Effect of Biodegradable Multiple Pesticides on Aquatic Biospecies

Abstract

The subject of pesticides usage has become a serious threat to sound ecological sustainability. In this regard, the effects of biodegradable multiple pesticides on aquatic biospecies have been discussed in detail. They are always different forms of pesticides in the aquatic environment. These pesticides are bioavailable in both water body and sediments, and the aquatic species do feed on water and sediment materials. The pesticides are also capable to bioaccumulate and biomagnify along the food chain. These attributes pose serious risks to human health and the sound ecological system that is needed for life sustainability. Cancer, infertility, lesions, headache, dizziness, eye irritation, vomiting, dermal diseases, and gastrointestinal problems have been observed as the direct pesticides effects on biological populations in several countries. The needs for different safety guidelines required for pesticides manufacturing and usage have been recommended.

1. Introduction

Aquatic ecosystems are complex systems that are the compass of nutrients, biotic pelagic and benthic communities, pools of detritus and that have the bulk of both water and sediment [1, 2]. Anthropogenic activities lead to multiple types of stresses, including emissions of pesticides and nutrients into the environment [3, 4]. These pesticides are capable of affecting species in the aquatic ecosystems and the nutrients can cause eutrophication. Emissions of pesticides can also lead to accumulation in the environmental compartments of water and the complex matrix that forms the sediment. Simultaneous pesticides bioaccumulation into organic substances such as biota and detritus prove to have an adverse effect on aquatic bio-species. Various toxicokinetic models have described these types of accumulations [5].

1.1 Environmental pollution

Recently, the cry for environmental pesticides pollution is heard from every nook and crannies of the world. Pollution of pesticides has now become a distinct threat to the very existence of mankind and animals on this earth. It is a problem challenge for our days. In the past, man has been disturbing the balance of nature for comfort, wealth, and ego, but now nature has started disturbing the balance of nature. In the late century, there has been growing concern in developing countries and developed countries over the pollution effects from sources, such as sewage, pesticides, and trade effluents discharged from domestic habitations and by the industrial units [6].

The immediate catastrophic effects of pesticides pollution by some industrial units and agricultural application of pesticides have pointed out the essence of its environmental effects: prevention and control. There is now a global awareness that pesticides production and utilization activities in the future time need to be assessed for their environmental hazard or effects without any form of compromise to the said assessment. Too much rise in pesticides application and their industrial production activities in the past have led to the emission of harmful pesticides into human and aquatic habitats and have led to various ecological issues.

Disturbance of pesticides emission has become a serious threat to both human and animals life and it puts the ecosystem out of balance. Maintenance of ecological balance and environmental purity due to the sudden increase in the production of pesticides and their applications in both the home and agricultural sector should be the inclusive concern of each member of society. This situation could be improved through awareness program creation, which must gain the support of people from all works of life with the aim of enlighten them on its pros and cons and their responsibilities that will meet up with the global standard. Pesticides pollution under discussion here has a different meaning and environmental disorder to different biological organisms. Human beings feed on aquatic animals, fishes and drink untreated water. Thus, they are more susceptible to multiple pesticides effects than aquatic animals that feed on prey and uptake water only. This discussion cannot exclude how water is important to all living organisms as it sustains life as the human body depends on water for about seventy percent (70%) to function normally.

Yichen et al. [5] also pointed out the indisputable dependability of water by living organisms as it functions in every living organism cell and cell is said to be the smallest unit of life. In order to reduce and prevent the issues of pesticides pollution in an aquatic habitat, law enforcement agencies have primary responsibilities of ensuring that laws and implantation of pesticides used must be seriously put in place. Companies or industries operating along rivers, seas, and lakes banks, to mention a few, need to redirect their discharge wastes formally channeled into water bodies to a sustainable environment (Figure 1) [7].

Figure 1.

Environmental pollution.

1.2 Pesticides and environmental pollution

Pesticides pollution have different routes into aquatic organism domesticated habitat such as leaching from the agricultural farm, erosion from farmlands during rainfall, and become available in the water body through spills from industrial effluents and discharges of environmental wastes into water bodies [8]. Pesticides have different meanings to different people. Generally, pesticides are large classification or group of chemical substances that are developed to model and thereafter substitute for a unique molecule in a particular biological process. This implies that the mode of action of pesticides is peculiar to specific organism, plant, or grass such as pests, weeds to mention a few [9].

The issue of poor quality of water is of the utmost environmental problem in the human health-related issues [10]. Pollution from pesticides has contributed to the said threat and it will continue to gain more ground in as much as they are present in water bodies. The primary aim of pesticides production is mostly for specific targeted organisms or plants but their effects are non-targeted as it affects humans, animals, and plants and produces range of toxicity effects which include carcinogenicity [11] and have the ability to disrupt endocrine [12].

