Read the passage and answer the questions that follow : Few of Man's…

Read the passage and answer the questions that follow : Few of Man's activities have zero environmental effect. For centuries, societies have suffered a wide variety of environmental damage, not least in terms of the air pollution that primitive, uncontrolled methods of combustion caused. People of Roman Britain, with fires in their huts, found the smoke a hazard to health and examination of human skulls shows a pitting that indicates a high frequency of sinusitis. The UK was the first country to widely experience massive industrial development based on coal. Between 1580 and 1680, imports of coal to London increased from 20,000 tonnes a year to 360,000 tonnes and London became a city of 'great stinking fogs'. These were only really to disappear some years after the episode in December 1952 when cold temperatures and moist air resulted in the condensation of moisture on particles in the air from coal combustion. Over a radius of 20 miles the resulting fog rendered the atmosphere opaque and it was found that in the week ending 13 December 1952 there had been an excess of 2851 over the usual weekly number of deaths. In response the Clean Air Acts of 1956 and 1968 dealt mainly with smoke in cities. Two decades after the smog disaster the Control of Pollution Act (1974) was brought in and systematically began the long haul towards comprehensive improvements in air quality as part of overall environmental protection. Similar experiences were encountered across Europe and North America during the 20th century. Between 1580 and 1680, imports of coal to London increased ____.