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Association of Collegiate Schools of Planning and Association ofEuropean Schools of Planning, Joint Internatinal Congress,Ryerson Polytechnic University, Toronto, July 26-28 1996

SOLID WASTE REUSE AND URBAN AGRICULTURE—DILEMMAS IN DEVELOPINGCOUNTRIES: THE BAD NEWS AND THE GOOD NEWS

CHRISTINE FUREDY, URBAN STUDIES PROGRAM, FAC. OF ARTS,and TASNEEM CHOWDHURY, DIVISION OF SOCIAL SCIENCE,

YORK UNIVERSITY, NORTH YORK, ONTARIO *[EMAIL: FUREDYQYORKU.CA]

INTRODUCTION

Today, two strongly promoted urban management strategies for thedeveloping countries are urban agriculture and reduction/reuse of solidwaste. These strategies, promoted both to conserve and increaseresources and assist low-income groups, include some interdependent andcomplementary activities. Urban waste reduction and reuse involves,among other•things, composting of urban organic wastes (especially incities of developing countries where the organic fraction of municipalsolid waste (MSW) is high) and the feeding of kitchen and food wastesto domestic animals and livestock. Discussions of urban agriculture(UA) frequently point out that city farming often absorbs urban solidwaste, thus reducing the volume of waste and the need to collect andtransport wastes to distant dumps. In practice, urban farmers in manycities acquire municipal wastes as resources. (Cf. UNDP 1996, p. 141;Lewcock 1994).

The combination of urban organic wastes (UOW) and urban agriculture(UA) creates particular issues in the modern urban setting. On the onehand, the interests of urban waste reduction mesh well with thepromotion of UA, since urban and peri-urban farmers are in need oforganic matter as soil conditioner/fertilizer and animal feed, andcities and towns wish to conserve disposal space and reduce the costsof municipal solid waste management (MSWM). At the same time, sometensions occur between public health officials (with their concernsabout diseases affecting both humans and animals and accidentsassociated with the reuse of municipal solid wastes) on the one hand,and the proponents of urban agriculture (who emphasize job creation andincreased food production, especially for the urban poor) on the other.The fundamental issue was pointed out by the Ad Hoc Panel of theAdvisory Committee on Technology Innovation for the Board on Scienceand Technology for International Development of the National Researchcouncil (USA) in 1981:

I am grateful to Peter Kolsky for suggestions and RaymondAsomani-Boateng for comments. Glen Richardarp, environmentalconsultant, gave some help with the tables. C F"

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The strongest negative factor in the use of human and animalwastes for the production of food, feed or fertilizer is thepossibility of disease transmission, which would negate thegains derived from the use of the waste. (p. 134)

Health risks are typically low priority in settlements where peoplelack basic needs. For instance, we tolerate squatters buildingshelters with flammable materials. But in the long run, if standardsof living are to rise, the risks have to be faced and ameliorated inwhatever ways are feasible. The boost being given to UA in thedeveloping countries suggests that the time has come to detail the mainhealth risks and promote discussion of how they can be countered.While the risks associated with the use of human excreta andwastewaters have been researched for many years (see Shuval et al.1987, NRC 1981) there has been no parallel or integrated discussion ofthe similar (although less extensive) risks of solid waste reuse.

In this paper, I introduce the basic issues of public health arisingfrom solid waste reuse in urban agriculture. I am not writing as aplanner, so much as suggesting preliminary ways that developmentadvisors and urban planners can understand these concerns and developframeworks and criteria for reducing the public health risks of usingof urban solid wastes in urban agriculture.

The scope of this discussion is confined to municipal solid wastes(household-commercial-institutional). It does not include separatelymanaged special wastes or segregated human excreta and wastewater, e.g,septage and sewage sludges, and sludge cakes.

MAIN PRACTICES OF URBAN ORGANIC WASTE REUSE IN DEVELOPING COUNTRIES

The state of Karnataka in India has a simple proverb: "waste is food."1

In traditional settlements in many parts of the world, the age-oldhabit of returning household wastes to the food chain persists.Kitchen peelings and food leftovers are fed to animals, selectedorganics are fed into fish ponds, and wastes are composted for homegardens. Where there is intensive farming in peri-urban areas, areasthat typcially receive MSW, the farmers frequently exploit the productsof MSW decomposition in various ways. In addition to old practices,others, such as community vermicomposting (composting through wormculture), are growing in the urban areas of some regions like SouthAsia and Andean countries.

The following table lists the main types of solid waste reuse in urbanagriculture with comments on the practices.

TABLE IMAIN PRACTICES OF URBAN ORGANIC WASTE REUSE IN DEVELOPING COUNTRIES

Types ofsolidwaste, (orsite)

Kitchen,restaurantand canteenfood wastes

Regularmixedmunicipal

Kitchen andyard wastes

Materialsincluded

Raw peelingsand stems,rotten,freshfruits andvegetablesand leftovercooked foods

Full range oflocaldomestic,instit'nl,commercialsolid wastes,with smallindustrialwastes,biomédicalwastes,humanand animalexcreta

Kitchenwastes withsome gardentrimmings,grasscuttings

Practices

Food wastemay be fed toanimalswithin thehouse orcompound, ordeposited onnearby dumpsfor animalsto forage.Also sold forcommercialuse (by localfarmers ; orauctioned tolarge poultryor pig farms)

In South-eastand SouthAsia farmersbuy MSW offgarbagetrucks andapply it tosoil,immediatelyor after 5-14days.

