The determination of acute oral toxicity on honey bees is required for the assessment and evaluation of chemicals prior to their registration as pesticides (Regulation EC No 1107/2009 of the European Parliament and of the Council of 21 October 2009). In this way, the acute oral toxicity test is conducted to determine the toxicity of all types of compounds to bees (pesticides, specifically, are tested as AIs or as formulated products). The methodology outlined in this section is a general approach of the laboratory test with oral applications and does not present all the details of the referenced guidelines.
Usually an oral exposure study is intended to determine the LD50 (see section 220.127.116.11.) and the results are used to define the need for further evaluation. Although the LD50 is a common aim of these studies, oral exposure tests can be used to determine NOAEL (see section 8.4.3.). When the LD50 cannot be determined because a given compound has a low toxicity, a limit test may be performed in order to demonstrate that the LD50 is greater than the standard value of 100 µg of AI/bee.
Data from oral LD50 calculations can be used to generate HQ for each compound of interest (see section 18.104.22.168). The LD50 calculation provides a raw value only. This result has to be related to the exposure of honey bees in field conditions.
- When the HQ < 50, the product can be considered of low acute risk to adult worker honey bees when ingested. The HQ does not predict product toxicity to brood or the occurrence of any sub-lethal effects on adults or brood.
- When the HQ > 50, more tests are required in semi-field or field conditions for a better evaluation of impact (cf. European scheme for the assessment of impact of PPPs - Guidelines commonly used refer to EPPO (2010b), OECD (1998a) and French CEB (2011). All are similar with main differences occurring on number of the number of replicates.