The wide usage of pesticides are detected across different nations such as Europe’s freshwater. In Ireland, pesticides are present beyond the European Union (EU) permission limit bound on different numbers of inspections [8, 13]. In Europe, freshwaters in the UK were found to be susceptible to pesticide pollution and in Germany, groundwater and sediment materials were specifically polluted due to pesticides applications and discharge [14].

EC legislators have provided different legislation or laws in place to prevent or minimize the discharge of pesticides and their applications in their environment. The legislation includes Water Framework Directive [15], the strategy for the prevention of endocrine-disrupting compounds [16], and the Stockholm convention [17].”

The normal water purification tools or equipment have proved inefficient to remove toxic pesticides substances from water bodies [16]. The need to have an efficient method is of utmost importance to be researched. Up to now, the best efficient pesticides removal methods include photocatalysis and adsorption [18, 19].

Human activities like land cover change, urbanization and industrialization have impaired ecosystems for several decades in order to increase the access to natural resources for an exponentially growing population [20, 21]. The activities of humans have led to the impairment of the planet earth’s boundaries and are causing biodiversity loss and climate changes [22, 23]. Keeping the account of human activities on the global freshwater, land use, acidification of oceans, rivers, lakes, and streams are already tending to a threshold value [22]. Rockström et al. [22] in their study have noted that the human population is facing un-quantifiable threats due to freshwater contamination by different forms of contaminants that are unknown in an aquatic environment.

More than 14 million different chemical compounds exist, out of which above 100,000 synthetic chemical compounds are frequently used in consumer products in different countries of the world for different purposes [24, 25]. Thus, an uncertain number of chemicals may potentially be released into the aquatic environment by diverse routes like point sources, remobilization from contaminated sediments, and groundwater input (Figure 2) [26].

Figure 2.

Pesticides pollution.

1.2.1 Routes of pesticides into aquatic environment

A lot of literature has identified different routes of pesticides to the aquatic environment [27, 28]. It was observed mainly that the rate at which pesticides enter the aquatic environment is not the same with all pesticides. The routes mainly depend on the physiochemical properties, that is, the ability of pesticides to persist for several years or a decade in an environment without totally losing their concentrations. The land use and climate changes facilitate pesticides entering into an aquatic environment where it was not originally applied. Majorly, pesticides enter into aquatic environment through wind drift during pesticides applications, erosion due to rainfall immediately after pesticides applications to agricultural farmland, migration of living organisms that were affected by the pesticides concentration into the aquatic environment, and through drainage to mention a few.

1.3 Mixture of pesticides effect

In an aquatic environment, different contaminants especially pesticides pollution have been found with different names and concentrations. These pesticides have been found to integrate with each other and form different pesticides with different concentration levels in aquatic habitat [29].

In this century, many agricultural investors (e.g., farmers) have priority for growing high-yielding species of different crops to meet the increasing population demand for food. However, one of the essential phenomena of this subject of discussion is that varieties are that most of those crops are highly prone to different diseases and pests [30], which was evidence to cause about 40–50% of crop loss [31]. As a result of this information, the use of pesticides to protect crops from those pests and diseases, and reduce crop lost, herewith improving the yield quality as well as quantity became necessary [32, 33, 34]. In Bangladesh, pesticides were introduced in 1951 but their uses were negligible until the end of the 1960s [35]. An exponential increase in their uses have occurred from 7350 metric tons of active ingredient of pesticides in 1992 to about 45,172 metric tons in 2010 [34].

One of the major reasons for the high rate of pesticides application in some countries such as Bangladesh is due to the adoption of the government policy to increase the control of pests and diseases of crops through a chemical measure process in order to increase overall crop yield and to prevent and control crops losses [34].

More so, about eighty-four (84%) of pesticides significant materials are in the family of 242 trade names of a different group of chemicals namely: organochlorine compound, carbamates, organophosphate, neonicotinoids, pyrethroids, nitro compound, heterocyclic pesticides that are registered in Bangladesh and other parts of the world and are used in the agricultural sector and household applications [35]. However, organochlorine pesticides have been banned in Bangladesh in 1993 [36] and in many countries of the world because of the nature of their toxicities in both human and aquatic environments and they are capable to bioaccumulate and biomagnify in the biological process of feeding such as food chain [37, 38]. Considering other group of pesticides available, the organophosphorus pesticide has gained popularity in the application by farmers in Bangladesh. In addition, more than 35% of their farmers use organophosphorus pesticide to treat varieties of crops for protection reasons [39].”

