The Food and Agriculture Organization wrote in Chapter 2 – Health risks associated with wastewater use:
The survival of pathogens and how they infect a new host needs to be understood in developing a programme to eliminate or minimize health risks. The importance and complexity of the rural health problem for those living and working where wastewater is used is beyond the scope of this document. The focus of this document will be on the concern with those who handle, prepare or eat the crop after it has been harvested. The health issues associated with wastewater use for the handlers, preparers and consumers of the crop can be broken down into a series of questions (each will be covered in more detail in subsequent sections of this document):
What types of pathogens are likely to be present in the wastewater?
How many and what types of pathogens reach the field or crop?
Are these pathogens likely to survive in sufficient numbers and for sufficient time to be infectious to the handler or consumer?
How significant is the infection route for the various pathogens?
Which crops carry the highest potential for carrying infections to the handler or consumer?
Are there guidelines or limits available to measure the potential for health risk?
Types of pathogens present in wastewater
Wastewater or natural water supplies into which wastewater has been discharged, are likely to contain pathogenic organisms similar to those in the original human excreta. Disease prevention programmes have centred upon four groups of pathogens potentially present in such wastes: bacteria, viruses, protozoa and helminths. There have been extensive reviews published on the range of these pathogenic organisms normally found in human excreta and wastewater. The most complete reviews are Feachem et al. (1983), Rose (1986) and Shuval et al. (1986a). The following short discussion is extracted from those reviews and is presented to establish a basic understanding of the pathogens and their abundance.
Bacteria. The faeces of a healthy person contains large numbers of bacteria (> 1010/g), most of which are not pathogenic. Pathogenic or potentially pathogenic bacteria are normally absent from a healthy intestine unless infection occurs. When infection occurs, large numbers of pathogenic bacteria will be passed in the faeces thus allowing the spread of infection to others. Diarrhoea is the most prevalent type of infection, with cholera the worst form. Typhoid, paratyphoid and other Salmonella type diseases are also caused by bacterial pathogens.
Viruses. Numerous viruses may infect humans and are passed in the faeces (> 109/g). Five groups of pathogenic excreted viruses are particularly important: adenoviruses, enteroviruses (including polioviruses), hepatitis A virus, reoviruses and diarrhoea-causing viruses (especially rotavirus).
Protozoa. Many species of protozoa can infect humans and cause diarrhoea and dysentery. Infective forms of these protozoa are often passed as cysts in the faeces and humans are infected when they ingest them. Only three species are considered to be pathogenic: Giardia lamblia, Balantidium coli and Entamoeba histolytica. An asymptomatic carrier state is common in all three and may be responsible for continued transmission.
Helminths. There are many species of parasitic worms or helminths that have human hosts. Some can cause serious illnesses and the ones that pass eggs or larval forms in the excreta are of importance in considering wastewater use. Most helminths do not multiply within the human host, a factor of great importance in understanding their transmission, the ways they cause disease and the effects that environmental change will have on their control. Often the developmental stages (life cycles) through which they pass before reinfecting humans are very complex. Those that have soil, water or plant life as one of their intermediate hosts are extremely important in any scheme where wastewater is used directly or indirectly.
The helminths are classified in two main groups: the roundworms (nematodes) and worms that are flat in cross section. The flatworm, in turn, may be divided into two groups: the tapeworms which form chains of helminths “segments” and the flukes which have a single, flat, unsegmented body. Most of the roundworms that infect humans and also the schistosome flukes have separate sexes. The result is that transmission depends upon infection with both male and female worms and upon meeting, mating and egg production within the human body….
Relative health risk from wastewater use
The discussion in the previous sections show that a broad spectrum of pathogenic microorganisms including bacteria, viruses, helminths and protozoa is present in wastewater and they survive for days, weeks and at times months in the soil and on crops that come in contact with wastewater. Early approaches to measuring the health risk from these pathogenic micro-organisms centred on detection. Based upon the fact that these micro-organisms could survive, detection in any of these environments was sufficient to indicate that a public health problem existed. It was then assumed that such detection showed evidence that a real potential for disease transmission existed (Shuval et al., 1986a; Shuval, 1991). This is a “zero-risk” approach. Throughout the years a number of standards and guidelines have been developed on this zero-risk approach. This led to standards for wastewater use that approached those of drinking water especially where vegetable crops were being grown…. http://www.fao.org/docrep/w5367e/w5367e04.htm
A University of Birmingham study questions the use of waste water in certain circumstances for use in agriculture.