Backyardcompostingfor homegardening,domestie animals(poultry,pigsgoats, cows)

Comments

Directfeeding ofhouseholdlivestock isprobably ratherlow-risk.

In China, farmersare told tocompost thewastes beforeapplying to thesoil, but thismay not be donelong enough tokill pathogensand parasites

Kitchen wastescomposted overlong periods mayconcentratepesticideresidues inplants grown inhome gardens

Kitchen,yard wastesfromcommunityhouseholdsand shops

Mixedmunicipalwastedeliveredtocentralizedcompostingplants

Organicwaste, butmay containotherhouseholdwaste aswasteseparation isoften notdonethoroughly

Mixedmunicipalwaste whichmay containproblematiclevels ofplastic film,smallindustries'wastes,broken glass,batteries andfluorescentlightstarters,biomédicalwastes, humanexcreta.

Cooperatinghousehold andinstitutionsare asked toseparateorganicwastes forcommunitycompost heaps

Compost iscollectedfromcentralized(municipal)plants byfarmers,sold, or usedin municipalparks, golfcourses,etc.

Compost heaps arelocated on vacantland, parks,often wherechildren play.Few projects haveinfrastructure toreduce hazardssuch as leachate.Rodents areattracted tocompost piles,for food, warmnesting places inwinter. Othervectors areflies,cockroaches,birds, etc.

Most centralizedcomposting plantshave eitherfailed or areoperating at lowcapacities.Products are hardto sell due toglass splintersand plastics.Where thoroughtesting has beendone of compostfrom mixed wastesin large cities,plants have oftenbeen closed owndue to heavymetal contamin'n.Pesticide levelsof organics inmarket wasteshave not beenresearched to anyextent.

Kitchen andyard wastesdeliveredtovermicompos-ting (VC)projects

Old garbagedumps

Samematerials asfor smallscalecommunitycomposting

Most is welldecomposedwaste, oftenseveral yearsold. In areasof highrecycling,extensivewasterecovery,there may berelativelylittlesyntheticmaterials inthe naturalcompost.

Compost issold ordistributedfrom smallvermicultureprojects,often locatedin parks.

The originaluse of"garbagefarming"referred tothe practiceof convertingold garbagedumps to farmplots.Garbagefarmingrepresentsthe mostextensive useof MSW forfoodproduction inthe worldtoday.

VC is growing inpopularity,especially inIndia and Andeancountries. Littleknown of healthrisks—pathogens,para.eggs, viruses maynot be destroyedunder the coolconditions of VC.VC bins and pitshave to beprotected byscreens as ratseat worms.

Provided the dumpdid not receivemuch industrialwaste, farming onold dumps may below risk in termsof infection.Injuries fromsharps arecommon.Respiratoryproblems fromdust. Sometimesfarmerscultivating olddump areas may"invade" thecurrent dump toplant seedlingsfortransportation orthey mayillegallyencroach at theedges of currentdumps.

Removalfromgarbagedumps

Cowdung

Welldecomposedmixedmunicipalwastes

Cowdung

Nearbyfarmerscollectcompost fromold dumps orclosedsections ofcurrentdumps.

Cowdung iscollectedfrom pasturesor roads,made intoround pattiesor dried onsticks to beused forfuel. Cowdungis also usedas fertilizerand as abindingingredient inplaster madeof mud.

A large garbagehill opposite thecity producemarket in YAngonis beinggraduallyeliminated by themining ofcompost, which isnow beingencouraged by thecity authoritiesin order toachieve freelevelling of thesite. Dustinhalation is apotential healthhazard forcompost miners.

The women andchildren whogather wet dungfor drying do nothave access toany washingfacilties whiledoing thisitinerant work.

Park andvergetrimmings,sweptleaves

Agriculturalwastes

Fruit seedsfromgarbagedumps

Twigs, grass,leaves,branches,etc.

Predominantlyagriculturalresiduesproduced byfarming, butmunicipalwastes may beused to asmall extent.

fruit seeds

When gatheredby poorpeople, thesewastes areused asanimal fodderor fuel.

Integratedorganic wasterecycling andacguacultureis mainlypractised inSouth Chinain peri-urbansericulture-fish-vegetable-poultry-pigfarms.

Seeds arecollected forhorticultureand directsale.

•

In some cases,these wastes aretaken by themunicipalauthoritydirectly to acompostplant.Completeand efficientdiversiondeprives poorresidents of fueland fodder.Municipaltrimmings may becontaminated withpesticides andvehicle pollutionresidues.

Usuallycontaminated withpesticides andherbicides. Theeffects ofconcentration incompost are notknown.

This was promotedas an urbanagricultureactivity in theJati Dua projectin Bandung in the1980s, wheremango seeds werethe major kindretrieved. Thisis a varient ofwaste picking,with all theattendant risksof that activity.

