Hazardous Waste 411Photo Researchers, Inc.The dangers of PCBs first became evident in Japan in
1968, where hundreds of people ate rice bran oil acciden-
tally contaminated with PCBs and consequently experienced
serious health problems, including liver and kidney damage.
A similar mass poisoning tied to PCBs occurred in Taiwan in- Since then, toxicity tests conducted on animals indi-
cate that PCBs harm the skin, eyes, reproductive organs,
and gastrointestinal system. PCBs are endocrine disrupters:
They interfere with hormones released by the thyroid gland.
Several studies have demonstrated that in utero exposure
to PCBs can lead to certain intellectual impairments in chil-
dren. PCBs may be carcinogenic; they are known to cause
liver cancer in rats, and studies in Sweden and the United
States have shown a correlation between high PCB concen-
trations in the body and incidences of certain cancers.
Although high-temperature incineration is one of
the most effective ways to destroy PCBs in most solid
waste, it is too costly to be used for the removal of PCBs
that have leached into soil and water. One way to remove
PCBs from soil and water is to extract them using sol-
vents. This method is undesirable because the solvents
themselves are hazardous chemicals, and these extrac-
tion methods are also costly.
Recently, researchers have discovered several bacte-
ria that degrade PCBs at a fraction of the cost of incin-
eration. Additional research is needed to make the
biological degradation of PCBs practical (Figure 16.14). - What is hazardous waste?
- What are two sources of dioxins? of PCBs?
dioxins—primarily in contaminated meat, dairy prod-
ucts, and fish—they store and accumulate the dioxins in
their fatty tissues (see the bioaccumulation and biomag-
nification discussion in Chapter 4). Because dioxins are
so widely distributed in the environment, virtually every-
one has dioxins in their body fat.
Dioxins cause several kinds of cancer in laboratory
animals, but the data conflict on their cancer-causing
ability in humans. A 2001 EPA report suggests that diox-
ins probably cause several kinds of cancer in humans and
likely affect the human reproductive, immune, and ner-
vous systems. Because dioxins are passed through human
milk, nursing infants are considered particularly at risk.
Measures to reduce dioxin emissions have led to
some success. A study supported by the Swedish Environ-
mental Protection Agency showed that dioxins in guil-
lemot eggs (a guillemot is a kind of a seabird) decreased
from 3.5 parts per billion (ppb) to around 1 ppb between
1969 and 2010 (Figure 16.13).
PCBs Polychlorinated biphenyls (PCBs) are a group of
209 industrial chemicals composed of carbon, hydrogen,
and chlorine. PCBs were manufactured in the United
States between 1929 and 1979 for a wide variety of uses: as
cooling fluids in electrical transformers, electrical capaci-
tors, vacuum pumps, and gas-transmission turbines; and
in hydraulic fluids, fire retardants, adhesives, lubricants,
pesticide extenders, inks, and other materials. Prior to the
EPA ban in the 1970s, PCBs were dumped in large quanti-
ties into landfills, sewers, and fields. Such improper dis-
posal is one of the reasons PCBs are still a threat today.
Dioxin concentrations in guillemot eggs,
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Studying bacteria that break
down PCBs in contaminated
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A microbiologist adds
soil to a “bioreactor”
to test the ability of
certain bacteria to
treat contaminated
soil.
Parts per billion of dioxinin guillemot eggs1969 1975 1981 1987
Year1993 2000 20060.00.51.01.52.02.53.03.54.0Adapted from the Swedish Environmental Protection Agency (2011). National Environmental
Monitoring, Seas and Costal Areas Programme Area.
Interpreting Data
How does the change in dioxin concentration
between 1969 and 1987 compare to the
change since 1987?