Dear All,
Bapak/Ibu sekalian, ada artikel berbahasa inggris yang menyangkut masalah bahaya
dioxin.
Semoga artikel dibawah ini bermanfaat.
Tetapi maaf bila ada yang tidak berkenan tentang subjek dioxin
Best Regard,
Ishmael+Indang+Iwan
RACHEL'S ENVIRONMENT & HEALTH WEEKLY #414 November 3, 1994
News and resources for environmental justice.
Environmental Research Foundation
P.O. Box 5036, Annapolis, MD 21403
Fax (410) 263-8944; Internet: [EMAIL PROTECTED]
===================================================================
POTENT IMMUNE SYSTEM POISON: DIOXIN
The immune system is a complex set of specialized cells and organs that defends
the body against attack by "foreign" invaders. When it functions properly, the
immune system fights off diseases caused by bacteria, viruses, fungi, parasites,
and cancer cells. "When it malfunctions, however, it can unleash a torrent of
diseases, from allergy to arthritis to cancer to AIDS," according to the federal
National Institutes of Health (NIH). [1]
At the heart of the immune system is the ability to distinguish between self and
nonself. A healthy immune system protects the "self" and attacks only the
"nonself." Virtually every cell in your body carries distinctive molecules that
identify it as self. Cells lacking a "self" marker are quickly perceived as
"foreign," attacked, and eliminated by the immune system.
The National Institutes of Health (NIH) describes the immune system this way:
"The immune system, which equals in complexity the intricacies of the brain and
nervous system, displays several remarkable characteristics. It can distinguish
between self and nonself. It is able to remember previous experiences and react
accordingly: once you have had chicken pox, your immune system will prevent you
from getting it again. The immune system displays both enormous diversity and
extraordinary specificity: not only is it able to recognize many millions of
distinctive nonself molecules, it can produce molecules and cells to match up
with and counteract each one of them. And it has at its command a sophisticated
array of weapons.
"The success of this system in defending the body relies on an incredibly
elaborate and dynamic regulatory-communications network. Millions and millions
of cells, organized into sets and subsets, pass information back and forth like
clouds of bees swarming around a hive. The result is a sensitive system of
checks and balances that produces an immune response that is prompt,
appropriate, effective, and self-limiting." [1]
The immune system can fail in two ways: if it is damaged, it can fail to attack
foreign invaders, and can thus allow infections or cancers to develop. On the
other hand, if the immune system fails to distinguish self from nonself, it can
overreact and attack the self, causing "autoimmune" diseases such as arthritis,
asthma, lupus, or Type I diabetes (insulin-dependent diabetes mellitus). Other
autoimmune diseases include scleroderma, Graves' disease, Addison's disease,
Hashimoto's disease, myasthenia gravis, lymphocytic adenohypophysitis (also
called Sheehan's syndrome), mucocutaneous candidiasis, Schmidt's syndrome, and
autoimmune thyroid disease.
Dioxin: Potent Immune System Poison
U.S. Environmental Protection Agency's (EPA's) 1994 draft reassessment of dioxin
emphasized that dioxin damages the immune system directly and indirectly. From
studies of rats, mice, guinea pigs, rabbits, cattle, marmosets, monkeys, and
humans, EPA concludes that even low doses of dioxin attack the immune system.
Dioxin directly reduces the number of B cells (immune cells that develop in the
bone marrow, then circulate throughout the blood and lymph, fighting off
invaders). And it reduces the number of T cells (immune cells that develop in
the thymus, then circulate throughout the body, attacking invaders), but
dioxin's attack on T cells seems to be indirect. EPA says, "One potentially
important indirect mechanism is via effects on the endocrine system. Several
endocrine hormones have been shown to regulate immune responses, including
glucocorticoids, sex steroids, thyroxine, growth hormone, and prolactin.
