8 June 2021 | Category: Food systems

Nutrient-rich diets increase food security, only if proper water quality is guaranteed

By Thijs de Lange

This is part 7 of a blog series on food systems. This article was written by Thijs de Lange, Vincent Linderhof and Stijn Reinhard.

In areas with poor water quality, often in the global South, the promotion of nutrient-rich diets with perishable foods like fruits, vegetables and fish, can deteriorate food safety. Perishable foods are prone to contamination with for instance heavy metals and bacteria. This is due to poor quality water resources from irrigation water, water used in food processing and the way meals are prepared. To ensure nutrient-rich diets, an integrated approach which combines food system and water system thinking is needed.

Both system approaches have different outcomes and focus on different interactions between actors in the systems. In the food system approach the value chain water is seen as an input. In a water system approach however, the interaction between water users is the core of this approach and efficient water use for food production can be an outcome. Wageningen University & Research has a leading role in both food systems and water systems. We can also take a leading role in bridging the gap and initiate integrated research to better understand food and water systems related to water quality and food security.

Broad spectrum of contaminants

Insufficient water quality contaminates food in several steps within the food supply system. The water used can be contaminated by a wide range of different contaminants and from different sources. Examples are pathogens (like viruses and bacteria), antibiotics, and pharmaceuticals from urban wastewater (sewage) and livestock or aquaculture production systems. Trace elements like mercury were reported from wastewater from industries and from natural presence in geogenic elements of arsenic. The latter is the case in groundwater layers in areas in Bangladesh. Other contaminants are cyanotoxins resulting from algae blooming, mycotoxins (toxins from fungi) or high concentration nitrogen and phosphorus from fertilizers. The degree and type of contamination depends on the geographical location. For example, wastewater in India shows higher pollution levels of heavy metals compared to wastewater in Africa due to the higher industrialization in India.

Food system activities pollute water resources

Although examples of excessive fertilizer and pesticide use in agriculture and aquaculture are well-known sources of water pollution, food processing and food consumption activities also contribute through wastewater discharges. For example, untreated wastewater from abattoirs discharged to a river upstream causes high amounts of pathogens, nitrogen and phosphate. When the water is used downstream for meal preparation or for drinking, people might be infected by the presence of pathogens.

Each type of production system is characterized by a specific kind of contamination and highly depends on the input used. In crop production, overuse of fertilizers leads to nitrogen contamination of surface waters which can cause nitrite pollution of groundwaters. Consumption of nitrite-polluted waters might cause nefarious effects (methemoglobinemia) in infants. Moreover, high concentrations of nitrogen and phosphorus induce algae blooming, which releases mycotoxins. Food contamination by mycotoxins led to neurological diseases.

A Bolivian farmer washing his harvested onions in a river (photo: Thijs de Lange).

Dangers to food safety and food security

Each food product has its unique characteristics on how it is affected by poor water quality. This depends on the region and the type of contamination. Here, we present two examples of food products which are affected by water quality throughout the food system: fruits and vegetables as well as fish and seaweed.

Water pollution offsets the nutrition value of fruits and vegetables

Consumption of fruits and vegetables is promoted for their richness of nutrients like vitamins. However, the consumption of raw fruits and vegetables, either prepared at home or by street vendors, is prone to contamination with pathogens in poor water quality regions. When fruits and vegetables would be heated before consumption in areas with poor water quality, food infections from pathogens could be avoided.

Pathogen contamination of fruits and vegetables can take place in different stages of the food supply system. In some areas, it is common practice to wash fruits and vegetables on street markets, although water resources are contaminated with pathogens. Consequently, contaminated products contaminate other products with water as medium. Similar examples exist on produce of fresh-cut vegetables in factories. Indirectly, the absence of good quality of water might contaminate leaf crops by faecal-oral transmission when processors cannot wash their hands according to hygiene standards. Obviously, these contaminations also occur at home during food preparation.

Since wastewater often contains high concentrations of phosphate and nitrogen, cases are described where farmers had a preference for wastewater over fresh water for crop irrigation. These farmers have higher production due to high nutrient concentration in the water and can at the same time save costs on fertilizer use. However, next to pathogen contamination, fruits and vegetables can be contaminated by irrigation water with high concentrations of heavy metals as these crops absorb heavy metal residues. These high levels are not removed throughout the different stages of the food system, so these crops are likely to be consumed. Moreover, the impact can be prolonged because heavy metals residues accumulate in the soil and later be absorbed by the leaf crops. Heating fruits and vegetables before consumption will not take out the heavy metals as is the case with pathogens. So, although the use of wastewater might increase local access to fruits and vegetables on markets, monitoring of especially heavy metals in wastewater is needed to avoid consumer health hazards.

Effect of water pollution on fish, seafood and seaweed

Fish and seaweed are considered as a healthier and sustainable alternative source of proteins compared to animal source proteins. Local stimulation of aquaculture to meet the growing protein demand is taking place on a larger scale. However, both fish and seaweed are prone to heavy metal contamination present in water bodies, whereby trace elements such as mercury can accumulate in the food. High concentrations of nitrogen and phosphate indirectly affects fish production. In 2017 in Norway, high concentration of nitrogen and phosphorus from inland waters induced algae blooming which resulted in cyanotoxins poisoning and killing of fish for consumption. In addition, consumption of cyanotoxin intoxicated fish by human would seriously harm their health.

The proper preparation of fish and seaweed can relax or strengthen the impacts of contamination. For example, the concentration of total arsenic in seaweed decreased after soaking and cooking. Conversely, the inorganic form of arsenic, which is highly toxic, substantially increased after cooking. Widely spread information on the consequences of food preparation is crucial if and to what extent food contamination might cause health hazards in the short or long run.

Improving water, sanitation and hygiene (WASH)

Access to good quality tap water plays a key role in reducing food contamination from pathogens. In major parts of the world, people have no  access to good quality (tap) water, and (improved) sanitation. In these areas, the use of poor-quality surface water or wastewater to produce crops – for own production and for local markets – lead to faecal-oral infections. Initiatives for certification of crops irrigated with clean water can ensure that consumers buy safe crops. However, when pathogen contamination takes place further along the food system supply chain, it might be questionable how effective this measure is. At least when it comes to pathogens.

Food security and water management (including WASH) are heavily interlinked. Nevertheless, the policy domains and research areas on food security and water management are often separate worlds of experts with their own networks in policymaking and research institutions. An integrated approach in which food systems and water systems thinking come together is crucial to coordinate and solve the contamination problems to stimulate healthier and safe diets and thus food security. At Wageningen University & Research we are working on almost all elements related to food and water systems, like waste water treatment, food safety, integrated water management, sustainable production systems and socio-economic studies on food systems. In this sense, we take a key role to towards more collaboration between these disciplines to come to integrated solutions.

Online Conference on One Water, One Health
This research will be presented at the IWRA 2021 Online Conference on One Water, One Health: Water, Food & Public Health in a Changing World. The presentation is scheduled for the session on How can science better inform public policy, governance and capacity building for water, food and health? on Wednesday June 9 at 16:45 (CET).
If you would like to attend the presentation, please register for free.

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By Thijs de Lange

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