Researchers from the National Park Service and Colorado State University are studying haze levels in Theodore Roosevelt National Park.
The Forum reports that haze has become more noticeable in park's north unit, which is surrounded by oil and gas development.
Haze and other air quality indicators have long been a concern around Theodore Roosevelt National Park and other parks in western North Dakota. Emissions are now on the rise with the dramatic increase in oil drilling and production.
Park chief of resources Bill Whitworth says the haze is increasing, but it's not every day.
Preliminary findings show a sharp rise in ammonium nitrate.
Once the results are in hand, officials will determine what if anything should be done to try to improve the issue.
Information from: The Forum