There are many hidden costs to human health and the natural environment related to the use of fossil fuels. That’s why renewable energy advocates have long argued that fossil fuels are not cheaper than clean energy. Now that solar and wind energy are beginning to beat oil, gas, and coal, more clarity about the hidden costs is also surfacing. A new British report “A Breath of Fresh Air” calculates that the U.K. can save up to $4 billion in health care costs, just by ending coal use. Every year. Air pollution is the second biggest public health threat after smoking, and kills 40,000 people a year, according to the report.