Pesticide Pollution in the Brazilian Pampa: Detrimental Impacts on Ecosystems and Human Health in a Neglected Biome

: The Brazilian Pampa biome covers half of Rio Grande do Sul state, in the extreme south of Brazil, creating an ecotone zone with the Atlantic Forest and bordering Pampa’s territory belonging to Uruguay and Argentina. Pampa is a non-forest biome mainly composed of grasslands and mosaics of grassland-forest vegetation. This biome shows signiﬁcant animal and plant diversity, contributing to the maintenance of important ecosystem services, including CO 2 capture, pollination, and water cycle regulation. However, forestry plantations, inappropriate cattle ranching, mining activities, unplanned urbanization, and the cultivation of monocultures (soy, rice, tobacco, and other cash crops) signiﬁcantly threaten the conservation of the Pampa biome. A major problem observed in the Pampa, due to the great connection of this biome with agricultural areas, is pesticide pollution, which signiﬁcantly affects the health of humans and animals that occupy the region. A robust body of evidence indicates that aquatic and terrestrial ecosystems in the Brazilian Pampa are extensively contaminated with pesticides, as indicated by studies involving animal biomarkers and pesticide analyses performed on water and soil samples. Human studies also suggest that pesticides affect different body systems, facilitating the onset of various chronic diseases. Brazil’s conservation actions and policies have a special focus on forest ecosystems, neglecting non-forest biomes and thus aggravating the problems related to Pampa’s conservation. In this article, we discuss some problems caused by pesticide pollution in the Brazilian Pampa, drawing attention to the need for intensiﬁcation of policies focused on the promotion of human and environmental health. Finally, we suggest the bioecological bioeconomy as an alternative for Rio Grande do Sul to progress its economic development but with less dependency on detrimental activities to the Pampa biome.

These problems affect not only the Pampa's biodiversity but also the living conditions of the human population. Although Rio Grande do Sul is one of the richest states in Brazil in economic terms, there is a concentration of municipalities with a reduced Human Development Index located in the Pampa region [31]. Of note, socioeconomic issues intensify the multiple environmental challenges observed in the Pampa.
In this article, we draw attention to the pesticide pollution in the Pampa biome, highlighting the need for Brazil, especially Rio Grande do Sul, to expand protection policies focused on this biome, which is usually neglected in terms of public attention and environmental protection policies [18,32]. The bioecological bioeconomy for Rio Grande do Sul's sustainable development is suggested as an alternative to economic activities linked to the degradation of the Pampa biome. The Pampa has huge biodiversity, with species belonging to several taxonomic groups. A recent study reported more than 12,500 species of plants, animals, fungi, and bacteria occurring in the Brazilian Pampa, representing 9% of all Brazilian biodiversity in an area that occupies 2% of Brazil's territory [21]. This biome performs several ecosystem services, such as CO2 capture, pollination, pest and disease control, and water cycle regulation [19,22]. Pampa's vegetation also has great ornamental [23,24], food, medicinal [25], and cosmetic [26] potential.

Current Scenario
Pesticides (synthetic agrochemicals) broadly refer to herbicides, fungicides, insecticides, and plant growth regulators used especially in agriculture. Brazil is a world leader in agricultural production and, consequently, a world's leading pesticide consumer, with 20% of worldwide pesticide usage occurring in the country [33,34].
Soybean, corn, and sugar cane production are together responsible for 82% of pesticide consumption in Brazil. Rio Grande do Sul is one of the Brazilian states that uses the most pesticides (~130 million L/year), along with Mato Grosso and Paraná. Soybean, rice, wheat, corn, and tobacco are the predominant crops in Rio Grande do Sul; all these cash crops are major pesticide consumers [35]. Of note, tobacco production uses the highest mean quantity of pesticides per hectare (60 L/ha) [35]. Therefore, the Pampa is considered a region with intense pesticide use [36]. Excessive use combined with inappropriate application of pesticides causes environmental contamination, especially in water bodies and soil [33,34].
Another study detected tebuconazole (detected concentration range: 1.99-3.66 µg L −1 ), imazethapyr (1.46-2.48 µg L −1 ), and clomazone (3-11.76 µg L −1 ) in water samples from the Uruguay River, Uruguaiana city, Rio Grande do Sul state [37]. Tests carried out with pesticide-contaminated water samples indicated that both the survival and reproductive viability of the free-living nematode Caenorhabditis elegans were altered in relation to controls, suggesting a risk to aquatic life [37].

