Year 8 Biological Sciences – Smoking Related Disease
By: Shayan Saebi

1. Smoking Related Disease – Coronary Heart Disease
Coronary heart disease (CHD) is the leading disease causing death around the world through smoking cigarettes (due to the inhalation of 7,000 different poisonous chemicals). CHD is a term, which happens when a waxy substance called plaque builds up inside the coronary arteries. These arteries, supply oxygen-rich blood to your heart muscle. This wax is a mixture fatty deposit and other waste substances called atheroma – as shown in Figure 1. When this plaque builds up in the arteries, this condition is called atherosclerosis and can be caused by lifestyle factors including:

High blood Cholesterol levels
Smoking
High blood pressure (hypertension)
Diabetes
Not taking regular exercises

Other risks for developing CHD include being obese or having a family history of CHD (which is the main cause of 80% of CHD patients).

Plaque narrows the coronary arteries and reduces blood-flow to your heart. After many years, this plaque starts to build up causing blood clots in your arteries. Blood clots can either partially block the arteries or fully block the arteries (which is the causes of heart attacks, strokes or even death).

If blood flow to your heart is reduced or blocked, you may have angina (chest pain or discomfort) or even in major cases a heart attack. Angina can feel like squeezing in your chest. The pain also can occur in your shoulders, neck, jaw, or back.

A heart attack is caused when oxygen-rich blood to a section of the body is cut off. If blood flow is not restored the cells of that section of the body will rapidly die. If not treated quickly, it can lead to serious health problems or even death.
Over time, CHD can have lethal effects including weakening the heart leading to heart failure. Heart failure is a condition in which your heart can’t pump adequate blood necessary for the consumption of your body therefore leading to many serious conditions.

2. How do the substances contained in cigarette smoke cause coronary heart disease?

Cigarettes are made from dried tobacco leaves and other ingredients to make it more pleasant. The smoke from these products creates complex chemicals, which is produced from the burning tobacco. Cigarette smoke contains many substances that can cause Coronary Heart Disease. See figure 2. A cigarette is made up of over 7000 chemicals with a single cigarette containing at least 60 cancer-causing chemicals (carcinogenic) and a further 400 other toxins (Centers for disease control and prevention, 2015). Some of the substances in cigarette smoke include:

Cyanide – Used in rat poison
Hydrogen Cyanide – Used in rat poison
Benzene – Found in crude oil
Ammonia – Used in toilet cleaner
Acetylene – Used as a fuel
Acetone – Used in nail polish remover
Toluene – Used to thin out paint
Phenol – Used in some fertilisers
Tar – Particular matter in cigarette smoke
Carbone monoxide – Found in car exhaust
Nitrogen oxide – Gas and air pollutant
Nicotine – The addicting substance in cigarette smoke
(Australian Government, 2015)
Scientists have found that the cigarette smoke created from these chemicals damages and kills the cells that line the lungs and airways. When cigarette smoke is breathed in it damages DNA cells and the genes that protect us from cancer. These genes are called p53 and are found in every cell in the human body. The p53 genes are a very important part of the cell and we need them to protect us from cancers. (Quit Victoria, 2015)

These cells get more damaged as more cigarette smoke and chemicals interfere with them. Coronary Heart Disease isn’t caused straight away from cigarette smoke but is caused when the cells keep getting damaged from cigarettes and cannot repair themselves quickly enough. Research has shown that for every 15 cigarettes smoked your DNA changes which could then cause the cell to become cancerous. (Cancer Research UK, 2015)

Coronary