Though older adults and people with weakened immune systems are most at risk for dire health outcomes related to extreme heat and air pollution, no one is immune, said Jun Wu, a professor in the department of environmental and occupational health at the University of California, Irvine. "They may think it's not a big deal, that it's only weak people or homeless people who may be at risk," she said, but that's not true. "The body has a limited capacity to handle stress," Wu said. And while extreme heat and air pollution impact the human body in different ways, the existence of one appears to worsen the impact of the other.

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