Pencemaran
Arsenik
Kajian terkini di USA
menunjukkan bahawa terdapat paras arsenik yang tinggi dalam beras dan jus epal
serta jus anggur. Bagaimana dengan keadaan di Malaysia? adakah makanan yang
kita makan selamat daripada keracunan arsenik? Arsenik
adalah bahan semulajadi dalam tanah yang pernah disembur dengan racun makhluk
perosak dan ditabur baja kimia untuk mendapatkan hasil yang lumayan. Arsenik
ini akan tersimpan lama dan kekal dalam tanah, seperti juga merkuri dan logam
berat yang lain. Disebabkan arsenik ini mudah larut air, maka ia mudah meresap
dari tanah ke dalam tumbuhan yang kita makan. Jadi sisa-sisa arsenik ini
terdapat pada semua bahagian tumbuhan, terutamanya di daun. Apabila tumbuhan
ini dimakan, maka arsenik ini akan masuk ke dalam tubuh manusia.
Disebabkan
padi ditanam di kawasan berair, ia lebih mudah menyerap arsenik berbanding
dengan tumbuhan daratan. Kajian juga menunjukkan arsenik dalam padi lebih
banyak terkumpul di bahagian kulit padi/sekam yang dibuang apabila padi
diproses untuk mendapatkan beras putih. Ini menunjukkan beras perang lebih
banyak mengandungi arsenik berbanding beras putih. Selain tumbuhan, makanan
laut juga banyak mengandugi arsenik yang berbahaya. Awas dengan suplemen
kalsium, diperbuat daripada makanan laut, yang mengandungi paras arsenik yang
tinggi. Terdedah kepada paras arsenik yang tinggi dalam badan boleh menyebabkan
kematian. Terdedah kepada paras arsenik yang sederhana menyebabkan penyakit
kardiovaskular, kesan kepada paru-paru dan masalah pernafasan yang lain,
masalah dalam perkembangan otak kanak-kanak, keguguran pada ibu hamil, dan
berat kelahiran bayi yang kurang berbanding normal.
Terdedah
kepada paras arsenik yang rendah dalam tempoh masa yang lama pula menyebabkan
pening kepala dan muntah-muntah, mengurangkan jumlah sel darah merah dan putih,
menyebabkan denyutan jantung tidak normal, merosakkan salur darah, menyebabkan
semut-semut atau kebas di tangan dan kaki. Arsenik yang tinggi juga dikaitkan
dengan kenaikan kadar kanser kulit, kanser paru-paru, dan lain-lain. Di antara
tanda-tanda seseorang itu terdedah kepada arsenik dalam tempoh yang lama ialah
mendapat kanser kulit, tompok-tompok hitam atau tahi lalat kecil-kecil di
tangan, kaki dan badan. Cara yang disarankan bagi mengelakkan pengambilan arsenik
daripada paip air ialah dengan menggunakan penapis air. Walaupun kandungan
arsenik yang berlebihan ini tidak dikesan di Malaysia, kita harus berhati-hati
dan mengambil langkah berjaga-jaga….Artikel berkaitan
dipanjangkan di bawah ini…
How arsenic gets into foods, and what it means for you.
By
Brenda Goodman, MA
Reviewed
by Louise Chang, MD
Recent investigations have
found the toxin arsenic in rice and apple juice. Consumer Reports published
results of their tests of 88 samples of apple and grape juices. Nine samples
had more arsenic than the federal government allows in drinking water. In a
separate analysis of government nutrition data, researchers commissioned by
Consumer Reports also found that Americans who reported drinking apple or grape
juice had arsenic levels in their urine that were 20% higher than people who
didn’t drink those juices. Similarly, researchers at Dartmouth Medical School
found that pregnant women who reported eating rice had higher levels of arsenic
in their urine than women who didn’t eat rice. Eating just half a cup of rice a
day, the researchers reported, could expose someone to just as much arsenic as
if they had been drinking water at the government’s maximum allowable limit. Should
you be worried about being exposed to arsenic in food? The author consulted
experts who study arsenic to answer your questions.
What is
arsenic and how does it get into foods?
Arsenic is a naturally
occurring element that’s found in soil and water. It has also been used by
farmers as a pesticide and a fertilizer. It is also used to preserve
pressure-treated wood. Like lead, mercury, and other heavy metals, arsenic can
persist in soil for years after it is applied to crops. Much of the rice grown
in the Southern U.S., for example, grows in paddies that were once cotton
fields. Cotton farmers are known to have used arsenic-based pesticides to
control bugs called boll weevils. Other studies have shown that arsenic content
in soil is higher around rivers and may be related to soil texture. Clay soils
have more naturally occurring arsenic. Because of its chemical structure,
plants mistake arsenic for necessary nutrients and readily absorb it from the
soil.
Are
there particular foods that it’s in?
“All plants pick up
arsenic,” John M. Duxbury, PhD, a professor of soil science and international
agriculture at Cornell University in Ithaca, N.Y., says in an email.