Pesticides in Soil
Pesticide contamination also affects terrestrial ecosystems. Imidazole contamination (concentration range < LOQ-37.77 µg Kg −1 ) was detected in agricultural soil samples from Rio Grande do Sul and Bahia states [34,38], consistent with data showing that phenylurea and imidazole are the chemical classes of pesticides with higher usage in the country [34]. In the same study [34], the potential risk of different pesticide classes to terrestrial life and human health was assessed using the RQ method, but no data concerning imidazole was available [34], indicating the urgent need to assess the potential impacts of pesticides found in soil on human and animal health.

A Neglected and Evolving Problem
The extension of pesticide pollution in Brazil is probably even greater than suggested by the available literature, since environmental contamination data for some states are scarce or non-existent [33] and the legislation for the use of pesticides has been relaxed in Brazil in recent years [39,40], including authorization for the use in Brazilian territory of an additional 562 pesticides (since 2021), many of them banned in Europe and North America [40]. Registration for the use of new pesticides in Brazil has been significantly facilitated since 2016 [39]. In fact, political pressure exerted by some politicians (bancada ruralista, or "ruralist bench") and members of the agribusiness sector facilitates the expansion of pesticide use in Rio Grande do Sul [41].
To the best of our knowledge, there is no data on the distribution of pesticide pollution levels in the different regions of the Brazilian Pampa. However, it is known that different regions of the biome show important variations in terms of geomorphology, landscape, socioeconomic development, and agricultural practices [13]. Indeed, while some areas have significant livestock activities, others are dominated by monocultures. Taken together, this information suggests that pesticide pollution is heterogeneously distributed in the Pampa, being concentrated mainly in areas of greater monoculture production.
It is important to stress that pesticide pollution also significantly affects the Argentine and Uruguayan Pampas. In the global analysis concerning the risk of pesticide pollution carried out by Tang et al. [9] and associated with additional data [42][43][44][45][46], it is evident that these risks are distributed throughout the international territory of the Pampa, encompassing Brazil, Argentina [42][43][44], and Uruguay [45,46], but in a heterogeneous way. Of note, Argentina was considered a "high-concern" region [9].
Finally, in addition to the amounts of pesticides used in agricultural practices, differences in pesticide-related issues are also affected by climatic aspects such as wind, sun radiation, and rainfall patterns [47,48] that can degrade or transport pesticide residues over significant distances. Climate change will therefore affect multiple aspects of pesticide pollution [48] in ways that are still difficult to predict.

