单选题
Now medical researchers are discovering a truism:
"alcohol and tobacco do not mix." These two substances, both dangerous to
health, act synergistically, each making the other more powerful and thereby
causing worse damage than either would do alone. Because of
this interaction, the person who both smokes and drinks heavily may be at a
greater risk of becoming ill than one who drinks like a fish, but never smokes
or who smokes like a chimney, but never drinks. To get an idea of how this
synergism may work, consider what happens when a smoker lights up a cigarette.
With each puff he inhales at least 4,000 different chemicals. These include
toxic hydrogen-cyanide, carbon monoxide and nitrogen-dioxide gases, and four
dozen compounds such as benzo pyrene and radioactive polonium 210. All are known
as carcinogens. Most chemical vapors in tobacco smoke get deposited in the
mouth, nose, throat and lungs in a coating called tar. It is in this tar that
most of the cancer--inducing potential of tobacco smoke lies. Then in a scenario
typical of chronic heavy drinkers--most of whom also smoke--our smoker feels
thirsty and washes down that smoke coating in his mouth and throat with whisky.
The alcohol in his drink is not in itself a carcinogen, but it may act as a
solvent, dissolving the tar-taped tobacco poisons, and easing the transport of
carcinogens across membranes. Our smoker continues to drink.
Soon he lights another cigarette and inhales deeply. Behind his embattled lungs,
meanwhile, his liver has gone on full alert to save his life. The three-pound
chemical factory, which cleans most toxins from the bloodstream, reacts to
alcohol as a foreign substance and metabolizes 95 percent of it into other
chemicals. But in turning its energy to clearing just one-half ounce of pure
alcohol--the amount in a standard drink--per hour from our drinking smoker's
blood, the liver's other metabolic functions suffer a sharp decrease. Poisons
from tobacco smoke that otherwise would be removed from his blood within minutes
are now allowed to flood his body for hours or days, depending on how much
alcohol the liver must dispose of. The person who smokes one or
two packs of cigarettes a day loses on average six to eight percent of his
blood's oxygen carrying capacity. If our heavy smoker's use of alcohol has led
to alcoholism, he is probably malnourished. This malnourishment compounds
problems he is having with insufficient oxygen. His brain cells are dying from
it. The synergistic effect of alcohol and tobacco may deliver a
powerful blow to the cardiovascular system as well as the upper respiratory
tract. For those prone to hypertension who drink more than two ounces of alcohol
a day, high blood pressure is common and with it the increased risk of stroke
and heart attack. For hypertensives who combine smoking and drinking, the risks
are even greater.
单选题
Which of the following can be the best title of this passage?