The Effects of Smoking

Smoking leads to emphysema and an increased risk of several different types of cancer, including lung cancer
- There are strong links between cigarette smoking and lung cancer and emphysema
- The majority of cases of lung cancer are caused by smoking

Graph correlation numbers of adults who smoke & lung cancer rates

Graph showing a correlation between numbers of adults who smoke and lung cancer rates over time

Note that as the general trend shows that as the number of adults who smoke decreases, so does the lung cancer rates a few years later (as cancer takes some time to develop)
The trend in the rate of developing lung cancer for women has been increasing, while in men it is decreasing
This is because the number of female smokers – unlike men – continued to increase in the 1950s and 1960s before starting to fall
As cancer takes some years to develop, a fall in female rates of lung cancer is likely to occur later

Chemicals in cigarettes include:
- Tar - a carcinogen (a substance that causes cancer)
- Nicotine - an addictive substance which also narrows blood vessels

Tar is a carcinogen and is linked to increased chances of cancerous cells developing in the lungs
It also contributes to the lung disease emphysema

Nicotine is addictive
It narrows blood vessels leading to increased blood pressure
It also increases heart rate
Both of these effects can cause blood clots to form in the arteries leading to heart attack or stroke

Tumours can develop in the respiratory system which is a consequence of the chemicals found in cigarette smoke
Tumours can interfere with the normal working of the lungs
Symptoms of lung cancer include:
- Coughing up blood
- A persistent cough
- Coughing an increased amount of mucus
- Back or shoulder pain
- Wheezing and breathing difficulties
- Sudden weight loss

Emphysema is a lung disease that can develop as a result of the chemicals found in cigarette smoke
Frequent infections can develop in the lungs of smokers which results in phagocytes (a type of white blood cell) being attracted to the tissues of the lungs
Phagocytes release enzymes that damage the alveolar walls which create large air spaces in the alveoli resulting in a smaller surface area for gas exchange
The consequences of this are breathlessness and wheezy breathing
- Once the disease progresses, people often need a constant supply of oxygen to stay alive

The breakdown of alveoli in emphysema reduces the surface area for gas exchange

The effects of smoking also damage the cilia cells and the mucus that line the airways of the respiratory system
The chemicals in cigarette smoke paralyse cilia which prevents them from working
The small particles found in cigarette smoke clog the mucus which prevents it from moving up and out of the airways instead it builds up blocking the smallest bronchioles
A smoker's cough is the attempt to move the mucus but it damages the epithelia resulting in scar tissue, which narrows the airways and makes breathing difficult
Dirt and pathogens contained within the mucus are not removed from the airways so frequent infections of the respiratory system can occur

The Effects of Smoking (WJEC GCSE Biology)