Impacts on Animals and Ecosystems
Environmental pesticide contamination is detrimental to wildlife, affecting the immune, nervous, and endocrine systems, as well as reproduction and behavior, and interfering with the survival of several animal groups. Pesticide-related neurotoxicity can alter animal behavior, foraging, and learning. Endocrine disruption induced by pesticides can trigger reproductive failure, higher mortality rates, and thus population decline. These detrimental changes affect several animal groups at varied intensities, including mammals, birds, reptiles, amphibians, fish, and invertebrates [49]. Additionally, pesticide-induced immunotoxicity can cause an increased infection rate by various pathogens, facilitating the spread of infectious and parasitic diseases in animal populations [49,50]. For example, pesticides were linked to increased trematode (parasitic flatworm) infection rates in amphibians (i.e., Rana pipiens), which were considered contributing factors to the global decline of amphibian populations [51].
The detrimental effects of pesticides are particularly evident on invertebrate populations, including economically relevant insect pollinators such as bees [49,52]. Gill et al. [53] showed that pesticide exposure affects bees at individual and colony levels. Pesticide exposure can trigger altered behavior in bees, resulting in reduced brood success and decreased colony size. Pesticide exposure was also associated with impaired foraging, an altered gut microbiome, and mortality due to homing failure in bees [49,54].
The effects of pesticides on wildlife can be direct (e.g., cellular toxicity, biochemical changes) or indirect (e.g., impairment of species interaction, disruption of food webs) [49], which may hinder a direct causal association of pesticide pollution with consequences for animals and ecosystems, making the deleterious effects of pesticides often neglected or even undetected. However, evidence of pesticide pollution in the Pampa is emerging from studies performed with animal samples.
Analyzing fish (Astyanax sp.) sampled in rivers of the Rio Grande do Sul, several researchers detected pesticides in fish tissues as well as biochemical changes associated with exposure to pesticides in the Pampa biome [55][56][57]. Biochemical changes were also observed in fish (Danio rerio) exposed in the laboratory to urban and agricultural effluents from the Pampa biome [55]. Moreover, changes in levels of lipid peroxidation and acetylcholinesterase (AChE), glutathione S-transferase (GST), and catalase (CAT) enzymes were reported in a study performed with D. rerio embryos exposed to water from the Vacacaí River contaminated with pesticides (ten fungicides, eight herbicides, and six insecticides were detected in the water) [58]. In a recent study [59], changes in levels of carbonyl proteins and activity of AChE and GSH in tissues of fish (Rhamdia quelen) experimentally placed in three sites of Vacacaí River reinforced the effects of pesticide pollution on the Pampa's aquatic fauna. The fungicide tebuconazole (0.30 µg L −1 ) and the herbicides bentazon (0.77-1.80 µg L −1 ), clomazone (0.31-0.41 µg L −1 ), clorimuron (<LOQ), and quin-clorac (0.40-0.45 µg L −1 ) were detected in water, and fish exposed to the sites closest to agricultural areas showed higher levels of biochemical changes compared to a control [59].
Phyllomedusa iheringii (leaf frog) tadpoles sampled in nearby agricultural areas of the Pampa biome also showed altered biochemical markers linked to environmental imbalances, especially pesticide pollution [60]. Pires et al. [61] reported that agricultural land use and related changes in water chemistry affected the taxonomic heterogeneity of the Brazilian Pampa's communities of Odonata (hemimetabolous insects with an aquatic larval stage). It is possible that pesticide pollution is at least partially associated with this result, although pesticides were not evaluated in the study [61].
Pesticide pollution in the Pampa is not limited to aquatic environments. Traces of pesticides were detected in honey samples from Rio Grande do Sul, evidencing the widespread presence of these pollutants in the environment and their entry into food webs [62]. Of note, recently the death of millions of bees in Rio Grande do Sul was associated with pesticide exposure [63], although other factors (e.g., pathogens, nutritional problems) may have contributed to the illness and death of bees in the state [64].
The ecosystem services attributed to different species can be categorized as (i) provisioning services (e.g., food, ornamental resources, fiber, fuel, genetic resources), (ii) regulating services (e.g., pollination, pest regulation, air quality regulation, seed dispersal), (iii) supporting services (e.g., provisioning of habitat, nutrient and water cycling, soil formation), and (iv) cultural services (e.g., education, recreation, ecotourism, sense of place, cultural heritage) [65]; and many of these ecosystem services are affected by the use of pesticides [66]. Knowledge about the specific ecosystem services provided by the different animal, plant, and microbial species of the Pampa biome is still limited. Similarly, knowledge about the impacts of pesticide use on the reduction of ecosystem services in Pampa is scarce. It is essential that this knowledge be advanced so that we can develop specific protection goals focused on the conservation of Pampa's biodiversity and ecosystem services. Finally, protection goals must consider the Precautionary Principle, the Pollution Prevention concept, the Ecological Threshold concept, the Ecological Recovery concept, and the Functional Redundancy concept to elaborate strategies of risk assessment and management and to better define protection goals for this biome (see Nienstedt et al. [66] for more information about these principles and concepts, as well as the selection of protection goals).

