Human Gas Exchange » Smoking Effects on Health

What you'll learn this session

Study time: 30 minutes

The harmful substances in cigarette smoke
Short-term and long-term effects of smoking on health
How smoking damages the respiratory system
Diseases caused by smoking, including lung cancer and COPD
The effects of passive smoking
Statistics about smoking-related illness and mortality

Smoking and Its Effects on Health

Smoking is one of the leading preventable causes of death worldwide. Despite widespread knowledge about its harmful effects, millions of people continue to smoke. Understanding how smoking affects the respiratory system and overall health is crucial for making informed decisions about tobacco use.

Key Definitions:

Tobacco smoke: A complex mixture containing over 7,000 chemicals, including at least 70 known carcinogens.
Tar: A sticky substance in cigarette smoke that contains most of the carcinogens and coats the lungs.
Nicotine: An addictive substance in tobacco that causes physical dependence.
Carbon monoxide: A poisonous gas in cigarette smoke that binds to haemoglobin in red blood cells.
Passive smoking: The inhalation of smoke by persons other than the active smoker.

Harmful Substances in Cigarette Smoke

🚬 Tar

Tar is a sticky brown substance that contains most of the carcinogens in tobacco smoke. When inhaled, it coats the lungs and can:

Damage the cilia in the airways
Cause excess mucus production
Lead to chronic bronchitis
Contain chemicals that cause cancer

⚡ Nicotine

Nicotine is the addictive component of cigarettes that keeps people smoking. It:

Increases heart rate and blood pressure
Causes blood vessels to constrict
Creates physical dependence
Triggers dopamine release in the brain, creating pleasure

☠ Carbon Monoxide

Carbon monoxide (CO) is a poisonous gas that:

Binds to haemoglobin 200 times more strongly than oxygen
Reduces oxygen-carrying capacity of the blood
Causes oxygen starvation in tissues
Forces the heart to work harder to deliver oxygen

🔬 Other Harmful Chemicals

Cigarette smoke contains thousands of other harmful substances including:

Formaldehyde (used to preserve dead bodies)
Benzene (found in petrol)
Hydrogen cyanide (used in chemical weapons)
Radioactive elements like polonium-210

Effects on the Respiratory System

Smoking has both immediate and long-term effects on the respiratory system. The damage builds up over time, leading to serious respiratory diseases.

Short-term Effects

Irritation of airways: Smoke irritates the trachea and bronchi, causing inflammation.
Increased mucus production: The body produces more mucus to trap the harmful particles.
Coughing: A natural response to clear irritants from the airways.
Reduced lung function: Even short-term smoking can reduce lung capacity.
Shortness of breath: Especially during physical activity.

Long-term Effects

💊 Damage to Cilia

Cigarette smoke paralyses and eventually destroys the cilia (tiny hair-like structures) that line the airways and help to remove mucus and debris. This leads to the "smoker's cough" as the body tries to clear mucus without functioning cilia.

🦠 Alveolar Damage

Smoking damages the alveoli (air sacs) in the lungs, breaking down the walls between them and creating larger, less efficient air spaces. This reduces the surface area for gas exchange and leads to emphysema.

💧 Mucus Hypersecretion

Chronic exposure to smoke causes goblet cells to multiply and produce excessive mucus. This narrows the airways and creates an environment where bacteria can thrive, leading to frequent infections.

Smoking-Related Diseases

Chronic Obstructive Pulmonary Disease (COPD)

COPD is a progressive disease that makes it hard to breathe. It includes two main conditions:

💦 Chronic Bronchitis

Chronic bronchitis is characterised by:

Inflammation of the bronchi
Excessive mucus production
Persistent cough with phlegm
Narrowed airways making breathing difficult

💥 Emphysema

Emphysema involves:

Destruction of alveolar walls
Formation of larger, inefficient air spaces
Reduced surface area for gas exchange
Trapped air in the lungs making it hard to breathe out

Lung Cancer

Smoking is the leading cause of lung cancer, responsible for about 85% of cases. Carcinogens in tobacco smoke damage the DNA in lung cells, leading to uncontrolled cell growth. Lung cancer has a poor prognosis because:

Symptoms often don't appear until the disease is advanced
It can spread (metastasise) to other parts of the body
Treatment options may be limited in later stages

Case Study Focus: Lung Cancer Statistics

In the UK, lung cancer is the third most common cancer, with around 48,500 new cases diagnosed each year. The 10-year survival rate is only about 10%, largely because most cases are diagnosed at an advanced stage. However, if caught early, survival rates improve significantly. This highlights the importance of smoking cessation and early detection programs.

Other Health Effects of Smoking

Smoking affects nearly every organ in the body, not just the lungs:

Cardiovascular system: Increased risk of heart attack, stroke and peripheral vascular disease due to narrowed blood vessels and increased clotting.
Reproductive system: Reduced fertility in both men and women, complications during pregnancy and increased risk of birth defects.
Digestive system: Increased risk of mouth, throat, oesophageal and pancreatic cancers.
Immune system: Weakened immune response, making smokers more susceptible to infections.
Skin, hair and nails: Premature ageing, yellowing of fingers and nails and slower wound healing.

Passive Smoking

Passive smoking (also called secondhand smoke or environmental tobacco smoke) occurs when non-smokers breathe in smoke from other people's cigarettes. This smoke contains the same harmful chemicals as directly inhaled smoke.

Health Risks of Passive Smoking

For adults: Increased risk of lung cancer, heart disease and stroke.
For children: More likely to suffer from respiratory infections, ear infections, asthma attacks and sudden infant death syndrome (SIDS).
During pregnancy: Exposure to secondhand smoke can lead to low birth weight and other complications.

Did You Know?

There is no safe level of exposure to secondhand smoke. Even brief exposure can be harmful to health. This is why smoking has been banned in enclosed public places and workplaces in the UK since 2007.

Benefits of Quitting Smoking

The good news is that the body begins to recover as soon as someone stops smoking:

⏱️ Short-term Benefits

After 20 minutes: Heart rate and blood pressure drop
After 12 hours: Carbon monoxide level in blood drops to normal
After 2 weeks: Circulation improves and lung function increases

📅 Medium-term Benefits

After 1-9 months: Coughing and shortness of breath decrease
After 1 year: Risk of coronary heart disease is half that of a smoker
After 5 years: Risk of mouth, throat and oesophageal cancer is halved

🗓️ Long-term Benefits

After 10 years: Lung cancer death rate is about half that of a smoker
After 15 years: Risk of coronary heart disease is the same as a non-smoker
Overall: Life expectancy approaches that of people who never smoked

Summary

Smoking has profound effects on the respiratory system and overall health. The harmful substances in cigarette smoke damage the airways, alveoli and blood vessels, leading to serious conditions like COPD and lung cancer. Passive smoking also poses significant health risks to non-smokers. Understanding these effects is crucial for making informed decisions about tobacco use and for supporting public health measures aimed at reducing smoking rates.

🧠 Test Your Knowledge!