Tobacco prevention articles 1: Whats In Tobacco Smoke?

Whats In Tobacco Smoke?

(Extract from the leaflet Whats In Tobacco Smoke? )

There are over 4000 chemicals in tobacco smoke. The number of chemicals is not so important. What matters is how toxic they are and how much of the toxins are present. Tobacco smoke is a complex mixture of compounds produced by burning tobacco. Chemicals are present as:

•	Gases (carbon monoxide, acrolein, hydrogen cyanide, nitrogen oxide)
•	Liquid vapours (formaldehyde, methane, benzene, ammonia, acetone)
•	Tiny particles or tar (phenols, nicotine, naphthalene)
•	Metals (arsenic, cadmium, nickel, chromium, lead)
•	Radioactive compounds (polonium 210, potassium 40, lead 210)

‘Sidestream’ smoke comes from the burning end of a cigarette and ‘mainstream’ smoke from the mouth end. Chemicals are inhaled into the lungs. Many pass through the lungs, into the blood stream and are pumped around the body.

Nicotine delivery
Cigarettes are highly engineered products, designed to deliver regular doses of nicotine.
Cigarette tobacco is blended from two main leaf varieties:
1. Yellowish ‘bright’, or Virginia tobacco contains 2.5-3% nicotine
2. ‘Burley’ tobacco contains 3.5-4% nicotine


Where do the chemicals in tobacco smoke come from?

•	Tobacco plants contain nicotine, a toxin that plants use to prevent animals from eating it.
•	Tobacco leaves absorb radioactive substances such as polonium 210 from the air.
•	Agricultural chemicals (fertiliser, pesticide, insecticide, fungicide) and compounds in the soil are absorbed through the roots. These include arsenic and cadmium.
•	Processing and curing (drying) tobacco produces nitrosamines.
•	Hundreds of flavourings and additives are used to make smoking easier and better tasting.
•	Cellulose filters and cigarette paper contain chemicals. Filters stop some particles but not gases.

Cigarette paper and filter
Nicotine and tar delivery can be modified by the cigarette paper. Porous paper lets more air into the cigarette, dilutes the smoke and reduces the amount of tar and nicotine reaching the lungs. Filters are made of cellulose acetate and trap some tar from inhaled smoke. Filters cool the smoke, making it easier to inhale more deeply.


What else is in tobacco smoke?
Fillers
These consist of stems of tobacco plants, mixed with water. It varies among cigarette brands.

Agricultural chemicals
Herbicides, insecticides, fungicides, fertilisers are agricultural chemicals routinely used in tobacco growing. Tobacco is imported so it not known which agricultural chemicals are in the cigarettes.

Additives and flavourings
Over 600 additives are allowed in UK cigarettes. They are added during the manufacturing process to make tobacco products more acceptable to the user. Reasons for additives include:

•	To add flavour. Sweeteners; sugar, honey, liquorice and cocoa reduce harshness of the smoke.
•	To lessen irritation. Menthol numbs the throat.
•	To change the chemistry of nicotine. Ammonia increases the addictiveness of nicotine.
•	To change smoker’s bodies. Chemicals in liquorice and cocoa open the airways to allow more nicotine and tar into the lungs. Other additives make the brain more receptive to nicotine.
•	To keep tobacco moist to prolong shelf life.
•	To control the burn temperature.
•	To treat the cigarette paper.

Inhaled vs. ingested
Chemicals that are inhaled cause more damage than ingesting them because lungs are better than intestines at absorbing them. For example, our guts absorb about 6% of cadmium in our food, but our lungs absorb 60% of inhaled cadmium.

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