“Concentrations in leaves of plants are much higher than in grains of plants.
Thus, leafy vegetables can contain higher levels of arsenic than rice,
especially when they are grown on arsenic-contaminated soils.” But because we
eat a much lower volume of leafy greens compared to other kinds of foods,
“arsenic intake from this
source is also low,” Duxbury says. Rice appears to be particularly vulnerable
to arsenic contamination because it grows in water. Arsenic dissolves easily in
water. So drinking water has long been monitored as a source of exposure to
arsenic. Because rice is grown in paddies, which are flooded with water, it can
be exposed to higher amounts of arsenic than plants grown in drier soils,
Duxbury says. Tracy Punshon, PhD, a research assistant professor at Dartmouth
College in Hanover, N.H., has X-rayed rice grains to see where they store
arsenic. She found that arsenic concentrates in the part of the grain called
the germ, which is removed to make white rice. That means brown rice has higher
concentrations of arsenic that white rice. Studies by Scottish researchers have
found higher levels of arsenic in rice grown in the U.S. than in basmati or
jasmine rice from Thailand or India. The highest levels of arsenic in
U.S.-grown rice came from Southern states. The lowest levels were detected in
rice grown in California. Seafood also has high levels of arsenic, though most
experts believe the form of arsenic in seafood to be nontoxic. Calcium
supplements made from seafood may also contain high amounts of arsenic.
What
are the potential health consequences?
At very high levels,
arsenic can be fatal. At lower levels, arsenic can cause nausea and vomiting
and decrease the amount of red and white blood cells produced by the body. It
also causes abnormal heart rhythms, may damage blood vessels, and causes a pins
and needles sensation in the hands and feet. However, far less is understood
about what happens to people when they are exposed to low levels of arsenic
over a long period of time. “This is a relatively new area of research,” says
arsenic expert Ana Navas-Acien, MD, PhD. It’s clear that arsenic is associated
with higher rates of skin, bladder, and lung cancers, says Navas-Acien, an
assistant professor of environmental health sciences and epidemiology at Johns
Hopkins Bloomberg School of Public Health in Baltimore. “When a substance is a
carcinogen, it’s generally a carcinogen through the whole range of exposure
levels,” she says. At lower levels, it probably causes fewer cases of cancer,
though the risk is still there. Beyond cancer, she says, more evidence suggests
that low to moderate levels of exposure — just about the U.S. standard for drinking
water of 10 parts per billion — may cause cardiovascular disease. Chronic
arsenic exposure may also affect the lungs, leading to breathing problems. In
children, Navas-Acien says emerging evidence suggests that arsenic may cause
problems with brain development. Arsenic may also contribute to problems with
pregnancy like miscarriages and low birth weight.
Should I
stop drinking juice, or should my kids?
People shouldn’t shun the
juice aisle, says Richard W. Stahlhut, MD, MPH, a toxicologist at the University
of Rochester in New York. But it’s probably not a bad idea to cut back if you
or your kids drink a lot of juice, Stahlhut says, or to be careful about the
kinds of juice that you drink. “Anytime you can easily avoid something, avoid
it,” he says, but don’t drive yourself crazy. “You can’t be perfect. If the
goal is perfection, you’re doomed,” Stahlhut says. “The rest of us are getting
exposed.”
Is
organic juice/rice/other foods any better, in terms of arsenic risk?
Since arsenic persists in
the soil for years, organically grown produce isn’t any safer than
conventionally grown food, Duxbury says.
Is
arsenic tested for in foods?
The FDA tests for arsenic
in some foods through a program that looks for harmful substances in food.
There is no standard for arsenic in foods, and the FDA says that when it finds
inorganic arsenic — the toxic kind — it considers those findings on a
case-by-case basis and takes regulatory action where necessary. In September,
the FDA said it was considering setting a standard for fruit juice.
What are
the signs that someone may have gotten too much arsenic from their diet?
Chronic exposure to arsenic
has very few symptoms, especially at the low levels seen in Western countries. Long-term
exposure to arsenic from water is known to cause skin discoloration that looks
like freckles or small moles on the hands, feet, or trunk.
What
should you do if you experience those symptoms?
If you’re concerned you may
have been exposed to arsenic in food or water, a doctor can test for arsenic in
your blood, urine, hair, or fingernails. If you’re concerned you may be getting
arsenic from well water, you can test the well and use water filters to remove
the arsenic from your drinking water.
What is
the difference between organic and inorganic arsenic?
In the environment, arsenic
combines with oxygen, chlorine, and sulfur to form inorganic arsenic compounds.
In plants and animals, arsenic combines with hydrogen and oxygen to form
organic arsenic compounds. Inorganic kinds of arsenic are thought to be the
most dangerous for human health, but very little is known about organic
arsenic. “This is a controversial topic with an ongoing debate amongst
toxicologists,” Duxbury says.
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