Carbon monoxide is a silent, toxic gas
Definition
Carbon monoxide
A toxic, colourless and odourless gas that reduces the amount of oxygen transported by the blood.
Definition
Haemoglobin
The substance in red blood cells that binds to oxygen and transports it around the body.
- Carbon monoxide, CO\text{CO}CO, is toxic, colourless and odourless.
- Because it has no colour and no smell, it is very hard to detect.
- In the blood it binds to haemoglobin in the place normally taken by oxygen.
- This reduces the amount of oxygen the blood can carry around the body.
- A shortage of oxygen can cause fainting, a coma or death.
Key Idea
Carbon monoxide is dangerous because you cannot sense it and it starves the body of oxygen by taking oxygen's place on haemoglobin.
Sulfur dioxide and oxides of nitrogen harm lungs and cause acid rain
Definition
Sulfur dioxide
A gaseous atmospheric pollutant that irritates the respiratory system and contributes to acid rain.
Definition
Oxides of nitrogen
Gaseous compounds containing nitrogen and oxygen that irritate the respiratory system and contribute to acid rain.
- Sulfur dioxide, SO2\text{SO}_2SO2, and oxides of nitrogen, NOx\text{NO}_xNOx, are acidic gases.
- Breathing them in causes respiratory problems, such as irritated airways and worse asthma.
- In the air they dissolve in water and fall as acid rain.
- Acid rain damages trees, lakes and buildings made of limestone or metal.
Common Mistake
- Both sulfur dioxide and oxides of nitrogen cause acid rain, not just one of them.
- These gases cause respiratory harm; this is not the same as the oxygen-blocking effect of carbon monoxide.
Particulates dim the skies and damage health
Definition
Particulates
Tiny solid particles suspended in the air that can damage human health and affect the amount of sunlight reaching Earth's surface.
- Particulates are tiny solid particles, including soot, carried in the air.
- Breathed deep into the lungs, they cause respiratory problems and other health damage.
- High in the atmosphere they reflect sunlight back into space, causing global dimming.
- Global dimming is a fall in the amount of sunlight reaching Earth's surface.
Exam technique
- Match each effect to its pollutant: carbon monoxide gives less oxygen in the blood; sulfur dioxide and oxides of nitrogen give acid rain and breathing problems; particulates give global dimming and health problems.
- For a named pollutant, give both a health effect and, where it applies, an environmental one.
Self review
- Give three properties of carbon monoxide that make it dangerous.
- How does carbon monoxide reduce the oxygen carried by the blood?
- Which two gases cause acid rain, and what else do they harm?
- What is global dimming, and which pollutant causes it?
- Give one health effect and one environmental effect of particulates.
