(AP) - The breathtaking scenery and pristine air in a rural area of Wyoming has been fouled by an unlikely culprit in the last week: smog.

Pollution is smudging the air and residents in the Upper Green River Basin are complaining of watery eyes, shortness of breath and bloody noses. State regulators urged the elderly, children and people with respiratory conditions to avoid strenuous or extended activity outdoors. Day-care centers are keeping kids inside for recess.

The cause of the pollution spike is blamed on weather patterns and the natural gas-drilling boom. Drilling of new wells and gas-field equipment release substances that contribute to ozone pollution.

Preliminary data show ozone levels got as high as 124 parts per billion in the Upper Green River Basin, that's two-thirds higher than the EPA healthy standard and above the worst day in Los Angeles in 2010.