Assertion: great smog | /r/HasProperty | the worst air-pollution event
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text: London has suffered since the 13th century from poor air quality, which worsened in the 1600s, but the Great Smog is thought to be the worst air-pollution event in the history of the United Kingdom, and the most significant in terms of its effect on environmental research, government regulation, and public awareness of the relationship between air quality and health.