Nicotine, the major drug found in tobacco, is a stimulant. A stimulant is a is a drug that increases the activity of the central nervous system. When tobacco is inhaled, nicotine is absorbed into the bloodstream through the lining of the mouth and through the lungs. Nicotine is quickly transported throughout the body, penetrating the brain, all other organs, and, in pregnant women, the fetus.

Now what are the effects of tobacco? Nicotine increases blood pressure and heart rate while decreasing the oxygen supply to body tissue and the blood supply to the hands and feet. Nicotine is an addictive drug. In addiction, the user of a drug becomes dependent on the drug and cannot function comfortably without it. Nicotine is a poison-60 mg of nicotine is a lethal dose for an adult. But nicotine is not the only poison found in tobacco. There are more than 2,000 potentially toxic chemical compounds produced when tobacco is burned. collectively, these are called tars.
Tars are complex mixtures of chemicals and smoke particles produced by burning tobacco. Tars paralyze the cilia that line the air passages. Cilias move particles out of the air passages and protect from diseases-causing microorganisms. Tars irritate the nose, throat, trachea, and bronchial tubes, causing sore throat and coughing.
Eventually, tars settle in the lungs. The result is reduction in breathing capacity and increased susceptibility to infections. The lungs of a smoker look much
different from those of a none smoker due to accumulation of tars.

Why are most sunsets red? For exactly the same reason that the sky is blue. When the Sun is at the horizon, its rays have to travel through more atmosphere, and the green, blue, and violet light get scattered the most-filtered out of the light, basically. By the time the light reaches our eyes-and the clouds above us-it’s made up largely of yellow, orange, and especially red. That’s why the sky sometimes almost appears to be on fire at sunset and sunrise.