18.104.22.168.2. Contact LD50
The acute contact toxicity test is conducted to determine the inherent toxicity of pesticides and other chemicals to bees. The results of this test are used to define the need for further evaluation. The contact LD50 is part of the tiered approach; from laboratory to semi-field to field. The tiered approach is implemented in the EU. The contact LD50 is assessed for the risk assessment of sprayed PPPs to adult worker bees. The result, a certain dose expressed as µg or ng AI or formulation per bee or per gram of bee is an academic parameter and does not express the hazard of the product in the field. This depends on the concentrations and the field application and is assessed in the HQ (EPPO, 2010b) or RQ (EPHC, 2009) (see 8.4.2.). When an HQ calculation results in a value lower than 50, the risk to bees is considered to be low. When performing acute contact studies, a toxic standard (positive reference, such as dimethoate) should be used. The results from the test with the toxic standard provide information on potential changes in sensitivity of the test organisms (in time) and consequently the suitability of these populations for further testing. Additionally, information on the precision of the test procedure is generated.