UPA, health and the urban environment

By Patricia Robertson,2014-04-01 19:16
7 views 0
UPA, health and the urban environment


    Urban and Periurban Agriculture, Health and Environment

    Discussion paper for FAO-ETC/RUAF electronic conference “Urban and

    Periurban Agriculture on the Policy Agenda“

    August 21 September 30, 2000

This discussion paper is prepared by Henk de Zeeuw, Co-ordinator of the Resource Centre

    on Urban Agriculture and Forestry (RUAF), ETC, the Netherlands; and Karen Lock, Visiting research fellow, London School of Hygiene and Tropical Medicine, UK.

I. Introduction

    This working group will deal with the health and environmental aspects of urban and periurban agriculture (UPA). UPA can have both negative and positive effects on the health and environmental conditions of the urban population. The positive aspects include reduction of urban food insecurity, improved access to food and improved diets of the urban poor, better physical and psychological health of the population due to greater physical activity, outdoor relaxation and ameliorated sanitation and greening of the direct living environment.

    We invite participants in this workshop to report and discuss both positive and negative impacts of UPA on health and the environment, although most of the above-mentioned positive impacts on health will be dealt with more extensively in the workshop on „UPA, 1nutrition and food security‟‟. The working group on UPA, health and environment - and thus also this paper - will mainly focus on the health risks of UPA and seek to formulate effective policies at city and national levels, that prevent or mitigate such risks.

    Urban agriculture can be defined as the growing of plants and the raising of animals for food and other uses within urban areas (intra-urban agriculture) and in the fringe of urban areas (periurban agriculture), and the processing and marketing of the resultant products. UPA systems include root crops, vegetables, aromatic and medicinal herbs, fruit crops, and livestock of all shapes and sizes. A smaller number deals with other plants, such as ornamentals and tree seedlings. Within food crops, the more perishable and relatively high-valued vegetable and animal products and by-products are better represented. Food and non-food production is often mutually complementary, often along gender lines, they reinforce not only food security but also income benefits, at individual and household levels. Urban farmers are mainly small-scale family enterprises, but also medium sized and larger enterprises are encountered. Urban agriculture (especially and more so intra-urban agriculture) is often done in addition to other employment.

    Like rural agriculture, UPA entails risks to health and the environment, if not managed and carried out properly. It is essential to address the health risks associated with urban agriculture for two main reasons (Flynn 1999):

    I. to protect consumers from contaminated foods and farm workers from occupational

    hazards; and

    II. to secure the support of municipal and national authorities for sustainable urban

    food production.

     1 We invite readers with an interest in nutritional and food security impacts to participate in the discussion in the UPA and Urban Food Security group as well.



    City authorities have often been reluctant to accept urban agriculture because of perceived health risks. Nevertheless, in most cities in developing countries (as well as in many countries in transition in Eastern Europe), urban agriculture is practised to a substantial scale, despite prohibitive laws and regulations. Hence, rather than general laws prohibiting urban agriculture, which are largely ineffective, policies are needed that actively manage

    the health risks related to urban agriculture.

    To formulate urban agricultural policies that improve the health of the urban population, it is important to critically examine the evidence for both health risks and benefits. We need to look at how the risks of urban agriculture can be minimised and the benefits increased. In order to be able to do so, we must specify the environmental conditions under which UPA-related health problems occur (i.e., type of agriculture, farm management practices, characteristics of the location, etc.) and the groups that are most vulnerable to those impacts, and the factors that determine this vulnerability (e.g. poverty, gender, age, main occupation). We must also discuss what factors currently restrict the urban poor from engaging in safer agricultural and food practices, as well as the capacity of city authorities to implement certain policy measures and to calculate their cost-effectiveness.

