Pesticides in Agriculture and Environment

Pesticides applied worldwide in conventional agriculture for pest, disease and weed control are critical to increased productivity, but can provide harmful effects on non-target organisms. Given its toxicological, environmental and agricultural relevance, pesticide science comprises an important area of research, not only for scientists working in the field of agriculture, but also for several other professionals, where the subject requires a multidisciplinary approach. Important aspects of pesticides residues in marketed grains in Brazil, contamination of water resources by pesticides, bioaccumulation of pesticides in non-target organisms, are highlighted in this book, in addition to advantages and disadvantages of hormesis to herbicides in agricultural production, and phytoremediation technique to herbicides-polluted soils. We are sure that readers will find a lot of useful information, even if they are only partially interested in a few chapters. In this book entitled "Pesticides in Agriculture and Environment" are covered several topics on current and valuable research on pesticide science.

Brazil is a world reference in agricultural production. In the grain sector, the country reached a record in the 2019/2020 harvest, with production above 257 million tons, and the forecast of “Companhia Nacional de Abastecimento” (CONAB) is new record in the 2020/2021 crop (CONAB, 2020 and 2021b).

However, with increased productivity and growing dietary needs, pesticide use has increased. Herbicides, fungicides and insecticides constitute the classes of pesticides with the highest consumption and economic importance (PELAEZ et al., 2016). In Brazil, one of the largest pesticide consumers in the world, the use and marketing of these products has maintained high rates over the last few years. The “Sindicato Nacional da Indústria de Produtos para Defesa Vegetal” (SINDIVEG) points out that more than 600,000 tons of formulated products were marketed in the country in 2019.

It is important that the use of pesticides is made following the recommendation standards, in order to avoid contamination, both of the grains, as well as of the environment and the applicator. However, studies indicate the presence of residues of various pesticides in food matrices, which is a source of concern (ABRASCO, 2015; ANVISA, 2016). These contaminations occur due to several factors such as drift, use of doses above the recommended, non-respect of the grace period, use of products not registered for the crop or non-observation of the time of application (AZEVEDO and FREIRE, 2006; ABRASCO, 2015).

Water is one of the most important natural resources for the maintenance of life, being essential its preservation and its quality control. Among the sources of contamination that most affect the environment and water resources, pesticides that are used indiscriminately in agriculture stand out (DELLA-FLORA et al., 2019; REIBER et al., 2020).

The use of pesticides in agriculture occurred in the year 1950, in the United States, in what became known as the green revolution, and between 1960 and 1970 this movement was established in Brazil, receiving great fiscal incentive from the government (LOPES and ALBUQUERQUE, 2018). Therefore, the increase in the use of these chemicals has occurred with population growth in recent decades and consequently with the increase in demand for more food products to supply the population (SEVERO et al., 2020). Currently, Brazil is one of the main consumers of pesticides, standing out in the world's agricultural production (BARRETO et al., 2020).

The factors that affect the fate of these products in the environment are the way they are used and handled, the environmental conditions and the physical-chemical properties of pesticides and soil (DELLAMATRICE and MONTEIRO, 2014). In addition, with the removal of riparian forests and with inappropriate soil and crop management, pesticides can be transported to water sources by runoff and/or runin or percolating in the soil profile by leaching, due to rain or irrigation of crops where it was applied (DELLAMATRICE and MONTEIRO, 2014; SEVERO et al., 2020).

Bioaccumulation is defined as the process of accumulation and enrichment of contaminants in organisms over time and encompasses two important concepts: bioconcentration and biomagnification. Bioconcentration is the accumulation of contaminant in the body through its direct absorption of the environment and biomagnification is the accumulation of the contaminant through the body's diet, leading to increased concentration of the contaminant in the highest trophic levels of the food chain. First, for bioaccumulation to occur, it is necessary to show the body to the contaminant. this exposure is dependent on the bioavailability of the contaminant, which can be understood as its part in the environment that is potentially available to be bioconcentrated and biomagnified. among the various types of bioavailable contaminants, a large group draws attention: pesticides applied in agricultural areas. Pesticides are substances used to control weeds, insects, fungi, bacteria and other organisms that, under certain specific conditions, are considered pests in crops.  More than 4 million tonnes of pesticides are applied annually in agricultural areas worldwide (FAO, 2018), with expectations of Increase over the years due to population growth and higher demand for food.

In 1943, the term hormesis was first used to define the beneficial effect of toxic substances to a certain characteristic of an organism (SOUTHAM and EHRLICH, 1943). In plants, the effect of hormesis can be promoted by many chemicals, such as herbicides (DUKE et al., 2006). To describe the hormesis, dose-response curves are generally used.

Regarding the hormetic effect, there are differences of opinion, because while some researchers consider hormesis an induced adaptive response, others consider that hormesis occurs at any cost, and may also lead to less development of another part of the plant that did not suffer hormesis.  In plants, the hormetic effect comes from different stimuli that vary depending on the species, the moment the product is applied, which chemical molecule is applied and the way the product acts in the plant's metabolic process (REIS et al., 2021).

The use of pesticides is an indispensable practice in technical agriculture, avoiding the reduction in crop productivity and increasing the quality of the final product. Pesticides can be divided into different classes, among which one can mention herbicides, fungicides, acaricides and insecticides. Herbicides are the most widely used pesticide class on a large scale and are efficient tools in weed control, and have low cost compared to other control methods and reduce labor dependence (RAMBORGER et al., 2017).

Some herbicides have a long residual effect, which allows weed control for a longer period, thereby reducing the number of applications (PROCOPIO et al., 2009a).  However, the presence of the herbicide in the soil for a prolonged period can cause damage to susceptible crops (carryover) in rotation/succession systems, negatively impact non-target organisms, especially beneficial soil microorganisms, in addition to raising the risks of leaching and contamination of soils and surface and groundwater (VIEIRA et al., 2007; DAN et al., 2012; LANE et al., 2012; OTTO et al., 2012; SILVA et al., 2014). Thus, as a form of decontamination of soils submitted to herbicide applications, the development of bioremediation strategies is being demanded, reducing environmental and agronomic impacts.