This somewhat sketchy summary of waste reuse practices indicates manypotential health issues, more diverse than the usual issues raised indiscussions of urban agriculture.

PUBLIC HEALTH CONCERNS IN RELATION TO URBAN AGRICULTURE

In the development of human settlements, a primary motivation forregulating or even forbidding practices of food production has beenconcerns about human health, from infections to accidents. Some of theearliest known regulations in human settlements pertain to animalraising and consumption (cf. Jewish and Muslim prohibitions onconsumption of pork; kosher and halal regulations).

But, on many occassions, what really constitutes a public health riskhas been defined flexibly by local authorities. For instance, whenBritain was under seige during the Second World War, regulationsagainst raising animals in urban areas were relaxed to encourage localfood production (Hough 1981). Europeans have been prepared, inemergencies, to adopt practices that they would condemn at other times.From about 1943, Germans were encouraged to use their excreta inbackyard gardens; despite a long history of concern with hygiene andpublic cleanliness in Germany, the Nazi government was too preoccupiedat the time to monitor these practices.

It is worth remembering this historical flexibility when judging thepractices of poor citizens in cities of developing countries today.

It is also worth remembering how sketchy our understanding is ofspecific causal factors in the health status of particular low-incomepopulations living in unsatisfactory conditions [cf. the currrent workof the Stockholm Environment Institute, comparing intra-urbandifferentials in health , environmental conditions and socio-economicstatus in Accra, Jakarta and Sao Paulo.( McGranahan and Songsore 1994,Songsore and McGranahan 1995)].

The focus of attention in healthrisks are humans. Urban agriculture,however, includes animal rearing, so that an additional concern is theways in which animals' health may be affected by problematic practiceswhich can result in infections from humans, injuries from sharps ingarbage, and so on.

BOX 1

HUMAN GROUPS AND ANIMALS AT RISK FROM REUSE OF MSWORGANXCS UNDER CONDITIONS OF POOR MANAGEMENT

Waste workers: (i) waste collectors and dump operators;(ii) compost miners;(iii) waste pickers of wood, cinders,coconut husks, seeds

Infants and children: accompanying waste workers(e.g. pickers); playing in wasteland; guarding animals,plants

Farmers : (i) farming on old dump sites;(ii) applying MSWorganics;(iii) applying low quality compost from MSW

Residents: people living close to large compostingplants/sites, esp. infants and the aged in such settlements

Consumers : (i) of food produced from soil using low qualitycompost; (ii) of meat livestock fed unsterilized wastefood, or foraging from solid waste containers, grazing ongarbage dumps; (iii) of water contaminated by untreatedleachates from compost plants and piles

Food handlers: sellers of produce, cooks

Livestock: fed unsterilized and/or contaminated waste food, orforaging from solid waste containers, grazing on garbage dumps

The following box lists the main factors that should be taken intoaccount in attempts at risk assessment in municipal solid wastemanagement.

BOX 2

FACTORS IN TRANSMISSION OF INFECTIONS, INJURIES FROM SOLID WASTEREUSE

Waste materialscomposition and origin of organic waste materials; esp.whether source-separated or mixed; whether human excretaare presentexposure of wastes to vectors; prevalence of disease amongvectors (e.g. yersjnia pestis in fleas on rats)

Biological factorssurvival time of prevalent pathogens (relevant topathogens)

Cultivation techniquesmethods of application of waste/compost; composting timeand methodstype of crops grown on soils receiving wastes; mono ormulticroppingperiods of crop growth

Animal characteristics and exposuretypes of animals fed organic wastes; their propensity toharbour parasites, etc.use of animals in plowing, transportationprevalent wild and stray animals (e.g. rabid dogs atdumps)

Human characteristics, exposure, hygienic habitstype of exposure: primary handlers of waste; composters;field or pond workers; crop handlers; consumersimmunity levels and hygiene practices of handlers,consumershealth of animal keeperscooking, food preparation, habits of consumers

Site characteristics and physical infrastructuresiting of acquifers, wells vulnerable to MSW leachatesavailability of sanitation for workers

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TABLE II: WASTE-LINKED DISEASES AND CONDITIONS RELEVANT TO URBAN AGRICULTURE

Waste-Linked Disease

Injuries, ChronicDisease

-snake, scorpionbites

-cuts from sharpwastes leading toinfection

-burns from firesin waste piles

-chemical burns orwounds

•toxication andcancers fromexposure tohazardous waste andgases

-chronic respiratoryand ópthalamicdiseases fromexposure to dustand gases

-trauma or deathfrom collapse ofhuge waste piles

Most at Risk (referto Box 1)

-waste workers,esp.pickers

-waste generators-waste workers, esp.pickers, farmers

-waste workers

-waste workers

-waste workers-residents

-waste generators-waste workers-residents

-waste workers

Contexts

-open dumps, garbage farms

-primary collect'n points (poor storage)-open dumps; compost plants; farms usingMSW

