established widespread distribution of these chemicals in many areas of the world’s oceans from
equatorial to polar regions and to depths of 4000–
5000 m in the Atlantic Ocean. Biota with significant
lipid (fat) in their body tissues tended to accumulate
DDT family compounds and PCBs much more than
biota with lower lipid content. Marine mammals and
birds accumulated higher concentrations of DDT
compounds and PCBs, presumably due to being near
the top of the food web (biomagnification of contaminants), and having a high body lipid content
(especially for marine mammals and birds).
Analyses of surface seawater samples (both dissolved and particulate) and samples of the atmosphere over the oceans established the presence of low
concentrations (ranges of 0.01–1 ng kg
À1 water or
0.001 ng m
À3 of air) of DDT family compounds and
PCBs. Very low concentrations and difficulties in
avoiding contamination from the sampling ship and
the sampling gear made measurement of deep seawater samples problematic. The few deep-water
samples analyzed documented that the concentrations of DDT and PCBs were not higher than
about 0.001 ng kg
À1 of water. Confirmatory measurements were not made for years thereafter because
of intense debate among chemical oceanographers
about how to make reliable measurements for these
compounds at very low concentrations in sea water.
In contrast, the underlying sediments had accumulated sufficient concentrations, because of sorption
on particles and deposition, to allow undisputed
measurements of both DDT and PCB in deep ocean
surface sediments.
Several surveys and research programs documented much higher concentrations of DDT and
PCBs in coastal waters and coastal ecosystems
compared to open ocean ecosystems; especially near
urban areas for DDT and PCBs, and in coastal regions near agricultural drainage areas for DDT, as
might be expected given patterns of use for these
compounds and probable release to the environment.
1980s to the Present Day
Open Ocean Recent measurements of PCBs and
DDT family compounds in surface sea water and air
samples over the ocean on a regional oceanic scale
are few and are exemplified in Figure 2(A–D).
Despite the paucity of data, some important findings
are evident. There are higher concentrations of DDT
in surface sea waters and air overlying the oceans
near south-east Asia in comparison to the other areas
sampled. This is consistent with environmental
concerns associated with continued use of DDT in
the Asian continent, South Asia subcontinent, and
Oceania areas beyond the years when DDT use was
curtailed or eliminated in the developed countries of
North America, Europe, Japan, and Australia. The
PCB concentrations in the surface sea water are in
the range of 1–60 pg kg
À1 and in the overlying
atmosphere 3–600 pg m
À3 . The distribution of
concentrations is more even across the areas sampled
compared to DDT (Figure 2). This is consistent with
the continued presence of PCBs cycling in the
environment as a result of past releases, leakage from
landfills and products containing PCBs still in use,
and perhaps continued new uses even though PCB
manufacture has been eliminated or severely reduced
in many countries.
Recent progress with measuring low concentrations of PCBs in deep ocean waters has enabled a
few measurements of deep ocean waters. A depth
profile of the sum of concentrations of several chlorobiphenyl congeners for a station in the eastern North
Atlantic (Figure 3) documents higher concentrations
in surface waters with decreasing concentrations with
depth as expected due to the greater contact of the
surface waters with the atmosphere and contemporary environment. However, all the concentrations are very low in comparison to concentrations
found in near-shore waters, lakes, and rivers. Concentrations in the deepest waters are below or at detection limits of the analytical methods used. PCBs in
mid-depth and deeper waters are most likely a result
of the flux of particles from the surface water carrying
sorbed PCBs in and on particles to deeper waters.
There has been considerable progress during the
1980s and 1990s in understanding the role and details
of particles as conveyers of chemicals from the surface
ocean to deep waters and sediments. As the particles
sink through the deep waters, desorption and disaggregation of particles and subsequent desorption
releases PCBs. Therefore, it is likely, though not
proved due to lack of a series of data over time, that
current deep water concentrations of PCBs reflect
inputs from particle fluxes over the total time of PCB
use and release to the environment; for example inputs from peak use in North America and Europe
during the 1950s to 1960s.
Deep-water sediments contain low concentrations
of DDT and PCBs in the range of 1–100 ng g
À1 dry
weight or parts per billion. Relatively few deepocean benthic (bottom dwelling) animals have been
analyzed, but those that have been analyzed contain
detectable concentrations of DDT and PCBs in the
range of 0.001–1 mg g
À1 dry weight. Analyses of a
few samples of mid-water fish in the deep ocean
document the presence of PCBs in a pattern that
reflects metabolism of the PCBs after uptake. Although small in numbers of samples analyzed,
166 CHLORINATED HYDROCARBONS
equatorial to polar regions and to depths of 4000–
5000 m in the Atlantic Ocean. Biota with significant
lipid (fat) in their body tissues tended to accumulate
DDT family compounds and PCBs much more than
biota with lower lipid content. Marine mammals and
birds accumulated higher concentrations of DDT
compounds and PCBs, presumably due to being near
the top of the food web (biomagnification of contaminants), and having a high body lipid content
(especially for marine mammals and birds).
