The correct answer is option 4, i.e 1, 2 and 4 only. Air pollution Air pollution refers to any physical, chemical or biological change in the air. It is the contamination of air by harmful gases, dust and smoke which affects plants, animals, and humans drastically. This can be in the form of excessive gases like carbon dioxide and other vapours that cannot be effectively removed through natural gaseous cycles. There are two types of Pollutants that cause air pollution i.e Primary pollutants and Secondary pollutants. Primary pollutants are the pollutants that directly cause air pollution like Lead, Fly Ash, Metallic Oxides and Nano-particles etc. Secondary pollutants formed by the reaction of primary pollutants like Carbon monoxide (CO), Carbon dioxide (CO2), Chlorofluorocarbons (CFCs), Ozone (O3), Nitrogen oxide (NOx), Volatile organic compounds (VOCs), Benzene, Biological pollutants, Asbestos and Radon etc. Carbon monoxide (CO), Nitrogen oxide (NOx), Benzene, Ozone (O3) and Chlorofluorocarbons (CFCs), are pollutants that are not tolerated by human beings even at very low levels. Hence option 4 is correct There are some air pollutant and their health impact listed below. Pollutants Description Impacts Lead One of the most hazardous heavy metals Additive to fuels and other products Mixed with water and food Nervous system damage Digestive issues Kidney damage Impacts on intelligence etc Fly Ash Particles of oxides and other heavy metals Aluminium silicate Silicon dioxide (SiO2) Calcium oxide (CaO) Heavy metal contamination of crops and vegetables Nervous system damage Kidney damage etc Nanoparticles Diameters less than 100 Nanometers Responsible for the formation of dust clouds, Ozone depletion. Lung inflammation Heart problems. Carbon monoxide (CO) Highly toxic Can not be tolerated even at a low level. Produced from internal combustion engines due to incomplete combustion. Other sources are volcanoes, forest fires, etc. It is a greenhouse gas. Carbon monoxide poisoning. Produces carboxyhemoglobin reducing the oxygen-carrying capacity of the blood. Carbon dioxide (CO2) It is not very toxic as other greenhouse gases Heavier than air. Sources are volcanoes, fire, etc. It is a greenhouse gas. CO2 is an asphyxiant gas, causing unconsciousness or death. If a high concentration of CO2 is inhaled like dizziness, headache, etc. Carbonic rain in high polluted areas. Chlorofluorocarbons (CFCs) Used in refrigerators, air conditioners, aerosols, etc. Highly destructive to the Ozone layer. Cataracts. Weakened immune system. Skin cancer Ozone (O3) Very useful in the Stratosphere but harmful at the ground layer or in theTroposphere It’s produced due to industries and vehicular emissions. It is a greenhouse gas. Has toxic effects. Causes watery and itchy eyes. Nitrogen oxide (NOx) Forms due to the reaction between oxygen and nitrogen at high temps such as in combustion engines and industries. Respiratory issues in humans. Formation of SMOG, acid rain (nitric acid) and the greenhouse effect. Sulphur dioxide (SO2) Pungent smelling colourless gas produced from mostly volcanic activities, industrial processes and production of sulphuric acid. Respiratory issues, premature deaths and death of certain nerves when inhaled. Volatile Organic Compounds (VOCs) Volatile Organic Compounds (VOCs) are a large group of carbon-based chemicals that easily evaporate at room temperature. Irritations in eyes, skin, nose and throat. Long-term exposure can cause serious damage to the liver and other organs. Benzene Found in petrochemicals and used as a fuel additive Increases cancer risk and a major cause of bone marrow failure. Ethylene Used in plastic and chemical industries in the production of Polyethylene and other polymers. Excess exposure can cause headaches and dizziness. Ethylene oxide is a carcinogen Asbestos Occurs naturally as a fibrous mineral. Prolonged exposure and inhalation can be very harmful and can cause fatal illness.