Page 481 - Environment: The Science Behind the Stories

Figure 17.18 In most U.S. cities,
1 32 air is slowly becoming cleaner.
Seattle 22 This map shows numbers of days
1 Cleveland Philadelphia with unhealthy air from 2002 to 2010
Portland 28 for 35 metropolitan areas, according
3 Chicago 58 5 to the Air Quality Index (AQI). The AQI
23 Minneapolis 23 Boston
2
2
Sacramento Pittsburgh 37 combines data on CO, NO , SO ,
17 9 Detroit and particulate matter. Days with
Salt Lake City Indianapolis New York AQI values over 100, shown here,
6 indicate unhealthy air and NAAQS
4 21 Columbus 33
San Francisco 2 Denver 8 18 14 Baltimore violations. Data from U.S. EPA.
Las Vegas St. Louis Cincinnati Charlotte 30
13
11 Memphis Washington
Phoenix 27
15 15 10
74 14 Nashville
Dallas Birmingham Atlanta
San Diego
2
Los Angeles 33 8 Orlando
New Orleans 11
Houston 4
Tampa Miami

2002 2003 2004 2005 2006 2007 2008 2009 2010

WeigHiNg tHe iSSUeS Should we regulate greenhouse gases

yOUr regiON’S Air QUALity Locate where you live on the as air pollutants?
map in Figure 17.18. How does your nearest major city com- Although industrialized nations have reduced most sources
pare to others in its air quality? Has it improved its air quality of air pollution, they are continuing to release vast quantities
in recent years? Now explore one of the EPA websites that of the greenhouse gases (p. 502) that are driving global cli-
lets you browse information on the air you breathe: www mate change (Chapter 18). As a result, our emission of carbon
.airnow.gov, www.epa.gov/aircompare, or www.epa.gov/air/ dioxide and other gases that warm the lower atmosphere is
emissions/where.htm. What factors do you think influence the arguably today’s biggest air pollution problem. Industry and
quality of your region’s air? Propose three steps for reducing
air pollution in your region.

Toxic pollutants pose health risks

We are also reducing emissions of toxic air pollutants, sub-
stances known to cause cancer, reproductive defects, or neu-
rological, developmental, immune system, or respiratory
problems in people and other organisms. Under the 1990 Clean
Air Act, the EPA regulates 187 toxic air pollutants produced by
a variety of activities, including metal smelting, sewage treat-
ment, and industrial processes. These pollutants range from the Cancer risk
heavy metal mercury (from coal-burning power plant emissions 1–25 in a million
and other sources) to VOCs such as benzene (a component of 25–50 in a million
gasoline) and methylene chloride (found in paint stripper). 50–75 in a million
Based on monitoring at 300 sites across the United States, 75–100 in a million
scientists estimate that toxic air pollutants cause cancer in > 100 in a million
1 out of every 20,000 Americans (50 cancer cases per 1 mil- Figure 17.19 Risks for cancer throughout the United States
lion people). The latest national assessment mapped how these are mapped in the EPA’s most recent national-scale assess-
elevated risks vary geographically for cancer (Figure 17.19), ment of toxic air pollutants. Darker colors reflect higher risk. At
as well as for non-cancerous respiratory ailments. Areas such least 80 toxic air pollutants are carcinogens, including formalde-
as the Los Angeles region experience high health risks, but hyde, benzene, naphthalene, and others. Geographic patterns for
nationwide the EPA estimates that Clean Air Act regulations non-cancerous respiratory ailments are similar. Data from U.S. EPA,
on facilities such as chemical plants, waste incinerators, dry 2011. 2005 National-Scale Air Toxics Assessment.
cleaners, and coke ovens have helped to reduce emissions of What is the cancer rate due to toxic pollutants in the
480 toxic air pollutants since 1990 by more than 42%. location where you live?

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