HUMAN ACTIVITIES HAVE INCREASED AIR POLLUTION

In a number of ways, however, humans have surpassed volcanoes as sources of pollution. In the United States alone, for example, industrial and other human activities have been depositing about 20 million tons of sulfur dioxide in the air every year since around 1950 By one estimate, human activities account for about 70 percent of all sulfur that enters the global atmosphere. To 

The cloud of sulfur dioxide generated by the June 15,1991, eruption of Mount Pinatubo reached India in 4 days. (The black strips indicate missing satellite data.) By July 27, the sulfur dioxide cloud had traveled around the globe. 

AEROSOLS AND PARTICULATES FACILITATE CHEMICAL REACTIONS INVOLVING POLLUTANTS 

Larger solid particles, called particulates, tend to setde to the ground faster than the particles that form aerosols and hence do not play as big a role in 

During scrubbing of industrial gaseous effluents, a fine mist of water captures and removes solid particles that have diameters as small as 0.001 millimeter. 

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Exposure to tobacco in several forms is associated with an increased risk of cancer in addition, several active ingredients, such as nicotine, have been demonstrated to be addictive. Tobacco smoke is a significant indoor air pollutant. It includes 4000 components, some regulated as human carcinogens. Second-hand smoke is a particular concern for children s health and is not only associated with an increase in lifetime risk of cancer, but an increased risk of developing respiratory conditions such as bronchitis, pneumonia, and asthma. 

Our modem society is irrevocably dependent on chemicals. Over the past decades chemicals have been developed, manufactured and used in increasing numbers and amounts by a steadily growing number of industries, both in developed and developing countries. At present more than 100,000 of 11 million known chemical substances are traded internationally and about 1000 new ones are introduced into commerce each year. As nations develop their industrial activities, the production and use of chemicals rise in parallel to the standard of living and the consequent increase in life expectancy. Though chemicals have made possible many of the benefits which modem society enjoys, they are also among the chief pollutants of the human environment, as substantial quantities of a wide variety of chemicals are released to the air, water and land from the above-mentioned activities. 

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