Consequences of Pesticides on Human Health
The human health problems associated with pesticides are also extremely worrying in Brazil [52]. Human pesticide intoxication increased by 126.8% between 2007 and 2011 in the country [67]. More recently, Buralli and Souza [68] reported a 94% increase in human pesticide intoxication in Brazil, considering the 2009-2019 period. This data indicates a continuous increase in the detrimental impacts of pesticides on the health of Brazilians in the last 15 years. In Rio Grande do Sul state, the pesticide poisoning rate increased from 1.99/100,000 inhabitants in 2011 to 7.56/100,000 inhabitants in 2018, with 60% of poisoning cases linked to agricultural practices (poisoning by "pesticide for agricultural use"). The remaining poisoning cases were associated with pesticides used in non-agricultural practices ("pesticide for domestic use", "pesticide for public health use", "rodenticide", and "product for veterinary use"). Spraying and dilution were the main triggers of pesticide poisoning [69]. Cases of pesticide intoxication are probably even more frequent because there is a huge under-notification, especially in acute intoxication cases [35,67].
Epidemiological evidence indicates an association between pesticide use/poisoning and suicide behavior in Brazil [80], a problem particularly relevant in Rio Grande do Sul, where a high suicide rate of 11.3 cases per 100,000 inhabitants/year is observed (for comparison, Brazil's rate is 5-6 cases per 100,000 inhabitants/year) [81]. Easy access to pesticides, the potential effects of these products on the central nervous system, and socioeconomic pressures linked to agricultural production, among other factors, can contribute to the increased suicide rate observed in the Rio Grande do Sul, which, many times, even involves the use of pesticides as a death-inducing agent [69,80,82].
Beyond the direct effects caused by pesticides on multiple organisms and ecosystems, environmental contamination by heavy metals and other potentially toxic elements (PTEs) resulting from the production and application of pesticides chronically harms human health [83]. In this sense, increased concentrations of Mg, Al, Si, P, S, and Cl were observed in cells from agricultural workers from Espumoso city (Rio Grande do Sul) exposed to pesticides, and these findings were associated with genetic damage [73]. Although Espumoso is located in the Atlantic Forest biome, its proximity to the Pampa indicates that issues concerning human exposure to pesticide-related PTEs extend far beyond the Pampa biome and agricultural areas.
Finally, pesticides can cause imbalances in food webs and induce changes in ecological niches and natural habitats directly through their effects on animals (as discussed in the previous topic) and indirectly through the facilitation of major land-use changes. These processes are strongly associated with the emergence and spread of human infectious disease outbreaks, especially those triggered by vector-borne pathogens [84,85].

