Agrochemical Pollutants

by

Kathleen Bowmer

• LAST REVIEWED: 28 March 2018
• LAST MODIFIED: 28 March 2018
• DOI: 10.1093/obo/9780199363445-0093

Introduction

Pesticides and fertilizers are widely used in agriculture. They are essential to the production of food and fiber for a growing world population, but they become pollutants when they damage nontarget organisms. Some herbicides are also applied directly to water to control aquatic plants and algae. Pesticides include a vast array of herbicides, insecticides, fungicides, and nematicides and are widely variable in chemical structure, benefit, and impact. Nontarget organisms include people who may consume contaminated food or water; adjacent crops damaged by spray drift; bees and wildlife; subsequent crops in rotation with the target crop; and aquatic life in rivers, lakes, and estuarine and coastal waters, where sea grasses and coral are particularly vulnerable. The agricultural use of pesticides and their impact on human health through spray contact, food, and drinking water has been extensively covered in the literature, so this review focuses on the risk of other environmental impacts and opportunities for risk reduction or avoidance. The risk to nontarget organisms from pesticides depends on the extent of use, inherent toxicity (acute and chronic), transport away from the site of application, persistence, adsorption by suspended material, and concentration-time patterns of exposure that are affected by dilution and hydrology. Bioaccumulation in the food chain has led to the banning of chlorinated hydrocarbon insecticides in most countries of the world. Fertilizers include nitrogen (N) and phosphorus (P), which are applied to agricultural crops with substantial benefits for increased yield, but also with impacts on the aquatic environment through leaching of nitrogen compounds and soil erosion of adsorbed phosphates. Consequences of nutrient enrichment (eutrophication) include algal blooms that disrupt aquatic ecology and compromise the utility of the water through the production of taints and toxins. Toxic heavy metals have also been associated with fertilizer application. Opportunities for reduction of risk include effective registration procedures, restriction or regulation of use, sewage and storm-water effluent treatment, interception of agricultural pollutant source (e.g., by riparian strips), and treatment to remove pollutants prior to use. Major challenges include the difficulties of isolating the effects of agrochemical fertilizers from other pollutant sources such as sewage and animal effluents, complexities of relating land use to water quality and river condition, and costs of measuring trace amounts of chemicals. Ecotoxicology is the science of measuring the acute and chronic response of aquatic organism to pollutants. Interpretation is complicated by the synergistic effects of cocktails of pollutants, and by interaction with stressors such as salinity, temperature extremes, and turbidity. The review concludes with a section on achieving sustainability through changes in agricultural practice and use of catchment-scale approaches.

General Overviews

The role of pesticides in feeding an increasing world population is described in Godfray, et al. 2010. Several books provide comprehensive information on the chemistry, use, and toxicology of pesticides. These include assessment of the environmental impact of agrochemical pesticide and fertilizer use in dryland farming systems (“diffuse sources”), though it should be noted that irrigated cotton, rice, and sugarcane are major pesticide users, especially in the developing world (Murray 1994), and urban “point” sources are increasing in importance (US Geological Survey 2017). Bowmer 2011 describes the links between land use and river health, putting agrochemicals (pesticides and fertilizers) into a broader context of water management and planning. Wohl 2014 provides overviews of pollutant impacts on river systems in the United States and internationally. Progress in environmental management is provided for member countries by Organisation for Economic Co-operation and Development 2008. US Environmental Protection Agency 2017 provides a comprehensive international database. In recent times, stringent registration processes have reduced the risk of pesticides to nontarget organisms, either through controlling sales or through permits and labels for use in practice (Organisation for Economic Co-operation and Development 2016). Also, much safer and less persistent pesticides are available, and new methods of analysis are available for rapid and inexpensive determination of traces of pollutants (Hennion and Barcelo 1998).

• Bowmer, K. H. 2011. Water resource protection in Australia: Links between land use and river health with a focus on stubble farming systems. Journal of Hydrology 403:176–185.

