The ice core samples from the Upper Fremont Glacier indicated that levels of mercury increased dramatically during the industrial revolution and have decreased significantly since the mid-1980s. It is believed that the decrease in mercury deposition since the 1980s coincides with the passage of the Clean Air Act.
The ice core samples from the Upper Fremont Glacier demonstrate a correlation between industrial activity and mercury levels, with a subsequent decrease in mercury deposition coinciding with the implementation of the Clean Air Act.