Introduction

The Food and Agriculture Organization (FAO), states that a pesticide "is the substance or mixture of them, intended to prevent, destroy or control pests, including vectors of human or animal disease; unwanted species of plants or animals that cause lasting damage or others that interfere with the production, processing, storage, transportation and marketing of food; agricultural commodities, wood and wood products, fodder for animals or products to which can be applied to control insects, arachnids or other pests" (^{FAO, 1990}).

Regardless of its benefits, it is clear that pesticides are chemicals deliberately toxic, created to interfere any particular biological system and lacks real selectivity. Affecting simultaneously and in varying degrees, both "target species" as other categories of living beings, particularly humans (^{Wania, 1998}). This is because only 10 percent of applied pesticides reach the target organism and a high percentage is deposited on the soil, water and sediment, affecting other organisms (^{Ortiz-Hernández, 2011}). In addition, prolonged use of pesticides commonly results in residues in food and continuous exposure to by different paths, generating widespread concern about potentially adverse effects that these chemicals have on humans (^{Osman, 2011}).

Regarding to Argentina, in the last 15 years the agricultural frontier expanded from 15 to 30 million hectares cultivated, generating changes in land use in various regions of the country. Contrary to what happened with the expansion of mechanized agriculture in other countries and in Argentina in the early twentieth century, the possible negative effects on the environment of a process of this magnitude were mitigated by the incorporation of new agronomic concepts and innovative technologies; including direct seeding, increased use of fertilizers, new rotations and planning criteria, among others. With 2.8 million km² Argentina has extremely fertile land that perfectly fit for agricultural and livestock production (^{Viglizzo et al., 2006}).

Following this, the consumption of pesticides in our country has consolidated and this consolidation has set such products as one of the fundamental pillars of growth for production in view of the expected medium-term evolution. Trends in consumption of these products have characteristics that are reflected in different evolutions of markets analyzed by crop. Each of these markets has a number of influential variables, among which may include market-related variables (price, origin of goods, supply, etc.), related to crops variables (higher or lower incidence of adversity during a cycle, genotype characteristics, etc.), variables related to products (control amplitude, level of substitution, control effectiveness, possibility of making mixtures) and other variables (^{CASAFE, 2003}).

Assuming toxicities, its impact on the environment and living beings is why was set as a goal of this work to design a rubric that allows to qualify indirectly the environmental impact of different pesticides, and that can be used to establish criteria for better use of these products in agricultural areas.

Materials and methods

Study area. The study area focused in the town of San Vicente, province of Santa Fe, Argentina, within the Castellano department (31° 43' 00" S, 61° 35' 00" W) (Figure 1). The climate in Santa Fe has two gradients, one heat from north to south, and another hydric from east to west. By the thermal regime can be defined as temperate climate without cold season in the south and warm temperate in the north; and by the hydric regime varies from humid to sub-humid from east to west. The terrain is flat with an average height of 40 masl (^{Lewis and Collantes, 1974}).

Figure 1. Location of the study area. Town of San Vicente, Santa Fe, Argentina. Urban area and crop surrounding área that was delimited. 

The Province of Santa Fe is one of the most significant agricultural producers in the country. The agricultural sector accounts for about 65% of total gross income generated by the rural sector. Related to land use, in recent years has been observed a progressive expansion of agriculture regarding livestock. But current agricultural expansion is not the same type to that from three or four decades ago, since there is no available surface from the best soils; from now on, the expansion would be feasible by intensifying surface currently in use and by expansion on land less suitable and higher productive risk. The main crops for both Santa Fe as for the study area are soy, corn, wheat, sunflower and sorghum (^{MinAgri, 2010}).

A total area of about 5 000 ha nearby town of San Vicente (Figure 1) where information necessary to obtain the different types of crops grown and pesticides applied by ground spray was collected. For this a survey was applied to workers, farmers, agronomists and sellers of plant protection products. For each case they were asked the following information: crop, type of pesticide that is applied with spray (trade name and active ingredient) and its action or class (fungicide, insecticide, etc.).

Taking as basis the matrix designed by Fernández et al. (2003) a scale that would allow to indirectly assess substances in relation to different factors was design, being these related to health and damage to the environment, and thereby obtain a wider view of the effects caused by different pesticides. Calling this, assessment of environmental impacts (VIA) and what it was sought with this is to have more extensive data than those provided by the plant protection products. This allows to have a deep level of criteria when monitoring the damage caused by the use of pesticides in the environment.

The following factors were considered:

Ecotoxicology: toxicological category, toxicity in bees, birds and fish.

Human toxicity: carcinogenicity, neurotoxicity, endocrine disruption, genotoxicity and irritative capacity.

Environmental behavior: persistence in water / sediment, persistence in soil and bio-concentration.

Then these factors were included in the following categories: low - medium - high - very high.

Next are defined the various characteristics of each factor considered in the environmental assessment of pesticides according to ^{WHO / PAHO (1990)}; ^{IARC (2008)}; ^{EPA (2012)}.

Toxicological category: different toxicological classes in which pesticides may be included. That is, acute toxicity of the active ingredient.

Toxicity to birds, bees and fish: the ability of a chemical to cause damage to the structure or functions of the living organisms or even death.

Carcinogenicity: is the induction of normal growth, messy and potentially unlimited from cells of a tissue or organ.