  DOI: 10.1016/j.jhydrol.2011.03.050

  This research review investigates the many confounding factors that complicate the link between land use and river condition, including climate change, bush fires, farm dams, afforestation, river regulation, and impacts of introduced species. The use of indicators, risk frameworks, and biophysical modeling is advocated, as well as revitalization of regional and catchment scale approaches.

• Godfray, H. C. J., J. R. Beddington, I. R. Crute, et al. 2010. Food security: The challenge of feeding 9 billion people. Science 327.5967: 812–818.

  DOI: 10.1126/science.1185383

  This review article provides a context for the need for agrochemicals. Growing competition for land, water, and energy, in addition to the overexploitation of fisheries, will affect our ability to produce food, as will the urgent requirement to reduce the impact of the food system on the environment. The effects of climate change are a further threat. A multifaceted and linked global strategy is needed to ensure sustainable and equitable food security.

• Hennion, M. -C., and D. Barcelo. 1998. Strengths and limitations of immunoassays for effective and efficient use for pesticide analysis in water samples: A review. Analytica Chimica Acta 362.1: 3–34.

  DOI: 10.1016/S0003-2670(97)00608-9

  This text reviews the strengths and limitations of immunoassays for effective and efficient use of pesticide analysis in water samples.

• Murray, D. L. 1994. Cultivating crisis: The human costs of pesticides in Latin America. Austin: Univ. of Texas Press.

  This compact, sobering, and readable paperback is described as an excellent interdisciplinary case study for students. It describes the high price of the “Green Revolution” on massive pesticide independence and environmental damage in the Third World, with a focus on Central America.

• Organisation for Economic Co-operation and Development. 2008. Environmental performance of agriculture in OECD countries since 1990. Paris: OECD.

  This electronic report of nearly three hundred pages provides comprehensive sections on agricultural land use, nitrogen and phosphorus use, regional balances, pesticides, water quality, soil erosion, and progress at the farm scale. Trends in performance are provided for thirty countries using novel indicators. The work is well referenced and additional data is available on each country.

• Organisation for Economic Co-operation and Development. 2016. OECD Government Web Sites for Pesticide and Biocide Review Reports. Paris: OECD.

  This web page provides links to government websites for pesticide registration (Australia, Canada, Netherlands, UK, and US). Links are also provided for joint FAO and WHO meetings on pesticide residues and toxicological information.

• US Environmental Protection Agency. 2017. Pesticide Registration. Washington, DC: EPA.

  The process of registering a pesticide is a scientific, legal, and administrative procedure. The EPA examines the ingredients of the pesticide; the particular site or crop where it is to be used; the amount, frequency, and timing of its use; storage and disposal practices; and a wide variety of potential human health and environmental effects. The company that wants to produce the pesticide must provide data from studies that comply with testing guidelines.

• US Geological Survey. 2017. Pesticides. Reston, VA: US Geological Survey.

  This web page from the USGS National Water Quality Assessment Program (NAWQA) is well illustrated with maps and figures that show widespread occurrence of pesticides in streams and groundwater in the United States. The frequency of pesticide contamination was found to be greater than expected. While average concentrations in streams and wells rarely exceeded standards and guidelines established to protect human health, concentrations of pesticides approached or exceeded guidelines for aquatic life and wildlife, particularly in urban areas.

• Wohl, E. 2014. River pollution. In Oxford Bibliographies in Environmental Science. New York: Oxford Univ. Press.

  This Oxford Bibliographies review provides a comprehensive account of river pollution that includes pesticides, nitrates, phosphorus, and sediments, together with other pollutants such as heavy metals and pathogens. River basin case studies describe the combined effects of these and other pollutants on human communities and on the aquatic environment. These studies include the Yangtze, China; Clark Ford, Montana, USA; Cyahoga, Ohio, USA; Danube, Europe; Illinois, USA; Murray-Darling, Australia; and Nile, Africa.