Importantly, TCDD [dioxin] and other related compounds have been shown to alter
the activity of these hormones." [2, pg.9-49]
EPA goes on to say, "It is important to consider that if an acute exposure to
TCDD even temporarily raises the TCDD body burden at the time when an immune
response is initiated, there may be a risk of adverse impacts even though the
total body burden may indicate a relatively low average TCDD level." In other
words, a single dose of dioxin at the wrong time may damage your immune system's
ability to protect you.
EPA then says, "Furthermore, because TCDD alters the normal differentiation of
immune system cells, the human embryo may be very susceptible to long-term
impairment of immune function from in utero [in the womb] effects of TCDD on
developing immune tissue." In other words, dioxin can prevent the immune system
from developing properly in an unborn child, with lifelong consequences, EPA
believes. "Animal studies suggest that some immunotoxic responses may be evoked
at very low levels of dioxin exposure," EPA says. [2, pg.9-50]
Linda Birnbaum, director of research at the U.S. EPA Health Effects Laboratory
in Research Triangle Park, N.C., was the leader of EPA scientific team
reassessing dioxin. She says, "Dioxin appears to be a carcinogen in fish,
rodents, and other mammals, including humans. But dioxin can also modulate
[modify] the immune system resulting in an inability to fight disease. It is a
very powerful immunosuppressant. But it can also upregulate [excite] the immune
system so that you start becoming hypersensitive, developing autoimmunity and
allergies. Depending upon the stage [of growth] of the animal and the species,
sometimes you observe immunosuppression and in other cases you observe
upregulation." [3, pg.4]
Birnbaum goes on to describe Taiwanese children, exposed to dioxin-like
chemicals, who had unusually frequent respiratory infections and ear infections
(otitis). Further, she described an Inuit population in Quebec with elevated
levels of dioxin in their bodies from eating the fat of marine mammals (seals);
their children have "very high incidences of respiratory infections and otitis
[ear infections], and also a very decreased take of vaccinations," Birnbaum
says. [3, pg.11] In other words, vaccinations don't work well in these children,
perhaps because their immune systems have been damaged.
Birnbaum says there is no threshold for immunotoxic responses to dioxin; [3,
pg.14] in other words, there is no level of dioxin below which the immune system
is not affected. Put another way: any amount of dioxin seems to do some damage
to the immune system, at least in animals; there is no "safe" dose.
In laboratory mice, a single tiny dose of dioxin causes increased deaths when
the mice are challenged with an influenza virus. [4] It is worth emphasizing
that the effective dose of dioxin is very small: 10 nanograms of dioxin per
kilogram of bodyweight (10 ng/kg) harms the mouse immune system enough to
increase the death rate from influenza virus. To get 10 ng/kg into perspective,
consider that a single 5-grain aspirin tablet taken by a 150-pound adult is a
dose of 4.7 MILLION nanograms of aspirin per kilogram of bodyweight (4,761,936
ng/kg). For an adult human to get a dose of aspirin equivalent to the dose of
dioxin that harms the mouse immune system, you would have to divide a single
aspirin tablet into 470,000 pieces (nearly half a million pieces) and eat only
one piece. Is the human immune system as sensitive to dioxin as the mouse's? No
one yet knows.
What about animals more human-like than mice? Tom Webster of the Boston
University School of Public Health cites evidence that the number of immune
cells in rhesus monkeys is changed by a dioxin body burden of 270 ng/kg; in
marmosets, the number of immune cells is changed at only 6 to 8 ng/kg of dioxin.
"While the medical implications of this effect are unknown, it appears to occur
at about the average human body burden of dioxin-like compounds," he says. In
other words, average residents of North America carry 7 to 9 ng/kg in their
bodies now, and 6 to 8 ng/kg alters the immune systems of marmosets. [4, pg.8]
"Similar effects [immune cell alterations] were seen in the children of mothers
who lived in dioxin-contaminated Times Beach, Missouri during and after
pregnancy," Webster notes, citing work by Gerson Smoger and others. [4,pg.7]
This past summer, German researchers published a study of the health of 158
chemical workers who had been exposed to dioxin in 1953 during an industrial
accident at a BASF chemical plant. [5] The 158 exposed workers were compared to
161 unexposed workers. The dioxin-exposed workers experienced more frequent
infections and parasitic diseases during the 36 years after exposure, consistent
with immune system damage. Especially noticeable were increases in respiratory
infections, thyroid diseases, disorders of the peripheral nervous system, and
appendicitis. Mental disorders were also increased. All together, the
highly-exposed group had 18% more recorded episodes of illness than the control
group.