-open dumps; illegal dumps

-unprotected handling of mixed MSW

-open dumps; contaminated aquifers & wells

-open dumps; poorly managed compost plants

-open dumps; compost mining sites

Bacterial, Viral orParasitic Disease

-bacterial (tetanus.staphylococcus,streptococcus) orviral(AIDS,hepatitis B)bloodinfections frominjuries caused bysharp wastes

-eye (trachoma,conjunctivitis) andskin (mycosis,anthrax) infectionsfrom wastegenerated dust

-respiratoryinfections(bacterial or viralpneumonia) fromwaste generatedinfected dust

-viral (dengue,yellow fever) orparasitic(malaria,filariasis,schistosomiasis)diseasestransmitted byvectors living orbreeding in waste

-waste workers-farmers

-waste workers-residents

-waste workers-residents

-waste generators-waste workers-residents-livestock

-waste workers-farmers-livestock

-open dumps, esp. those receivingunregulated biomédical wastes; compostplants processing mixed MSW

-dumps, landfills, compost plants

-dumps, landfills, compost plants

-dumps, esp. in wetlands; settlementswithout drainage infrastructure andgarbage collection (squatter

settlements)

-bacterial, viral orparasitic entericdiseasestransmitted by:

1)insects androdents feeding onwastes

2)accidentalingestion of wastefood

3)drinking watercontaminated byleachate

4)food contaminatedby leachate

-zoonosis carried bystray animals androdents feeding onwaste (rabies,plague, tick-borne fevers}

-waste generators-waste workers-farmers-livestock

-waste workers, esp.pickers-farmers-livestock, esp.foragers

-waste workers-farmers-residents-livestock-consumers-food preparers

-waste workers-consumers

-waste workers, esp.pickers-farmers-residents-livestock

-leachate ponds at garbage dumps; dumps;informal dumps; open storage containers;waste piles

-dumps; open storage containers; wastepiles

-squatter settlements, etc

-poor hygienic conditions for sale andpreparation of food

-dumps; squatter settlements, settlementsadjacent to compost plants

Developed from "Summary of waste-linked diseases and conditions with their causes or

pathway of transmission" in Girault, Christen and Brown {1996, in press).

The conclusion reached by a survey of the health effects of the use ofwastewaters in agriculture sponsored by the World Bank in 1980s maywell be largely applicable to the use of municipal solid wastes in UA,as currently practiced in some countries (notably China and India):

Wastewaters cary the spectrum of fecally excreted humanpathogens endemic in the community, including helminths,protozoans, bacteria, and viruses. Their concentrations andtheir persistence, even in generally unfavourableenvironments... are great enough to create the potential forhuman infections. (Shuval et al., 1986).

In other words, where mixed municipal wastes are applied directly tosoils, where composting is done inefficiently, where source separationof organics for composting is not thorough, and organic wastes arecontaminated by biomédical or toxic substances, we can expect that thetypical pathogens will survive and may infect composters, farm workers,animals, and ultimately consumers. The additional hazards of urbanorganic wastes are injuries from sharps, respiratory and opthalmicproblems from dust and further problems of accidents, fainting and evendeath from landfill gases and cave-ins.

POOR LIVING ENVIRONMENTS: THE GOOD NEWS?

Many factors govern the potential for infections to seriously affectlarge numbers of people. As suggested in Box 2, the actual risks forany category of people undertaking activities such as those included inUA will depend largely upon their general health status, whatimmunities they have acquired, hygiene habits and their general livingconditions. It is ironic that the poorer the environmental conditionsand the economic status of a community, the less the residents may besusceptible to some of the risks from waste reuse. This has beenestablished in studies of wastewater reuse. Shuval et al (pp. 298-299), note:

Some endemic pathogens, such as enteroviruses, are so infectiousand so common in the household environment of the developingcountries that most infants acquire lifelong immunity at anearly age, with the result that additional extrenalenvironmental exposures do not lead to quantifiable excessdisease, even under the most insanitary conditions. In manyof these countries, multiple routes of concurrent infectionby enteric pathogens from contaminated water and food andpoor personal and domestic hygiene may be at such intenselevels that additional exposure resulting from uncontrolledwastewater irrigation will be an insignificant cause ofexcess disease. However, when such routes become restrictedor are blocked, exposure the the same level of pathogens ...may then lead to detectable levels of disease. This may beparticularly true for countries at the higher socio-economiclevels.

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This may be regarded as the "good news" for the health aspects of UA.Most of the current practitioners in the LDCs are of low economicstatus; they frequently live in inadequate housing and in precariouslocales. Hence, they are exposed to multiple sources of infection and,those that live to adulthood are less susceptible to infections(although not less susceptible to injuries) associated with reusingorganic wastes for food production. This is not to deny that "an* overdose7 of toxins will poison even the most accommodating biologicalsystem." (Dalhammer and Mehlmann, p. 46)

This protection through immunity, however, gives little comfort tomiddle and upper class consumers of the products. And, as foodproduction improves (directly or indirectly) the standard of living ofpoorer urbanités, it becomes more important to control risky practicesin order to maintain the advances in public health.

