eChapters

Environmental contaminants are defined as substances introduced into the environment, either naturally or anthropogenically, that pose potentialharm to living organisms and ecosystems (Masindi and Muedi, 2018).These contaminants include a diverse range of pollutants, such as chemicalagents, biological contaminants and physical pollutants (Ahmed et al.,2021). Understanding these contaminants and their toxicity is of paramountimportance, given their profound implications on human health, biodiversityand the overall functioning of ecosystems (Samuel et al., 2023).Environmental contaminations are pervasive in nature and originated fromdiverse sources. Industrial activities are major contributors, releasing heavymetals, organic solvents, and particulate matter into air, water and soil(Williams, 2019). Similarly, agricultural practices contribute to contaminationthrough excessive use of fertilizers and pesticides, which often runoff intoaquatic systems, causing eutrophication and harming aquatic life (Zahoor and
Mushtaq, 2023). Urbanization and improper waste management have alsointensified the problem with plastics and emerging contaminants finding theirway into ecosystems (Singh et al., 2022). Even natural events like volcaniceruptions and forest fires contribute to environmental contamination, thoughtheir impacts are often localized and episodic compared to the persistent andwidespread pollution caused by human activities (Ernst, 2012).The study of environmental contaminants and their toxic effects is of vitalimportance for several reasons in today’s context of escalating global pollution(Hussain and Reza, 2023). First, it provides insights into the health risks posedto humans and wildlife (Pereira et al., 2015). Many contaminants, such as lead,mercury and polychlorinated biphenyls (PCBs), are known to have chronic andacute toxic effects on biological systems, affecting neurological, reproductivand immune functions (Priyadarshanee et al., 2022). These substances interactwith biological systems in complex ways, often leading to adverse outcomessuch as bioaccumulation, oxidative stress, endocrine disruption and ecologicalimbalances (Satkar et al., 2024). Heavy metals like lead and mercury are
known to accumulate in organisms and disrupt critical biological functions,while synthetic chemicals like bisphenol A (BPA) can interfere with hormonalsystems, resulting in reproductive and developmental issues (Pan et al., 2024).Such impacts underscore the need to understand how these substances interactwith living organisms, identify their exposure thresholds and mechanisms oftoxicity to formulate strategies for risk assessment and mitigation (Kumar andSingh, 2023).

Ruminants, including cattle, buffalo, sheep and goats are highly efficient at digesting fibrous plant materials, thanks to their specialized stomach anatomy comprising the rumen, reticulum, omasum, and abomasum. However, these animals are also susceptible to the accumulation of toxic minerals in the rumen or rumino-reticulum, which can significantly affect their health, productivity, and survival. This chapter delves into toxic minerals, their sources, mechanisms of toxicity, clinical manifestations, and potential mitigation strategies.
The rumen and reticulum, as integral parts of a ruminant’s digestive system, are central to the efficient fermentation and digestion of fibrous feeds. However, these chambers are also vulnerable to toxic minerals from environmental, dietary, and water sources. Toxic minerals can disrupt the rumen ecosystem, impair digestion, and negatively impact animal health. The rumen and reticulum serve as fermentation chambers, hosting billions of microbes that break down complex carbohydrates, synthesize volatile fattyacids (VFAs), and produce microbial proteins essential for ruminant health. 
However, toxic minerals can interfere with this delicate balance, leading to reduced microbial efficiency, impaired digestion, and systemic toxicity.  Toxic minerals are naturally occurring or anthropogenically introducedelements that become harmful when consumed in excessive quantities. Toxic minerals, also known as heavy metals or trace mineral contaminants, are naturally occurring elements that can become hazardous when their concentrations exceed the physiological tolerance of ruminants. The following are some of the most problematic toxic minerals for ruminants:
Lead (Pb)
Arsenic (As)
Cadmium (Cd)
Mercury (Hg)
Fluorine (F)

Abstract
Toxicants, whether naturally occurring or synthetic, present significant threats to aquatic ecosystems, leading to severe ecological damage and health hazards. These pollutants—such as pesticides, heavy metals, microplastics, and pharmaceuticals—contaminate water bodies through various routes, including industrial discharges, agricultural runoff, and insufficient wastewater treatment. They interfere with biological processes, causing problems like neurological damage, reproductive issues, and changes in water chemistry. Understanding the processes of bioaccumulation, biomagnification, bioconcentration, bioavailability and detoxification is essential for grasping how these contaminants impact aquatic organisms and human health. The rise of emerging pollutants, like microplastics and pharmaceuticals, adds further complexity, posing new challenges to ecosystem stability. Addressing these issues requires effective management and mitigation strategies, including reducing pollutant sources, improving waste treatment, and utilizing advanced detection techniques. Through research on these toxicants and their interactions, it is possible to better evaluate their effects, craft effective environmental policies, and implement measures to safeguard both aquatic ecosystems and public health.
Keywords: Toxicants, Bioaccumulation, Biomagnification, Bioconcentration, Bioavailability, Detoxification