    I. Overview of the major categories of health risks associated with UPA

    The main health risks associated with UPA can be grouped into the following categories:

a. contamination of crops with pathogenic organisms (e.g. bacteria, protozoa, viruses or

    helminths), due to irrigation by water from polluted streams, or inadequately treated

    waste water or organic solid wastes;

    b. human diseases transferred from disease vectors attracted by agricultural activity;

    c. contamination of crops and/or drinking water by residues of agrochemicals;

    d. contamination of crops by uptake of heavy metals from contaminated soils, air or water;

    e. transmission of diseases from domestic animals to people (zoonosis) during animal

    husbandry, processing or meat consumption;

    f. human diseases associated with unsanitary postharvest processing, marketing and

    preparation of locally produced food; and

    g. occupational health risks for workers in the food-production and food-processing


    Although there is no directly comparable information about the global burden of disease for each of these categories of health risks, we have presented them above in a sequence corresponding with our estimate of their importance for human health (from highest to lowest risk). This is open for debate.

    A review of the available literature indicates that, although insight into the potential health risks of urban and periurban agriculture is growing, detailed information on the actual health impacts of UPA is scant. Many of the health risks are not specific to UPA, and much of the following discussion is taken from the wider agricultural literature. Further specification for 2urban conditions is urgently required.

    II a. Contamination of crops with pathogenic organisms by re-use of urban wastewater and

    organic solid wastes

     2 When discussing the quality of urban-produced food, it is recommended to compare it with data on the quality of the food supplied from rural areas or from abroad. For example, cases have been reported in which rural-produced food contained more heavy metals or residues of agrochemicals than urban-produced food.



a. Re-use of urban organic solid wastes

    The main use of solid waste is as a soil improver (household wastes, market refuse, sewerage, night soil, manure, fish wastes, and agro-industrial wastes). Agro-industrial wastes, household refuse and market wastes are also used to produce feed for livestock and fish.

    Composting is the most common form of processing urban organic wastes. Composting reduces several health risks by:

    - getting refuse „off the street‟ and so reducing health hazards related to inadequate

    refuse collection and disposal (and associated risks like transmission of diarrhoea and

    dysentery by houseflies, increased breeding of mosquitoes and contamination through

    scavenging animals);

    - by sanitising waste through heat destruction of some pathogens, including helminth

    eggs found in night soil.

    There are four main health risks related to the re-use of organic wastes: 1. Pathogens may not be destroyed (especially helminth eggs in night soil) if the compost

    is not properly prepared (too low temperature). The risk is greatly enhanced if organic

    materials are mixed with human excreta from latrines, manure or hospital waste, causing

    pathogens to breed.

    2. Improperly maintained compost heaps may attract rodents (which may be reservoirs of

    diseases) and insects (which may be vectors of diseases).

    3. Non-biodegradable fragments may cause injuries, skin infections, respiratory problems

    and other occupational problems of waste pickers, waste selectors and others involved

    in the composting process.

    4. Heavy metal contamination due to mixing of organic materials with industrial waste (due

    to occasional dumping of industrial wastes in open spaces within residential areas,

    among others).

b. Irrigation with improperly treated wastewater

    Liquid waste from domestic sewage is widely used for irrigation and fertilisation of field crops, perennials and trees, biogas production, and fish ponds. A large part of the wastewater used is untreated or poorly treated.

    Wastewater contains various bacteria, protozoan parasites, enteric viruses and helminths. These risks are not limited to official wastewater but often also apply to rivers and other open water sources, as indicated by figures gathered by Westcott (FAO, unpublished, cited in Birley and Lock, 1999): 45% of 110 rivers tested carried faecal coliforms levels higher than the WHO standard for unrestricted irrigation.

    There are many forms through which untreated wastewater can lead to human diseases in UPA. Coliform bacteria are mainly transmitted to humans from wastewater via the

    contamination of crops irrigated with wastewater. Another route is by consumption of contaminated meat from domestic animals that ingested tapeworm eggs from faeces in untreated sewage. Poorly treated sewage may contain viable stages of the hookworms that live in moistened soils and affect agricultural workers who expose their bare skin to the soil. Transmission of pathogens may also take place by fertilisation of fish ponds with human and animal wastes (e.g. overhanging latrines, overhanging poultry cages, ducks, addition of urban night soil and use of wastewater).