Analyses of surface seawater samples (both dissolved and particulate) and samples of the atmosphere over the oceans established the presence of low
concentrations (ranges of 0.01–1 ng kg
À1 water or
0.001 ng m
À3 of air) of DDT family compounds and
PCBs. Very low concentrations and difficulties in
avoiding contamination from the sampling ship and
the sampling gear made measurement of deep seawater samples problematic. The few deep-water
samples analyzed documented that the concentrations of DDT and PCBs were not higher than
about 0.001 ng kg
À1 of water. Confirmatory measurements were not made for years thereafter because
of intense debate among chemical oceanographers
about how to make reliable measurements for these
compounds at very low concentrations in sea water.
In contrast, the underlying sediments had accumulated sufficient concentrations, because of sorption
on particles and deposition, to allow undisputed
measurements of both DDT and PCB in deep ocean
surface sediments.
Several surveys and research programs documented much higher concentrations of DDT and
PCBs in coastal waters and coastal ecosystems
compared to open ocean ecosystems; especially near
urban areas for DDT and PCBs, and in coastal regions near agricultural drainage areas for DDT, as
might be expected given patterns of use for these
compounds and probable release to the environment.
1980s to the Present Day
Open Ocean Recent measurements of PCBs and
DDT family compounds in surface sea water and air
samples over the ocean on a regional oceanic scale
are few and are exemplified in Figure 2(A–D).
Despite the paucity of data, some important findings
are evident. There are higher concentrations of DDT
in surface sea waters and air overlying the oceans
near south-east Asia in comparison to the other areas
sampled. This is consistent with environmental
concerns associated with continued use of DDT in
the Asian continent, South Asia subcontinent, and
Oceania areas beyond the years when DDT use was
curtailed or eliminated in the developed countries of
North America, Europe, Japan, and Australia. The
PCB concentrations in the surface sea water are in
the range of 1–60 pg kg
À1 and in the overlying
atmosphere 3–600 pg m
À3 . The distribution of
concentrations is more even across the areas sampled
compared to DDT (Figure 2). This is consistent with
the continued presence of PCBs cycling in the
environment as a result of past releases, leakage from
landfills and products containing PCBs still in use,
and perhaps continued new uses even though PCB
manufacture has been eliminated or severely reduced
in many countries.
Recent progress with measuring low concentrations of PCBs in deep ocean waters has enabled a
few measurements of deep ocean waters. A depth
profile of the sum of concentrations of several chlorobiphenyl congeners for a station in the eastern North
Atlantic (Figure 3) documents higher concentrations
in surface waters with decreasing concentrations with
depth as expected due to the greater contact of the
surface waters with the atmosphere and contemporary environment. However, all the concentrations are very low in comparison to concentrations
found in near-shore waters, lakes, and rivers. Concentrations in the deepest waters are below or at detection limits of the analytical methods used. PCBs in
mid-depth and deeper waters are most likely a result
of the flux of particles from the surface water carrying
sorbed PCBs in and on particles to deeper waters.
There has been considerable progress during the
1980s and 1990s in understanding the role and details
of particles as conveyers of chemicals from the surface
ocean to deep waters and sediments. As the particles
sink through the deep waters, desorption and disaggregation of particles and subsequent desorption
releases PCBs. Therefore, it is likely, though not
proved due to lack of a series of data over time, that
current deep water concentrations of PCBs reflect
inputs from particle fluxes over the total time of PCB
use and release to the environment; for example inputs from peak use in North America and Europe
during the 1950s to 1960s.
Deep-water sediments contain low concentrations
of DDT and PCBs in the range of 1–100 ng g
À1 dry
weight or parts per billion. Relatively few deepocean benthic (bottom dwelling) animals have been
analyzed, but those that have been analyzed contain
detectable concentrations of DDT and PCBs in the
range of 0.001–1 mg g
À1 dry weight. Analyses of a
few samples of mid-water fish in the deep ocean
document the presence of PCBs in a pattern that
reflects metabolism of the PCBs after uptake. Although small in numbers of samples analyzed,
166 CHLORINATED HYDROCARBONS