Pesticide Load—A new Danish pesticide risk indicator with multiple applications

Pesticides provide growers with an effective tool for the control of damaging crop pests preventing yield losses that could jeopardise food security. In recent years the potentially adverse effects of their use on human health and the environment has received increasing attention by the public and the competent authorities. In this context reliable pesticide risk indicators are pivotal to assess the potential risk associated with the use of pesticide. Several pesticide risk indicators, serving various purposes, have been developed over the years. Recently, a new pesticide risk indicator, the Pesticide Load (PL), was introduced in Denmark. The PL has replaced the Treatment Frequency Index (TFI) as the official pesticide risk indicator. The PL consists of three sub-indicators for human health, ecotoxicology and environmental fate, respectively. For each of the three sub-indicators a pesticide load (PL) is calculated and expressed as the PL per unit commercial product (kg, L or tablet). PL for human health (PLHH) is based on the risk phrases on the product label, while PL for ecotoxicology (PLECO) is calculated on basis of the LC/LD/EC50 values of the active ingredients for acute toxicity to mammals, birds, fish, daphnia, algae, aquatic plants, earthworms and bees and NOEC values for chronic toxicity to fish, daphnia and earthworms. PL for environmental fate (PLFATE) is calculated on basis of the half-life in soil (DT50), the bioaccumulation factor (BCF) and the SCI-GROW index. PL does not consider the actual exposure, i.e. it reflects the relative risks associated with the use of pesticides. Besides using PL for monitoring the yearly trend in pesticide use and load, the PL was also used for setting up a new pesticide tax scheme and for setting quantitative reduction targets. In Denmark, it is now compulsory for farmers to upload their pesticide use data, i.e. the annual pesticide statistics and the calculation of the PL can be produced on basis of pesticide use data rather than sales data that may not reflect the actual use by farmers. Because pesticide use data is available for each farm, maps providing detailed information on pesticide use in different regions can be produced. From 2010/11 to 2013/14 only minor differences were observed in the PL and, overall, similar trends were observed for the PL and TFI. Significant geographical differences, which could be attributed to differences in crop rotations, were apparent when estimating PL for each of the four major groups of pesticides (herbicides, fungicides, insecticides and plant growth regulators). The maps produced from the pesticide use data revealed significant variation in PL for ecotoxicological effects on aqueous organisms and bees as well as environmental parameters such as leaching potential. It is suggested to use the maps to identify ‘hot spots’ and design monitoring programmes or to launch initiatives that can reduce the PL. By linking information on mode of action to each commercial pesticide product it was also possible to obtain detailed information on the use pattern of the various pesticide modes of action, which is relevant information assessing the risk of evolution of pesticide resistance.