Neurotoxicity: refers to effects on the central nervous system, peripheral nervous system and sense organs.

Endocrine disruption: an endocrine disruptor is a chemical capable of altering the hormonal balance and cause various adverse effects on health.

Genotoxicity: alteration in the genetic material or in its associated components, produced by a chemical agent in sub-toxic exposure levels.

Irritative capacity: the ability of a substance to cause injury, irritation or allergy at skin, eyes and mucous membranes level.

Persistence in soil and water/sediment: the concept of persistence is often related to the residence time of a chemical in the environment. At longer residence time, greater persistence. Mean lifetime (DT₅₀) of the substance is a measure of its persistence.

Bioaccumulation or bioconcentration: these are terms used to describe the increase in the concentration of a chemical in an organism in relation to the concentration of the same substance in the surrounding medium.

To determine the assessment of impacts using the following equation:

Where: ET_total= ET₁ + ET₂ + ET₃ + ET₄; TH_total= TH₁ + TH₂ + TH₃ + TH₄; CA_total= CA₁ + CA₂ +; CA₃ + CA₄.

The values of each of the variables are presented in Table 1.

Table 1. Scale values used for each of the variables. 

Getting the different data:

Ecotoxicology: These data are obtained from the pesticide label. It is information that is reflected in the products so it is easily accessible. It can be found the name from the technical sheet.

Human toxicity: These data can be extracted from different sources: from the Environmental Protection Agency (EPA) and the International Agency for Research on Cancer (IARC), through their official websites. Although you can also extract data from laboratories and universities through toxicology reports of different products. Under "irritative capacity" is taken into account mucous membrane, skin and eyes; therefore when one of these is affected a 5 is placed. Since many pesticides can cause skin lesions and not in eyes or mucous, for example.

Environmental behavior: these data are drawn from work done by laboratories, universities, institutions, as well as product labels, in some cases can have this information (especially the persistence in soil).

Assumptions to consider: when no information was found about some of the different categories proceeded to place the lowest value 1. And it was clarified with an asterisk (*) in the matrix. In the case of products that come with more than one active ingredient, i.e., more than one substance, it proceeded to analyze both separately and place the one with greatest impact.

Results and discussion

From the surveys was obtained that the main types of crops grown are soybeans, wheat, corn, sunflower, sorghum and alfalfa. Regarding to pesticides obtained 32 products, of which 15 are insecticides, 10 are herbicides and 7 are fungicides that are applied by spraying. For details of the different pesticides see ^{Schaaf (2013)}. The results of the environmental impact assessment (VIA) from the different pesticides are listed in Table 2. In a comparative and demonstrative way detailing in Table 3 the values for toxicological categories of different pesticides and VIA value obtained in this work.

Table 2. Calculation and final assessment for the different pesticides used in San Vicente, Santa Fe, Argentina. 

Regarding the results of this preliminary study it was found that intensive agriculture currently taking place in the town of San Vicente, providence of Santa Fe requires a significant amount of pesticides to ensure growth and good crop development sown in the area. According to data obtained most of surveyed pesticides are insecticides, followed by herbicides and fungicides.

Taking model values it is observed that most pesticides used have middle toxicity (43.75%), followed by high and low toxicity (21.88%) and finally the very high toxic (12.5%). Regarding to this assessment tool designed for this study, called VIA, it can be noted that it is of interest for environmental diagnosis and management of the use of pesticides applied with spray. As it not only takes into account toxicity in humans, but also of other living beings, the impact on water and soil. This assessment can be taken into account from different points of view as there are pesticides whose toxicity is low for humans but is considerable for fish, birds and bees. This is interesting because there may be beekeepers and poultry farms that may be affected.

In addition to this can be noted that there are pesticides with green bands (class IV) whose environmental impact assessment (VIA) is moderate or high. If we consider specific cases of products sold, those that should remain in the spotlight, both by toxicity category as for its high toxicity values (VIA), chlorpyrifos, endosulfan, fipronil, clap, cypermethrin, methamidophos, lufenuron, abamectin 2-4 D, poseidon and lambda are pesticides that require close monitoring because of its high and very high impact on the environment, especially considering the proximity to the urban area. This must be taken into account for monitoring and final diagnosis in cases of environmental management of pesticide use.

Conclusion

This tool and methodology of analysis proposed is a study and indirect interpretation of pollution that can generate certain pesticides on the environment in agricultural areas. It has been taken as reference parameters of importance such as ecotoxicology, human toxicity and environmental behavior, clarifying that it is important to emphasize that the indiscriminate use of pesticides has generated numerous problems, especially cumulatively to medium and long term (^{Ortiz et al., 2011}).

Highlights that from technical and scientific material easily accessible, embodied in a simple and easy application formula, it can obtain relevant data to make an impact assessment of pesticide use and propose monitoring for the use of these products.

It takes into account different components, where the assessment and table for toxicity category of pesticides helps us to have a comprehensive picture, identify high toxicity pesticides and plan prevention projects from data obtained from impact that products have on the environment. It is also recommended that this should be implemented within a baseline for the development of future plans for use/pesticides application, which parts from information on all environmental issues that may arise in different areas of study. It could develop regional planning in agricultural areas and nearby populated areas, recommending practices and application products. Finally to clarify that this work developed in a sector from the center of the Province of Santa Fe is a pilot study on a relatively small scale, this is a new tool and that it may be subject to change and improvement.