Assignment Code: MEV-004/TMA/2022-23

Course Code: MEV-004

Assignment Name: Environmental Toxicology

Year: 2022-2023

Verification Status: Verified by Professor

Total Marks 100

Attempt any five questions. All questions carry equal marks. 5x20=100

1. Define Environmental toxicology. Describe some sources of toxicants harmful to the environment and human health.

Ans) Environmental toxicology is a field of science that looks at the harmful effects of different chemical, biological, and physical agents on living things. It is a multidisciplinary field. Ecotoxicology is a branch of environmental toxicology that looks at how dangerous chemicals affect populations and ecosystems.

Rachel Carson is known as the "mother" of environmental toxicology because she made it a separate branch of toxicology with the publication of her book Silent Spring in 1962. This book talked about the effects of pesticide use that was not controlled. A lot of Carson's books was based on a series of reports by Lucille Farrier Stickel about how the pesticide DDT hurt the environment. At any point in their lives, organisms can be exposed to different kinds of poisons. Some organisms are more sensitive to poisons than others.

The position of an organism in its food web can also change how toxic it is. When an organism stores toxic substances in fatty tissues, this is called bioaccumulation. This can lead to a trophic cascade and the biomagnification of certain toxic substances. When something breaks down, it gives off carbon dioxide and water into the environment. This process is usually limited in places where toxic chemicals are in the environment.

Harmful chemical and biological agents like toxicants from pollutants, insecticides, pesticides, and fertilisers can hurt an organism and its community by reducing the number of species and the kinds of species that live there. Changes in the way people live affect the ecosystem by making it less stable and productive. Even though laws passed in the early 1970s were meant to reduce the harmful effects of environmental toxicants on all species, McCarty has warned that "longstanding limitations in the implementation of the simple conceptual model that is the basis of current aquatic toxicity testing protocols" could lead to an impending "dark age" in environmental toxicology.

Sources

Toxic agents can be chemical, physical, or biological, and they can make the body sick. There are chemical (like cyanide), physical (like radiation), and biological agents that are toxic (snake venom). There are many toxic substances, and there are different ways to group them. Classification can be done by both types of exposure and types of users. These are some of the different poisons:

Natural Pollutants

Pollutants can also be released by the way things work in nature. For example, volcanoes emit particulate matter, sulphur dioxide, hydrogen sulphide, and methane. Smoke, unburned hydrocarbons, carbon monoxide, nitrogen oxides, and ash are all things that come out of forest fires. If you breathe these in, they can be bad for your health. Particles are given off by dust storms, and salt particles are given off by the oceans. Pollen and spores are made by plants, and they can cause breathing problems and allergic reactions.

Water pollutants

Surface waters can get dirty from both single and multiple sources. The discharge of industrial waste into water is an example of a point source. A nonpoint source of pollution is when farmers put fertilisers and pesticides on their fields. When it rains, these chemicals get into the surface water. Organic and inorganic wastes, as well as dangerous chemicals, are found in industrial wastes that are dumped into waterways. When people drink this contaminated water, it makes them sick.

Soil pollutants

When trash is not thrown away properly, the soil also gets dirty. Domestic waste, solid waste, electronic waste, municipal waste, and agricultural waste, all of which contain chemicals that are bad for living things, are some of the things that pollute the soil. More agricultural toxins, like pesticides that don't break down, stay in the soil for a long time and get into the food chain, which is bad for health. Organochlorine compounds like DDT, aldrin, dieldrin, and chlordane are the most dangerous and toxic pesticides.

2. Describe the various exposure routes of toxicants in the human body with suitable examples.

Ans) The amount of toxicant that gets to the target tissue, such as bone, fat, and so on, depends on how much of the toxicant is absorbed, where it goes in the body, how it is broken down, and how quickly it leaves the body. The cell membrane lets only certain things through. So, only certain things can get through. This depends on how well the substance dissolves in lipids and other things. Most dangerous substances move through cell membranes by diffusion, and lipids make up 75% of cell membranes.

A toxicant's electric charge is also an important factor in how it spreads. So, toxic substances that aren't ionised spread more easily than those that are. Phagocytosis is a very important part of how the body gets rid of particles that get into the lungs. Asbestos dust and silica dust are taken in by white blood cells in the respiratory tract through a process called phagocytosis. Pinocytosis is the process by which the small intestine absorbs substances that dissolve in water.

Plasma

The way proteins bind to plasma in humans can be different between and within chemical classes. It is also unique to each species. Humans are the only species whose bodies bind acidic drugs better than any other. There are also other things that can change the number of proteins in the plasma. Serum albumin can go down because of pregnancy, poor nutrition, carcinogenesis, a liver abscess, kidney disease, or old age. The levels of á1-glycoprotein can go up with age, inflammation, infections, being overweight, kidney failure, or stress. These qualities cause changes in the body's temperature, acid-base balance, and the way chemicals bind to proteins.

