Pesticides
A pesticide is something that prevents, destroys, or controls a harmful organism (pest) or disease, or protects plants or plant products during production, storage and transport. The term includes, amongst others: herbicides, fungicides, insecticides, acaricides, nematicides, molluscicides, rodenticides, growth regulators, repellents, rodenticides and biocides.
When they are applied on crops, usually with a spraying equipment, they partly end up in the
environment through different mechanisms, as summarized
here
.
When these molecules, explicitly designed to kill or damage certain organisms, end up in soil
and aquatic ecosystems, they become a potentially significant ecological stressor and may cause
risks for the environment as well as for human health.
Concerns for the unintentional consequences of pesticides in the environment have triggered the
development of the European legislation on pesticides, which presently includes two main
instruments:
- a regulation on the authorization of individual pesticides: Regulation (EC) No 1107/2009
- a Framework Directive on the sustainable use of pesticides: Directive 2009/128/EC of the European Parliament and of the Council of 21 October 2009 establishing a framework for Community action to achieve the sustainable use of pesticides
The regulation on the authorization of individual pesticides defines rules for the examination of active substances potentially used in pesticides. Active substances are subject to an assessment of their risks for human health and the environment and, if the risks are judged acceptable, they are authorized for use in plant protection products at European level. Individual EU Member States are responsible for the authorization of specific plant protection products containing authorized active ingredients. Authorizations are granted for a limited period of time, and the list of authorized substances (hence products) changes with time both because of non-renewal of existing authorizations, and of development of new substances by the industry.
The assessment of risks is conducted considering conventional scenarios of application of pesticides to crops in different climates and soils. Hydrological and biogeochemical models allow simulating the fate and transport of active substances in soils and water under these scenarios. Model simulations yield calculated environmental concentrations, which are finally interpreted in terms of risk taking into account the toxicity of the substance. The scenarios used in risk assessment should be in principle protective, in the sense that they should represent reasonable worst cases, hence concentrations found in the real world should be typically below those simulated, and evaluated as acceptable, when a substance is authorized. However, due to the complexity of the real world compared to its schematization in models, it is possible that measured concentrations are higher. Knäbel et al., 2012 and Knäbel et al., 2014 show evidence of higher-than-expected concentrations found for insecticides and fungicides in surface waters, calling for a revision of the simulations used in the regulatory process. Stehle and Schulz, 2015 argue that agricultural insecticides may be a threat to surface waters at the global scale.
The information on pesticide use presently available in Europe is rather limited. EUROSTAT publishes only data on the sales of pesticides by broad classes, aggregated by EU member states.
Although this or similar information has been used in the past in modeling exercises aimed at the mapping of pesticide concentrations (e.g. Ippolito et al., 2015, Pistocchi et al., 2009, Pistocchi et al., 2011), it would be necessary to know the quantities of individual active ingredients actually used, virtually for all crops with the detail of the field, in order to characterize pesticide pollution in Europe and to make informed decisions about possible management measures. This type of information may exist for some European countries, but is far from being available for the majority of the EU Member States. Moreover, in order to better understand the real impact of pesticides, it may be opportune to account for how different species come into contact with pesticides depending on their respective ecological niches, foraging habits etc. (Long and Krupke, 2016, Topping et al., 2015, Rico et al., 2015). More, in general it would be important to upgrade the current risk assessment methods by addressing the landscape scale as well as the cumulative impact of multiple pesticides and other stressors (Streissl et al., 2018).
Pistocchi et al., 2018, use measured concentrations in European rivers (referred mostly to years up to 2009) to back-calculate the losses of pesticides included in the list of priority substances of the Water Framework Directive (WFD – Dir. 60/2000/EC), finding that, on average, one hectare of agricultural land in the EU loses from less than 20 mg to more than 180 mg per year of pesticides, including those banned in the previous years (Terbutryn and Chlorfenvinphos in 2002; Atrazine, Simazine, Heptachlor in 2004; Endosulfan in 2005; Alachlor in 2006; Dichlorvos in 2007; Dicofol in 2008).
In parallel to the discipline of individual active substances, the Framework Directive on the sustainable use of pesticides
aims to achieve a sustainable use of pesticides in the EU by reducing the risks and impacts of pesticide use on human health and the environment and promoting the use of Integrated Pest Management (IPM) and of alternative approaches or techniques, such as non-chemical alternatives to pesticides. EU countries have drawn up National Action Plans to implement the range of actions set out in the Directive. The main actions relate to training of users, advisors and distributors of pesticides, inspection of pesticide application equipment, the prohibition of aerial spraying, limitation of pesticide use in sensitive areas, and information and awareness raising about pesticide risks. EU countries must also promote Integrated Pest Management
Integrated Pest Management (IPM) is based on the following principles:
- prevention and/or suppression of harmful organisms
especially by:
- crop rotation;
- adequate cultivation techniques (e.g. density and timing of crops, resistant/tolerant cultivars and seed and planting material, balanced fertilisation, liming and irrigation/drainage practices);
- hygiene measures (e.g. regular cleansing of machinery);
- protection and enhancement of important beneficial organisms, also by protecting their habitat.
- monitoring of pests and precise application of pesticides only when needed, and with the minimum possible impact, reduced doses or extents of application;
- preference for biological, physical and other non-chemical methods to chemical methods if possible;
- attention to avoid development of resistance mechanisms in pests.
