In both domestic and international agricultural
markets, expanding the use of irradiation can help to reduce the
need for methyl bromide for the post-harvest control of insect pests.
Currently, irradiation treatments have been approved for a variety
of food use applications by the U.S. Food and Drug Administration
(FDA). The United States Department of Agriculture (USDA) Animal
and Plant Health Inspection Service (APHIS) Plant Protection and
Quarantine Service (PPQ) has outlined policy positions regarding
the development and use of irradiation treatments for quarantine
pest control, and is actively seeking ways to incorporate additional
irradiation uses into their plant protection program (USDA 1995,
USDA 1996a, 1996b, 1996c). Furthermore, research has been conducted
to determine optimal irradiation dosages for controlling pests and
maintaining produce quality, a variety of irradiation technologies
have been commercialized worldwide, and there is extensive data
available on the capital, operating, and per unit treatment costs
associated with irradiation projects. In addition, recent market
studies have generally found that consumers are willing to buy irradiated
produce (Morrison 1992). In fact, research conducted in Florida
indicated that consumer acceptance for such commodities is high,
and many actually prefer the methods to traditional chemical fumigation
Food irradiation is a process by which products are exposed to
ionizing radiation to sterilize or kill insects and microbial pests
by damaging their DNA. The FDA permits three types of ionizing radiation
to be used on foods: gamma rays from radioactive cobalt-60 and cesium-137,
high energy electrons, and x-rays. Although all three have similar
effects, gamma rays are most commonly used in food irradiation because
of their ability to deeply penetrate pallet loads of food (Forsythe
and Evangelou 1993, Morrison 1989). Gamma irradiation equipment
irradiates packaged or bulk commodities by exposing the product
to gamma energy from cobalt-60 in closed chambers, which range in
size from single modular pallet irradiators to large research or
contract irradiation facilities. Absorbed dose is measured as the
quantity of radiation imparted per unit of mass of a specified material.
The unit of absorbed dose is the gray (Gy) where 1 gray is equivalent
to 1 joule per kilogram (ICGFI 1991, NAPPO 1996).
Benefits of Irradiation
There are several benefits of expanding the use of irradiation
treatments to control pests infesting perishable and non-perishable
commodities in the United States. First, irradiation may be useful
for preventing the movement of quarantine species possibly present
in trade commodities into areas where such pests are not established
(USDA 1996b). From an economic standpoint, irradiation, therefore,
has the potential to increase trade opportunities between nations,
especially from major fruit and vegetable producing countries with
high infestation rates (ICGFI 1994). Irradiation also can be used
to reduce the risk of infection and disease caused by foodborne
pathogens (Moy 1991). Although consumers have concerns associated
with the safety of irradiation technology and its effects on food,
research indicates that properly irradiated food does not pose a
risk to consumers (Thorne 1983, OTA 1985). In fact, the potential
for human health impacts from exposure to foodborne pathogens is
believed to be substantially reduced through the use of irradiation
(OTA 1985, Morrison et al. 1992).
