Sitting next to a fire holds great pleasure for most of us. So does the smoky flavour wood-smoke brings to food. But daily use of firewood in poorly ventilated households can have hidden health consequences, particularly for women and children.
According to Professor Tony Cunningham of the School of Plant Biology, University of Western Australia, the 2.4 billion people in developing countries, notably in Africa and Asia, who use solid biomass fuels such as wood, charcoal and dung for cooking and heating are especially at risk.
Sometimes, he said, those risks are avoided through local knowledge.
“Euclea divinorum trees, for example, are widely known across southern Africa by their local name ‘ichitamuzi', which means ‘to split the family’. Local people believe that if the wood is used, it will cause arguments in the household. As a result, under customary law, this species is totally avoided as a fuel wood, even when wood is scarce,” he said.
“There more than a grain of truth in this belief,” explained Cunningham. “Not only does Euclea wood produce lots of smoke, it contains diterpenes that can have serious health consequences when inhaled.”
Professor Cunningham, who is also a Senior Associate with the World Agroforestry Centre (ICRAF), was speaking at an event titled ‘What’s Cooking on Farms? Tree Diversity for Health, Fuel and Nutrition,’ on 17 October 2012. The symposium was organized by the Centre on the sidelines of the just-ended Conference of the Parties to the Convention on Biological Diversity (CBD COP11) in Hyderabad, India.
“It is very important to choose the right tree for fuel wood in order to limit health risks from inhaling smoke with particular toxic compounds,” he said.
“Even better known by local people as woods to avoid are umthombothi (Spirostachys africana) in Africa, and in South Asia, the mangrove species Excoecaria agallocha. Both contain a diterpene called excoecarin, which causes serious gastric problems when used as firewood,” said Cunningham, who has more than three decades' experience working with communities in the developing world.
He elaborated that other species can harbour compounds with more subtle yet just as insidious effects on human health, greatly increasing the risk of respiratory and chronic disease.
“Some tree species also contain polycyclic aromatic hydrocarbons that are carcinogenic when inhaled in wood smoke. And smoke with this type of hydrocarbon, and certain metal ions, leads to eye cataracts,” he said.
In developing countries, trade in fuel wood and charcoal is big business. For instance, the World Bank (2009) estimated the Tanzanian charcoal industry to be worth US$ 650 million annually.
However, along with charcoal, fuel wood is becoming more expensive, and steadily getting out of the reach of poorer households.
“As you get depletion of species through land conversion and charcoal burning, poorer families find they can no longer afford to buy non-toxic ‘good woods’ or clean-burning charcoal. They end up using whatever wood they can find, including that of species that were traditionally avoided because of their harmful smoke. This puts them in greater danger of various cancers and other ailments,” said Cunningham.
He was quick to add, however, that wood remains a preferred household fuel for billions.
“Even with rural electrification, the use of wood for cooking will be with us for a while, due to the relatively high cost of electricity.”
Cunningham said that in order to limit the health risks associated with the ‘wrong’ fuel wood, there was an urgent need to step up the cultivation of trees that produce good quality fuel woods, and at the same time study and communicate the effects of different types of wood fuel on people’s health.
He recommended using participatory processes that combine modern science and local knowledge to select tree species with low toxin levels. These should be cultivated widely in agroforestry systems, specifically for use as household fuel and for burning charcoal.
“Well known ‘good’ firewood species include ‘umfomothi’ (Newtonia hildebrandtii) and ‘itsatsalitsane’ (Pteleopsis myrtifolia). Both are used to smoke Strychnos fruit pulp for long-term storage,” said Cunningham.
“However, these trees are slow growing, so what is needed is selection of faster-growing trees that produce wood with high calorific value that has no toxic compounds. Acacia and Faidherbia trees have great potential in this regard.”
“If we can grow the right fuel woods, we can greatly limit the health risks associated with toxic smoke inhalation in households. At the same time we will gain the numerous other benefits trees bring,” he concluded.
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Link to Professor Cunningham’s presentation
Related links:
AgroForestryTree Database - Agroforestry species listing with descriptions:
Database showing species that make good fuel wood
Lessons from eastern Africa's unsustainable charcoal trade –A working paper in PDF format
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Event description:
What's cooking on farms? Tree diversity for health, fuel and nutrition
