Impacts and Effects of Air Toxics
by Brian Noel
Air toxics are pollutants known to cause or suspected of causing cancer or other serious health effects. On the federal landscape, air toxics are classified as hazardous air pollutants (HAPs) by the U.S. Clean Air Act and the U.S. Environmental Protection Agency (EPA). Several states have established lists of air toxics that encompass significantly more chemical compounds than the EPA-maintained HAP list. HAPs are regulated by a specific group of rules at the federal level, the National Emission Standards for Hazardous Air Pollutants (NESHAPs), and most states have specific regulations to control emissions of air toxics which focus on the projected off-site impact of air toxics emitted from industrial or commercial activity. (See the February 2017 issue of EM for more detail.)
While environment, health, and safety managers and environmental engineers typically focus on the sources of emissions of air toxics, their control, and compliance with state and federal regulations, in this issue, we focus on the presence of air toxics outside of the facility's fence line. The articles herein investigate some well-known air toxics and discuss a novel approach to quantifying ambient concentrations of others.
In August 2018, EPA published the results of the 2014 National Air Toxics Assessment (NATA), the sixth since 1996.The NATA is intended to assist state and local air agencies address areas which are projected to be most affected by air toxics, as well as the sources of those contaminants. For the regulated community, the NATA provides insights into the air toxics which are most impactful to human health in the United States, as well as the long-term trends for emissions of air toxics in the country. The 2014 NATA results indicate that approximately one-half of the nationwide cancer risk resulting from air toxics in the ambient air comes from formaldehyde formed from chemical reactions of other contaminants emitted to the atmosphere. Direct emissions of formaldehyde and its prevalence in common industrial and household products also contribute to the presence in the ambient air. Two insightful articles are included to examine the issue.
In the first article, “Formaldehyde—A Leading Air Toxic,” by Dr. Stephen Zemba and colleagues at Sanborn, Head & Associates, Inc., the authors provide considerable background on formaldehyde's properties and health risks, as well as discussing sources of formaldehyde emissions and a summary of relevant data presented on formaldehyde in the 2014 NATA.
Next, Michael T. Lannan and Katherine B. Mears, both with Tech Environmental, focus on the formation of formaldehyde resulting in lean burn combustion aimed at reducing emissions of another air pollutant, nitrogen oxides, in their article “Lean-Burn Reduces NOx, but is this Benefit a Formaldehyde Concern?”. They also examine challenges associated with emissions of formaldehyde from such engines and considerations for determining realistic off site impact of those sources.
Evaluating off-site impact of emission sources is common practice for industrial facilities. However, evaluating the potential of the off-site impact from a historical manufacturing facility on neighboring areas presents additional challenges. Paul Scott and colleagues at CARDNO CHEMRISK in, “Air dispersion modeling for historical community exposure reconstruction—Evaluation of the approach and its uncertainties,” present a case study of another air toxic—asbestos. The case study at an asbestos-based brake manufacturer illustrates interesting impacts from various aspects of emissions from a representative manufacturing facility.
In addition to predicting off-site impact of emissions of air toxics through air dispersion modeling, some states have established monitoring programs to quantify ambient concentrations of air toxics in specific areas. While it is commonplace to utilize traditional ambient air monitoring technologies for monitoring air toxics, the U.S. Forest Service has taken a novel approach to evaluating the presence of toxic air contaminants in ambient air by studying moss in Portland, Oregon.
In this issue of EM, we reprint with permission a related story that focuses on one air toxic of high concern in “Cadmium and the Portland Moss and Air Quality Study.” This study provides interesting insight into the use of a non-traditional technique for identifying and understanding ambient levels of cadmium. The full 2016 U.S. Forest Service study, “Elemental Atmospheric Pollution Assessment Via Moss-Based Measurements in Portland, Oregon,” discusses several more air contaminants and is available in full from the U.S. Forest Service website.