Cobalt [Co, 27]
93
Cobalt has both beneficial and harmful effects on human health. Cobalt is bene ficial
for humans because it is part of vitamin B 12 , which is essential to human health, and is
used for the treatment of anemia, also for pregnant women. At very high exposure levels,
it increases red blood cell production. Exposure of humans and animals to levels of Co
normally found in the environment is not harmful. Occupational, increased exposure to
Co occurs in several industries.
Harmful health effects of Co can also occur. Workers who breathed air containing 0.038 mg Co/m 3 (about 100,000 times more than normal concentration in ambient air), for 6 hours, had a trouble breathing. Serious effects on the lungs, including
asthma, pneumonia, and wheezing, have been found in people exposed to 0.005 mg
Co/m 3 , while working with hard metal, a Co–W carbide alloy. People exposed to
0.007 mg Co/m 3 , at work have also developed allergies to Co, which resulted in
asthma and skin rashes (ATSDR 2004b).
Increased lung cancer risk is related to exposure to hard-metal dust containing
Co and W carbide. International Agency for Research on Cancer (IARC) established
that Co metal with tungsten carbide is “probably carcinogenic to humans” (Group 2A),
Co metal without W carbide is possibly “carcinogenic to humans” (Group 2B), and
Co sulfate and other soluble Co(II) salts are possibly “carcinogenic to humans”
(Group 2B) (IARC 2006).
A radioactive isotope, 60 Co is sometimes used in the radiation therapy, for cancer
treatments. Co treatment in radiation therapy has been found to be more effective
in shrinking tumors and destroying cancer cells in the lungs than other isotopes.
However, exposition to radioactive Co may be very dangerous to health. Radiation
from radioactive Co can also damage cells in body during eating, drinking, breathing, or touching anything that contains radioactive Co. Exposure to lower levels of
radiation might cause nausea, and higher levels can cause vomiting, diarrhea, bleeding, coma, and even death (ATSDR 2004b).
Human dietary intake of Co is highly variable. Most of the Co ingested is inorganic. Vitamin B 12 , which occurs almost entirely in food of animal origin, accounts
for only a very small Co fraction. Vegetables contain inorganic Co but little or no
vitamin B 12 . Richest sources of Co are some products of animal origin, nuts, chocolates, and rice (Table 13.3). No specific RDA is suggested for Co.
The estimated population average intake of Co is reported to be (in mg/day):
0.005–0.04 in the United States; 0.011 in Canada; 0.012 in the United Kingdom;
and 0.029 in France. These figures are most likely included already in the contribution of products from animals routinely supplemented with Co(II) compounds
(EFSA 2012b).
13.7 ANIMALS
Cobalt is also essential for the health of animals, especially of cattle and sheep, which
can synthesize vitamin B 12 in the digestive tract by microbial action. Efficiency in
the incorporation of Co in vitamin B 12 in ruminants is low and inversely related
to the Co intake. This incorporation rate may range from 3% to 15%. Besides
covering the requirements for vitamin B 12 synthesis, Co may play a role in rumen