelihoods of smallholder farmers and herders.
Sufficient rain can revitalize plant growth and help reduce nitrate accumulation. However, after a drought-breaking rainfall or irrigation inflow, rapid growth in water-stressed plants could result in dangerous accumulation of another toxic compound called hydrogen cyanide or prussic acid.13 Examples of plants that can accumulate prussic acid are cassava, flax, maize, sorghum, sudangrass, arrow grass, velvet grass, apricot, peach, cherry, elderberry, and apple.12
Another important category of toxin associated with changing climate is mycotoxins, chemical by-products of fungal growth. Mycotoxins can cause severe damage to the health of animals and humans even at small concentration. Mycotoxin- producing fungi infect many crops such as coffee, groundnut, maize, oilseeds, peanut, sorghum, tree nuts, and wheat. An estimate in 1998 suggested that mycotoxins contaminated at least 25 per cent of cereals worldwide14,15
Aflatoxins are a type of mycotoxin produced by a species of Aspergillus fungi. About 4.5 billion people in developing countries are exposed to uncontrolled and unmonitored
56 Acute exposure can be lethal, while
chronic exposure can lead to cancer. Evidence further suggests it may also stunt foetal and infant development, block nutrient uptake, and suppress immunity.17
Poorer
farmers may feed mouldy grains to livestock, but this is not a safe option. Aflatoxins and other mycotoxin contaminants can reduce animal productivity and increase mortality, and they can persist in animal-sourced food products such as milk to impair human health and nutritional status.18
Photo Credit: UN Photo/James Bu
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