COMMUNITY COMPOSTING AND GARBAGE FARMING EXAMPLES OF CONCERNSRE: CURRENT PRACTICES

ïn order to illustrate some of the problems that may arise withparticular practices of waste reuse, I comment here on small-scalecomposting and practices that have been dubbed "garbage farming."(I am leaving aside composting at centralized plants as this has beensubject to more analysis than other forms of composting with organicsfrom multiple sources.)

Community and small—scale composting

The safety of compost generated from multiple sources, and other risksassociated with composting, mainly depends upon the following factors:

a) the thoroughness of separation of organics at the household andinstitutional level;

b) the care taken in the composting process;c) the general health of the waste generators;d) levels of immunity acquired by consumers of foods grown on the

compost;e) accumulation of pesticides in organic residues (little is known

about the associated risks).

Comments on some of these aspects are contained in Table I. Somefurther comments are:

Source separation: Thorough source separation of organics forcomposting and vennicomposting is done in many developed countriestoday. To achieve the same levels of purity in cities of developingcountries, considerable education and monitoring is necessary.Householders in cities of CLDCs are highly motivated to separate outthose materials that can be sold to itinerant buyers, but suchseparation is not sufficient to ensure uncontaminated kitchen wastes.Frequently one finds in the kitchen waste turned over the communitycomposting projects: household biomédical wastes (including sanitary

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napkins), broken glass, syringes and razor blades. Since householderscannot usually sell their organics to community projects, there is noeconomic incentive for thorough separation; the waste generators haveto learn the ecological motives for separating organics more carefullythan they are used to doing.

Sharps in composted organics can injure all handlers and farm animalsalso. Even very fine sieving of compost does not eliminate finefragments of glass and hyperdermic needles. In very poor peri-urbanareas, farm workers are usually barefooted.

Research at the National Environmental Engineering Research Institutein India, on the agricultural use of municipal solid wastes, hashighlighted the acidic pH values of leachate from MSW and itspropensity to dissolve metals (Olaniya & Bhide 1995).

A growing concern is the accumulation of plastics in agricultural land.Even the farmers have noted the deterioration of soils, in Shanghai,Dar es Salaam, Eritrea, and Vietnam. (Furedy, field notes 1988;Midmore 1994, p. 71).

Health of waste generators: This factor has never been examined, but itseems obvious that if the community from which the wastes are taken hashigh levels of disease, the chances that the wastes taken forcomposting will contain pathogens is high, especially if feces arepresent. Regardless of the standard for the composting process, thehandlers of these organics are exposed to some risk of infection.

Levels of immunity and tolerance: As suggested above, the specificlevel of risk with regard to viruses, protozoans, bacteria andhelminths may be much lower for low-income groups than for populationsthat have been more "protected." It is worth noting that in someregions, community composting and vermicomposting are being carried outin middle-class neighbourhoods, with manual workers from poor groups(e.g. street dwellers). Hence the workers may well be less vulnerableto disease — although still vulnerable to injuries — than theconsumers of food produced from the compost.

Pesticide accumulation in source-separated organic wastes: Sincebackyard and community composting in developing countries use a highproportion of fruit and vegetable peelings, with few tree and shrubclippings, the proportion of pesticide residues in the compost may behigh compared to compost produced from more diverse organics. There isno research comparing the pesticide residues in compost from mostlyfruit and vegetable peelings as against that from the more diverseorganics.

Although composting of solid wastes is technically easy, yet, as thescenarios above suggest, there are many ways in which the safety of theend product may be compromised. The most successful small scalecomposting projects have been those done within institutions such asschools, religious institutions and work complexes such as are found in

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Chinese cities. These may also produce the safest compost, since thecomposting process is well- supervised. These are not, however,strictly speaking, "community" composting projects in that the wastesdo not come from multiple sources.

Garbage farming

The most risky use of MSW in food production are the direct applicationof mixed municipal wastes to soil,or inadequate composting of thewastes. Such direct application is routinely practised in some peri-urban areas in China and India, although it may be against cityregulations. Truncated composting is a habit in many areas, althoughdocumentation of this is rare.

The writing about garbage farming in the former wetland areas east ofCalcutta in the last few years has brought to light some information onfarming practices with municipal solid wastes.

A member of the Institute for Wetland Management in Calcutta, Dr. NitaiKundu, noted, in 1994, that the general practice of farmers whopurchased or received wastes directly off the city garbage trucks wasto leave the wastes for two weeks before digging the material into thesoil.

In describing the "garbage farming procedure" of this area, Giri(1995), presenting a paper at the workshop on "Urban Agriculture andsustainable Development" in Calcutta, wrote:

The cultivators ask the (Calcutta Municipal) Corporation truckdrivers to unload refuse at the cultivation sites against somesmall payments. Garbage is left there for five to seven days forfermenting. Subsequently the decomposed wastes are mixed with thesoil and land is prepared for the sowing of seeds or the plantingof saplings... Primarily, market garbage is used for cultivationpurposes.

