The Arctic at Risk:
A Circumpolar Atlas of Environmental Concerns
by Stephanie Pfirman, Kathleen Crane, Kim Kane, and Tania
Simoncelli
Organochlorines
Hexachlorocyclohexanes (HCH)
Characteristics
Hexachlorocyclohexane (HCH) is a halogenated hydrocarbon. It is volatile
because of its low molecular weight. HCH is often sold as a mixture of five
isomers called technical HCH. The gamma isomer of HCH has properties similar to
DDT and is known as lindane. HCHs are conservative pollutants and tend to
accumulate in food chains.
Production and Use
Lindane came into use in the 1940's as a contact poison for insects. It has a
faster but less protracted effect on insects than does DDT (Encyclopedia
Britannica, 1990). Because it is volatile and stable at high temperatures, it
has been used to fumigate crops and orchards. While technical HCH was banned in
Canada in 1971 and in the United States in 1979, lindane is still used for a
range of purposes in both countries and in western Europe (Voldner and Ellenton,
1987; McConnell et al., 1993). HCH is also widely used in the agricultural
sector in southern Asia by India, China, and other countries (Clark, 1992).
Transport Pathways
Lindane persists for decades in the environment (Duffus, 1980). Because of
its volatility, more than 99% of it may be lost to the atmosphere following
application (Clark, 1992).
Flux of HCH from the atmosphere to the ocean is favored when the
concentration is high in the atmosphere and when the water temperature is low
(McConnell et al., 1993). In general, marine water bodies play a role as a sink
for HCHs (Iwata et al., 1993). Volatilization from water bodies may occur when
water temperatures rise in summer, and when atmospheric concentrations are low.
Cold Arctic water bodies are important sinks for HCHs. Concentrations of HCH are
highest near the Arctic ocean surface and decline rapidly with depth in the
ocean. This type of distribution indicates that HCH is input mainly from gas
exchange with the atmosphere, as well as from river run-off and sea ice melt
water (Muir and Norstrom, 1994).
Humans are exposed to HCH primarily through consumption of seals, as well as
narwhals, caribou, and fish (Kinloch et al., 1992).
Environmental Distribution
Worldwide, shipboard measurements indicate that atmospheric HCH
concentrations are greatest in the Bay of Bengal and the Arabian Sea, which are
close to pesticide application regions in southeast Asia (Iwata et al., 1993).
Both atmospheric and oceanic measurements show that HCH contamination of the
northern hemisphere is much greater than that of the southern hemisphere. High
values in the northwest Pacific are suspected to originate from the lower and
mid-latitude countries of Asia (Tanabe and Tatsukawa, 1980; Iwata et al., 1993).
However, because most use is presently in low-latitude regions, there is now
less contamination of the mid-latitude ocean than was observed in the 1980's
(Iwata et al., 1993). Typically, the level of HCH in the mid-latitude Atlantic
Ocean is today about 0.14 ng/l (Iwata et al., 1993).
In comparison to other organochlorines, HCH has been measured fairly
extensively in circumpolar Arctic waters. Among the organochlorines presented in
this study, HCH had the highest concentration in both freshwater and seawater.
This is typical of the worldwide distribution of HCH (Iwata et al., 1993): in
contrast to PCBs and DDT, HCH is more water soluble and so tends to dissolve in
seawater rather than being associated with particles (Muir and Norstrom, 1994).
However, concentrations of HCHs are higher in these northern waters than in
most of the rest of the world's oceans. HCHs are less volatile at low
temperatures; low water temperature reduces transfer of HCHs to the atmosphere,
so more of it remains in the water (Muir et al., 1992; Iwata et al., 1993).
Concentrations in the Chukchi and Bering seas and in the Gulf of Alaska averaged
about 1.7 ng/l (Iwata et al., 1993). Values above 5 ng/l are observed in the
Beaufort Sea (Hargrave et al., 1988). River water in northern Quebec has
"strikingly high" levels of HCHs, which approach and at times exceed
the Canadian Council of Resource and Environment Ministers (CCREM) guideline
level of 10 ng/l (Lockhart et al., 1992).
Potential Health Effects
Fish are killed by HCH concentrations of about 1 ug/g (ppm) in water. HCH is
known to be more toxic to rainbow trout at low as compared to high temperatures,
for other species the temperature dependence is mixed (Lockhart et al., 1992).
Unfortunately, while most toxicology deals with the gamma isomer of HCH, the
alpha isomer is more pervasive in the Arctic (Lockhart et al., 1992).
There are high levels of HCH in several Russian rivers, most notably the Ob,
apparently due to the use of the pesticide lindane. DDT is present in Arctic
rivers, ranging from 0.03 ng/litre in rivers flowing into Hudson Bay to 5 ng/litre
in the Ob River. Russian rivers also have high levels of PCBs. The levels of
POPs in some Russian rivers draining into the Arctic may be higher than those
found in urban North America and Western Europe.
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