Standard Guidance for Dosimetry for Sterile Insect Release Programs
Importancia y uso:
4.1 The major use of factory-reared insects is in sterile insect release programs (for example, Sterile Insect Technique, or SIT) for suppressing or eradicating pest populations (2, 3). Large numbers of reproductively sterile (irradiated) insects are released into an area where a wild “target population” of the same species exists, or sterile insects are released into an area as a preventative measure to protect against the wild pest establishing. The wild population is reduced to the extent that the sterile males are successful in mating with wild females. The radiation dose absorbed by the factory-reared insects should be within a range that induces the desired level of sterility without substantially reducing the ability of factory-reared males to compete with wild males for mates. In some cases, sterile females may also be released as part of an SIT program. Species targeted by SIT programs are typically major pests affecting agriculture or human health, so the assurance by standardized dosimetry that insects have been properly irradiated is of crucial importance to agriculture growers, agricultural regulators, public health officials, and the public (3). The irradiator operator must demonstrate by means of accurate absorbed-dose measurements that all insects have received absorbed dose within the specified range.
4.2 Another use of factory-reared insects is in the production of parasitoids for release against populations of insect pests (4). Parasitoids are insects that spend the larval stage feeding within or on the body of a “host” species, typically killing the host. In some parasitoid programs, factory-reared host insects are irradiated before being offered to parasitoids. This eliminates the need to separate unparasitized hosts from parasitoids so that fertile, unparasitized host insects are not inadvertently released into the field.
4.3 An additional use of factory-reared insects is for testing detection traps for fruit flies and moths, and testing mating disruption products for moths.
4.4 Factory-reared insects may be treated with ionizing radiation, such as gamma radiation from 137Cs or 60Co sources, or X-radiation or electrons from accelerators. Gamma irradiation of insects is often carried out in small, fixed-geometry, dry-storage irradiators (5). Dosimetry methods for gamma and X-ray irradiation of insects have been demonstrated and include useful procedures for measuring the absorbed dose distribution throughout the volume of the irradiation container(s) in these small irradiators (ASTM Practice 52116 and Refs (1, 6)) as well as large-scale gamma irradiators (ASTM Practice 51702 and Ref (7)).
4.5 Specifications for irradiation of factory-reared insects include a lower limit of absorbed dose and may include a central target dose and an upper limit. These values are based on program requirements and on scientific data on effects of absorbed dose on the sterility, viability, and competitiveness of the factory-reared insects.
4.6 To demonstrate control of the radiation process, the absorbed dose must be measured using a calibrated dosimetry system. Regulations or policies under which the facility operates may require the calibration to be traceable to appropriate national or international standards. The radiation-induced change in the dosimeter is evaluated and related to absorbed dose through calibration (ASTM Practice 51261).
4.7 For each irradiator, absorbed-dose rate at a reference position within the irradiated volume of insects or simulated product is measured using a transfer or reference standard dosimetry system. That measurement provides a basis for calculating the duration of irradiation, conveyor speed, or other parameter required to deliver the specified absorbed dose to the insects.
4.8 Absorbed-dose mapping for establishing magnitudes and locations of minimum dose (Dmin) and maximum dose (Dmax) is performed using actual product or simulated product (5).
Subcomité:
E61.04
Volúmen:
12.02
Número ICS:
17.240 (Radiation measurements)
Palabras clave:
absorbed dose; biological control; cesium-137; cobalt-60; electron accelerator; dosimeter; dosimetry; gamma; insect irradiation; insect rearing; ionizing radiation; irradiation; irradiator characterization; parasitoid rearing; radiation; sterile insect technique; SIT; X-radiation; ICS 17.240;