Science Daily reported in Irrigating vegetables with wastewater in African cities may spread disease:
Urban farmers growing vegetables to feed millions of people in Africa’s ever-growing cities could unwittingly be helping to spread disease by irrigating crops with wastewater, a new study reveals.
Experts discovered that wastewater collected from canals used for urban agriculture in Burkina Faso was rich in virulent human pathogens which cause gastroenteritis and diarrhea — a major cause of death in low and middle-income countries.
Researchers at the University of Birmingham led an international team from Burkina Faso, Cameroon and Germany in studying wastewater samples from three canals in the capital Ouagadougou — a city of 2.2 million inhabitants.
After identifying a wide range of antibiotic resistance genes in the water, they concluded that using wastewater for urban agriculture in the city posed a high risk of spreading bacteria and antimicrobial resistance among humans and animals.
With the urban population in sub-Saharan Africa expected to rise from 400 million (2010) to 1.26 billion in 2050, according to UN estimates, agriculture in towns and cities is recognised as a vital way of contributing to food security and alleviating poverty….
Dr Blaise Bougnon from the University of Yaounde (Cameroon), commented: “Some 200 million urban dwellers are reported to be engaged in urban agriculture world-wide and, in some cases, produce up to 90 per cent of cities’ demand for perishable vegetables, according to UN research.
“Over 80 per cent of domestic and industrial wastewater generated in low and middle-income countries is discharged untreated into the environment. Because of its low cost, availability and nutrient content, urban agriculture relies on wastewater for irrigation.”
There is an increasing number of bacteria that are multi-resistant against common antibiotics and cannot be treated by current therapies. Antibiotic resistance has led to the need for more expensive drugs, which many cannot afford, resulting in increased morbidity and mortality.
Between 50 and 90 per cent of antibiotics administered to humans and animals are excreted as a mixture of parent drug and metabolite forms, with significant levels of active drug ending up in the environment, where they may persist in soil and aquatic ecosystems.
The study found evidence in the canal water samples of pathogens commonly responsible for waterborne diseases which could lead to people directly or indirectly exposed to these wastewaters suffering from acute diarrhea, chronic gastritis, and gastroenteritis.
In low and middle-income countries 842,000 people die annually from diarrhea, according to the World Health Organisation, because of inadequate water, sanitation, and hygiene. https://www.sciencedaily.com/releases/2018/10/181012102225.htm
Citation:
Irrigating vegetables with wastewater in African cities may spread disease
Date: October 12, 2018
Source: University of Birmingham
Summary:
Urban farmers growing vegetables to feed millions of people in Africa’s ever-growing cities could unwittingly be helping to spread disease by irrigating crops with wastewater, a new study reveals.
Journal Reference:
Blaise P. Bougnom, Cheikna Zongo, Alan McNally, Vito Ricci, François X. Etoa, Sören Thiele-Bruhn, Laura J.V. Piddock. Wastewater used for urban agriculture in West Africa as a reservoir for antibacterial resistance dissemination. Environmental Research, 2019; 168: 14 DOI: 10.1016/j.envres.2018.09.022
Here is the press release from the University of Birmingham:
Irrigating vegetables with wastewater in African cities may spread disease
October 12, 2018, University of BirminghamUrban farmers growing vegetables to feed millions of people in Africa’s ever-growing cities could unwittingly be helping to spread disease by irrigating crops with wastewater, a new study reveals.
Experts discovered that wastewater collected from canals used for urban agriculture in Burkina Faso was rich in virulent human pathogens which cause gastroenteritis and diarrhoea – a major cause of death in low and middle-income countries.
Researchers at the University of Birmingham led an international team from Burkina Faso, Cameroon and Germany in studying wastewater samples from three canals in the capital Ouagadougou – a city of 2.2 million inhabitants.
After identifying a wide range of antibiotic resistance genes in the water, they concluded that using wastewater for urban agriculture in the city posed a high risk of spreading bacteria and antimicrobial resistance among humans and animals.
With the urban population in sub-Saharan Africa expected to rise from 400 million (2010) to 1.26 billion in 2050, according to UN estimates, agriculture in towns and cities is recognised as a vital way of contributing to food security and alleviating poverty.
