Page 386 - Environment: The Science Behind the Stories

structure allows asbestos to trap heat, muffle sound, and resist milk of European mothers have fallen substantially. In the
fire. Because of these qualities, asbestos was used widely as United States, however, there has so far been little movement
insulation in buildings, as well as in other products. Unfor- to address the issue. The dangers posed by fire retardants such
tunately, its fibrous structure also makes asbestos dangerous as PBDEs have caused some to question the stringent flam-
when inhaled. When asbestos gets lodged in lung tissue, the mability standards that often make the use of such chemicals
body produces acid in an attempt to eliminate it. The acid necessary. As stated by Linda Birnbaum of the National Insti-
scars the lung tissue but does little to dislodge or dissolve the tute of Environmental Health Sciences, “I don’t question the
asbestos. Within a few decades, the scarred lungs may cease need for flame retardants in airplanes, but do we need them in
to function—a disorder called asbestosis. Asbestos can also nursing pillows and babies’ strollers?”
cause certain types of lung cancer. Because of these risks,
asbestos has been removed from many schools and offices. Risks must be balanced against rewards
However, the removal process can release some asbestos into
the air, increasing people’s exposure, so in some cases the The job of toxicologists and other scientists who study envi-
best approach is to encase the material in place. ronmental health hazards is to learn as much as they can about
Lead poisoning is another indoor health hazard. When the hazards, but the rest of us need to take this information
ingested, lead, a heavy metal, can cause damage to the brain, and weigh it against any benefits we obtain from exposing
liver, kidney, and stomach; learning problems and behavio- ourselves to the hazards. With most hazards, there is some
ral abnormalities; anemia; hearing loss; and even death. Lead tradeoff between risk and reward, and we must judge as best
poisoning among U.S. children has greatly declined in recent we can how these compare. In regard to bisphenol A, its use-
years as a result of education campaigns and government reg- fulness for many purposes means that despite its health risks,
ulations that phased out lead-based paints and leaded gasoline we may as a society choose to continue using it. The avail-
starting in the 1970s. Today lead poisoning can result from ability of safer and affordable alternatives is important in such
drinking water that has passed through the lead pipes common decisions. Industry is finding replacements for BPA polymers
in older homes or from ingesting or inhaling lead-containing in baby bottles and water containers, but until a replacement
dust produced by the slow wearing-away of leaded paint. is found for it as an epoxy liner for food cans, it will likely
We have succeeded in removing significant sources of continue to serve this function.
lead exposure in the United States, but modern Americans are As we review the impacts of toxic substances throughout
still exposed to elevated levels of lead. For example, millions this chapter, it is important to keep in mind that artificially
of children’s toys and other items exported from China were produced chemicals have played a crucial role in giving us
found to contain lead-based paint in recent years. The result- the standard of living we enjoy today. These chemicals have
ing consumer outcry in the United States forced recalls of helped create the industrial agriculture that produces our food,
these items, and China eventually agreed to limit and monitor the medical advances that protect our health and prolong our
the use of lead-based paint in its manufacturing. lives, and many of the modern materials and conveniences we
In 2012, the Centers for Disease Control (CDC) adopted use every day. It is appropriate to remember these benefits
an advisory panel’s recommendation and lowered the danger as we examine some of the unfortunate side effects of these
threshold for lead levels in children’s blood from 10 micro- advances and as we search for better alternatives.
grams/deciliter to 5 micrograms/deciliter. This decision was
based on numerous studies that showed adverse effects of lead
on neurological development at blood lead levels below the Toxic Substances and Their
previous standard. Effects on Organisms
One recently recognized hazard is a group of chemicals
known as polybrominated diphenyl ethers (PBDEs). These
compounds provide fire-retardant properties and are used in Our environment contains countless natural substances that
a diverse array of consumer products, including computers, may pose health risks. These include petroleum, oozing natu-
televisions, plastics, and furniture. They are emitted during rally from the ground; radon gas, seeping up from bedrock;
production and disposal of products and may also release and toxins, toxic chemicals manufactured in the tissues of CHAPTER 14 • Envi R onm E n TA l H EA lTH A nd T o xi C ology
into the air at very slow rates throughout the lifetime of prod- living organisms. For example, toxins can be chemicals that
ucts. These chemicals persist and accumulate in living tissue, plants use to ward off herbivores or that insects use to defend
and their abundance in the environment and in people in the themselves from predators. In addition, we are exposed to
United States is doubling every few years. many synthetic (artificial, or human-made) chemicals, some
Like bisphenol A, PBDEs appear to act as hormone dis- of which also have toxic properties.
ruptors; lab testing with animals shows them to affect thyroid
hormones. Animal testing also suggests that PBDEs affect the Synthetic chemicals are all around
development of the brain and nervous system and may cause us—and in us
cancer. Concern about PBDEs rose after a study showed that
concentrations in the breast milk of Swedish mothers had Tens of thousands of synthetic chemicals have been manu-
increased exponentially from 1972 to 1997. U.S. studies also factured (TAble 14.2), and synthetic chemicals surround us in
show rising concentrations in breast milk. The European our daily lives. Each year in the United States, we manufac-
Union decided in 2003 to ban PBDEs, and industries in ture or import 113 kg (250 lb) of chemical substances for
Europe phased them out. As a result, concentrations in breast every man, woman, and child. Many of these substances find 385

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