Van Eerdt et al., 2014, examine in details the costs and effectiveness of on-farm measures to reduce aquatic risk of pesticides in the Netherlands, finding that these measures (as part of IPM) can have considerable effect. The most effective options are the reduction of unintentional application of products outside of target crops, and the replacement of higher-risk pesticides with lower-risk alternatives. In arable crops, the authors find buffer strips to have a significant potential to reduce risk to aquatic ecosystems. They stress that, in spite of the clear improvement of crop profitability that can be achieved with IPM, farmers are still partly reluctant to adopt it for reasons of lack of awareness or, sometimes, impracticable IPM measure implementation. However, the agribusiness is increasingly aware of the challenge to crop productivity posed by the current trend in reducing the number and risk of available chemical pesticides (e.g. Lamichhane et al., 2016, Hillocks, 2012, Damos et al., 2015). On the other hand, critics say that IPM is not sufficiently ambitious to achieve sustainability in crop production. Hamlyn, 2015 argues that the Framework Directive on sustainable pesticide use limits itself to "a narrow agenda of risk management rather than genuinely and ambitiously adopting the true principles of sustainability". The Special Rapporteur on the right to food at the UN’s General Assembly has recently addressed the issue of pesticides as a major threat to human health and ecosystems, stressing how the use of pesticides "can have very detrimental consequences on the enjoyment of the right to food" (UN, 2017), and indicating the perspective of organic farming or agroecology as a way beyond IPM.
References
Damos, P., Escudero Colomar, L.A., Ioriatti, C. (2015). Integrated fruit production and pest management in Europe : the apple case study and how far we are from the original concept. Insects, 6, 626-657.
Hamlyn, O. (2015). Sustainability and the failure of ambition in European Pesticides Regulation. Journal of Environmental Law, 27, 405-429.
Hillocks, R.J. (2012). Farming wiht fewer pesticides : EU pesticide review and resulting challenges for UK agriculture. Crop protection, 31, 85-93.
Ippolito, A., Kattwinkel, M., Rasmussen, J.J., Schaefer, R.B., Fornaroli, R., Liess, M. (2015). Modeling global distribution of agricultural insecticides in surface waters. Env. Poll., 198, 54-60.
Knäbel, A., Meyer, K., Rapp, J., Schulz, R. (2014). Fungicide field concentrations exceed FOCUS Surface water predictions: urgent need of model improvement. Env. Sci. Technol., 48, 455-463.
Knäbel, A., Stehle, S., Schaefer, R., Schulz, R. (2012). Regulatory FOCUS Surface Water models fail to predict insecticide concentrations in the field. Env. Sci.Technol., 46, 8397-8404.
Lamichhane, J.R., Dachbrodt-Saaydeh, S., Kudsk, P., Messean, A. (2016). Toward a reduced reliance on conventional pesticides in European agriculture. Plant Disease, vol. 100, no.1.
Long, E.Y., Krupke, C.H. (2016). Non cultivated plants present a season-long route of pesticide exposure for honey bees. Nature Communications, 7: 11629.
Pistocchi A, Vizcaino P, Hauck M. (2009). A GIS model-based screening of potential contamination of soil and water by pyrethroids in Europe. Journal of environmental management. 2009 Aug; 90(11):3410-21.
Pistocchi, A., Dorati, C., Aloe, A., Ginebreda, A., Marce’, R. (2018). River pollution by priority chemical substances under the Water Framework Directive: a provisional pan-European assessment. Submitted.
Pistocchi, A., Groenwold, J., Lahr, J., Loos, M., Mujica, M., Ragas, A.M. J. , Rallo, R., Sala, S., Schlink, U., Strebel, K. , Vighi, M., Vizcaino, P. (2011). Mapping Cumulative Environmental Risks: Examples from the EU NoMiracle Project. Environmental Modeling & Assessment: Volume 16, Issue 2 (2011), Page 119. DOI 10.1007/s10666-010-9230-6.
Rico, A., van den Brink, P.J., Gylstra, R., Focks, A., Brock, T.C.M. (2015). Developing ecological scenarios for the prospective aquatic risk assessment of pesticides. Int. Env. Ass. Manag. 12, 510-521.
Stehle, S., Schulz, R. (2015). Agricultural insecticides threaten surface waters at the global scale. PNAS, 112: 5750-5755.
Streissl, F., Egsmose, M., Tarazona, J.V. (2018). Linking pesticide marketing authorizations with environmental impact assessments through realistic landscape risk assessment paradigms. Ecotoxicology, 27: 980-991.
Topping, C.J., Craig, P.S., de Jong, F., Klein, M., Laskowski, R., Manachini, B., Pieper, S., Smith, R., Sousa, J.P., Streissl, F., Swarowsky, K., Tiktak, A., van der Linden, T. (2015). Towards a landscape scale management of pesticides: ERA using changes in modelled occupancy and abundance to assess long-term population impacts of pesticides. Sci. Total Env., 537: 159-169.
Van Eerdt, M., Spruijt, J., van der Wal, E., van Zeijts, H., Tiktak, A. (2014). Costs and effectiveness of on-farm measures to reduce aquatic risks from pesticides in the Netherlands. Pest Manag. Sci., 70 – 1840-1849.