At the other end of the list are cities in Canada and the United States, which benefit from lower population density, favorable climates and stricter air pollution regulation.

污染最轻的是美国和加拿大的城市，原因是它们的人口密度低，气候怡人，并且空气污染管理规定非常严格。

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At the other end of the list are cities in Canada and the United States, which benefit from lower population density, favorable climates and stricter air pollution regulation.

在污染排行中最靠后的是加拿大和美国的城市，受益于较低的人口密度、优越的气候和较严格的空气污染法规。

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These arguments center largely around the idea that current air pollution regulation is good enough as-is, and that any further restrictions are aimed at tackling environmental issues and climate change, both typically seen as luxuries in a down economy.

FORBES: Two New Reasons to Worry about Air Pollution: Obesity and Diabetes

The debate over air pollution and, more specifically, the regulation of air pollution, raged on this week as the Environmental Protection Agency (EPA) watered down its cross-state pollution rule and House Republicans moved to delay new rules on toxic air pollution from cement plants, solid waste incinerators, and industrial boilers.

FORBES: Two New Reasons to Worry about Air Pollution: Obesity and Diabetes

Increasingly, health research seems to be pointing to a need for stricter regulation of air pollution.

FORBES: Two New Reasons to Worry about Air Pollution: Obesity and Diabetes