    Furedy (1996) points out that official attitudes towards the health risks associated with re-use of urban wastes have historically changed with necessity. Furthermore, she believes



    that perceived health risks of the re-use of urban wastes in agriculture are overstated and that regulations of waste re-use are frequently outdated or lack comprehensiveness. Armar-Klemesu et al. (1998) indicate that the major sources of bacterial contamination of fresh vegetables may draw from the distribution, handling and marketing system rather than from production.

Prevention and control measures suggested in the literature:

    - Improved intersectoral linkages between health, agriculture, waste and environmental

    management; well-defined priorities and joint strategies; adoption of clear waste re-use

    policies for urban agriculture which are based on health criteria and impact assessments

    of waste re-use schemes in agriculture.

    - Waste separation at source; regular collection of organic refuse; prevention of mixing

    household waste with waste of hospitals and non-agroindustries.

    - Establishment of decentralised composting sites; securing the application of proper

    composting methods (temperature, duration) to ensure killing of pathogens; recognition

    of the various informal actors involved in the processing of urban wastes and the

    marketing of recycled products; enabling clean water supply and sanitation services at

    dump and processing sites.

    - Identification of quality standards for municipal waste streams and composts produced

    from them; monitoring of quality of soils, irrigation water from rivers and wastewater

    outlets, and of composts; certification of safe production areas; restriction of crop choice

    in areas where wastewater is used but water quality cannot be guaranteed. - Establishment of adequate wastewater treatment facilities with appropriate water

    treatment technologies (e.g. waste stabilisation pond systems rather than sludge

    treatment plants - the former are cheaper to establish and maintain and retain more


    - Farmer education on management of health risks (for workers and consumers)

    associated with re-use of waste in agriculture, including:

    a. avoidance of direct exposure to wastewater and soils treated with wastewater, e.g. by

    using boots and protective clothing, and regular washing of hands and feet;

    b. adaptation of crop choice in wastewater-treated land: e.g. it is not appropriate to grow

    fresh salad crops like tomato, lettuce, parsley, cucumber and mint in poorly-treated

    water; these could be replaced by fodder, fibre, wood and seed crops; and

    c. application of drip irrigation or other localised irrigation methods (rather than sprinkler,

    gravity or spraying). Irrigation with wastewater must be stopped three weeks prior to


    - Consumer education (scraping and washing of fresh salads; eating only well-cooked

    crops, meat and fish from wastewater-fed crops, animals and ponds).

    - Fish farmer education regarding precautions in the management of wastewater-fed fish


    The workshop participants are invited to discuss the cost-effectiveness and applicability of these suggestions and to propose other measures.

    II b. Diseases transmitted by disease vectors attracted by agricultural activity

    Malaria occurs in many environments but particularly in areas where irrigation is practised. Adaptation of malaria mosquitoes to urban environments has been observed worldwide. However, most malaria is found on the periphery of the cities where mosquitoes breed in ricefields, riverbanks and garden wells. The malarial mosquito breeds mainly in relatively clean water.



Filariasis is transmitted by the mosquito, Culex quienquefasciatus, which breeds in standing

    water which is highly polluted with organic matter. This is typical of dense human settlements (e.g. pit latrines, blocked sewage drains, cesspits and septic tanks, soak pits and poorly designed sewage-treatment plants. Filariasis is spreading rapidly due to urbanisation.

    The Aedes mosquito, which is the main vector of dengue, breeds in water containers that include much solid waste (e.g. tin cans, coconut husks, rubber tyres, water storage jars).

    Chagas disease has recently been emerging in periurban areas mainly in Latin America.