In addition, by interfering with cell division, irradiation inhibits
sprouting in tubers, bulbs, and root vegetables (potatoes, onions)
and can delay ripening of some tropical fruits, resulting in an
extended shelf life for many foods. In turn, longer shelf lives
will enhance trade opportunities between nations by extending time
constraints under which fresh produce must be delivered to more
distant geographic markets or by allowing the use of slower and
less expensive modes of transportation (Kader 1986, Moy 1991, OTA
Uses of Irradiation
Irradiation is used as a pest control tool in over 40 countries,
including the United States, Russia, Great Britian and Brazil (Nordion
1995). The disinfestation of grain as it enters the Soviet Union
at the Black Sea Port of Odessa, estimated at over 500,000 metric
tons per year, is one of the largest documented commercial industrial
applications (Giddings 1991). In the United States, the FDA approved
low-doses irradiation for wheat, wheat flour, and potatoes in the
early 1960s. In 1984 and 1985, the FDA approved irradiation of spices
and pork, and in the following year, approved low-dose irradiation
(up to 1 kGy) to control insects in foods and extend the shelf life
of fresh fruits and vegetables (Kader 1986, Morrison 1989). Irradiation
has also been used to sterilize food for U.S. hospital patients
and astronauts (Morrison 1992). Further, irradiation disinfestation
has been found to be effective for treatment of dried fruits, spices,
nuts, cut flowers, lumber, and wood chips (ICGFI 1994, Marcotte
1992, Morrison 1989, OTA 1985). At doses below 1 kGy, irradiation
is an effective treatment against various species of fruit flies,
mango seed weevils, naval orange worms, potato tuber moths, codling
moths, and other insect species of significance to quarantine situations
(Kader 1986). For irradiation to be approved as a quarantine treatment
in the United States, either as a single treatment, or as part of
a combined approach (e.g., systems approach), USDA/APHIS/PPQ will
require that the level of efficacy be scientifically demonstrated,
and that efficacy be demonstrated under commercial settings (USDA
Effective Dosages and Impact on Produce Quality
Because foods differ in their radiation dose requirements, densities,
as well as specific packing configurations (Kunstadt et al. 1990),
research has focused on insect mortality, morbidity, and sterilization,
as well as the effects of ionizing radiation on fruit quality. The
effects of irradiation depend on the dose absorbed. Low doses (up
to 1 kGy) inhibit sprouting in tuber, bulb and root vegetables,
inhibit the growth of asparagus and mushrooms, and delay physiological
processes (ripening, etc.) in such fruits as banana, mango, and
papaya. Medium doses (1 to 10 kGy) extend the shelf life of commodities,
eliminate spoilage and pathogenic microorganisms, and improve the
technical properties of food. Lastly, high doses (10 to 50 kGy)
can be used for industrial sterilization and decontamination of
certain additives or ingredients (Morrison 1992, ICGFI 1994, OTA
1985, Kader 1986).
In 1984, the International Consultive Group on Food Irradiation
(ICGFI) convened in Washington, D.C., to develop a set of guidelines
for the irradiation of fresh produce. The group established minimum
doses that could provide effective treatments against most arthropod
pests (ICGFI 1994). Doses used to disinfest foods and agricultural
products are usually between 0.15 kGy (minimum dose for fruit fly
sterilization and to prevent larval development) and 0.30 kGy (to
control other species of insects and mites), but may go as high
as 1 kGy (Forsythe and Evangelou 1993, Marcotte 1992). While research
has proven irradiation to be effective at sterilizing pest insects,
there is concern as to how quarantine inspectors would tell the
difference between sterile and non-sterile insects that physically
appear the same.
Unless already established, the correct dose required for a specific
commodity infested with a specific pest must be determined through
testing. Results of some of the studies that have investigated dose
- Research on the mango seed weevil in the U.S. has shown that
irradiation at doses of 0.30 kGy prevented adult emergence from
infested fruit (ICGFI 1994).
- USDA researchers in Florida found that radiation doses as low
as 0.30 kGy were effective in eliminating plum curculio (Conotrachelus
nenuphar), and blueberry maggot (Rhagoletis mendax), without altering
overall fruit quality (Hallman and Miller 1994).
- Researchers at Washington State University conducted a series
of tests on 'Rainier' cherries and determined that irradiation
levels as high as 0.30 kGy had no effect on composition, color,
or taste. They also concluded that doses of 0.15 and 0.25 kGy
were effective in controlling cherry fruit flies and codling moths,
respectively (Drake et al. 1994).
- Studies done at the U.S. Horticultural Research Laboratory in
Florida (USDA/ARS, Orlando) showed that irradiation doses up to
0.75 kGy were sufficient in controlling apple maggot (Rhagoletis
pomonella), blueberry maggot (Rhagoletis mendax), and plum curculio
(Conotrachelus nenuphar), without doing any damage to the fruit's
composition or taste (Miller and McDonald 1994).