Professor Laura Piddock, from the University of Birmingham’s Institute of Microbiology and Infection, commented: “Using wastewater for agricultural irrigation represents a very serious health risk, not least as it increases exposure to faecal pathogens. Wastewater appears to be a ‘hot spot’ for antibiotic resistant bacteria in Burkina Faso.”
“We urgently need further investigations to determine the extent that exposed populations are affected by this health issue. There is also an urgent need to improve global access to clean water, sanitation, and hygiene in low and middle-income countries to help prevent bacterial resistance spreading from the environment to people.”
Dr. Blaise Bougnon from the University of Yaounde (Cameroon), commented: “Some 200 million urban dwellers are reported to be engaged in urban agriculture world-wide and, in some cases, produce up to 90 per cent of cities’ demand for perishable vegetables, according to UN research.
“Over 80 per cent of domestic and industrial wastewater generated in low and middle-income countries is discharged untreated into the environment. Because of its low cost, availability and nutrient content, urban agriculture relies on wastewater for irrigation.”
There is an increasing number of bacteria that are multi-resistant against common antibiotics and cannot be treated by current therapies. Antibiotic resistance has led to the need for more expensive drugs, which many cannot afford, resulting in increased morbidity and mortality.
Between 50 and 90 per cent of antibiotics administered to humans and animals are excreted as a mixture of parent drug and metabolite forms, with significant levels of active drug ending up in the environment, where they may persist in soil and aquatic ecosystems.
The study found evidence in the canal water samples of pathogens commonly responsible for waterborne diseases which could lead to people directly or indirectly exposed to these wastewaters suffering from acute diarrhoea, chronic gastritis, and gastroenteritis.
In low and middle-income countries 842,000 people die annually from diarrhoea, according to the World Health Organisation, because of inadequate water, sanitation, and hygiene.
Explore further: Scientists map the distribution of antimicrobial resistance across Chinese major cities
More information: Blaise P. Bougnom et al. Wastewater used for urban agriculture in West Africa as a reservoir for antibacterial resistance dissemination, Environmental Research (2018). DOI: 10.1016/j.envres.2018.09.022
Journal reference: Environmental Research
Provided by: University of BirminghamRead more at: https://phys.org/news/2018-10-irrigating-vegetables-wastewater-african-cities.html#jCp
The International Water Management (IWMI) Institute researches water issues.
The IWMI listed crucial research issues in the safe use of waste water in agriculture:
Studies in Pakistan, Ghana, Vietnam and Mexico have examined both the positive and negative impacts of wastewater reuse for agriculture. Current IWMI work on wastewater can be found here http://www.iwmi.cgiar.org/publications/briefs/wle-towards-sustainable-intensification-briefs/
Key research questions
• What are the dangers of uncontrolled wastewater irrigation in terms of public health and pollution?
• How can the nutrient value of wastewater be assessed?
• What sustainable practices are being used that can be transferred to benefit poor rural areas in other countries?
• From a public health perspective, which crops are the best candidates for wastewater irrigation and which should be avoided? http://www.iwmi.cgiar.org/issues/water-and-health/wastewater-use-for-agriculture/
The Water Project researches issues related to water supply and sustainabliy.