    Poor disposal of organic solid waste (animal manure, crop residues and other farm refuse) may also attract rodents and flies that may be carriers of diseases (e.g. plague), and scavenging by domestic animals (e.g. cats, pigs and rats) is associated with a range of food-borne diseases such as amoebic and bacillary dysentery

Suggested prevention and control measures (please comment):

    - Co-operation between the health sector and the natural resource management sector

    (solid waste management, water storage, sewerage, agriculture and irrigation) is

    essential to reduce vector-borne diseases. Filariasis control is not sustainable until

    related urban problems, like solid-waste management, are solved in an integrated way

    (drains are often blocked by garbage due to ineffective collection systems). Solid waste

    management is also essential for the control of dengue and dysentery (as well as rodent

    control programmes).

    - Water tanks and irrigation systems (especially in periurban areas) need to be properly

    designed to prevent malaria.

    - Application of slow-release floating formulations to control the malarial vector;

    mosquitoes breeding in latrines and stagnant polluted waters can be controlled

    effectively by the use of expanded polystyrene balls.

II c. Residues of agrochemicals

    Urban agriculture provides various potential exposure pathways to agrochemicals including occupational and environmental exposure and consumption. The intensive use of agrochemicals (fertilisers, pesticides, fungicides) may lead to residues of agrochemicals in crops or groundwater, and negative effects on the health of agricultural workers. Because of differences in usage, the level of risk of crop or groundwater pollution due to agrochemicals is higher in intensive commercial horticulture, especially for vegetables, than in traditional and subsistence farming (WHO Commission on Health and Environment 1992).

    Acute poisoning due to agrochemicals can cause a range of symptoms which are often not correctly diagnosed (e.g. dizziness, diarrhoea, headache, memory impairment, convulsions, coma, liver and kidney impairment and lung fibrosis). Agrochemicals are also a major source of suicide worldwide.

    Chronic illnesses have been associated to residues in foodstuffs due to concentration of agrochemicals in the food chain, including vegetables, red meat, poultry and eggs, and residues can be found in human milk (FAO and WHO 1988).

Suggested prevention and control measures include:

    - farmer education on the proper management of agrochemicals;

    - promotion of ecological farming practices and replacement of chemical pest and disease

    control by IPM (integrated pest and disease management);



- better control of sales of banned pesticides;

    - introduction of cheap protective clothing and equipment; and

    - monitoring of residues of agrochemicals in groundwater.

    Please share with us your experiences with the proposed measures and available alternatives.

II d. Uptake of heavy metals from contaminated soils, water and air

    The main causes of soil pollution from heavy metals (including lead, cadmium, chromium, zinc, copper, nickel, mercury, manganese, selenium, mercury and arsenic) are irrigation with water from streams and wastewater contaminated by industry, the application of contaminated solid wastes and the use of former industrial land contaminated by spilled oil and industrial wastes.

    Important sources of heavy metals are smelters, refineries, manufacturing plants, vehicles, metalliferous mines, ceramic industry (lead and cadmium), leather tanneries (chromium salts), lignite-based power plants, aluminium industry, electronics industry, and metallurgical industry. Some heavy metals precipitate in sewage sludge, which can therefore contain rather high concentrations.

    The heavy metals may accumulate in the edible parts of crops that are consumed by people or fed to animals. Plant uptake of heavy metals varies, which opens the possibility to adapt the choice of crops in relation to the degree and type of contamination. Generally, the highest amounts of heavy metals accumulate in the leaves, whereas the lowest contents are located in seeds. Beans, peas, melons, tomatoes and peppers show very low uptake figures. Plant uptake of heavy metals (especially of cadmium and lead) also varies with soil pH (Iretskaya and Chien, 1999).

    Though heavy metal content in soils of most cities in developing countries are so high as to be able to cause acutely toxic symptoms, their increased concentration in the human food chain over a long period can provoke detectable damage to health (carcinogenic and mutagenic effects).