Five to seven days is not sufficient for complete decomposition andstabilization, nor, indeed is two weeks, since no designed piling isused, it is quite likely that the temperatures of the waste piles donot reach a height sufficient to destroy helminth eggs. I suspect thatmany farmers dig the wastes directly into the soil. I know fromobservation that all farmers do not leave muncipal garbage piled at theedge of their fields—this would be very obvious to a visitor to thefarms. There are two reasons why they would not wish to leave thewastes even for a week: that they have acquired city garbage off theCorporation's trucks is too obvious, but, more importantly, they are ina hurry for the organic material. No one has advised these farmers ofany risks associated with immediate application and there is nomonitoring service to enforce a rule against it.

Since the paper presenter from the University of.Calcutta (Giri) didnot comment on the truncated decomposition period, it would appear that

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she was not aware of any health risk associated with it.

Chinese sanitation officers in cities that export MSW for use in urbanfringe garbage farms are well aware that many farmers do not compostthe wastes according to the specified standards; they frankly admitthat they do not have the resources to enforce these standards (Furedy,field notes, Guangzhou, June 1998). The general policy of the Chinesegovernment seems to be to encourage the shift to artificial fertilizerswhile seeking foreign assistance in constructing regular landfills toreceive municipal wastes. (There are a few centralized compost plantsbut the total amount of compost produced in them is negligible).Furthermore, monitoring of the health of municipal and farm workersappears to be declining with the retraction of socialism, the end ofcommunes, etc. (Yeung 1993, p. 8).

We do not know whether there are specific patterns of disease andvulnerability that can be attributed to poor practices in small scalecomposting and garbage farming, but truncated and casual composting isnever recommended by proponents of composting (Rosenberg and Furedy1996) . These are the kind of monitoring issues that should be pursuedin cases of garbage farming.

REGULATION RE HEALTH RISKS IN CITIES OF DEVELOPING COUNTRIES

It is very common for health considerations to be adduced as a reasonfor restricting UA. But, while public health officials undoubtedlyrecognize the main problems, the actual regulations designed to controlor reduce these in cities of developing countries (particularly in sub-sanaran Africa and south and south-east Asia) are haphazard. In manycases, regulations from colonial regimes remain on the books.Sometimes, the health risks mentioned in particular are not the mostcommon or serious ones. Regulations are rarely enforced, exceptfollowing health emergencies.

Some of the most stringent regulations relate to the keeping ofanimals, especially cattle and pigs. The concern about pig keeping andthe difficulty of dealing with the resultant highly polluting wastesbecame so high in Singapore that the country banned pig raisingaltogether in the late 1980s. In most cases, however, the approach tourban regulation is not based on a comprehensive framework forunderstanding the health risks. For instance, as regards food producedfrom composted wastes, the focus is almost invariably on the consumersof the products only; there is virtually no attention to the producersand handlers.

Modern developments in pollutants are very rarely mentioned in typicalregulations. Admittedly, it is extremely difficult to estimate anyrisks from new chemicals as very little is known about xenobioticcompounds, their environmental chemistry or the ability of biota tometabolize or degrade them (Dalhamman and Mehlmann, p. 49).Nevertheless, the possibility of the presence of such compounds as aresult of organic waste contamination should be flagged (see Midmore,

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P. 71). .

If the regulations about health risks are often haphazard, theenforcement of regulations is even more so. With virtually no researchon the etiology of disease specifically resulting from UA practices,the result is that health departments have little to guide them inassessing the actual risk of different practices. Vague generalitiesabout public health characterize the rationales for whatever specificregulations or guidelines exist in cities of LDCs, with the exception,perhaps, of regulations pertaining to the use of excreta andwastewaters in some cities. Since most UA is informal, it is naturallydifficult to advise, monitor, and regulate.2

ADVOCATES OF URBAN AGRICULTURE ON HEALTH RISKS

What have the advocates of UA had to say about health risks when theypromote urban organic waste reuse?

Almost all discussions of UA express a genuine concern about the healthaspects related to food production and animal raising; it would besurprising if they did not. What is striking, however, is how littleis actually said on the subject. The most detailed recent discussionis in the recent UNPD book on urban agriculture (1996, pp. 197-204),where the main issues are set out. But this amounts to only a fewpages and scattered references. Most of the discussion,understandably, concerns problems of human excreta reuse and wastewaterirrigation. The reuse of municipal solid wastes, which is stronglyadvocated by the book, is addressed only vaguely from a health riskstandpoint.

There appears to be a lack of systematic thinking about this issue inprojects on UA. Evidence of this comes from the set of paperssponsored by the Internatinal Development Research Centre (IDRC) underthe Cities Feeding People programme. In 1993, key researchers indeveloping countries were asked to prepare overviews on urbanagriculture research in major regions (e.g. East and Central Africa,Latin America, East Asia, etc.) In contracting for these reviews, theEnvironment and Natural Resources Division specifically asked thewriters to refer to health aspects. Almost all the reviewers dutifullydid this, in rather vague terms. They noted the lack of research onthe topic. A major aspect of this assignment was to suggest areaswhere research is needed, opportuntiies for research and even researchtopics. In spite of the emphasis earlier in the papers on the healthaspect, not one of the reviewers suggested a research project on thisaspect, or even mentioned it in the projects proposed. (Consideringthat the IDRC had a good department on health until fairly recently, itis disappointing to see the lack of guidance given by the CitiesFeeding People project in this respect).

