Reduced Drive Days During Ozone Season

Before we jump into this, here are a few basics about ozone.

• Ozone is good if it's high up in the atmosphere (stratosphere, ozone layer, where the "hole" in the ozone layer once was). This ozone filters out/blocks some ultraviolet light (what causes sunburns, skin cancer).
• Ozone is bad if its where we can breathe it (troposphere, ground-level). While ozone is helpful in some places, inside human lungs is definitely not one of those places.
• Denver has had an ozone problem for years. At risk of oversimplifying, there's a standard that's meant to protect public health and the Denver area front range can't meet it (higher than desired ozone levels). That means the most sensitive members of our public (elderly, people with lung diseases) may experience difficulty breathing when the ozone is elevated.
• Ground-level ozone forms when volatile organic compounds (VOC) and oxides of nitrogen (NOX) react in the presence of sunlight. Too bad we have so much sun in Colorado...
• Ozone season is the period of time when conditions are best for ground-level (bad) ozone to form. In Denver, this period is from May through September thanks to the long days (more sunshine) and presence of VOC and NOX.

Now that we have that covered, we can talk about the implications of high ozone. When a standard the EPA has established cannot be met, the Clean Air Act imposes increasingly restrictive requirements on that area. These requirements are meant to "clean up" the area so one day it will meet the standard. An area that does not meet a particular standard is called a nonattainment area. Here's a PDF map of the Denver ozone nonattainment area. Here's an interactive map of all the nonattainment areas in the United States (turn on the layers of interest in the menu in the upper right).  If an area is designated nonattainment and still cannot meet the standard, the designation and associated implications get worse over time.

Currently, the Denver area is classified as moderate nonattainment and is expected to be redesignated as serious within several months. Perhaps the most talked about subject regarding the Denver nonattainment area is the major source threshold. Major sources of air pollution (way over simplified: sources that emit more than a certain amount of pollution) have to comply with many more rules than smaller sources. Some examples are best available control technology (BACT) analysis, modeling for visibility and gaseous deposition, and air quality monitoring. These analyses are reserved for major sources not only because they're resource intensive, but also because the scale of the emissions at these types of facilities warrant additional analyses to ensure things like human health and important protected environments (e.g., national parks) are protected. If an area is meeting the air quality standard (in attainment), the major source threshold is 250 tons per year (tpy). With each nonattainment redesignation, that threshold drops (see below) requiring more and more facilities to perform these analyses. There are certainly benefits to (a) having a higher major source threshold, and (b) remaining below that threshold. That gets too political for this blog.

Nonattainment Designations (Major Source Thresholds for VOC or NOX)

• Extreme (10 tpy)
• Severe (25 tpy)
• Serious (50 tpy)
• Moderate (100 tpy) <-- currently we're here, expected to increase to serious soon
• Marginal (100 tpy)
• Attainment (250 tpy)

Although stationary industrial facilities have the potential to emit pollutants that contribute to the ozone problem, so do I personally. I commute to work at least four days per week driving more than 200 miles per week (not including driving other than commuting). And guess what? My car emits VOCs and NOX, two of the three things necessary to form ozone. The third, remember, is sunlight...

This ozone season, we are encouraging our employees, our Colorado-based clients, and other contacts to work from home or use public transit during days with high forecasted ozone concentrations. If you'd like ozone forecast emails, please sign up here.

There is something we need to talk about honestly, though. We get it, you do laundry when you work from home. You probably even run to the grocery store, post office, and out to lunch, too. We won't tell your boss. Heck, you might even drive more than if you just went into the office. If you're considering implementing this practice in your personal life or in your workplace, we kindly ask you to consider the actual miles driven on high ozone days in an effort to lower the regional ozone problem.

Nate