    Puschenreiter et al. (1999) conclude that, after considering the several available pathways to reduce the transfer of heavy metals to the human food chain, urban soils with slight heavy metal contamination can be used safely for gardening and agriculture if proper precautions are followed. However, Birley and Lock (2000) argue that little is known of the chronic health effects of consuming tiny amounts of heavy metals over long periods of time, and that further research is needed.

Suggested prevention and control measures encountered in the literature, include the

    following (please qualify and/or add alternative measures):

    - definition of norms regarding crop restrictions according to type and level of

    contamination of agricultural soils; testing of agricultural soils and irrigation water for

    heavy metals;

    - a minimum distance is recommended between fields and main roads and/or boundary

    crops to be planted beside roads to reduce contamination of crops by lead and


    - soil treatment for immobilisation of heavy metals: application of lime increases pH and

    thus decreases the availability of metals, except for selenium; application of farmyard

    manure reduces the heavy metal content of nickel, zinc and copper (but may increase



    cadmium levels); iron oxides (like red mud) and zeolites are also known to absorb heavy

    metals like cadmium and arsenic;

    - washing and processing of contaminated crops may effectively reduce heavy metal

    content: good results were obtained for lead (less so for cadmium) in green beans,

    spinach, potatoes, whereas peas virtually showed no change;

    - use of plants like Indian grass (Brassica juncea, L) can be used for biological

    remediation of polluted soils or streams (when planted in hydroponic beds); and - more research on chronic health impacts of heavy metals

II e. Zoonosis

    Zoonotic diseases are infectious diseases transmitted through direct contact of human beings with animals during production processes or ingestion of contaminated animal products.

    Two major bacterial diseases carried by cattle are bovine tuberculosis and brucellosis. Bovine tuberculosis is transmitted via the ingestion of contaminated unpasteurised milk from infected cows, and causes symptoms similar to respiratory tuberculosis. Bovine tuberculosis is transmitted via the ingestion of contaminated unpasteurised dairy products or through direct contact with infected animal material (blood, urine) and forms a main occupational hazard of livestock farmers and slaughterhouse workers. It can also spread by air-borne transmission and inhalation (e.g. in the neighbourhood surrounding a slaughterhouse).

Taeniasis and cysticercosis (beef and pig tapeworm) are transmitted by consumption of

    meat infected with tapeworm eggs congested by animals that scavenge on human faeces, or of crops irrigated with improperly treated sewage. Pig tapeworms create more severe effects in humans than beef tapeworm. Trichinosis is transmitted by consumption of infected meat of pigs that scavenge on food waste and dead animals.

    Anthrax is most common in people who work with livestock or work in animal product industries (e.g. tannery). It can be transmitted through a cut in the skin, by inhalation of bacterial spores or consumption of infected meat.

Leptospirosis (Weil‟s disease) is transmitted through the contact of humans with infected

    animal urine or contaminated feedstuff or by swimming in or drinking from water supplies contaminated with animal urine.

    Salmonella and campylobacter can be transmitted through contamination of animal feed. Animals (especially poultry) shed pathogens in their faeces in slaughterhouses, which may infect the meat. The wastewater discharge from intensive poultry farms can carry heavy loads of these micro-organisms and may contaminate drinking water supplies.

Suggested preventive and control measures include:

    - collection of better prevalence data for the most important zoonosis; - consumer education regarding thermal treatment of all milk and dairy products and

    proper cooking or freezing of meat products;

    - restriction of uncontrolled movement of livestock in urban areas (e.g. stall feeding)

    and/or improvement of the urban waste-collection system;

    - strict slaughterhouse regulations; having pig carcasses infected with tapeworms (which

    is sometimes a very high percentage) condemned;

    - simple laboratory antigen-testing for anthrax infection of suspect animal products (like

    carcasses and hides); disinfection of wool and fur;

    - control of import of dogs and sheep in areas where Trichinosis is rare;



    - prevention of genetic reassortment between avian viruses in pigs and human viruses

    (e.g. human influenza A) by not linking pigs and poultry in combination with fish pond

    operations; and

    - composting of manure before application.


