#83 Effects of tobacco smoke on the respiratory system

Tobacco smoke contains irritants and carcinogens. 

Its 4 main toxic chemicals: carbon monoxide, nicotine, smoke particles and tar.

Carbon monoxide:

- combines with haemoglobin in RBC ---> prevents them transporting O_­2­.

Nicotine:

- addictive ---> continual smoking

Smoke particles:

- irritate air passages ---> inflammation + increase mucus production ---> chronic bronchitis.

- presence of smoke particles in alveoli + coughing = emphysema (breathlessness)

Tar:

- a carcinogen: increase risk of lung cancer ( cell division out of control)

- lines air passages:

    - increase mucus production

    - paralysing + damaging cilia

    ---> bronchitis

Some of the substances in tobacco smoke.  

Common misconceptions

Remember that only nicotine and carbon monoxide enter the blood. Tar and smoke particles do not – they stay in the lungs. 

Sample question

The table shows the percentage of haemoglobin which is inactivated by CO present in the blood of taxi drivers in a city. 

City taxi drivers	Percentage of Hb inactivated by CO
Daytime drivers	Non-smokers Smokers	2.3 5.8
Night-time drivers	Non-smokers Smokers	1.0 4.4

i) Suggest two sources of the CO inhaled by these taxidrivers          [2marks]

ii) Some daytime drivers have 5.8% of their Hb affected. Using information from the table, explain which source contributes most to this effect.        [2 makrs]

iii) Suggest a reason for the differences, shown in the table, between daytime and night-time drivers.                                                                          [1 mark]

Studen’s answer

i) 1. cigarette smoke ü

   2. breathing by passengers û

ii) It must be cigarette smoking because non-smokers have less of their Hb affected. ü

iii)Therer could be less car exhaust fumes, containing CO, at night. ü

Examiner’s comments

In part (i), the second answer if biologically incorrect (we breath out CO₂, not CO. The other correct answer was car exhaust gases.

In part (ii), the answer and the explanation were correct.

Part (iii) war a good answer.