208 CHRISTINE FUREDY
9.5. HEALTH ISSUES IN ORGANIC WASTE REUSE
Because the reuse of urban organic wastes is so varied and is largely conducted infor-
mally, the potential health implications are very complex.
Health risks may be associated with every aspect of reuse, including: transportation
and handling of organic wastes; processing; the application of organics from mixed
municipal wastes to soils; cultivation on old dumps; and feeding animals with wastes.
Many actors are involved, and there are risks of human-animal disease links.
A thorough general overview of potential problems related to this topic can be found
in the report Health Impacts of Peri-urban Resource Development (Birley and Lock,
1999) which covers organic waste reuse in urban and peri-urban agriculture. A
summary of problems and possible control measures can be found in the March 2001
issue of Urban Agriculture Magazine. De Zeeuw and Lock classify the main problems
as:
- survival of pathogenic organisms in residues
- zoonosis associated with animal wastes
- increase of disease vectors
- respiratory problems from dust and gases
- injuries from sharp fragments
- contamination of crops from heavy metal take-up and agrochemical residues via
wastes and their leachates.
It is often asserted that composting of urban organic wastes eliminates or substantially
reduces any health risks to farmers and consumers The reality is not so straightfor-
ward. Decomposition must take place at a temperature of at least 60° Centigrade to
destroy most pathogens and the product should be matured for several weeks (Brunt
et al., 1985). A question mark hangs over vermicomposting, which takes place at
lower temperatures. In Europe, anaerobic processing of organic wastes is required
prior to vermicomposting, but this is not done in vermicomposting in developing
countries (Furedy, 2001).
At the present time, few organic wastes are being safely composted in Africa and Asia.
Far more organic wastes enter food production via ‘garbage farming’ (i.e. use of
municipal solid wastes) on farms, cultivation of old dumps, and animal feeding than
via composting, and these activities are rarely controlled. Hence, the numbers of
persons at risk must be very large.
There has been, however, little specific research on these health risks. If testing is done
of soils or compost, it is usually for the occurrence of heavy metals and even then,
there is no agreement on appropriate standards for safe heavy metal bioaccumulation
for the wide variety of crops grown (Furedy, 2001). An encouraging result of patho-
genic tests is cited by Brook and Davila (2000). Tests were done of compost from