Environmental Chemistry Test - 22

Smog is an air pollutant that refers to smoky fog. It causes premature death from a respiratory disease, increases the frequency of birth defect but does not cause mutation. Effect on the health of snowfall is mainly concerned with respiratory defects due to improper ventilation.

Pesticides can affect individual plants and animals in two ways. 

Ultraviolet radiations are highly energetic radiations which may cause harmful mutagenic changes. The stratosphere present in the atmosphere contains ultraviolet radiation absorbs the harmful ultraviolet radiation and protects us from several chronic diseases. Only ozone effectively absorbs the most energetic ultraviolet light, known as UV-C and UV-B, which causes biological damage. The protective role of the ozone layer in the upper atmosphere is so vital that scientists believe life on land probably would not have evolved - and could not exist today - without it.

90% of naturally occurring atmospheric ozone occurs in the stratosphere. Stratospheric ozone is very important, it removes almost all incoming UVA, and 70% of the incoming UVB at equator, 90% at poles. All aircraft produce water, CO$$_2$$, CO etc. in exhaust gases. Most commercial flights are confined to the troposphere, but high-level supersonic aircraft inject pollutants into the stratosphere, which leads to the thinning of the ozone layer. Of these nitrogen oxides are especially harmful. 

Acid rain is acidic with a pH of below 5.6. Rain becomes acidic because of gases that dissolve in the rain. Approximately 70% of acid rain is a result of dissolved sulfur dioxide ($$SO_2$$), which forms sulphuric acid. The remaining 30% or so comes from various nitrogen oxides (mostly $$NO_2$$ and $$NO_3$$, which has collectedly called NOx). There are also a small percentage of hydrochloric acid and carbonic acid.

Pollution leads to the addition of harmful components in the environment which adversely affect the quality of the environment. CFCs is an organic compound and a volatile derivative of methane, ethane, and propane. It is known as Freon. They are used as a refrigerant. The radical chlorine escapes from CFC in the presence of UV radiation and is long lived in the upper atmosphere where it catalyzes the conversion of ozone into oxygen molecule.

Explanation:

Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions (low $$pH$$). 

A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum). Pyrethroids now constitute the majority of commercial household insecticides. In the concentrations used in such products, they may also have insect repellent properties and are generally harmless to human beings in low doses but can harm sensitive individuals. Pyrethroids are axonic excitoxins, the toxic effects of which are mediated through preventing the closure of the voltage-gated sodium channels in the axonal membranes. The sodium channel is a membrane protein with a hydrophilic interior. This interior is a tiny hole which is shaped precisely to strip away the partially charged water molecules from a sodium ion and create a favorable way for sodium ions to pass through the membrane, enter the axon, and propagate an action potential. When the toxin keeps the channels in their open state, the nerves cannot repolarize, leaving the axonal membrane permanently depolarized, thereby paralyzing the organism. So, pyrethroids are largest group of insecticides of plant origin. Thus, option C is correct.