TAR
Tar is a term that describes a collection of solid particles that smokers inhale when they light a cigarette.
It is a mixture of lots of chemicals, many of which can cause cancer. When it settles, tar forms a sticky, brown residue that
can stain smokers’ teeth, fingers and lungs.
Because tar is listed on
packs, it is easy to believe that it is the only harmful part of cigarettes. But some of the most dangerous chemicals in tobacco
smoke are present as gases, and do not count as part of tar. This means that cigarettes with less tar still contain all the
other toxic chemicals.
ARSENIC
Arsenic is one of the most dangerous chemicals in cigarettes. It can cause cancer as well as damaging
the heart and its blood vessels.
Small amounts of arsenic
can accumulate in smokers’ bodies and build up to higher concentrations over months and years. As well as any direct
effects, it can worsen the effect of other chemicals by interfering with our ability to repair our DNA.
Fish and seafood can be
major sources of arsenic, but in a form that is less toxic and more readily removed from the body. In contrast, tobacco smoke
contains arsenic in a more dangerous form.
BENZENE
Benzene is a solvent used to manufacture other chemicals, including petrol. It is well-established
that benzene can cause cancer, particularly leukaemia. It could account for between a tenth and a half of the deaths from
leukaemia caused by smoking.
Tobacco smoke contains large
amounts of benzene and accounts for a big proportion of our exposure to this poison. The average smoker inhales about ten
times more benzene than the average non-smoker.
And some studies have
estimated that the amount of benzene that a person inhales through second-hand smoke over their lifetime could increase their
risk of cancer.
CADMIUM
Cadmium is a metal used mostly to make batteries. The majority of cadmium in our bodies comes from
exposure to tobacco smoke. Smokers can have twice as much cadmium in their blood as non-smokers.
Studies have found that
the amounts of cadmium present in tobacco smoke are capable of affecting our health. It is a known cause of cancer,
and can also damage the kidneys and the linings of the arteries.
Our bodies have proteins
that mop up harmful chemicals like cadmium, but the amounts in smoke can overload these proteins. Cadmium can
also prevent our cells from repairing damaged DNA. Because of this, it can make the effects of other chemicals even worse.
FORMALDEHYDE
Formaldehyde is a smelly chemical used to kill bacteria, preserve dead bodies and manufacture other chemicals.
It is one of the substances in tobacco smoke most likely to cause diseases in our lungs and airways.
Formaldehyde is also a known cause of cancer. It is believed that even the small amounts in second-hand
smoke could increase our lifetime risk of cancer.
Tobacco smoke is one of
our major sources of formaldehyde exposure. Places where people smoke can have three times the normal levels of this poison.
POLONIUM
Polonium is a rare, radioactive element and polonium-210 is its most common form. Polonium
strongly emits a very damaging type of radiation called alpha-radiation that can usually be blocked by thin layers of skin.
But tobacco smoke contains
traces of polonium, which become deposited inside their airways and deliver radiation directly to surrounding cells.
The lungs of smokers can
be exposed to four times more polonium than those of non-smokers and specific parts may get a hundred times more radiation.
One study estimated that someone smoking one and half packs a day receives the equivalent amount of radiation as someone having
300 chest X-rays a year.
CHROMIUM
Chromium is a metal used to make metallic alloys, dyes and paints and comes in different types. Chromium
III or ‘trivalent chromium’ is most commonly used. It is available as dietary supplements and is harmless.
On the other hand, chromium
VI or ‘hexavalent chromium’ is very toxic, is found in tobacco smoke, and is known to cause lung cancer. It
allows other cancer-causing chemicals (such as polycyclic aromatic hydrocarbons) to stick more strongly to DNA and damage
it.
1,3-BUTADIENE
1,3-butadiene or BDE is an industrial chemical used in rubber manufacture. Some scientists believe that
of all the chemicals in tobacco smoke, BDE may present the greatest overall cancer risk. It may not be as good at causing
cancer as some of the other chemicals listed here, but it is found in large amounts in tobacco smoke.
POLY AROMATIC
HYDROCARBONS
Polycyclic aromatic hydrocarbons or PAHs are a group of powerful cancer-causing chemicals that can damage DNA and set cells
down the road to becoming tumours. One of these chemicals – benzo(a)pyrene or BAP – is one of the most
widely studied of all tobacco poisons. BAP directly damages p53, a gene that normally protects our bodies against cancer.
NITROSAMINES
Nitrosamines are a group of chemicals that can directly danmage DNA like (PAHs). They are found
in small amounts in food. But tobacco products, including those that are chewed rather than smoked, are by far our largest
source of exposure to these chemicals. Even though they are found in relatively small amounts in cigarettes, they are very
strong cancer-causing chemicals.
ACROLEIN
Acrolein is a gas with an intensely irritating smell and is one of the most abundant chemicals in
cigarette smoke. It belongs to the same group of chemicals as formaldehyde and acetaldehyde, both of which can
cause cancer.
Until now, it wasn’t
clear if acrolein causes cancer as well, but recent experiments suggest that it can. We now know that acrolein
can cause DNA damage that is similar to the damage seen in lung cancer patients. Since smoke contains up to 1,000 times more
acrolein than other DNA-damaging chemicals, it could be a major cause of lung cancer.
Acrolein also stops our cells from repairing DNA damage, like arsenic and cadmium. And
like hydrogen cyanide, it kills the hairs that normally clean our lungs of other toxins.
OTHER CHEMICALS
Some of the other cancer-causing
ingredients of tobacco smoke include:
- metals, such as nickel, lead, cobalt and beryllium. While you may be exposed to some of these metals through domestic items or food, inhaling
them in tobacco smoke is worse, because they are easily absorbed by the lungs.
- acetaldehyde, which is also
formed in your tissues when you drink alcohol – it is responsible for many nasty hangover symptoms
- hydrazine, a very toxic chemical
used mainly in rocket fuel
With repeated smoking, the vast mixture of chemicals
in tobacco smoke can affect almost every organ in the body.
Chemicals in cigarette smoke affect the entire body. This is why smoking causes so many diseases, including a dozen
types of cancer, heart disease and various lung diseases.
The above diagram shows
just some of the types of cancer that are caused by smoking.
As soon as you take a puff
on a cigarette or breathe in someone else’s smoke, poisonous gases like formaldehyde will start to irritate your
eyes, nose and throat.
Lungs and
respiratory system
When you inhale the smoke,
it damages the tissues of your airways and lungs. Chemicals like nitrogen oxide can constrict your airways, forcing your lungs
to do more work and making breathing more difficult.
Hydrogen cyanide, carbon monoxide and ammonia weaken the natural cleaning mechanisms that clear
your lungs and airways of toxins. This means that other dangerous chemicals, bacteria and viruses that you inhale stay inside
your lungs.
Radioactive polonium-210
becomes deposited at the points where your airways split to connect to your lungs. This can subject local cells to much more
radiation than they would otherwise experience.
From the lungs, cancer-causing
chemicals and other poisons in tobacco smoke are absorbed into your bloodstream. These poisons are then carried to other parts
of your body.
Heart and
blood vessels
Many tobacco poisons such
as arsenic and hydrogen cyanide can directly damage the cells that line your heart and its blood vessels.
Nicotine and carbon monoxide cause blood vessels to constrict. Smoke also increases your level
of blood cholesterol and as a result, raises your chances of developing a blood clot.
Gases such as carbone monoxide
and nitrogen oxide reduce your blood’s ability to transport oxygen. This lowers the amount of oxygen reaching
your brain and other organs and reduces your energy levels.
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