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Wonderful to see new and familiar faces at Association for Environmental Health and Sciences Foundation. Stop by and see us at booth 33. ... See MoreSee Less

Craig Cox, CPG will be presenting two posters during the Poster Sessions at the 28th Annual International Conference on Soil, Water, Energy, and Air. (Abstract numbers: 144 & 145) Come see the Mini-PinTM at booth 33! ... See MoreSee Less

#BBGroundgas18 Great opportunity to meet everyone at the Groundgas Conference today in London ... See MoreSee Less

Vapor Pin and our Europe distributor Ribble-Enviro will be exhibiting at the
Ground Gas 2018: Assessing and managing ground gas risk
Date: 01 March 2018 - Venue: Holiday Inn London - Kensington High Street, London, Wrights Lane W8 5SP
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Enjoyed listening to Tony McDonald with AZ solutions talk about pilot test at the Southeastern States VI Symposium. ... See MoreSee Less

Soil Gas Control Systems in New Construction (CC-1000). This new standard addresses RRNC construction for virtually
every building that is larger than a one- and two-family
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Great seeing everyone at last night's MSECA event. ... See MoreSee Less

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Vapor Pin Newsletter

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March 2018


Vapor Intrusion – The Four Horsemen: Benzene, Chloroform, Naphthalene, and Trichloroethene

In vapor intrusion, “background” is contamination in indoor air that came from outdoor (ambient) air or from interior sources, such as cleaning products, paints, and plastics. Owners of facilities associated with soil or groundwater contamination might be obliged to mitigate vapors at their own and at surrounding properties, and if they can’t distinguish between vapor intrusion and background, they might be paying for someone else’s problem. Worse, most vapor-mitigation systems prevent soil gas from entering the building, and if vapors are from background, the system won’t help.

EPA’s 2011 report on background contamination shows some interesting trends. The authors compiled the results of indoor-air samples collected from residences with no known or suspected vapor intrusion. As seen in Figure 4 from this report, below, benzene, chloroform, and TCE were present in 91%, 68%, and 43% of residences, respectively. Naphthalene does not appear on this graph, because its molecular weight is somewhere between those of volatile organic compounds (VOCs) and a semi-volatile organic compounds (SVOCs), and was often excluded from VOC sampling. But the toxicity and volatility of naphthalene, together with its widespread occurrence in background, have earned it a place on the list of vapor-intrusion compounds, and on the list of problem compounds. According to the Montana Department of Environmental Quality’s 2012 background investigation, naphthalene was detected in 40 out of 50 residences with no known vapor intrusion.

Figure from USEPA 2011, Background Indoor Air Concentrations of Volatile Organic Compounds in North American Residences, EPA 530-R-10-001.

Where do these compounds come from? Benzene is the B in BTEX – benzene, toluene, ethylbenzene, and xylenes, all of which are widely associated with gasoline and other fuels. Benzene poses the greatest problem of the BTEX compounds, since the other three have comparatively low toxicity. Benzene is also the base for countless manufactured chemicals, so of course, benzene is commonly detected in the subsurface, and is a common constituent of concern for vapor intrusion. Benzene is also ubiquitous in ambient air, especially in metropolitan areas, due to vehicular traffic and fuels. Benzene also can be expected in background in buildings with attached garages, due to its presence in vehicular gas tanks, gas-storage cans, and lawn equipment.

Chloroform is normally present in chlorinated water, and not surprisingly, chlorine is common in indoor air. But tap water is not the only source, and perhaps, not the most important source of chlorine in indoor air. At vapor-intrusion conferences, speakers often report high levels of chloroform in indoor air, but when I ask them where they think it came from, they rarely have an answer. However, a number of recent investigations have focused on sewer gas, and found that dry plumbing traps, breached toilet-wax rings, loose pipe fittings, and other conditions often allow sewer gas to enter buildings, bringing chlorine with it. Whatever the source of chloroform in background, Massachusetts’ 2008 Technical Update – Residential Typical Indoor Air Concentrations indicates a median concentration for chloroform of 1.9 ug/m3. The residential VISL in Ohio is 1.2 ug/m3. Good luck with that.

At one time, naphthalene was the main ingredient in mothballs, but it’s been replaced by chlorinated compounds to reduce the risk of fire. Naphthalene is typically associated with coal and the heavier petroleum oils. Naphthalene has the lowest residential indoor-air VISL of the big four compounds, at 0.83 micrograms per cubic meter (0.83 ug/m3), using Ohio standards of 10-5 cancer risk, and a hazard index of 1 for non-carcinogenic compounds. Consequently, the lab’s reporting level for naphthalene, even using 6-liter “Summa” cans, might exceed indoor air screening levels, unless results are reported to Method Detection Levels (MDLs). Reporting to MDLs generally results in the detection of numerous additional compounds, making data validation and interpretation more complicated and costly. The additional information seldom changes the final assessment, but if ya’ gotta, ya’ gotta.