Factors influencing the response of fresh fruits and vegetables
to irradiation include the type of commodity and cultivar, production
area and season, maturity at harvest, initial quality, and post
harvest handling procedures. Similarly, environmental conditions
during irradiation (temperature and atmospheric composition), and
dose rates are also influencing factors (ICGFI 1994, Kader 1986,
OTA 1985, Morrison 1992). The relative tolerances of fresh fruits
and vegetables to irradiation doses below 1 kGy are listed in Table
||Apple, cherry, date, guava,
longan, muskmelon, nectarine, papaya, peach, rumbutan, raspberry,
strawberry, tamarillo, tomato
||Apricot, banana, cherimoya, fig, grapefruit,
kumquat, loquat, lychee, orange, passion fruit, pear, pineapple,
plum, tangelo, tangerine
||Avocado, cucumber, grape, green bean, lemon,
lime, olive, pepper, sapodilla, soursop, summer squash, leafy
vegetables, broccoli, cauliflower
Source: Kader 1986.
The actual cost of food irradiation is influenced by dose requirements,
the food's tolerance of radiation, handling conditions (i.e., packaging
and stacking requirements), construction costs, financing arrangements,
and other variables particular to the situation (Forsythe and Evangel
1993, USDA 1989). Irradiation is a capital-intensive technology
requiring a substantial initial investment, ranging from $1 million
to $3 million (or possibly more for special applications). In the
case of large research or contract irradiation facilities, major
capital costs include a radiation source (cobalt-60), hardware (irradiator,
totes and conveyors, control systems, and other auxiliary equipment),
land (1 to 1.5 acres), radiation shield, and warehouse. Operating
costs include salaries (for fixed and variable labor), utilities,
maintenance, taxes/insurance, cobalt-60 replenishment, general utilities,
and miscellaneous operating costs (Kunstadt et al., USDA 1989).
Based on a review of public information on the costs of treating
a variety of food items with irradiation, Table 2 presents data
on the per-unit costs for gamma irradiation and methyl bromide treatments
for selected crops. Although irradiation is more expensive than
fumigating with methyl bromide, the cost of irradiation may be offset
by its many benefits, including reduced damage to fruits and vegetables
and an extended shelf life. Furthermore, it is likely that irradiation
costs will decrease in the future as the number of commercial irradiators
and volumes of treated commodities increases. In addition, the relative
proportion of the treatment cost is small when compared to the value
of the commodity. Furthermore, other related costs (i.e., harvesting,
packaging, storage, processing, and transportation costs to bring
the commodity to market) further reduce the percent contribution
of irradiation treatments, making it a relatively insignificant
Table 2. Comparison of Estimated Post-Harvest Treatment
Costs for Selected Crops
(cents per pound)
(cents per pound)
||0.88 to 0.94
||2.5 to 8.1
||0.88 to 0.94
||0.9 to 4.2
||0.88 to 0.94
||Data not available
Sources: Forsythe and Evalgelou 1993 and 1994, Morrison 1989.
- Drake et al. 1994. Effects of Low Dose Irradiation on Quality
of 'Rainer' Cherries. Proceedings from the 1994 International
Conference on Methyl Bromide Alternatives and Emissions Reductions.
- Forsythe and Evangelou. 1993. Costs and Benefits of Irradiation
and Other Selected Quarantine Treatments for Fruit and Vegetable
Imports to the United States of America. Issue Paper. Proceedings
of An International Symposium on Cost-Benefit Aspects of Food
Irradiation Processing Jointly Organized by the International
Atomic Energy Agency, The Food and Agricultural Organization of
the United Nations, and the World Health Organization. Aix-En-Provence,
Vienna. March 1-5, 1993.
- Forsythe and Evangelou. 1994. Costs and Benefits of Irradiation
versus methyl bromide fumigation for disinfestation of U.S. fruit
and vegetable imports. U.S. Department of Agriculture, Economic
Research Service, Agriculture and Trade Analysis Division, Washington,
D.C., March 1994.
- Giddings. 1991. Radiation Disinfestation of Agricultural Commodities.
Nordion International, Inc. Kanata, Ontario, Canada.
- Hallman and Miller. 1994. Irradiation as an Alternative to Methyl
Bromide Quarantine Treatment for Plum Curculio in Blueberries.
Proceedings from the 1994 International Conference on Methyl Bromide
Alternatives and Emissions Reductions. Kissimmee, FL.
