Answer to Question 1
ANSWER: To indicate the air quality in a particular region, the EPA developed the air quality index (AQI). The index includes the pollutants carbon monoxide, sulfur dioxide, nitrogen dioxide, particulate matter, and ozone. On any given day, the pollutant measuring the highest value is the one used in the index. The pollutants measurement is then converted to a number that ranges from 0 to 500. When the pollutants value is the same as the primary ambient air quality standard, the pollutant is assigned an AQI number of 100. A pollutant is considered unhealthful when its AQI value exceeds 100. When the AQI value is between 51 and 100, the air quality is described as moderate. Although these levels may not be harmful to humans during a 24-hour period, they may exceed long-term standards. The AQI is color-coded, with each color corresponding to an AQI level of health concern. The color green indicates good air quality; the color red, unhealthy air; and maroon, hazardous air quality.
Answer to Question 2
ANSWER: The discovery of the ozone hole added urgency to the development of an international agreement called the Montreal Protocol, which was signed in 1987. This agreement, one of the first in United Nations history to be ratified by every member, established a timetable for diminishing CFC emissions and the use of bromine compounds (halons), which destroy ozone at a rate 50 times greater than do chlorine compounds. One sign of the success of the Montreal Protocol is that since the 1990s there has been a decrease in the atmospheric concentrations of most ozone-depleting gases.
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