First, the bad news. (Nowadays, good environmental news gets muffled mention, if that.)
The bad news is a rising US trend in unhealthy air days.
The Environmental Protection Agency considers an unhealthy day one in which a major air pollutant exceeds national standards anywhere. Major pollutants are ozone, particulates, nitrogen oxides, carbon monoxide, and sulfur dioxide.
Since 2014, the annual total of unhealthy days has risen each year except for a small dip in 2016. Last year’s total, according to the EPA’s annual air trends report published this month, was 799. The 598 unhealthy-day total of 2014 was the low point during 2000-18.
Until 2003, though, these numbers exceeded 2,000.
Air-quality problems linger in cities. That’s all the bad news evident on an EPA summary graphic.
Nationally, air-pollution metrics are improving despite sharp increases in gross domestic product and vehicle-miles traveled and steady or slightly rising population and energy-consumption levels.
Between 1970 and 2018, EPA reports, combined emissions of six key pollutants fell by 74% while the US economy grew by 275%.
During 2016-18, decreases continued: NOx 8.7%, fine particulate matter (PM2.5) 1.9%; coarse particulate matter (PM10, including lead) 1.2%, SO2 7.8%, carbon monoxide 7.2%, and volatile organic compounds 3.3%.
During 1990-2018, average air concentrations of key pollutants have fallen by 21% for ground level ozone (8-hr), 39% (for PM2.5 (annual from 2000), 26% for coarse particulate matter (24-hr), 89% for SO2 (1-hr), 57% for NOx (annual), 82% for lead (3-month average from 2010), and 74% for CO (8-hr).
The environmentally despondent will consider these developments less important than climate change, about which news isn’t all bad.
EPA says US emissions of carbon dioxide in 2017, the latest data year, were up 22% from their level of 1970. That’s bad news.
Yet CO2 emissions have fallen every year but two since 2007, when they were 57% above the 1970 baseline. That’s good news.
In keeping with media practice of the day, good CO2 news appears here last. But it appears.