Conclusions and Perspectives
In addition to the abusive use of pesticides, the Pampa is increasingly challenged by several other problems and human activities that threaten its biodiversity, especially the loss of vegetation cover for agriculture, livestock, and forestry plantations [18,30,86,87]. These problems further aggravate the impacts of pesticide pollution on the health of humans, animals, and ecosystems.
Historically, Rio Grande do Sul had a prominent role in the Brazilian environmentalist movement [88]. This leading role has gradually fallen into oblivion over the years and is currently quite limited. Rio Grande do Sul needs to recover its prominent position in the Brazilian environmental agenda. Since grassland receives less media attention than Amazon or rainforest biodiversity, it is fundamental to realize the problems faced by the Pampa biome with the expansion of environmental policies focused on Pampa conservation. Initiatives and organizations such as the Coalizão pelo Pampa-Pampa Coalition [89], Instituto Curicaca-Curicaca Institute [90], Rede Campos Sulinos-South Brazilian Grasslands Network [91], and the Comitê dos Povos e Comunidades Tradicionais do Pampa-Committee of the Traditional Peoples and Communities of the Pampa [92] must be strengthened and expanded. In addition, political will and the legal apparatus aimed at reducing the use of pesticides need to be stepped up.
Monitoring and inspection of the use and commercialization of pesticides in the Rio Grande do Sul are carried out by the Secretary of Agriculture, Livestock, Sustainable Production, and Irrigation of the state [93]. However, although Rio Grande do Sul is one of the Brazilian states that most commonly uses pesticides, specific laws and public policies concerning pesticide use are insipient in the state. Of note, Rio Grande do Sul is part of the "Uruguay-Argentina-Brazil" triple border, a region where large amounts of illegal pesticides enter Brazil [93]. Considering this aspect and the huge impacts of pesticide use on Rio Grande do Sul's ecosystems and human population [94], state authorities must increase inspections of pesticide use and curb the entry of illegal pesticides through the triple border. The growing and indiscriminate use of pesticides must be controlled by frequent testing of pesticide residues in food and drinking water, which are important contamination sources for the population [95]. Even with all these actions being put into practice, it could be difficult to measure the effects of pesticides on Pampa's ecosystems and biodiversity [94].
Research institutions can collaborate with the conservation of this biome by developing more studies concerning Pampa's biodiversity and the impacts of anthropogenic activities on the biome. We stress that limited information about pesticide pollution in the Pampa is available, and therefore additional studies need to be carried out to better describe the impact of this problem in southern Brazil.
Actions to prevent, mitigate, and restore the impact of land-use changes and related pesticide pollution must also be investigated and applied. Environmental education actions should be promoted to make rural producers aware of the inappropriate use of pesticides. The use of adequate personal protective equipment by workers handling pesticides must be reinforced by continuous surveillance and education campaigns. In addition, food production strategies less dependent on the use of pesticides (e.g., permaculture, integrated pest management) should be encouraged.
It is important to stress that a high and abrupt reduction in pesticide use will result in losses in production per area that could impact especially smaller producers that have lower revenues from their production. Therefore, it is essential that measures to reduce pesticide use be accompanied by economic alternatives for farmers impacted by potential reductions in their income. Training, courses, and financial subsidies to support the development of businesses based on agroecology and artisanal products are viable alternatives. In Rio Grande do Sul, free fairs and e-commerce are also means that help producers of organic and traditional crops market their products in large centers (e.g., Porto Alegre city) [96,97], with great potential for expansion of sales of organic products through these means. In addition to these alternatives, farmers' stores, producers' markets, door-to-door sales (box schemes), and direct harvesting by consumers at production units (pick your own) are emerging options to advance the trade in pesticide-free products in Rio Grande do Sul. These above-mentioned alternatives make up the so-called "short chains and alternative agrifood networks" [98].
Rio Grande do Sul must also develop programs to strengthen the "bioecological bioeconomy", the arm of the bioeconomy based on biodiversity and processes that "optimize the use of energy and nutrients, promote biodiversity, and avoid monocultures and soil degradation" [99] in a regionally concentrated system (e.g., focused on products with territorial identity) [99], in addition to the "biomaterial bioeconomy", which emphasizes upgrading and conversion of biological raw materials into higher value-added products [99,100]. In the context of the problems discussed in this article, bioeconomy includes the use of Pampa's biodiversity as a source of useful molecules for the pharmaceutical, cosmetic, and food industries; increasing ecotourism focused on the diverse Pampa's landscapes; and the better use of native plant species in gastronomy and gardening. More information about these and other bioeconomic alternatives can be found in Ellwanger et al. [100].
Developing a bioecological bioeconomy would help the Rio Grande do Sul reduce its economic dependence on activities that are highly harmful to the environment, such as cash crop plantations. The basic conditions for this transition already exist. Rio Grande do Sul (i) has one of the highest gross domestic products (GDPs) in Brazil [101]; (ii) has a robust higher education system; (iii) is considered a leader in the field of technological innovation; (iv) is one of the Brazilian states that produce the most scientific research (reaching 11.5% of the national production) [102]; in addition to (v) bordering two countries, Argentina and Uruguay, which would facilitate integrated conservation programs, also based on tourism. These and other factors could facilitate the bioeconomy's development in Rio Grande do Sul and should be better used to overcome economic models that contribute to the pollution and degradation of the Pampa biome.
Finally, we recognize that the alternatives to facing the problems related to pesticide pollution in the Pampa biome described in this article are limited compared to the size of the problem. However, we hope that this article will contribute to expanding the discussions about the most effective actions and ways to limit the harmful impacts of pesticides on Pampa's biodiversity and human population.

Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is not applicable to this article.