|
|
Chlorin and TTHM
Cl -
Chlorine
A green, highly reactive gas, chlorine is the most abundant halogen,
comprising nearly two percent of the seas and used in all of our
laboratory classes. Karl Scheele discovered chlorine in 1774, but
believed it to be an oxide of a ficticous element, murium (which is
why hydrochloric acid is also known as muriatic acid.) Murium was
never found, but Humphrey Davy recognized it's elemental quality in
1810. The oxide is a strong acid.
Chlorine and water threatment
Chlorine disinfecting technology has almost completely eliminated
from our lives the risks of waterborne diseases such as typhoid
fever, cholera, and dysentery. However, the health benefit of
chlorination has introduced some possible risks from the byproducts
of the disinfecting process.
Total Trihalomethanes (TTHM) are a byproduct of chlorinating water
that contains natural organics. Trihalomethanes are present in
virtually all chlorinated water supplies.
TTHM are linked to increased risk of cancer. Several studies suggest
a small increase in the risk of bladder cancer and colorectal
cancer. Beyond the cancer and reproduction concerns, chlorination
by-products may be linked to heart, lung, kidney, liver, and central
nervous system damage. Besides, TTHM are linked to reproductive
problems, including miscarriage. Exposure to TTHMs is not limited
only to water you drink. 10 minute shower produced more absorbtion
of TTHM through the skin than drinking 5 glasses of water.
Of the THMM compounds, Dibromochloromethane was the most closely
associated with cancer risk, (0.6 ug/l to cause a one in one million
cancer risk increase) followed in order by Bromoform, Chloroform,
and Dichlorobromomethane. These distinctions among the specific
chemical by-products of is a result of toxicological, not
empidemiological studies. Current regulations limit the
concentration of these four chemicals added together (total
trihalomethane or TTHM levels) to 100 ug/l. TTHM can be be found in
chlorinated water supplies and in the air of buildings where running
water and showers release the chemicals into the room, however, the
EPA has determined that this airborne exposure is minimal compared
to that from consumption.
http://www.cdc.gov/ncbddd/folicacid/index.htm
|