- ICGFI. 1991. Facts About Food Irradiation. International Consultative
Group on Food Irradiation, Fact Sheet Series, May 1991.
- ICGFI. 1994. Irradiation as a Quarantine Treatment of Fresh
Fruits and Vegetables. A report of the Working Group Convened
by ICGFI, U.S. Department of Agriculture, Washington, D.C., March
22 to 25, 1994.
- Kader 1986. Potential Applications of Ionizing Radiation in
Post-harvest Handling of Fresh Fruits and Vegetables. Food Technology,
Volume 40, Number 6, June, 1986, pp. 117-121.
- Kunstadt et al. 1990. Economics of Food Irradiation. P. Kunstadt,
C. Steeves, D. Scaulieu, Nordion Technical Paper. Market Development,
Food Irradiation Division, Nordion International Inc. Kanata,
- Marcotte. 1992. The Practical Application of Irradiation Disinfestation
for Food and Agricultural Commodities. Proceedings from the 1992
International CFC and Halon Alternatives Conference, Washington,
D.C. September 1992.
- Miller and McDonald. 1994. Irradiation as an Alternative Quarantine
Treatment to Methyl Bromide for Blueberries. Proceedings from
the 1994 International Conference on Methyl Bromide Alternatives
and Emissions Reductions. Kissimmee, FL.
- Morrison. 1989. An Economic Analysis of Electron Accelerators
and Cobalt-60 for Irradiating Food. Rosanna Mentzer Morrison.
U.S. Department of Agriculture, Economic Research Service, Technical
Bulletin #1762, June, 1989.
- Morrison. 1992. Food Irradiation Still Faces Hurdles. Food Review.
October-December, pp. 11-15.
- Morrison et. al. 1992. Irradiation of U.S. Poultry -- Benefits,
Costs, and Export Potential. Food Review. October-December, 1992,
- Moy. 1991. Plant Quarantine Treatment by Irradiation: Potential
Benefits and Barriers in International Trade. Proceedings from
the International Plant Quarantine Congress. Kuala Lumpur, Malaysia.
- NAPPO. 1996. NAPPO Standards for Phytosanitary Measures. Guidelines
for the Use of Irradiation as a Phytosanitary Treatment. Draft
for the Secretariat of the North American Plant Protection Organization,
Nepean, Ontario, Canada, July 1, 1996.
- Nordion. 1995. World Suppliers of Contract Gamma Processing
Services - 1995. Nordion International, Inc., Kanata, Ontario,
- OTA. 1985. Food Irradiation: New Perspectives on a Controversial
Technology. Rosanna Mentzer Morrison and Tanya Roberts, Office
of Technology Assessment, Congress of the United States, Washington,
DC. December 1985.
- Thorne. 1983. Developments in Food Preservation. Applied Science
Publishers Ltd., S. Thorne, ed., Essex, England. Chapter 2.
- USDA. 1995. The application of irradiation to Phytosanitary
problems. Position Discussion Document IV, U.S. Department of
Agriculture, Animal Plant Health Inspection Service, Plant Protection
and Quarantine, Washington, D.C., September 1995.
- USDA. 1996a. Papaya, Carambola, and Litchi from Hawaii. Federal
Register, U.S. Department of Agriculture, Animal Plant Health
Inspection Service, Washington, D.C., Volume 61, No. 142, pp.
38108 - 38114.
- USDA. 1996b. The application of irradiation to phytosanitary
problems. Federal Register, U.S. Department of Agriculture, Animal
Plant Health Inspection Service, Washington, D.C., Volume 61,
No. 95, pp. 24433 - 24439.
- USDA. 1996c. Methyl bromide alternatives newsletter. U.S. Department
of Agriculture, Washington, D.C., January, 1996.
More information on the irradiation of agricultural products is
available from the USDA Food
Safety and Inspection Service .
Please note that this publication discusses specific proprietary
products and pest control methods. Some of these alternatives are
now commercially available, while others are in an advanced stage
of development. In all cases, the information presented does not
constitute a recommendation or an endorsement of these products
or methods by the Environmental Protection Agency (EPA) or other
involved parties. Neither should the absence of an item or pest
control method necessarily be interpreted as EPA disapproval.
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