Agriculture Reference
In-Depth Information
7
The Role of Water and Water Testing in
Produce Safety
Charles P. Gerba
Introduction
Water plays a usually overlooked role in terms of importance in produce safety. It is
not only essential in the growth of crops, but also in their processing. Water is used
in the cooling of produce, removal of debris, decontamination, washing of equipment,
and personal hygiene. The microbial quality of this water is important in ensuring that
contamination of the produce does not occur during these events. This is especially
true of this commodity because the produce is often eaten with no or little processing.
The importance of high-quality source water and its separation from human wastes
was recognized by the Romans more than 2,000 years ago. The development of the
germ theory of disease a little more than 100 years ago provided the basis for modern
water quality treatment and personnel hygiene. These two practices together have
played the biggest role in disease reduction in human history, more so even than the
development of antibiotics and vaccinations. The pathogens most commonly transmit-
ted by produce are enteric pathogens transmitted by the fecal-oral route and are
excreted in large numbers in both the feces of man and animals. For example, human
rotavirus may be excreted in numbers as great as 10
11
per gram (Gerba 2000) and
Salmonella
10
10
(Feachem and others 1983). When one considers that only 1-10
viruses are needed to cause an infection, a small amount of feces in the water can
have a signifi cant impact on disease transmission to susceptible populations (Gerba
and others 1996).
The largest use of freshwater in the world is in agriculture, with more than 70%
being used for irrigation. Approximately 240 million ha, 17% of the world's cropland,
are irrigated, producing one-third of the world's food supply (Shannan 1998). Nearly
70% of this area is in developing countries. Irrigation of food crops with untreated
domestic sewage has long been associated with the transmission of infectious diseases.
As a result, the use of wastewater for irrigation is forbidden or the wastewater must
be highly treated and rigorously monitored in developed counties. Irrigation with
sewage or sewage-contaminated surface waters in developing countries is fairly
common and usually not regulated. Although guidelines for wastewater reuse have
been developed by the World Health Organization (WHO 2006), their application in
developing countries is diffi cult, due to inadequate institutional capability and general
lack of fi nancial resources.
Ideally water used for application of herbicides and pesticides and for washing
would receive complete treatment similar to that required for drinking water because
direct contact of the water with the produce occurs. In the United States surface water
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