Unit-iv unit-iv environmental Hygiene

Coal dust explosion (China, 1942 and Chasnala, India, 1957)

• Coal dust explosion (China, 1942 and Chasnala, India, 1957)
• Forest fires (South East Asia, 1997-98): impact on health & productivity
• Nitrogen oxide & hydrocarbons present in the atmosphere (following use of petrol by the automobiles) reacted with sunlight
• Toxic compounds were produced through a photochemical reaction between sunlight & the two pollutants
• The photochemical smog pollution of 1969 has been reported in detail as a part of episode 104 (associated with hurricane Camille emanating from Gulf of Mexico)

Air pollution: a historical perspective

Classification of air pollutants

A wide variety of pollutants are present in the atmosphere

In order to understand their impact on health & ecology, & to evolve appropriate strategies for their control, the pollutants are classified in a number of ways:

• Source of emission,
• Physico-chemical characteristics &
• Effects on life processes

Sources of air pollutants

Natural sources
Man induced activities

• Geochemical contamination,
• Photochemical reactions,
• Change in climatic conditions,
• Volcanic eruptions,
• Gaseous discharge from marshes & swamps,
• Forest fires
• Dust, fog & radiation fall-outs
• Microbial agents

Sources

• Incineration: wood, coal, petroleum products,
• Automobile industry: oxides of sulphur & nitrogen, carbon monoxide, smoke & fly ash
• Oil refineries
• Iron/steel mills, fertilizer plants & rendering units metal fumes & fluorides into the atmosphere
• Agricultural, textile, paper & pharmaceutical industries
• Dust particles: milling, crushing /grinding
• pesticide & drug residues
• Organic/inorganic vapours