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EPA NAAQS Review for Ground Level Ozone

Updated: Jun 29, 2021

Ozone is one of 6 criteria pollutants as classified by the EPA. Tropospheric ozone, ground level ozone, forms when pollutants (NOx & VOCs) react with sunlight forming ozone, one of the primary constituents of smog. Common sources of NOx and VOC include anthropogenic emissions, biogenic emissions and industry sources. Ground level ozone is the resulting culmination of these varying sources plus environmental factors like warmer temperatures and inversions - these collective factors create the conditions for ozone to form or not form. An atmospheric science background is not needed to see if your region/city overall ozone formation is trending up or down. Rather, ozone alerts are widely broadcasted to the US public for purposes of alerting any potential health risks, and secondly, to attempt the curtailment of anthropogenic emissions by recommending bits like "bike don't drive" or "pack your lunch." The general public's knowledge on the formation and chemistry behind ground level ozone probably ranges heavily and would be unrealistic to factor into this discussion. That said, the public does appear to embrace the primary connection that if your region/city is no stranger to ozone formation and air quality alerts, then your air quality is lower than desired.

In an increasingly globalized world, with developing nations and growing populations, ozone and air pollution will continue to pose health issues and deaths for at-risk populations. In the United States alone, it is estimated 122 million people live in “non-attainment areas”, areas that do not meet the 70 ppb standard. A 2004 study from John Hopkins Bloomberg School of Public Health concluded a strong correlation between mortality rates and rising ground level ozone, prior to the EPA’s 2008 and 2015 revisions. A recent 2021 report only serves to bolster the importance of achieving national ambient air quality standards (NAAQS) in the US. The report published by the American Lung Association (ALA) titled, "State of the Air 2021", finds that despite some nationwide progress on cleaning up air pollution, more than 40% of Americans—over 135 million people—are living in places with unhealthy levels of ozone or particle pollution.”

Ozone is higher during spring and summer months; this is referred to as ozone season. Ozone levels are higher during these months due to direct UVA sunlight, warm temperatures, and light wind speeds. These conditions allow NOx and VOCs more reaction time with sunlight, creating ground-level ozone. New Mexico has recently targeted ozone precursors (VOC & NOx) from oil and gas production equipment, with a newly proposed draft rule under the state’s Ozone Attainment Initiative. Meanwhile a number of states, including Texas, require ozone season emissions to be included for annual emission inventories. State-environmental bodies like the TCEQ or NMAQB will analyze reported emission inventories to understand compliance and overall trending against state implementation plans (SIPs). In short, SIPS are EPA approved comprehensive plans developed by states to implement, maintain and enforce NAAQS and Clean Air Requirements (CAA). The marriage between real-time atmospheric data and SIPs derived from regulatory framework is both complex and a massive undertaking. There will likely be no shortage of attention, domestically and abroad, for regions with poor air quality (or nearing it) and the proven health risks associated. Furthermore, it's realistic to expect that this attention is also directed to what industry/government is doing or not doing to affect change or improve air quality.

The EPA reviewed the air quality criteria and the national ambient air quality standards (NAAQS) in December 2020 for photochemical oxidants including ozone, and retained the current standards, without revision citing “EPA’s decision is based on its judgment that the current NAAQS protect the public health, with an adequate margin of safety, including the health of at-risk populations, and protect the public welfare from adverse effects."

However, there is concern of the EPA’s NAAQS review process: “Some stakeholders, interest groups, and Members of Congress have criticized the timeliness of past NAAQS reviews, which routinely have not been completed within the five-year review cycle. Others question whether expedited NAAQS decisions are able to reflect the latest science and if the scientific basis is rigorous and unbiased.”

Currently, the NAAQS for ground-level ozone sits at 70 parts per billion (ppb) indicating that concentration of ozone is directly linked to harmful respiratory effects and overall decreased lung function. The EPA recommends that individuals limit outdoor exposure during times of elevated ozone concentration. To support the general public's awareness on air quality, the EPA has created a scale called the Air Quality Index (AQI) based on NAAQS and can help users understand current conditions and forecasted conditions.

As 2021 continues to be a considerable year for worldwide growth and economic output, it will be interesting to see if the US retention of 70 ppb remains despite domestic awareness linking air quality with public health. This topic is no longer on the back page of the newspaper and headlines can apply to both regulators and industry. A number of factors might affect the 70 ppb NAAQS threshold to be reviewed before the scheduled 2025 review - but for now, Amerigo will closely watch the conversation and update this discussion. Please reach out to us and share your feedback and sentiment below.


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