I think there are several reasons for this gap in the discussions ofurban agriculture: one is simply that the work that could be applied tothe health risks of UA is published in sources that are not readily

19

accessible to UA scholars and practitioners, especially those indeveloping countries. Another source of blockage may be that UAadvocates are intent upon breaking down the traditional resistance ofurban adminstrators (including health officers) to UA activities; todraw attention to potential risks (albeit usually of a different natureto those that old urban regulations aim to combat) may seeminadvisable. And, since research ideas are being evolved throughnetworks of like-minded people, and the UA groups are not connected tothe epidemiologists and veterinary and agricultural researchers withexpertise on health risks, such discussion as takes place —and thereis little enough of it—bypasses the UA advocates. There are simplesolutions for such blockages, which are noted in the next section.

CONTROL MEASURES: DEVELOPING FRAMEWORKS AND EXPERTISE

The assumption of UA advocates that the marriage of urban agricultureand waste solid reduction/treatment will contribute to better health inthe long run, through improved nutrition and incomes, is reasonable.Nevertheless, the summary information presented here shows that thereare legitimate concerns that must be addressed in the management andfacilitation of agricultural and waste management practices.

My preliminary suggestions are for the promoters of UA to draw upon theinterdisciplinary expertise on human waste reuse in agriculture andacquaculture, to use the frameworks of environmental risk assessment toinvolve UA stakeholders in awareness of risks and ameliorative measuresand, to link UA scholars and practitioners with public health andepidimiological experts for focussed research on key issues.

scholars and practitioners of UA do not need to "reinvent the wheel"in devising measures to reduce health risks. At a general level, theprocedures of environmental risk assessment and health risk assessmentcan be applied to workshops and working groups on urban agriculture. Auseful discussion, with simple but instructive diagrams, that suggestshow discussion and research can be organized to systematically examinepublic health (and ecological) issues, is contained in: Environmenta1Risk Assessment for Sustainable Cities, in the Environmental Technologyseries of UNEP's International Environmental Technology Centre(Kaputska et al., 1996). Such diagrams can be the basis for researchand stakeholder workshops in UA.

Examples of the diagrams used are given here:

20

More specifically, with regard to epidemiological concerns, theconsiderable work on the reuse of human excreta and sewage waters inagriculture can be the starting point for understanding the relatedhealth risks and ameliorative measures when solid wastes are used forgrowing crops and feeding animals.

Ursula Blumenthal and Sandy Cairncross at the London School of Hygieneand Tropical Medicine have devised the following diagram to show themain relationships of contamination, risk and measures for the use ofhuman wastes in agriculture.

Figure l

Generalized model of the effect of different control measures inreducing health risks from waste

FULLTREATMENT

HNO PROTECTIVE

MEASURES

CROPRESTRICTIONA HUMANEXPOSURECONTROL

a

PARTIALTREATMENT* HUMANEXPOSURECONTROL

F

CROPRESTRICTION

A

APPLICATIONMEASURES

PARTIALTREATMENT

* CROPRESTRICTION

E

HUMANEXPOSURECONTROL

C

PARTIALTREATMENT

0

I POND TREATMENT I CONVENTIONAL TREATMENT

KEY TO LEVEL OF CONTAMINATIOWouter bands)/RISK(inner bands)

LOW SAFE BARRIER

\

•v-

c

CO

occupational healthenvironmental healthdomestic livelihoodliveabilitycultural heritage

Environmental Risk Assessment

RESOURCES•Ir. weMr, «oil. Mou

Problem Identification

wildlifenatural vegetationagricultureforestswetland*streams/lakes

1^ ^ Human H M M I ••"

RlillAtMUIMM

1• '•" - • Ecological "

RWc AaaeMflMiu

Hazard Problom Formulation

Exposure - Response

I I

R(«k Characterisation I Rlak Characterisation I. . _ _J

Environ mental Risk Assessment

Problem Identification

tslorcohcern

Hazard Identification

Dose Response

Risk Characterisation to Humanindividuals and Populations

Risk Management

Figure 16. The Human Health Risk Assessment component of Environmental Risk Assessment^

Devising a similar matrix for risks levels and control measuresassociated with the reuse of solid wastes could assist more systematicdiscussion for amelioration of the problems.

If the recommendations of the World Health Organization, sound as theseare, were to be followed, risk reduction seems an overwhelming task:

The only rational way of dealing with the public healthaspects [of MSWM] a comprehensive way is the put the healthaspects into strategic planning context for the overall MSWMsystem....A comprehensive public health impact assessmentshould be made mandatory at the project design stage....Theprocess should be repeated every five years to keep track ofunforseen developments and to establish the information basefor rational decision-making in the future. In the finalanalysis, public education and consciousness raising shouldbe the cornerstone of any mitigation effort. (Girault,Christen and Brown 1996)

It is not likely that such an ideal vision will guide the reuse ofurban solid wastes as an element of solid waste management, even in themost modern cities, in the immediate future.