Q1. Alpha naphthyl thiourea is less toxic

1. In an empty stomach
2. With oily food
3. Full stomach
4. Not affected

Q2. A rodenticide that blocks tricarboxylic acid cycle by competitive inhibition of the enzyme aconitase

1. Fluoroacetamide
2. Pindone
3. Chloralose
4. All the above

Q3. ANTU is less toxic in an empty stomach a) In an empty stomach it will irritate the stomach wall resulting in vomiting and throwing away the poison and hence no toxicity.

1. Absorb only with fatty materials
2. Immediate absorption and detoxification
3. All the above
4. None of the above

Understanding the Toxicity of Macrolide Endectocides

Introduction

Macrolide endectocides are a class of compounds widely used in veterinary medicine to combat internal and external parasites in livestock and companion animals. While these medications have proven to be effective in controlling parasites, there are concerns regarding their potential toxicity and adverse effects on animals and the environment.

Whar are Macrolide Endectocides

Macrolide endectocides belong to a group of compounds derived from naturally occurring macrolide antibiotics, such as avermectins and milbemycins. These compounds have broad-spectrum activity against various parasites, including nematodes, arthropods, and ectoparasites like ticks and mites. Some commonly used macrolide endectocides include ivermectin, doramectin, moxidectin, and eprinomectin.

Toxicity Concerns

While macrolide endectocides are generally safe and effective when used according to label instructions, there are instances where toxicity can occur. Factors influencing toxicity include:

Paracelsus recognized more than 400 years ago that it is “the dose that makes the poison.”Deliberate or inadvertent over dosages may cause illness, and a misplaced decimal in water or feed medication concentrations frequently results in toxicity. A general feature of modern complex poultry rations, feed mill equipment, and feed delivery to poultry farms is that any component included in a ration may at some time be mistakenly included at a higher than desired rate. This may occur through human or mechanical error. For example, sulfaquinoxaline poisoning occurs in meat-type chickens, even at recommended doses, because of high water intake in warm buildings, particularly in hot weather, or because of poor feed mixing.

Poisonous substances are widely distributed in nature. Poisoning occurs more frequently in free-range and backyard flocks and in village poultry where birds forage in neighboring gardens and fields or receive household waste and weeds cut from roadsides and fields. Some of these poisonings are malicious. Contaminated litter on the floor and in nest boxes is an added source of toxins in chickens not raised on wire.

1. ABSORPTION

Deals with the translocation of the xenobiotics. Passage of toxicant from site of adminstration to blood stream or systemic circulation.

Translocation may occur by following processes

a) Simple /Passive diffusion - most common route by which xenobiotic pass through the membranes:

? Down hill transport, No energy involvement

? It is not substrate specific.

? Small molecular weight (600) hydrophilic toxicants cross membranes by simple diffusion through aqueous pores.

? High molecular wt. hydrophobic molecules diffuse across the lipid domain of membranes.

? Follows Ficks Law of diffusion

? The rate of diffusion depends on their lipid: water partition coefficient value, Conc. Gradient, degree of ionization.

? Higher lipid: water partition coefficient and lower degree of ionization favours absorption of toxicants by this process.

Introduction

Fish is the cleanest animal, gets bath 24 hrs a day provided water is clean without any toxic material. Perhaps this was the scenario world over 5 decades ago. However, in the last few decades due to industrialisation, modernisation of agriculture and animal husbandry, human health care industry and city developments all have contributed to toxic material to water endangering the fish and the consumer, leave alone clean environment. In recent years, even intensive aquaculture also add several chemicals, pesticides, antibiotics contributing to pollution. Natural water bodies such as rivers, lakes, reservoirs, scoastal/marine waters are ultimate receivers of pollutants which also serve as the source of water for aquaculture. Although pollution control by treatment measures and awareness have improved over the years still there is a long way to achieve the clean water. Effect of toxins in aquaculture has multiple angles, differing from that of toxins on land animal. Fish depends heavily on water for respiration, physiology, reproduction, food and feeding and its very sustenance- as a supporting medium.

Aquaculture is expanding world over growing at 6-8% gradually involving more areas and species contributing a major share to total fish production with gradual decline in capture fisheries from the natural water bodies. Invariably, most of the natural water bodies are polluted with one pollutant or the other in the country. In addition, several pollutants are added to the system by various aquacultural practices. Although large quantity of information is available on aquatic toxicology, toxicology in aquaculture from health point view of fish and the consumer is meager and not focused. Against this background, it is very important to study, understand various toxicants, their mode of action, accumulation and effect on fish and the consumer. Toxicology in aquaculture is incomplete unless it includes or addresses safety of the consumers. Further, poisoning of fish in farms and wild deliberately or otherwise needs forensic studies/approach to address the issues.

