Significance and Use
4.1 The major use of factory-reared insects is in sterile release programs (for example, Sterile Insect Technique, or SIT) for suppressing or eradicating pest populations (1)5. Large numbers of reproductively sterile (irradiated) insects are released into an area where a wild "target population" of the same species exists. The wild population is reduced to the extent that the sterile males are successful in mating with wild females. The radiation dose to 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. 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 (1-4). The irradiator operator must demonstrate by means of accurate absorbed-dose measurements that all insects will receive 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 (5). Parasitoids are insects that spend the larval stage feeding within 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 Factory-reared insects may be treated with ionizing radiation, such as gamma radiation from 137Cs or 60Co sources, or X-rays or electrons from accelerators. Gamma irradiation of insects is usually carried out in small, fixed-geometry, drystorage irradiators (6-8). Dosimetry methods for gamma irradiation of insects have been demonstrated and include useful procedures for mapping the absorbed dose throughout the volume of the insect canister in these small irradiators (ASTMPractice E 2116 and Ref (9)) as well as large-scale gamma irradiators (ISO/ASTM Practice 51702 and Ref (10)).
4.4 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.
4.5 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 may be used to calculate the timer setting, conveyor speed, or other parameter required to deliver the specified absorbed dose to the insects.
4.6 Absorbed-dose mapping for establishing magnitudes and locations of Dmin and Dmax is performed using actual product or simulated product (9).
4.7 Dosimetry is part of a measurement quality assurance plan that is applied to ensure that the radiation process meets predetermined specifications (11).
1.1 This guide outlines dosimetric procedures to be followed for the radiation sterilization of live insects for use in pest management programs. The primary use of irradiated, reproductively sterile insects is in the Sterile Insect Technique, where large numbers of sterile insects are released into the field to mate with and thus control pest populations of the same species. A secondary use of sterile insects is as benign hosts for rearing insect parasitoids. The procedures outlined in this guide will help ensure that insects processed with ionizing radiation from gamma, electron, or X-ray sources receive absorbed doses within a predetermined range. Information on effective dose ranges for specific applications of insect sterilization, or on methodology for determining effective dose ranges, is not within the scope of this guide.Note 1
Dosimetry is only one component of a total quality control program to ensure that irradiated insects are adequately sterilized and sufficiently competitive or otherwise suitable for their intended purpose.
1.2 This guide covers dosimetry in the irradiation of insects for these types of irradiators: self-contained dry-storage 137Cs or 60Co irradiators, large-scale gamma irradiators, and electron accelerators. Additional, detailed information on dosimetric procedures to be followed in installation qualification, operational qualification, performance qualification, and routine product processing can be found in ISO/ASTM Practices 51608 (X-ray [bremsstrahlung] facilities), 51649 (electron beam facilities), 51702 (large-scale gamma facilities), and ASTM Practice E 2116 (self-contained dry-storage gamma facilities).
1.3 The absorbed dose for insect sterilization is typically within the range of 20 Gy to 600 Gy.
1.4 This guide refers, throughout the text, specifically to reproductive sterilization of insects. It is equally applicable to radiation sterilization of invertebrates from other taxa (for example, Acarina, Gastropoda) and to irradiation of live insects or other invertebrates for other purposes (for example, inducing mutations), provided the absorbed dose is within the range specified in .
1.5 This guide also covers the use of radiation-sensitive indicators for the visual and qualitative indication that the insects have been irradiated.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.