Pesticides applied on agricultural land have the capability to reach the aquatic environment through several ways which may include but are not limited to leaching of groundwater, spray drift, runoff of surface water, disposal of pesticides containers nearby or inside rivers, cleaning of pesticides equipment in rivers or lakes [40, 41, 42]. The indiscriminate use of pesticides and their disposal methods constitute a major threat to the aquatic organism and have led to eco-toxicological risk. More than sixty percent (60%) of animal protein emanated from fish [43]. Since fish serves as the major source of protein in man’s food, the indiscriminate use of pesticides in an aquatic environment needs to be reviewed as their toxic effects on fishes are harmful to their normal behavior, physiology and sometimes lead to their deaths [30, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54].

Different studies [55, 56] have shown the adverse effects of pesticides on fish species which include but not limited to histopathological alterations such as kidney, gonad, liver, and gill tissue. A study by Dutta and Maxwell (2003) reported that bluegill fish shows histopathological alteration in the ovary namely; cytoplasmic reaction, cytoplasm, and karyoplasmic clumping, necrosis, and thinning of follicular lining exposed to diazinon, atretic oocytes, and adhesion (Figure 3).

Figure 3.

Mixtures of pesticides.

1.4 Effect of pesticides on aquatic organisms

Manufacturers of pesticides especially those that are licensed by the legislators of their respective countries always ensure their products to be selective and specific to targeted organisms in terms of their toxicity effects. Yet, some of them are totally specific, a few of them are relatively specific while the majority of them are not due to their biodegradable process. Pesticides toxicity most times always depends on the mode of applications. Pesticides applied during wind action and those applied closely to rainfall time always drift from the specific area of application to the non-targeted area. Biodegradation and degradation of pesticides vary from one pesticides compound to another. This is always due to their respective elements that are made up of a particular chemical organic compound. Some are more toxic than their original parent compounds while others are less toxic during the splitting of the individual elements that are made up of the compounds [57].

The susceptibility of humans and animals to pesticides mixtures always produces toxicological interactions effects [58]. Exposure effects of multiple pesticides may be toxic or less toxic or have the same effects with exposure to their individual component. Most times, it is more poisonous to be susceptible to pesticides mixture than exposure to their respective individual element at different time period due to their effect of synergy [58].

Some of the related terminologies used for explaining toxicological interactions of exposure to multiple pesticides include but are not limited to:

1. Effect of synergy: This happens due to the greater effects of two pesticides affecting biological organism at the same time than the sum of their individual effects when they are applied individually or separately.

2. Effect of antagonist: This exists whenever two pesticides are applied at the same time and each of the pesticides action interferes with the other pesticide that was mixed or combined with.

3. Effect of additive: It usually takes place or happens whenever the addition of two pesticides has the same toxicity effects with the sum of the effects of the individual pesticides applied separately.

4. Potentiating: It happens when a pesticide produces a toxic effect anytime is applied together with another pesticide(s).

The effects of exposure to the interactions of pesticides depend on the quality of their application and the prediction of their effects requires enough information regarding the factors responsible for pesticides exposures such as magnitude, time, and toxicity to mention a few.

Antagonism process of pesticides interaction includes functional, chemical, dispositional, and receptor. Functional antagonism occurs when two pesticides counterbalance one another by opposite effects on the same physiological function. Chemical antagonism is a chemical reaction between two pesticides to produce a less toxic product [59].

Pesticides enter into the aquatic environment through different routes such as direct application of pesticides to rivers, seas, lakes, or any other water source to prevent or control weeds, pests, or diseases of crops [59]. Atmospheric nature may truly take place due to the movement of the spray of pesticides from crops surfaces or soil surfaces to the aquatic environment. Yeo et al. [60] noted from their work the effects of atmospheric concentration of pesticides compounds such as organochlorine pesticides which include: Dichlorodiphenyltrichloroethane (DDTs), heptachlor, endosulfan, chlordane, hexachlorocyclohexanes have reported to have minimum and maximum seasonal variation in a rural setting [61]. Furthermore, plantations have been shown to help in reducing surface soil erosion and influence pesticides biodegradation over time, and could lead to the concentration of pesticides in water [62] (Figure 4).

Figure 4.

Effect of pesticides on aquatic organisms.

1.4.1 Volatilization

Pesticides have the potential to change their state from one form of state of matter into another [63]. The process of the term pesticide volatilization is motivated and catalyzed by pesticides transportation such as soil, water, plant, and surface matrix sorption [64], transportation by air, and diffusion through the boundary layer. The following factors are said to influence the volatilization of pesticides which include physicochemical properties of pesticides [65] including vapor pressure, water solubility, Henry’s law constant, adsorption properties, and some environmental factors including soil moisture and soil/air temperature.