Liver and Kidney

Both of these organs are very sensitive to toxins and store more of them than any other tissue in the body. Organochlorine pesticides and organic solvents like trichloroethane and methyl chloroform are easily taken in by the liver because they are lipophilic. They can stay in the liver for a long time if they don't change into things that dissolve in water. Heavy metals that don't dissolve in water are often stored in the liver. Some poisons can also be kept in the liver. For example, the drug quinacrine, which is used to treat malaria, builds up in the liver because of reversible intracellular binding.

The concentration in the liver can be many thousands of times higher than the concentration in plasma. Bowman's capsule makes it hard for large molecules like proteins to pass through the walls of the kidney. Also, the cells of the proximal convoluted tubule can take in metals like cadmium and mercury that are not bound. Inside the cell, they bind to metallothionein. This makes the toxic substances stay in the kidneys longer. The liver stores ten times as much cadmium as the kidneys, and it can be kept there for at least 10 years. Last, bioaccumulation in the kidneys leads to kidney failure all the way to the end.

Blood

Toxins are mostly carried to their target tissues or reservoirs by the circulatory system and other parts of the bloodstream. Erythrocytes and lymph also move the harmful substances. Absorption also depends on how the body works and how the drug works physically and chemically. So, toxic substances move back and forth between the blood and the tissues. Most poisons move from the blood to the tissues by a simple process called diffusion.

Toxin distribution is also affected by the amount of tissue, the amount of blood flow, the size of the molecules, and how well they dissolve in lipids. Toxins that can get into water are kept here. Bisphenol A also goes after the blood when it comes in contact with heavy metals like arsenic, thallium, cadmium, and chlorinated pesticides. When the poisons get into the bloodstream, they bind to proteins in the plasma, such as albumin, transferrin, globulin, and lipoproteins. Most dangerous substances are known to bind to a protein in the blood called albumin.

Passage of toxicants across placenta

Toxins can pass through the placenta and harm the growing foetus through a process called diffusion. When the toxicants are lipid-soluble, it happens quickly and easily. So, the foetus is exposed to almost all drugs, even if the mother takes drugs with low lipid solubility.

3. What are chemical toxicants? Describe in detail the exposure classes with reference to air, water, and soil pollutants.

Ans) Chemical poisons are put into different classes based on what they are made of and how they hurt people. Toxosis is the name for any illness or condition that comes from being exposed to a poison. The word toxicosis is sometimes used instead of poisoning or being drunk. 1.Classes of exposure are the main way to group chemical toxins. 2. User classes.

Exposure Classes

The toxicants under this class are present in domestic and occupational environment. (Ex: food, water, air, soil).

User Classes

This type of toxicants includes drugs of abuse, therapeutic drugs, agricultural chemicals, food additives, metals, solvents, and combustion products.

There are many point and nonpoint sources that pollute surface water. A point source is something like the waste from an industrial plant or a sewage treatment plant. A nonpoint source is things like pesticides and fertilisers that run off into different bodies of water when it rains. The soil and water are polluted by things like organic waste, solvents, and inorganic wastes like toxic metals. Also, industrial accidents can cause a lot of pollution in the area. In addition to the pollutants listed above, pesticides, fertilisers, detergents, and metals are also important pollutants that come from cities. Permanent fertilisers and pesticides that are put directly on the soil move from the soil to the water and then into the food chain. In another way, they get into the water systems when they leach out of the soil or get washed away by rain.

When carbon monoxide gets into a person's body, it quickly combines with haemoglobin in the blood to make carboxyhaemoglobin, which stops oxygen from getting to the tissues and affects how the heart works. When the CO level is above 100 ppm, it can cause headaches, nausea, dizziness, and trouble breathing. Any level above 700ppm is always fatal. Coal is the source of the most sulphur, so when it is burned in factories, sulphur oxides are released into the air. When the sulphur oxides get into the lungs, they cause irritation. Nitrogen oxides are a part of photochemical smog. They are a lung irritant that can cause pulmonary edoema and bleeding.

Ozone is an oxidising gas that is made when sunlight reacts with other chemicals in the air. The ozone in the troposphere is called "bad ozone" because it is bad for you. Good ozone, on the other hand, is the ozone in the stratosphere that blocks UV radiation. Chlorofluorocarbons and other chemicals destroy the good ozone (CFCs). Lead is one of the dangerous pollutants in the air. It hurts the kidneys, the nervous system, and the development of red blood cells. It also hurts the nervous system, which can cause mental retardation and blindness. Lung fibrosis is caused by dust and fibres from coal, clay, glass, asbestos, and minerals. Pneumoconiosis is the most common disease seen in coal miners. Silicosis is caused by breathing in dusts with silica in them, and asbestosis is caused by breathing in asbestos fibres.

Lead gets into water through lead pipes and lead solder. Lead gets into the soil when lead dust from leaded gasoline and hazardous waste sites falls on the ground. Children often get lead poisoning, especially in older homes and homes in the city, where paint chips that contain lead can be eaten by children. The hematopoietic system and the nervous system are mostly hurt by lead's toxicity. At low levels of exposure, children show signs of being hyperactive, having a shorter attention span, having mental problems, and having trouble seeing. Both adults and children can get encephalopathy when the levels are high. Lead hurts the arterioles and capillaries, which causes brain swelling and death of neurons.

