Fresh mountain smog? 96% of national parks have hazardous air quality –study

Report finds popular parks such as Yosemite and Joshua Tree have pollution at levels that threaten visitors and wildlife

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Millions of tourists will head out into America's national parks this summer in search of fresh mountain air. But according to a new report they should instead expect dangerous levels of pollution; roughly 96% of the nation's parks are struggling with significant air quality issues.