1.4.2 Photolysis

Photolysis of pesticides occurs whenever pesticide compounds have adequate energy from light and causes decomposition of the compound molecules through either direct or indirect process [66].

Photolysis is also known to involve in some form of organic pesticides compounds reaction such as carbon bond, isomerization, decarboxylation, and ester cleavage [67]. Different type of photolysis rate of reaction always depends on the absorption spectrum of the pesticides involved (Dureja, 2012; [68]). Direct photolysis is said to take place when pesticide absorbs directly from light energy and result in some form of chemical reaction [69].

Pesticides mixture toxicity is always difficult or complex to predict their toxic effects. Various models that are used to predict a toxic mixture of pesticides effects are always based on their structures activity composition and are always formulated for the complex organic compound of heavy pesticides.

However, different pesticides mixtures are expected to change the behavior of biological species from their combined effects than those effects from the concentration of a single compound.

A lot of studies have been carried out on the pesticides effects in relation to different ecological settings which mainly focused on the restricted compound known as organochlorines [70, 71, 72]. This said organic compound is capable of assimilating into crops, animals, and entire ecosystem at high rates of pesticides concentration emission [73, 74].

1.4.3 Degradation of pesticides

Several researchers were able to point out that “the degradation of pesticides rates are faster and higher under hot weather. In addition, pesticides solubility is temperature-dependent, that is, the higher the temperature the more soluble it becomes and light intensity was also found to be responsible for the high rate of pesticides degradation [75].” More so, hydrolysis has been found as one of the factors that are responsible for the speedy degradation of pesticides especially when combined with changes in pH and aerobic/anaerobic conditions. The transformation process is mediated by living organisms such as plants, algae, bacteria, or fungi as a result of biodegradation. Complex pesticides like carbon compounds such as synthetic pesticides are used for crops growth as the nutrient substrate is capable of degrading into other compounds or elements [76, 77, 78].

Degradation process of the majority of pesticides is mostly affected by bacteria and fungi such as DDT pesticide, chlophyrifos, and cypermethrin. Some factors such as plants, animals (e.g., earthworms), soil moisture, temperature, pH, soil organic matter, carbon source concentration of pesticides greatly influence microbial degradation of pesticides [79, 80, 81, 82, 83, 84, 85]. On the whole, most of the microbial activities are found during warm temperatures and in moist soil [9].

During the application of pesticides to a specific area of concern, for instance, crops farm, such pesticides concentration may be watered down by irrigation, runoff water, leaching, rainfall, drainage to the non-targeted environment like groundwater usually pollute aquatic habitant. In addition, pesticides present in the atmosphere, water, soil, or sediment can be degraded via photolysis, hydrolysis, microbial degradation, and biotic uptake [9].

Few workers of the Environmental Protection Agency (EPA) have researched on the possible effects of combined pesticides on aquatic biological species, most especially fish. They reported from their studies that the combined effects of pesticides are often determined as a simulation of their separate effects. Their findings may not mirror the combined effects of pesticides as one may expect because pesticides exist in synergistic form. After their finding, much work has been published in respect of the toxicity effects of combined pesticides effects on fishes and other aquatic organisms. They later found out that accurate and comprehensive data are required to model the effects of pesticides mixture on aquatic and any other living organisms’ population.

The toxicity of pesticides on aquatic organisms can be measured in a number of ways. The World Health Organisation [86] measures the toxicity of pesticides under the following headings.

1. Toxicity effect of pesticide(s) on microorganisms;

2. Toxicity effect of pesticide(s) on aquatic organisms;

3. Toxicity effect of pesticide(s) on terrestrial organisms.

The World Health Organisation only reports the toxicity of individual pesticides in their study on the effects of pesticides on the targeted organism [86]. Most of the harmful pesticides such as LC50, LD50, and the physiochemical pesticides properties were considered (Figure 5).

Figure 5.

Degradation of pesticides.

1.5 Effects of pesticides on human health

The use and improper handling of pesticides during their application cause a lot of problems to human health in developing countries. Many studies have pointed out the occupational health hazards of farmers posed by the unsafe use of pesticides. The adverse effects usually observed by farmers after the usage of pesticides on their farms include but are not limited to eye irritation, vomiting, and headache. About eighty percent (80%) of farmers are aware of the adverse health symptoms poses by pesticides as a result of their intoxication at the time of their applications [42].