The role of toxicology in the evaluation of new agrochemicals

The widespread use of agrochemicals for crop protection may expose humans, animals, and the environment to toxic chemicals. Humans may be exposed during manufacture or application, and to a lesser extent as consumers of food products containing trace amounts of residues.

Strategies of toxicity testing

No-Observable-Adverse- Effect-Level (NOAEL)

A level in which the total diet that causes no adverse effect in treated animals when compared to untreated animals maintained under identical conditions. This NOAEL is expressed on a mg/kg of body weight/day basis. Chronic and sub chronic studies are need to be carried out in different species to determine NOAEL values.

It depends on how much of the substance an organism is exposed to, but all chemicals are toxic to some degree. Toxicology studies try to figure out the exact types and amounts of harmful effects, as well as the lowest doses that won’t have any negative effects (called the “No Observed Adverse Effect Level” or NOAEL). Most data come from studies with lab animals and cells that have been grown in a lab. Using these numbers and extrapolation or uncertainty factors, it is possible to figure out an Acceptable Daily Intake (ADI). This is the maximum amount of a substance that a person can take in every day without putting themselves at a very high risk of getting sick. These numbers will be compared to how people might be exposed to a compound in the environment, including through food. This will show if the use of an agrochemical is potentially allowed.

Livestock poisoning by plants is often a result of management errors, range conditions, or the type of animal, rather than just the presence of poisonous plants. Forage availability can be influenced by drought, overgrazing and snow storms, or altered grazing patterns. Animals can become overly hungry during transportation or other management activities that deprive them of food and water for extended periods of time, thus making them more likely to graze toxic plants. Grazing during the wrong season may compromise an animal's ability to select adequate and non-toxic forages (James, 1994).

The toxicity of plants varies with environmental factors such as site, temperature, precipitation, and light, time of day and stage of growth. For example, mature oak leaves are less toxic than young leaves. Cyanogenic plants such as arrow grass are more toxic following a frost or drought condition. Nitrates can be higher in plants following heavy nitrogen fertilisation or during a drought. Certain animal factors must also be considered in livestock poisoning by plants. For example, goats are considered to be comparatively resistant to lantana poisoning than cattle. A hungry animal is more susceptible to poisoning than a full one. A full rumen slows consumption and also dilutes the toxin. Though the animals are exposed to a large number of toxic plants when they are left for grazing, five will be discussed in detail in this chapter. These include lantana, ageratum, eupatorium, oak and ferns (James, 1994).

Cyanide poisoning

Cyanide poisoning occurs in animals due to sorghum and/or other chemicals and characterized by ataxia, incoordination, cystitis, paralysis, and death.

Etiology • Sorghum – drought resistant varieties.

• Fumigants, fertilizers,

• Pesticides.

• Industrial leakage/waste, electroplating.

• Photographic processes.

1. INTRODUCTION

Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism’s cells in an effort to produce energy, maintain life, or stimulate growth. A food contains some non-nutrients, some of which may even have a detrimental influence on the consumers, while some may be inert and have no effect. Nature has endowed many plants with the capacity to synthesize a wide variety of chemical substances that are known to exert a deleterious effect when ingested by animals and are called as antimetabolites. These substances are also referred to as antinutritional factors when they are present in food/feedstuffs and influence a metabolic pathway when introduced into and/or eaten by an organism.

There is a wide distribution of biologically-active constituents throughout the plant kingdom, particularly in plants, used as animal feed stuff and as human food. The knowledge that these compounds elicit both toxic and advantageous biological responses has given rise to several investigations in recent times as to their possible physiological implications in various biological systems. It is well known that plants generally, contain antinutrients acquired from fertilizer and pesticides and several naturally-occurring chemicals. Some of these chemicals are known as ‘‘secondary metabolites’’ and they have been shown to be highly biologically active. They include saponins, tannins, flavonoids, alkaloids, trypsin (protease) inhibitors, oxalates, phytates, haemagluttinins (lectins), cyanogenic glycosides, cardiac glycosides, coumarins and gossypol and the list is inexhaustible. Some of these plant chemicals have been shown to be deleterious to health or evidently dis-advantageous to human and animal health, if consumed in appropriate amounts. Most of these secondary metabolites elicit very harmful biological responses, while others are widely applied in nutrition and as pharmacologically-active agents. The pharmacological and other beneficial effects of these antinutritional factors in plants have been reviewed here.