The good news about control measures is that technically simpleinterventions, at a few points, might achieve considerable riskabatement. For instance, keeping organics pure at the main generationpoints in a city would eliminate risks from sharps, and contaminationfrom chemicals, biomédical substances and synthetic materials. Cropselection could be as effective with organic waste-based agriculture asit has been with wastewater-fed aquaculture and agriculture. Siteselection for composting could add another type of "barrier" topollution. Improved occupational protection and home hygiene are endsto be desired in and for themselves.

The bad news, as ever, is that such changes in personal behaviour andoccupational management are not easy to achieve when urban agricultureis practised informally by groups who are not "reached" by routineschool or community education and are not assisted by regular urbanmanagement. I am not as sanguine as the UNDP that "most potentialproblems can be easiy averted" (UNDP 1996, p. 197).

The development of internet networks provide the opportunity to linkexperts in public health and solid waste management for the developingcountries with those interested in urban agriculture. A model forproductive internet discussion is the recent joint one organized by theGlobal Action Plan International andthe World Health Organization, withSwedish and UNCHS funding (Dalhammar and Mehlmann 1996). It would beuseful if the facility established by the International DevelopmentResearch Centre (SGUA) could take a lead in facilitating collaborationto address the public health aspects of organic waste reuse.

23

BOX 3Some Internet Contacts Relevant to Health Aspects of waste Reuse

. Water and sanitation for developing countries:[water-and-san-applied-research: mailbase-admin@mailbase.ac.uk]

. Hygiene behaviour:Contact mailbase-admin@mailbase.ac.uk or D. L. Saywell@lut.ca.uk

, University of Lougnborough's GARNET (for solid waste management:Contact: D. L. Saywell@lut.ca.uk

. IDRC's Support Group on Urban Agriculture:http://www.idrc.ca/1istproc/sguaf-cl

. PROMEDpromed-ahead@usa.healthnet.org

. UNICEFRegional Water and Sanitation Network for Central America

Contact: tony.brandêunicef.un.hn

. Envirolinkrecycle@envirolink.org

CONCLUSION

Although this paper has focussed on setting out numerous potentialhealth concerns (the "bad news"), one can still say that municipalsolid wastes can be safely used in urban agriculture if adequatecontrol meassures are consistenty practised and workers and consumersadopted basic precautions and hygienic practices.

The "good news" is that there is little evidence at present to suggestthat health risks from the reuse of urban organic wastes (excludinglarge amounts of human excreta) are such as to constitute a matter ofgreat concern at present in UA.3 Most of those who practise UA indeveloping countries are poor people living in unsanitary conditions:hence, those who have survived infanthood have acquired severalimportant immunities. They are constantly exposed to sources ofinfection through impure water. Thus the risks (of infection) added byintegrating improperly treated solid wastes into their animal raisingand crop production may be insignificant and/or undetectable. Therisks of injuries and accidents may be no greater than if the workersengaged in other agricultural work. It remains for research toestablish just how risky are the activities noted in this paper.

Nevertheless, if the health risks are not better understood and controlmeasures are not promoted, disease and accidents will increase as UAspreads and standards of living rise.

24

It is not difficult to initiate discussion on this topic and to examineameliorative measures. Showing a willingness to confront potentialrisks and take action can only help the urban agriculture movement togain acceptance among urban planners. This is, indeed, the generalposition taken by UA advocates in the UNDP volume on urban agriculture(UNDP 1996, p. 197).

1. I am grateful to Prof. Narayana Rao of Madras for this proverb.

2. It is ironic that, while centralized composting carries greaterrisks of a contaminated product, it is easier to monitor municipalplants. It will be very difficult to monitor and advise scatteredcommunity and backyard compost piles, but the inputs into these typesof composting are likely to be relatively pure.

3. It is even difficult to estimate the risks and incidence of diseasefrom the use of sewage waters. In 1986, World Bank judged that therewere few credible epidemiological studies of health effects ofwastewater reuse in agriculture. There have been hundreds of studiesbut few present evidence that can meet standards of modern , .......,.„..,,epidemiological criteria (Shuval et al., p. 299). - . ̂ ^ .

It is not difficult to initiate discussion on this topic and to examineameliorative measures. Showing a willingness to confront potentialrisks and take action can only help the urban agriculture movement togain acceptance among urban planners. This is, indeed, the generalposition taken by UA advocates in the UNDP volume on urban agriculture(UNDP 1996, p. 197).

ENDNOTES

1. I am grateful to Prof. Narayana Rao of Madras for this proverb.

2. It is ironic that, while centralized composting carries greaterrisks of a contaminated product, it is easier to monitor municipalplants. It will be very difficult to monitor and advise scatteredcommunity and backyard compost piles, but the inputs into these typesof composting are likely to be relatively pure.

3. It is even difficult to estimate the risks and incidence of diseasefrom the use of sewage waters. In 1986, World Bank judged that therewere few credible epidemiological studies of health effects ofwastewater reuse in agriculture. There have been hundreds of studiesbut few present evidence that can meet standards of modernepidemiological criteria (Shuval et al., p. 299).

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