4. Describe carcinogens and their effects on the human body.

Ans) Carcinogens are chemical substances or mixtures of chemicals that cause cancer or make it more likely to happen. When these carcinogens are inhaled, swallowed, applied, or injected, they cause cancerous tumours or make them happen more often or faster. Cancer can also be caused by changes in the DNA of a cell.

Some of these changes can be passed down from parent to child. Others may be caused by environmental factors like a wide range of lifestyle exposures (diet, smoking, physical activity), naturally occurring exposures (ultraviolet light, radon gas, infectious agents), medical treatments (radiations, chemotherapy, hormonal drugs, immune suppressing drugs), workplace exposures (occupational hazards), pollution, and household exposures.

1. Direct Action or Ultimate Carcinogens: Direct action carcinogens, also called ultimate carcinogens, are those whose structure gives them the ability to cause cancer without the host organism's metabolism being turned on first. There are nitrosamines, epoxides, ethylene imines, and a-propiolactones in this group.

2. Procarcinogens: Procarcinogens include most chemical carcinogens that are not cancer-causing at first but become so when they are broken down in an organism. Some known procarcinogens are aminozoic colourants, aromatic hydrocarbons, aflatoxins, aromatic amines, and urethane.

3. Co-carcinogens: Co-carcinogens are chemicals that help the cancer-causing process along. They can't cause cancer by themselves, but they can make other substances more likely to cause cancer. In general, cocarcinogens act as boosters in tissues where the initiation stage shows up. Some viruses, tar, pesticides, hair dyes, tobacco, alcohol, and other things can also cause cancer to spread.

Effect on Human Body

There are both radiation and non-radiation physical carcinogens. Ionizing radiation and ultraviolet (UV) light are both types of radiation. Some types of cancer in people are thought to be caused by both types of radiation. In both cases, there is a change that looks like a mutation, followed by a long period of inactivity, which can last from 10 to 20 years or more. These radiations not only act as carcinogens (mutagens), but they also act as co-carcinogens and may make the effect of carcinogens worse during the different stages of a tumour’s beginning, growth, and spread.

Cancer is thought to be caused by a number of biological agents that can be passed on. Parasites, fungi, bacteria, and viruses are all examples of these. But the role of viruses in causing cancer is much more important. It is thought that around 20% of all cancers in the world are caused by viruses that keep coming back. Cancer of the urinary bladder is linked to an infection with the parasite Schistosoma haematobium. Cholangio-carcinoma, or cancer of the bile duct, is caused by the liver fluke Clonorchis sinensis.

5. Write short note on:

a) Mutagens

Ans) A mutagen is a physical or chemical agent, either made by nature or by people, that can change the structure or sequence of DNA.

Chemical Mutagens

Charlotte Auerbach was the first person to show that a chemical could cause mutations in cells. She did this in 1942 by showing that nitrogen mustard, a part of the poisonous mustard gas used in World Wars I and II, could do this. Since then, many more chemicals that can cause mutations to have been found, and there is a huge industry and government organisation devoted to finding them in food additives, industrial waste, etc.

Radiation

Radiation was the first thing that was known to cause changes in genes. Its effects on genes were first noticed in the 1920s. Radiation was first found in the 1890s. Roentgen found X-rays in 1895, and Becquerel found radioactivity in 1896. In 1898, Marie and Pierre Curie found out about radioactive elements. Atomic physics and the study of electromagnetic radiation were made possible by these three and other discoveries.

b) Detoxification

Ans) Detoxification, also called detoxication, is the process by which toxic substances are removed from the bodies of living things, including the human body. Detoxification is just the process of getting rid of harmful substances. The liver is the main organ in the body that does detoxification. Detox, which is short for "detoxification," can mean the period of withdrawal when an organism returns to homeostasis after long-term use of an addictive substance like alcohol, drugs, etc.

In biochemistry and medicine, detoxification can be done by removing the poison from the body, giving an antidote, or using dialysis or chelation therapy. In recent years, many doctors have been promoting different kinds of detoxification, such as detox diets.

However, a UK-based charitable trust says that most detox diet claims are not backed up by evidence. There are many ways to get rid of substances like alcohol and drugs. These methods are called alcohol detoxification and drug detoxification, respectively. In alcohol detoxification, a heavy drinker's system is brought back to normal after being used to having alcohol in it all the time for a long time. In drug detoxification, withdrawal symptoms are lessened or eliminated while the addict adjusts to life without drugs.

Detoxification (abbreviated as "detox") has many different meanings, from spiritual to scientific, and has been used to describe many different practises and procedures in the human body. In humans, detoxification is easier to say because the goal of the process is to get rid of harmful chemicals from the body. This process is also called the metabolic detoxification pathway.