• General considerations

 • Cyanide poisoning

 • Nitrate poisoning

 • Nitrite poisoning

 • Oxalate poisoning

 • Strychnine poisoning

 • Arsenic poisoning

 • Lead poisoning

 • Thalium poisoning

 • Ergot poisoning

 • Carbon monoxide poisoning

 • Phenothiazine poisoning

 • Pesticide poisoning

Certain constituents associated with plants are toxic. When such items are consumed by men and animals, they become hazardous. Mold growth on food items may be the cause of toxicity. Some of them are called mycotoxins. Aflatoxins are the best examples of such a group of compounds. Sometimes processing also produces some toxins. Fumigants, smoke and some metals (mercury, lead, cadmium, arsenic etc.) used for such purposes are some such toxic constituents. Pesticides used in protecting the crops and grains during storage remain on the items and the residues are hazardous.

Introduction

Chickens are considered one of the most important hosts in the epidemiology of Toxoplasma gondii infection because they are an efficient source of infection for cats that excrete the environmentally resistant oocysts and because humans may become infected with this parasite after eating undercooked infected chicken meat.

Poultry meat is an important part of cuisine, consumed widely all over the world; therefore, consumption of uncooked or not properly cooked poultry meat may pose a risk factor for T. gondii infection in humans or animals.

Practically every aspect of the chemistry of heavy metals in soil is related to the formation of complexes with organic matter. While monovalent cations (Na+, K+, etc.) are held mainly by simple cation exchange through the formation of salts with COOH groups (RCOONa, RCOOK), multivalent cations (Cu²+, Zn²+, Mn²+, etc.) form coordinate linkages with organic molecules.

A schematic diagram showing organic matter reactions involving metal ions in soils is given in Fig. 9.1. The metals present in the solution phase as charged species and as soluble metal-organic complexes (MChe), are shown to be influenced by the activities of higher plants and microbes, both of which serve as sources of water-soluble ligands for complex formation; some metals are held in insoluble organic complexes and are non-leachable and relatively unavailable to plants.

Q. 1 Improper wheel balancing results in :-
(A) Excessive tyre pressure       (B) Excessive tyre speed
(C) Excessive tyre wear             (D) All above

Tractor is a self-propelled power unit having wheels or tracks for operating agricultural implements and machines including trailers. Tractor engine is used as a prime mover for active tools and stationary farm machinery through power take-off shaft (PTO) or belt pulley.

Power tiller is a prime mover in which the direction of travel and its control for field operation is performed by the operator walking behind it. It is also known as hand tractor or walking type tractor. The concept of power tiller came in the world in the year 1920. Japan is the first country to use power tiller on large scale. Power tiller was first introduced in India in the year 1963. Power tiller is a walking type tractor. The operator walks behind the power tiller, holding the two handles of power tiller in his own hands. Power tiller may be called a single axle walking type tractor, though a riding seat is provided in certain designs. In agricultural applications it is often required to transmit the mechanical power from its source to the point of application. The main sources of power for agricultural machines, i.e., the diesel engine for self-propelled machines and the electrical motor for many stationary machines are primarily rotary power and are transmitted by means of belts and chains. Tractor power is utilized by traction, power-take-off drives (PTO) by fluid power.

INTRODUCTION
Tractors used for agricultural activities are used with many different agricultural implements for plowing, planting, harvesting and other operations. Tractors used for construction and industrial activities are used to pull and operate machinery used for transporting loads, digging, grading and other operations. Tractors and power tillers are pivotal machines that have revolutionized agricultural and industrial practices across the globe. These versatile vehicles have played an essential role in enhancing productivity, efficiency, and speed in a wide range of operations. In agriculture, tractors are used for various tasks such as plowing, tilling, planting, irrigation, and harvesting. They serve as the backbone of modern farming, significantly reducing labor costs and the time required to complete essential activities. Coupled with specialized implements, tractors can perform tasks with remarkable precision and consistency, resulting in increased crop yields and improved soil health. Power tillers, on the other hand, offer a more compact and affordable alternative to tractors, especially in regions where small-scale farming predominates. These machines are primarily used for tilling the soil, making them particularly valuable in cultivating land in small to medium-sized agricultural fields. Despite their smaller size and lower horsepower compared to tractors, power tillers are capable of performing various tasks such as weeding, leveling, and inter-row cultivation, providing farmers with a cost-effective solution for enhancing farm productivity. Both tractors and power tillers are indispensable in modern agriculture, as they provide the necessary power and efficiency to carry out a wide range of field operations. Moreover, these machines have found applications in construction, road development, and other industries, where they are used for tasks like hauling, digging, and leveling. With technological advancements, the capabilities