The outcomes of their study on the adverse effects of pesticides have similar results with other research works carried out in other developing countries. For instance, Dasgupta et al. [87] reported “negative health effects such as headache, dizziness, eye irritation, vomiting, dermal diseases and gastrointestinal problems after pesticide application in different parts of developing countries.” More so, a study by Miah et al. [88] found some similar negative health symptoms. Also, nausea in farmers that grow vegetables in south-east Bangladesh was attributed to pesticides effects. The majority of the negative health effects or signs were reported after the application of pesticides in some countries in South Asia like Pakistan, India, and Nepal [89, 90, 91].

However, most of the negative health issues reported by the farmers after pesticides application were due to their inability to follow safety measures on the labels of the pesticides such as spraying pesticides without the use of a nose and mouth mask, covering shoes, and without covering other part of their body effectively [87, 88].

Although, a report issued by Sumon et al. [42] stated that about 82% of farmers normally cover their faces and body with clothes during pesticides application. However, mere covering of the face and body are not enough preventive measures to observe during pesticides application. The more advanced ways of pesticides effects preventive measures during application require farmers or pesticides users to follow the guidelines stipulated by Kabir and Rainis [92]. In their study, they gave some preventive measures required by every pesticides applicator to observe during pesticides application which include: wearing gum-boots, hand gloves, masks during pesticides application and washing of spraying equipment, and taking bath immediately after application.

Furthermore, to reduce or eliminate the dilemma of pesticides risks, it must be the primary responsibility of both governmental and non-governmental organizations to shoulder the responsibility of creating awareness programs in the communities where the pesticides applicators lived. More so, the government must be responsible for the training of farmers to ensure that agricultural workers have good knowledge of the protective guidelines or measures. To achieve this, pesticides industries can bring about product stewardship programs making the industries themselves co-responsible for their products during usage in the field, and the storage. Furthermore, the public sector that is, the government needs to ensure basic training among the agricultural workers that use pesticides for farming to gather knowledge and to build awareness on the safe use and handling of pesticides and subsequently can introduce laws on the use of pesticides and the license for pesticide spraying only for the trained farmers.

In order to create a sound ecological environment, the total removal of harmful pesticides (Chlorfenvinphos, Diuron, Atrazine, Endosulfan, Alachlor, Pentachlorophenol to mention a few) that were banned as reported in their studies as a result of their persistence in the environment should be implemented without any form of compromise to the said assessments [15, 93, 94, 95].

Pesticide-related pollution has been causing a persistent and continuous environmental problem [96]. Pesticides pose potential risks to air and water quality, crops, animal health, and human health, to mention but just a few. Significant issues related to pesticide use and application, include over-application, contamination of surface and underground water [97], and drift to unintended targets environment thereby affecting non-target organisms.

Pesticide drift which signifies the amount of pesticide active ingredient that is deflected out of the treated area by the action of air currents has the potential to affect non-target organisms and the environment [98]. Greater proportions of pesticides concentration were unable to reach the targeted area [99]. However, the presence of pesticides concentration in an unwanted area always leads to the loss of some crops, wildlife population and sometimes cause chaos in natural environment [100]. In the past, the EU has experienced serious concerns about the dispersal of pesticides categorized as persistent organic pollutants (POPs). These POPs are capable of transporting across international boundaries far from their original sources, even to regions where they have never been used or produced (Figures 6 and 7) [101].

Figure 6.

Effect of pesticides on human health 1.

Figure 7.

Effect of pesticides on human health 2.

1.6 Field of ecotoxicological study

The increase in usage of pesticides on agricultural farms has led to ecosystems disturbance. As a result of this incident, the need for research on how pesticides should be applied to increase agricultural productivity without compromising the ecological standard became necessary over the years. The study of the effect of chemicals/pesticides on biological species is known as ecotoxicology. The science of ecotoxicology and environmental toxicology [102] includes:

1. Mathematics

2. Environmental biology and

3. Chemistry

Due to the involvement of different disciplines, they are different aims of ecotoxicology research [102] which include the following:

1. As a scientific discipline: It involves understanding the fundamentals of the interactions between chemicals and biological systems on different levels of complexity and curiosity-driven.

2. As a technological field: It connotes the development of bio-assays on various levels of complexity, for different compounds and different environmental compartments; development of models of distribution, fate and effects of chemicals in the biosphere; and chemical and analytic techniques.

3. As an input provider for environmental regulation: It provides the scientific basis for environmental quality standards that ensure ecosystem services; sustainable development and ecosystem health; provides clean-up goals and strategies; and provide options (Figure 8).

Figure 8.

Field of ecotoxicology.