Page 494 - Environment: The Science Behind the Stories

vulnerable. Moreover, scientists point out that further pollu-
tion reductions are needed if we are to fully restore ecosys-
tems in the Northeast and prevent further damage to property
and infrastructure.
While the United States, Canada, and Western Europe are
beginning to recover from acid deposition after cutting sulfur
emissions, acid deposition is becoming worse in industrial-
izing nations. Today China emits the most sulfur dioxide of
≤ 4.1 any nation and has the world’s worst acid rain problem, as a
4.5 result of extensive coal combustion in power plants and facto-
4.9 ries that often lack effective pollution control equipment. The
5.3 government is tackling the issue, but it faces a challenge as
≥ 5.7
the nation’s industrial sector continues to expand by leaps and
bounds.
(a) Acid deposition in 1990
Overall, data on acid deposition show that we have made
advances in controlling outdoor air pollution, but that more
can be done. The same can be said for indoor air pollution, a
source of human health threats that is less familiar to most of
us, but statistically more dangerous.

Indoor Air Quality

Indoor air generally contains higher concentrations of pol-
≤ 4.1 lutants than does outdoor air. As a result, the health impacts
4.5 from indoor air pollution in workplaces, schools, and homes
4.9 outweigh those from outdoor air pollution. The World Health
5.3
≥ 5.7 Organization (WHO) attributes nearly 3.5 million premature
deaths each year to indoor air pollution (compared with 3.3
(b) Acid deposition in 2011 million for outdoor air pollution). Indoor air pollution takes
nearly 10,000 lives each day.
Figure 17.31 Precipitation has become less acidic as a If this seems surprising, consider that the average U.S.
result of air quality improvements following the Clean Air citizen spends at least 90% of his or her time indoors. Then
Act. Average pH values for precipitation have risen between (a) consider the dizzying array of consumer products in our
1990 and (b) 2011. Precipitation remains most acidic in the North-
east and Midwest, near and downwind from (roughly east of) areas homes and offices that play major roles in our daily lives.
of heavy industry. Data from the National Atmospheric Deposition Program. Many of these products are made of synthetic materials, and
novel synthetic substances are not comprehensively tested for
In the area where you live, how did the pH of precipitation health effects before being brought to market (Chapter 14).
change between 1990 and 2011? Has precipitation Products and materials as diverse as cleaning fluids, insecti-
become more acidic or less acidic?
cides, furniture, carpeting, and the many varieties of plastics
all exude volatile chemicals into the air. CHAPTER 17 • AT m os PHER i C sC i E n CE , Ai R Qu A li T y, A nd Poll u T i on Con TR ol
At Hubbard Brook Experimental Forest in New Hamp- Ironically, some attempts to be environmentally prudent
shire, where scientists first studied acid deposition’s effects in during the “energy crises” of the 1970s (p. 562) worsened
the United States, researchers jumpstarted a long, slow recov- indoor air quality. To improve energy efficiency by reducing
ery by using a helicopter to distribute 50 tons of a calcium- heat loss, building managers sealed off ventilation in build-
containing mineral called wollastonite over one watershed. ings, and designers constructed new buildings with limited
Within three years of this experimental application, topsoil ventilation and with windows that did not open. These steps
pH rose from 3.9 to 4.2. Sugar maples (one of the forest’s saved energy, but they also worsened indoor air quality by
key tree species that had been declining) are now producing trapping stable, unmixed air—and pollutants—inside.
healthier foliage, thicker root growth, more seeds, and more There is good news, however. In both developing and
surviving seedlings. Over the next 50 years, scientists plan to developed nations, we have known and feasible ways to
evaluate the impact of calcium addition on the watershed’s address the primary causes of indoor air pollution.
soil, water, and life, and compare these results to watersheds
where calcium remains depleted.
As with ozone depletion, there is a time lag before the Burning fuelwood causes indoor pollution
positive consequences of emissions cuts kick in, so it will take in the developing world
time for acidified ecosystems to recover. Research in 2012
indicated that soils across the northeastern United States are Indoor air pollution has by far the greatest impact in the
showing signs of recovery, but that they remain degraded and developing world, where poverty forces millions of people 493

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