the absence of formulation toxicity data, combination toxicity is estimated assuming additive toxicity for organisms which are sensitive to at least two of the constituents in the mixture. The estimation method for combination toxicity is provided in Table X. If one active substance drives the overall toxicity (≥ 90%), then it is concluded that the toxicity is driven by the active constituent and additive toxicity is not considered further. If formulation toxicity data are available, the observed toxicity of the mixture is compared to the predicted toxicity based on active substance data which can be done for any ratio of active substances by calculation of the Model Deviation Ratio (MDR). If the MDR is within the range of 0.2 to 5, the mixture toxicity is assumed to be additive. If the MRD is <0.2, the mixture toxicity is considered to be less than additive (antagonistic) and if the MDR is >5, the mixture toxicity is considered to be more than additive (synergistic). Risk assessment tables Table 18 - Regulatory acceptable concentrations for soil organisms Taxonomic group Exposure Endpoint Assessment RAC factor Acute LC50 XX mg ac/kg dry soil 10 XX mg ac/kg dry soil Chronic NOEC XX mg ac/kg dry soil 1 XX mg ac/kg dry soil Chronic NOEC XX mg ac/kg dry soil 1 XX mg ac/kg dry soil RAC = regulatory acceptable concentration = endpoint / assessment factor Table 19 - Screening level assessment of risks to soil organisms Test organism Exposure Application rate (g ac/ha) PEC (mg ac/kg dry soil) RAC (mg ac/kg dry soil) RQ Macro-organisms Acute Chronic Micro-organisms Chronic Rate is cumulative rate of 3× 150 g ac/ha, 7-day interval between applications and DT50 XX days PEC = predicted environmental concentration in top 5-cm soil (mg ac/kg dry soil) = rate (g ac/ha)/750 RAC = regulatory acceptable concentration (from Table X) RQ = risk quotient = PEC / RAC, where acceptable RQ <1
Table 23 - Combination toxicity to non-target terrestrial plants Active 1 Active 2 Combination Fraction in combination 0.XX 0.XX 1.00 Effects on seedling emergence ER50 XX g ac/ha Test item Tier of testing Test species (or #species tested if >value) Reference ER50 XX g ac/ha Test item Tier of testing Test species (or #species tested if >value) Reference Measured: ER50 XX g ac/ha Test item Tier of testing Test species (or #species tested if >value) Reference Predicted: ER50 XX mg ac/kg bw Relative toxicity contributions: X% + X% MDR X Effects on vegetative vigour ER50 XX g ac/ha Test item Tier of testing Test species (or #species tested if >value) Reference ER50 XX g ac/ha Test item Tier of testing Test species (or #species tested if >value) Reference Measured: ER50 XX g ac/ha Test item Tier of testing Test species (or #species tested if >value) Reference Predicted: ER50 XX mg ac/kg bw Relative toxicity contributions: X% + X% MDR X References EFSA (European Food Safety Authority), 2014, Scientific opinion addressing the state of the science on risk assessment of plant protection products on non-target plants, EFSA Journal 12(7): 3800, 153pp, doi:10.2903/j.efsa2014.3800, available online: EPHC (Environment Protection and Heritage Council), 2009, Environmental risk assessment guidance manual for agricultural and veterinary chemicals, ISBN 978-1-9221173-38-7, available online: EPPO (European and Mediterranean Plant Protection Organization), 2003, Environmental risk assessment scheme for plant protection products: Chapter 12: Non-target terrestrial higher plants, PP3/13(1), EPPO Bulletin 33: 239-244.