50. NCERT Exemplar XXXII

 

Air pollutant is any agent or substance whose addition or increase in concentration beyond normal deteriorates the quality of air and affects the health of living organisms. A pollutant can be particulate matter or a gaseous substance.

Dust is classified as a particulate matter called suspended particulate moleculesuspended penultimate mattersuspended particulate matter (SPM) because it remains suspended in the air for a reasonable period of time. Dust is harmful to humans, plants, and animals and is considered an important (primary) air pollutant. Some of the harmful effects of dust are:

(a). Dust affects plant growth and health as it clogs reticulumribosomestomata and covers the surface of the leaf, preventing photosynthesis, respiration etc.

(b). Dust is a major cause of allergic reactions in humans, especially persistent asthmaseasonal asthmabronchial asthma and chronic bronchitis.

(c). Dust from various industries like cotton dust, iron mill dust, mine dust, flour mill dust etc., results in various carcinogenicrespiratorychronic problems like emphysaema, tuberculosis, etc.

(d). Dust also carries heavy toxic metals like Hg, Pb, CuZn, Fe, CaCa, Mg, Na etc., which are harmful to both animals and plants.

(e). Sometimes, the particulates accumulate in the middle layersupper layersbottom layers of the atmosphere to form large coloured clouds that hinder the passage of solar radiation and lower the temperature of the earth’s surface.