Ironically, the largest source of dioxin entering the environment today is
medical incinerators. Together, medical incinerators and municipal solid waste
(msw) incinerators account for 95% of all dioxin emissions into the air of the
U.S., according to U.S. EPA. [6,pg.2] The good news is: these technologies are
not needed and could be phased out rapidly, if public health authorities began
to take their DISEASE PREVENTION responsibilities seriously. Plans for new
incinerators could be easily abandoned. For both medical wastes and municipal
wastes, alternatives already exist that are cleaner, safer, and less expensive.
(The chief appeal of incinerators is political: massive campaign contributions
by the waste industry.)
Unfortunately, instead of planning to phase out incinerators, EPA has announced
plans to "regulate" incinerator emissions more tightly by requiring air
pollution scrubbers. Scrubbers will not decrease dioxin production, but will
move dioxin from the air emissions into the incinerator ash, which gets buried
in shallow pits in the ground. Thus, current public health policies are creating
a legacy of unpleasant surprises for our children.
@Peter
Montague
===============
[1] Lydia Woods Schindler, UNDERSTANDING THE IMMUNE SYSTEM [NIH Publication No.
88-529] (Bethesda, Md.: National Institutes of Health, July, 1988), pg. 1.
[2] U.S. Environmental Protection Agency, HEALTH ASSESSMENT DOCUMENT FOR
2,3,7,8-TETRACHLORODIBENZO-p-DIOXIN (TCDD) AND RELATED COMPOUNDS. VOL. III OF
III. [EPA/600/BP-92/001c] (Cincinnati, Ohio: U.S. Environmental Protection
Agency, August, 1994.) This is the official draft of "Chapter 9" of the EPA
dioxin reassessment, also known as the "risk characterization chapter."
Available free while supplies last; telephone (513) 569-7562 in Cincinnati.
[3] Linda Birnbaum, GREAT LAKES WATER QUALITY BOARD 102ND MEETING, CHICAGO,
ILLINOIS, JULY 15, 1993, PRESENTATION BY LINDA BIRNBAUM, U.S. EPA (Washington,
D.C.: International Joint Commission, Great Lakes Water Quality Board, Dec. 21,
1993), pg. 4. Available from us for $4.00.
[4] Tom Webster, DIOXIN AND HUMAN HEALTH: A PUBLIC HEALTH ASSESSMENT OF DIOXIN
EXPOSURE IN CANADA (Boston: Boston University School of Public Health, 1994),
pg. 7, citing unpublished work by Linda Birnbaum and others. Available from us
for $4.00.
[5] Andreas Zober and others, "Morbidity follow up study of BASF employees
exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) after a 1953 chemical
reactor incident," OCCUPATIONAL AND ENVIRONMENTAL MEDICINE Vol. 51, No. 7 (July
1994), pgs. 479-486.
[6] Lynn Goldman, STATEMENT OF LYNN GOLDMAN, M.D., ASSISTANT ADMINISTRATOR FOR
PREVENTION, PESTICIDES AND TOXICS, U.S. ENVIRONMENTAL PROTECTION AGENCY,
SEPTEMBER 13, 1994 (Washington, D.C.: U.S. Environmental Protection Agency,
September 13, 1994).
Kunjungi:
http://www.balita-anda.indoglobal.com
--------------------------------------------------------------------------
"Untuk mereka yang mendambakan anak balitanya tumbuh sehat & cerdas"
Berlangganan, e-mail ke: [EMAIL PROTECTED]
Berhenti berlangganan, e-mail ke: [EMAIL PROTECTED]
http://pencarian-informasi.or.id/ - Solusi Pencarian Informasi di Internet
