Environmental Health and Toxicology

There are a number of chemicals, which causes lung cancer and one of them is 3, 4- benzopyrene. Benzopyrene mutates three key positions in the p53 gene, which leads to lung cancer. Hence, the correct answer is option C.

Skeletal fluorosis or osteoporosis is a bone disease caused by excessive accumulation of fluoride in the bones. In advanced cases, skeletal fluorosis causes pain and damage to bones and joints. Due to a high fluorine concentration in the body, the bone is hardened and thus less elastic, resulting in an increased frequency of fractures. Other symptoms include thickening of the bone structure and accumulation of bone tissue, which both contribute to impaired joint mobility. Ligaments and cartilage can become ossified. As a result, bone flexibility decreases making the bone more amenable to fractures.

Airborne fluorides have caused more worldwide damage to domestic animals than any other air pollutant. Fluoride is not biodegradable and gradually accumulates in the environment through the food chain, in human and animal bodies, where it settles in bones and teeth. Thus, the correct answer is option A.

Pollution is defined as addition of harmful components in the environment which alters the composition of an environment. The harmful component is known as pollutant. Enriched air, also called as oxygen enriched air, or nitrox has more oxygen in it. The two most commonly used nitrox mixtures are 32% and 36% oxygen with less nitrogen. The most common use of nitrox mixtures containing higher than normal levels of oxygen is in scuba diving. The result of breathing elevated partial pressures of oxygen is hyperoxia, an excess of oxygen in body tissues. 

Hydrogen cyanide stops the transport of oxygen around the body and may also cause sudden loss of consciousness, weakness, headache, confusion, nausea, vomiting, irritation and eye infections. People with sensitive kidneys, respiratory tract (air passages and lungs), skin or thyroid are more prone to hydrogen cyanide poisoning. Part of the reason why hydrogen cyanide is considered potentially more dangerous is that some individuals are unable to detect it by smell which creates damage to neurons.

Many microbial agents can commonly move from an affected person to someone else in a variety of ways. Such disease-causing microbes can spread through the air. This occurs through the little droplets thrown out by an infected person who sneezes or coughs. Someone standing close by can breathe in these droplets, and the microbes get a chance to start a new infection. Examples of such diseases spread through the air are the common cold, pneumonia and tuberculosis. Obviously, the more crowded our living conditions are, the more likely it is that such airborne diseases will spread.

Arsenic poisoning is well-documented to cause 'crippling' skeletal deformities, a condition often referred to as arsenicosis, particularly in areas with high groundwater arsenic levels.

Lead is a cumulative toxicant that affects multiple body systems. Lead in the body is distributed to the brain, liver, kidney and bones. It is stored in the teeth and bones, where it accumulates over time. There is no known level of lead exposure that is considered safe. Lead can have serious consequences for the health of children. If lead accumulation occurs for long in body, it attacks the brain and central nervous system to cause coma, convulsions and even death. Children who survive severe lead poisoning may be left with mental retardation and behavioural disorders.

Ozone layer is part of earth's atmosphere. Ozone is basically found in stratosphere. Ozone layer contains high concentration of ozone formed due to reaction of oxygen with UV radiations. It is vital to human life on earth because it absorbs biologically harmful ultraviolet radiations from sun. Direct exposure of such rays can cause serious illness and skin problems. However ozone chemically forming in earth's surface is lethal in many ways.

Ozone depletion occurs widely in the stratosphere due to an increased amount of $ { CFC }{ s } $ which causes various types of skin cancer and mutations.

Thinning of ozone layer increases the amount of ultraviolet radiations reaching the earth surface. The increased UV-B radiation increases incidence of cataract, skin cancers herpes, dimming of eyesight, photo burning, snow blindness and deficient functioning of immune system. 

Ozone gas is found in the stratosphere of the atmosphere. The ozone layer protects the earth from the harmful ultraviolet rays emitted from the sun. Ozone layer depletion has many adverse serious environmental effects. It may result in global warming. The ultraviolet radiations exposure leads to skin cancer like malignant melanoma. It also increases the rate of ageing in an individual. It also has harmful effect on the eyes. It may cause cataract. Immune system is also affected by this harmful ultraviolet radiations. Apart from humans, ozone layer depletion affects marine, aquatic and other forms of life as well.

The ozone layer is present in the stratosphere above the Earth. The layer of ozone is responsible for the absorption of the harmful ultraviolet radiations from the solar radiations. Due to ozone depletion, these radiations enter the Earth's atmosphere and cause skin cancer. The radiations can also damage the eye and other exposed parts of the body. The radiations can also cause mutations like thymine dimer formation or breaking of the hydrogen bonds. 

Destruction of ozone can cause skin cancer, cataract and can hinder growth of plant. Ozone prevents the harmful radiations from reaching the surface of earth. The UV radiation has enough energy to cause adverse effects on all life systems, especially humans. It can destroy parts of DNA molecules that stores and propagate genetic information from one generation to another generation.