smog

Everyday

Dirty, smoky, foggy air over a city, caused by pollution from cars, factories and fires, often mixed with fog. tree →

In the lessons

In science and geography lessons smog is a key example of air pollution: it makes breathing hard, especially for people with asthma. The word was made from "smoke" + "fog". The Great Smog of London in the past killed thousands and led to clean air laws. Today many big cities issue smog warnings. Phrases: a smog warning, thick smog, photochemical smog.

Examples

• The city was covered in thick brown smog. tree →
• On smog days, children with asthma should stay inside. tree →
• Smog comes from car fumes and factory smoke. tree →
• London once had a terrible smog that lasted for days. tree →
• We couldn't see the mountains through the smog. tree →
• Cleaner cars help reduce smog. tree →

Note

Uncountable: "smog is", "some smog". A blend word: smoke + fog (like brunch = breakfast + lunch). Not the same as plain fog, which is just tiny water drops and is not polluted.