    I. Discussion Questions

    As was explained in the conference announcement, we will have three rounds of discussion. For each of these, we have formulated some leading questions. Participants should also feel free to put forward other questions that they feel should be discussed. Next to your contributions to each round's discussions, we also welcome case studies, „best

    practices‟, thematic papers and videos, which will be published on the information market (in the Urban Health section)

First session: Fact finding and situation analysis

    ; Which are the health risks associated with UPA that in your experience - cause major

    negative impacts on the urban population? Provide examples and references. What are

    the characteristics of the most affected population (gender, age, main occupation, socio-

    economic status, etc.)?

    ; Please summarise the local situation under which these health risks were encountered

    and the environmental conditions that in your opinion played an important role in

    creating these health risks.

    ; What positive impacts of UPA on health and environment did you observe? In your

    opinion, do the positive health impacts outweigh the negative impacts? How could we

    measure or evaluate this?

    ; What is the major contribution to the health risks currently associated with UPA? In your

    opinion- are the observed health risks primarily associated with urban poverty, with

    urban environmental management problems or with agriculture as such? Why so?

Second session: assessment of alternative policy measures

    ; Which policy measures were implemented in your city to prevent and/or diminish the

    health risks of UPA? (Whenever possible, specify such measures for each health risk


    ; What are the results obtained with each of these policy measures? Please specify any

    monitoring or evaluation of the policy.

    ; What factors are critical in obtaining good results with this policy? Please indicate key

    data regarding costs/benefits of the policy measures implemented, if available. ; What other policy measures in your opinion should be considered? For what reason?

    What costs/benefits would you expect?

Third session: from planning to action

    ; Based on your experience, what social and institutional actors should be involved in

    research, planning, implementation and evaluation regarding UPA, health and

    environment? What institutional arrangements would you recommend?

    ; What would be the recommended approach to follow in the planning of policies and

    action programmes regarding UPA, health and environment? Which are the basic

    principles to apply? What steps should be followed in the planning process, and what

    main activities be included in each step? Which methodologies and instruments are


    ; Please suggest concrete proposals regarding local action projects and make calls for

    co-operation and exchange (the latter will be published in the information market).



I. Selected References

    Armar-Klemesu M, Akpedonu P, Egbi G & Maxwell D. 1998. Food Contamination in urban

    Agriculture: Vegetable production using waste water. In: Armar-Klemesu M. and Maxwell

    D. (eds), Urban Agriculture in the Greater Accra metropolitan Area, Report to IDRC,

    (NMIMR, Legon).

    Birley MH and Lock K. 1999. Health and peri-urban natural resource production.

    Environment and Urbanisation, 10(1): 89-106.

    FAO & WHO. 1998. Guidelines for predicting the dietary intake of pesticide residues. Bulletin

     of the World Health Organisation, 66: 429-434.

    Flynn Kathleen. 1999. An overview of public health and urban agriculture: water, soil and

    crop contamination & emerging zoonosis. IDRC - Cities Feeding People Report 30.

    Furedy Christine. 1996. Solid Waste Reuse and Urban Agriculture dilemmas in developing

     countries; the bad news and the good news. Joint international Congress of the

     Association of Collegiate Schools of Planning and Association of European Schools of

     Planning, Ryerson Polytechnic University, Toronto.

    Iretskaya SN & Chien SH. 1998. Comparison of cadmium uptake by five different food

     grain crops grown on three soils of varying pH. Comm. Soil Sci. Plant Anal. 30: 441


    Puschenreiter Markus, Hartl Wilfried & Horak Othmar. 1999. Urban agriculture on heavy metal contaminated soils in Eastern Europe. Vienna: Ludwig Boltzmann Institute for Organic Agriculture and Applied Ecology.

    WHO Commission on Health and Environment. 1992. Report of the panel on food and agriculture. Geneva: WHO.


Report this document

For any questions or suggestions please email