According to the Water Project’s article, Facts about Water: Statistics of the Water Crisis:
783 million people do not have access to clean and safe water worldwide. 2
319 million people in Sub-Saharan Africa are without access to improved reliable drinking water sources 16 Sub-Saharan Africa is among the regions with the greatest drinking water spending needs, with the greatest investment needs in rural areas. 17
Two thirds or about 102 million of the 159 million people still using surface water live in Sub-Saharan Africa 14
1 in 9 people world wide do not have access to safe and clean drinking water. 13
443 million school days are lost each year due to water-related diseases. 4
In developing countries, as much as 80% of illnesses are linked to poor water and sanitation conditions. 5
1 in 3 people, or 2.4 billion, are without improved sanitation facilities. 14
695 million of a global 2.4 billion people living without improved sanitation facilities live in Sub-Saharan Africa. 16
Exposure to unsafe drinking water, inadequate sanitation and poor hygiene is a leading cause of cholera and a variety of infectious and tropical diseases in the African Region. 15
Half of the world’s hospital beds are filled with people suffering from a water-related disease. 8
Of Sub-Saharan healthcare facilities, 42% lack an improved water source within 500m, 16% lack improved sanitation, and 36% lack soap for hand washing. 14
Girls under the age of 15 are twice as likely as boys to be the family member responsible for fetching water. 2
The physical and time burden of water hauling was found to fall primarily on women and girls who make up 72% of those tasked with fetching water. 14
Women and girls are responsible for water collection in seven out of ten households in 45 developing countries. 14
Over half of the developing world’s primary schools don’t have access to water and sanitation facilities. Without toilets, girls often drop out at puberty. 3
Less than one in three people in Sub-Saharan Africa have access to a proper toilet. 2
In Sub-Saharan Africa, in the 38 countries for which data is available, hand washing prevalence is at best 50%. 16
84% of the people who don’t have access to improved water, live in rural areas, where they live principally through subsistence agriculture. 2 The average container for water collection in Africa, the jerry can, weighs over 40 lbs when full. 9
Almost two-thirds, 64% of households rely on women to get the family’s water when there is no water source in the home. 2
Globally we use 70% of our water sources for agriculture and irrigation, and only 10% on domestic uses. 1
Nearly 1 out of every 5 deaths under the age of 5 worldwide is due to a water-related disease. 6
According to the World Health Organization, for every $1 invested in water and sanitation, there is an economic return of between $3 and $34! 12
By investing in clean water alone, young children around the world can gain more than 413 million days of health! 7
The United Nations estimates that Sub-Saharan Africa alone loses 40 billion hours per year collecting water; the same as an entire year’s labor in all of France! 10
Research has shown that for every 10% increase in women’s literacy, a country’s whole economy can grow by up to 0.3%. 11
• Citations
1. AQUASTAT. Food and Agriculture Organization of the United Nations. “Water Use.” http://www.fao.org/nr/water/aquastat/water_use/index.stm
2. WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation. “Progress on Sanitation and Drinking Water 2010.” Available at http://www.wssinfo.org/
3. UNICEF. “Water, Sanitation and Hygiene” Updated May 2010. http://www.unicef.org/media/media_45481.html
4. United Nations Development Programme. “Human Development Report 2006: Beyond Scarcity: Power, Poverty and the Global Water Crisis.” 2006. Available at http://hdr.undp.org/en/reports/global/hdr2006/
5. United Nations. Statement by Secretary General Koffi Annan. June 2003. http://www.un.org/News/Press/docs/2003/sgsm8707.doc.htm
6. WHO/UNICEF. “Diarrhoea: Why children are still dying and what can be done.” 2009. available at http://www.unicef.org/health/index_51412.html.
7. World Health Organization. “Costs and benefits of water and sanitation improvements at the global level.” http://www.who.int/water_sanitation_health/wsh0404/en/
8. UNEP / UN-Habitat “Sick water? The central role of wastewater management in sustainable development. Available at http://www.grida.no/publications/rr/sickwater/
9. Jerry cans carry approx. 5 gallons of water so if a single gallon of water weighs 8.3 pounds, 5 gallons are 41.5 pounds.
10. United Nations Development Programme. “Resource Guide on Gender and Climate Change.” 2009. Available at http://www.undp.org/climatechange/library_gender.shtml
11. UNICEF. “Water, Sanitation and Hygiene” Updated May 2010. http://www.unicef.org/media/media_45481.html
12. World Health Organization. Executive Summary of “Costs and benefits of water and sanitation improvements at the global level.” http://www.who.int/water_sanitation_health/wsh0404summary/en/
13. Based on 87% of the global population using imprtoved sources. Found in WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation. “Progress on Sanitation and Drinking Water 2010.” Available at http://www.wssinfo.org/
14. WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation “2015 Report and MDG Assessment” Available from: http://www.wssinfo.org/
15. World Health Organization “WHO in the African Region” Available from: http://www.afro.who.int/en/clusters-a-programmes/hpr/protection-of-the-human-environment/programme-components/index.php?option=com_content&view=article&id=24&Itemid=122
16. World Health Organization “Key Facts from 2015 JMP Report” Available from: http://www.who.int/water_sanitation_health/publications/JMP-2015-keyfacts-en-rev.pdf?ua=1
17. World Health Organization “Global costs and benefits of drinking-water supply and sanitation interventions to reach MDG target and universal coverage” Available from: http://www.who.int/water_sanitation_health/publications/2012/globalcosts.pdf
Research about use of waste water is crucial because of the challenges the world faces about adequate water supply.
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