And, finally, TCE rounds out the list of four bad players. We’ve discussed TCE a number of times, including in the August 2017 edition of Focus on the Environment, but in case you haven’t heard, TCE drives most of the vapor-intrusion work in recent years, due to concerns over fetal heart defects. Much or most of the concern with vapor intrusion is tied to the risk of cancer, which generally develops over years or decades. Although, as discussed in previous articles, the link between TCE exposure and fetal heart defects is in doubt, EPA assumes that a single day of exposure to TCE is sufficient to cause harm, so regulatory agencies are prioritizing TCE sites and pushing for rapid vapor-intrusion assessments.

How do we deal with these four compounds in vapor intrusion? Primarily, one establishes whether they’re from vapor intrusion or background. This involves:

  • Determining if indoor constituents are present in soil gas. If not, they’re probably from background.
  • Comparing indoor air to outdoor ambient air. Contaminants in outdoor air represent, by definition, background.
  • Comparing ratios of indoor constituents to soil-gas constituents. Vapor migration from subslab to indoor air involves only dilution, so the ratios of chemical concentrations in indoor air should be pretty much the same as the ratios in soil gas.
  • Conducting a survey of vapor-forming substances inside the building as part of the initial vapor-intrusion assessment. Compounds with anomalously high concentrations in indoor air may be associated with these materials, or with activities and substances used during sampling.
  • Comparing indoor-air concentrations to EPA’s background report, and others. Common background constituents, e.g., BTEX, should generally be regarded as suspect.

More often than not, one or more of the problem compounds represent background, and cumulative risk from the remaining compounds is acceptable. Understanding the sources and significance of these four compounds is critical to eliminating unnecessary costs and efforts.

Author: Mort Schmidt is a Senior Scientist with Cox-Colvin & Associates, Inc. He received his BS and MS degrees in Geology and Mineralogy from The Ohio State University, and has been a Cox Colvin & Associates employee since 1997. His areas of expertise include vapor intrusion and contaminant investigation and analysis, and he currently serves as Cox Colvin’s Practice Leader – Vapor Intrusion Services. Mort is a Certified Professional Geologist with AIPG and is a registered Geologist in Indiana.


March 20, 2018: Craig Cox, CPG will be presenting two posters during the Poster Sessions at the 28th Annual International Conference on Soil, Water, Energy, and Air. (Abstract numbers: 144 & 145) Come see the Mini-PinTM at booth 33!

April 8-12, 2018: Craig Cox, CPG will be speaking and presenting a poster at the Eleventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Abstract number: 11, Session: H3. High-Resolution Site Characterization (HRSC), Presentation date and time: 4/11/18. 4:30pm- 6:30pm) Come see Vapor Pin® Enterprises & the Mini-PinTM at booth 304!

April 12, 2018: Please join Craig Cox, CPG and Laurie Chilcote at the Learning Lab Demonstration to be held, from 8:50am to 9:15am, at the Eleventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds. They will be demonstrating Tips and Techniques: Pilot Testing, Pressure Field Verification, Locating VOC Sources, and Evaluating VI Pathways using the Vapor Pin® . Come see Vapor Pin® Enterprises & the Mini-PinTM at booth 304!

Radon News

Radon Outreach & Education: The Ohio Indoor Radon program operates a federally funded indoor radon grant in cooperation with the U.S. Environmental Protection Agency (U.S. EPA) and a network of local health departments within the State of Ohio. Elevated levels of indoor radon is the primary cause of lung cancer among non-smokers. The United States Surgeon General warning: Radon Causes Lung Cancer – You Should Test Your Home.  For information on radon, click on the FAQ link to the left or call the ODH Radon Information Line, toll-free, at 1-800-523-4439.

Click here to read the latest on Ohio Radon News

Radon in Drinking Water: In many countries, drinking water is obtained from groundwater sources such as springs, wells and boreholes. These sources of water normally have higher concentrations of radon than surface water from reservoirs, rivers or lakes. To date, epidemiological studies have not found an association between consumption of drinking-water containing radon and an increased risk of stomach cancer. Radon dissolved in drinking-water can be released into indoor air. Normally, a higher radon dose is received from inhaling radon compared with ingestion. Click here to read more…