Thailand's Pollution Control Department declared air quality in the the Thai capital unhealthy, leading to the closure of 400 public schools through the end of the week.
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University of Oregon scientists used real dust from inside homes around Portland to test the effects of sunlight, UV light and darkness on bacteria found in the dust.
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Nitrogen oxide pollution in India and China is offsetting U.S. gains in cutting emissions, researchers say. This photo from October shows road traffic, along with smoke and smog, in front of the landmark India Gate in New Delhi.
California is looking into ways to reduce the use of gas-powered lawn and gardening equipment because they will soon surpass cars as the biggest polluters in the state.