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SIPs, NAAQS and Today's Big EPA Hearing on Denver Air Quality Explained
CDPHE

SIPs, NAAQS and Today's Big EPA Hearing on Denver Air Quality Explained

It was another rough summer for air quality in the Denver metro area, with at least twenty days hitting the unhealthy-for-sensitive-groups mark on the Air Quality Index scale. According to preliminary data, that’s a slight improvement over last year, but a years-long trend of elevated ozone pollution — leading to the region’s “F” air-quality rating from the American Lung Association — will be hard to reverse.

On Friday, September 6, federal regulators at the Environmental Protection Agency’s regional office in Denver are asking the public to weigh in on whether federal and state regulators should take new steps to better address the Front Range’s air-quality problem.

What does all this mean, and why should you care? Here's a crash course on federal clean-air rules, the trouble Denver has had complying with them, and what might change going forward.

What’s happening at the EPA on September 6?

The agency is holding a public hearing on a potential determination that the nine-county Denver Metro/North Front Range region has failed to meet the 2008 National Ambient Air Quality Standard (NAAQS) for eight-hour concentrations of ground-level ozone and should be reclassified from Moderate Non-Attainment to Serious Non-Attainment, thereby requiring additional elements in the Colorado Department of Public Health and Environment's corresponding State Implementation Plan (SIP).

…What? Okay, let’s start at the beginning: What is ozone?

In short, ozone is smog. It’s the primary component of the pale layer of haze that you see hanging over metro Denver in the summer, making the mountains barely visible. There are other forms of air pollution that fall under the catch-all term “smog,” but in the U.S. and especially in Denver, ozone is the big one.

You’ve probably heard of the ozone layer, a blanket of ozone that hangs very high in the atmosphere and shields us from harmful solar radiation — but ground-level ozone is a major public health hazard. In addition to ruining your mountain views, it can cause a variety of respiratory and cardiovascular problems, and chronic exposure can lead to asthma, chronic obstructive pulmonary disease (COPD) and even permanent lung damage.

Sounds bad. How can we get rid of it?

By driving less, driving cleaner cars, and reducing chemical emissions from oil and gas facilities and other industrial sites. Ozone levels spike in the summer because it forms in the air in the presence of direct sunlight, as the product of a chemical reaction between oxygen and certain gases, including nitrogen oxides, sulfur dioxide and volatile organic compounds. These ozone “precursors” come from cars, trucks, and any other machinery powered by gas or diesel, as well as from industrial sources — most notably the wells, storage tanks, compressor stations and other facilities that make up the oil and gas supply chain.

Why isn’t there some kind of law regulating all this stuff?

There is! In 1963, Congress passed the Clean Air Act, arguably the most important piece of public health legislation in U.S. history. It instructs the EPA to set federally-mandated air quality standards, the NAAQS, for six “criteria pollutants,” including ozone.

The ozone standard — specifically the eight-hour ozone standard, because regulators look at the average concentration over an eight-hour period — is currently 70 parts per billion (ppb), after the Obama administration revised it downwards in 2015. Trump’s EPA has fought to delay enforcement of this new, stricter limit, but that doesn’t matter for Denver, because we haven’t even met the old standard of 75 ppb, established in 2008.

In fact, Denver’s air quality has been so bad for so long that before 2008, we weren’t meeting the 1997 ozone standard, either; we’ve been playing catch-up for two decades. Failing to “attain” these federal standards gets you classified as a non-attainment area, and in 2004 the EPA officially designated a nine-county region in northeast Colorado as the Denver Metro/North Front Range Non-Attainment Area.

Are there consequences for failing to meet these standards for so long?

There are five escalating levels of non-attainment based on how long a region has violated the NAAQS, each of which requires states to enact stricter and stricter regulations on polluters. Three years of exceeding the standard means a region is in "marginal" non-attainment, six years is "moderate" non-attainment, and nine years is "serious" non-attainment. The EPA's looming decision on the Denver region is whether to classify it as a "serious" violator under the 2008 ozone standard.

Wait a second — you said "serious" means nine years of non-attainment, but the 2008 standards came into effect more than ten years ago. What gives?

In June 2018, then-Governor John Hickenlooper requested a one-year extension, and Trump's EPA, which is fighting to repeal or weaken pollution rules all over the country, was happy to oblige. His successor, Governor Jared Polis, withdrew the extension request in March. Technically, federal law required the EPA to downgrade the area to serious non-attainment as soon as Polis withdrew the request, but the agency is only just now getting around to it.

That's weird.

That's not a question, but yes. An environmental group took the EPA to court over the delay, and the agency basically admitted to a federal judge that it was dragging its feet.

What will change if the EPA says Denver is in serious non-attainment?

In the SIP for the non-attainment area, the major source threshold will fall from 100 to 50 tons per year, the offset ratio for the new source review program will rise from 1.15:1 to 1.2:1, the state will be required to demonstrate 18 percent reasonable further progress (RFP) over six years instead of only 15 percent, including milestone contingency measures, and much more.

Come on.

Okay, okay: State regulators will be required to strengthen a lot of existing air pollution rules and enact some new ones. A wider range of industrial sources will be subject to stricter permitting requirements and emissions controls, and regional officials will have to develop better, more detailed plans for reducing pollution from transportation.

Is there anything else I should be worried about?

You bet! For one thing, there's plenty of evidence that climate change is making ozone pollution worse. But there's good news, too: Since greenhouse gases are often "co-emitted" with ozone-forming pollutants, the two problems can be tackled together through many of the same emissions-reduction strategies. That's why tomorrow's EPA hearing will be closely watched by public health advocates and climate activists alike — and why the outcome of the agency's decision is so important.

The EPA will hold a public hearing on Denver air quality at 9 a.m. Friday, September 6, on the second floor of the EPA Region 8 office at 1595 Wynkoop Street.

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