1.7. essential for human [14]. The normal concentrations of

1.7.  Occurrence and
toxicity of cobalt

       Cobalt is a natural element with atomic number
(27). The only  cobalt stable isotope is
cobalt-59. there are many radioactive or unstable isotopes, two of them are
commercially important, cobalt-60 and cobalt-57. All isotopes of cobalt have
the same chemical behave and will therefore they have the same chemical effects
on your body.

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plants and animals naturally have small amount of cobalt.  However, it combined with other elements like
sulfur, oxygen and arsenic in the environment.
Cobalt also found in water in dissolved or ionic form, mostly in small amounts.
B12 is biochemically compound of cobalt which essential for human 14. The
normal concentrations of cobalt in blood and urine are about 0.1 to 2µg/L 15.

         Cobalt used to form alloys. These
alloys are harder and more resistance to corrosion, so they used in a number of
industrial applications such as aircraft engines, magnets, and cutting tools.
Cobalt compounds are used as colorants in paints, ceramics and glass. They added
in trace amount to agriculture and medicine.

           The concentration of cobalt in soil
varies widely, mostly ranging from 1 to 40 ppm. Plants growing in soil that has
less than 3 ppm of cobalt will have insufficient cobalt. On the other hand,
soils near mineral deposits, mining or industries manufacturing or using cobalt
alloys or chemicals may contain much higher levels of cobalt.

the air contains very small amounts of cobalt, less than 2 ng/m3. Daily
cobalt intake by inhalation is much less than the
amount intake in food and water however, this amount can increase in areas near
industries deal with cobalt or certain waste sites. Concentration of cobalt in water
is ranged from 1 to 10 ppb, but concentration may be higher in areas near
mining.  Drinking water usually have cobalt
levels less than 1–2 ppb.  We have most
of cobalt from food with average 11 micrograms /day. The recommended daily
intake of vitamin B12 is 6 micrograms which found in meat and dairy products.
people work in industries that related to cobalt metal and cobalt compounds are
exposed to higher levels of it.

has both harmful and beneficial effects on human health. Cobalt can use as a
treatment for anemia due to its ability to increase production of red blood
cell. Normal level of cobalt is not harmful, however excess of it is harmful. Breathing
air containing 0.038 mg cobalt/m3 for 6 hours will cause breathing
trouble . people exposed to 0.005 mg cobalt/m3 will have serious
lung problems.  Allergies to cobalt that
lead to asthma and skin rashes will be developed in case of exposed to 0.007 mg
cobalt/m3. Being exposed to radioactive cobalt may be very dangerous
to your health, because cells in your body will damage. The degree of damage
depends on the amount of radiation and its activity and the period of time that
you are exposed.

case you exposed to enough radiation, these will lead to a reduction in white
blood cell number, which may lower your resistance to infections, burn or
blister of  skin and lose hair. Th Cancer
patients that treated for long time may have these problems. Temporary
sterility may occur due to damage of reproductive system cells by radiation. Radiation
at low level can cause nausea and at higher levels it may cause bleeding, coma,
vomiting, diarrhea and even death. Some types of cancer can result from change
of cell genetic materials by radiation 14,1.          

            Nonradioactive cobalt didn’t cause
cancer in humans or animals. Absorbing a large amount of cobalt over longer
periods of time can lead to serious health problems, such as: Cardiomyopathy (a
problem where your heart becomes big and floppy and has problems pumping blood),
Deafness, Nerve problems, Ringing in the ears (tinnitus), Thickening of the
blood and Thyroid problems 16.