HEALTH CONSULTATION

OMAHA STEEL CASTINGS - DUNDEE NEIGHBORHOOD AIR
OMAHA, DOUGLAS COUNTY, NEBRASKA

BACKGROUND

The Douglas County Health Department (DCHD) asked the Agency for Toxic Substances and Disease Registry (ATSDR) to evaluate available air monitoring data on whether the levels of air toxics pose a potential health concern. Residents complain of smells and respiratory problems, including asthma, chronic coughing, burning eyes, runny nose, shortness of breath, etc., and are concerned that the levels of chromium, naphthalene, and phenols are the cause.

This report contains ATSDR's answers to the following questions:

MONITORING DATA

DCHD collected ambient air samples over a 3-day period (Nov, 5 and 13, and Dec. 10, 2002) at 3 different locations. The Eastern Research Group (ERG) analyzed those samples and provided DCHD with the monitoring data in January of 2003. DCHD subsequently asked the U.S. Environmental Protection Agency, Air Planning and Development Branch (U.S. EPA/APDP) to review that data. EPA completed its review in March and sent the results to DCHD on April 2, 2003.

EPA concluded that the only pollutants that were above any long-term health benchmarks were benzene and 1-3 butadiene. Of the SVOCs (semi-volatile organic compounds), only naphthalene and phenol were observed at all three monitors at levels significantly higher levels than those found elsewhere. None of the contaminants measured exceeded noncancer health benchmarks for chronic, lifetime exposure. Finally, EPA suggested that the observed ambient levels of chromium compounds "may pose a long-term excess cancer risk to the general public." Again, however, no non-cancer health benchmarks were exceeded.

In a letter dated April 17, DCHD asked ATSDR to address the issue of whether or not the levels of ambient air pollutants posed a potential health concern. While many different chemicals were monitored by DCHD during the Dundee Neighborhood Air Toxics Study, only those about which the community has expressed specific concerns are listed below. For chromium compounds, the average and maximum values are listed; for phenol and naphthalene, the full range of concentrations (i.e., min - max) is indicated.

• Chromium 0.0026 µg/m3 (max, 0.0589 µg/m3)
• Phenol 0.03 to 11.0 µg/m3 (0.007 to 2.86 ppb)
• Naphthalene 0.07 to 5.4 µg/m3 (0.013 to 1.03 ppb)

DISCUSSION

As noted earlier by EPA, except for benzene, 1,3-butadiene (of the VOCs), and chromium compounds (of the metals), none of the airborne substances detected by DCHD in ambient air samples collected during Nov-Dec 2003 were present at concentrations that exceeded any health-based comparison values. Maximum concentrations of benzene, 1,3-butadiene, and chromium compounds exceeded long-term, health screening values i.e., those based on potential cancer effects. However, lifelong exposure to even the maximum detected levels of these substances would not pose a cancer hazard to exposed residents. Cancer-based comparison values are generally based on the assumption that any exposure to a carcinogen, no matter how low, may increase a person's risk of developing cancer. EPA and ATSDR both find such cancer-based values to be useful screening tools. As EPA noted in its 1986 Carcinogen Risk Assessment Guidelines, "such an estimate, however, does not necessarily give a realistic prediction of the risk. The true value of the risk is unknown, and may be as low as zero."

Prolonged inhalation exposure to high, occupational levels of hexavalent chromium (CrVI) are carcinogenic to humans. Trivalent chromium (CrIII), the form most commonly found in environmental samples of "chromium compounds," is actually an essential nutrient. Environmental samples usually contain CrVI and CrIII in a ratio of about 1:7 . Nevertheless, if one were to assume, as a "worst-case exposure scenario," that the "chromium compounds" in the DCHD Study consisted exclusively of CrVI, and that residents were exposed chronically throughout their entire lives to the average detected level (0.0026 µg/m3), the resulting exposure dose would correspond to a hypothetical lifetime excess cancer risk of only 3.3 additional cases of cancer per 100,000 people. However, the lowest occupational exposure reportedly associated with elevated lung cancer in humans (40 µg/m3 for 1-49 years) is more than 15,000 times the average level detected in air by DCHD (ATSDR 2000).

EPA's reference concentration (RfC), which represents a level of chronic, inhalation exposure that would not be expected to produce any detrimental non-cancer effects during a human lifetime, is 0.1 µg/m3 for CrVI. That is 38 times higher than the average detected level of total chromium compounds (0.0026 µg/m3) in the DCHD study.

ATSDR's chronic EMEG (Environmental Media Evaluation Guide) for naphthalene in air is 2 ppb or about 10.5 µg/m3. The maximum concentration of naphthalene detected in air during the DCHD study was only half that (5.4 µg/m3). Furthermore, ATSDR's EMEG contains a built-in safety factor of 1000. In other words, the EMEG is 1000 times lower than the "less serious" LOAEL (Lowest Observed Adverse Effect Level) on which it was based, i.e., inflammation of the nose and lung in mice chronically exposed to 10,000 ppb naphthalene for most of their lives (ATSDR 1995). EPA's RfC is even more conservative; it is 3 µg/m3 and includes a safety factor of 3000 (IRIS).

Consumption of or dermal contact with large amounts of phenol in the concentrated liquid form could be both irritating and toxic. In smaller amounts, however, phenol is a common antiseptic and anesthetic ingredient in sore throat lozenges, sprays, and gargles (ATSDR 1998). Although EPA has established no MCL for phenol, several thousand ppb would be considered safe in drinking water. Because phenol is not particularly toxic via the inhalation route under normal circumstances, ATSDR has no health-based comparison values for phenol in air. However, for purposes of comparison, both the 8-hr Time-Weighted Average Threshold Limit Value (TWA-TLV) of the ACGIH and the 10-hr Recommended Exposure Limit (REL) of NIOSH are 5 ppm (>19,000 µg/m3) phenol in air which is more than 3000 times higher than the highest level of phenol detected in air during the DCHD study.

Limitations of the Data

Sampling was conducted appropriately for evaluating chronic (long term) exposures to chemicals. The most protective benchmarks for most chemicals detected are those based on chronic long-term exposures. Naphthylene and phenol, however, are better known for producing eye and throat irritation during peak short-term exposures, which subsides once air concentrations have dropped.

Since facility operations are heavier during the first shift, the facility is expected to produce more of these chemicals during the first 8-hours. Therefore, although the 24-hour sampling is adequate for evaluating long-term exposures, it is likely to underestimate the acute peak exposures necessary for evaluating the impact of the irritants.

CONCLUSIONS

Based on these limited data, ATSDR concludes that:

1. Airborne levels of SVOCs pose an indeterminate health hazard for Dundee neighborhood residents. While the levels of SVOCs measured do not present a health hazard, they may underestimate peak exposures.
2. Airborne levels of VOCs do not present a health hazard for Dundee neighborhood residents. Samples are appropriate for long term assessment and peak exposures are less of a concern.
3. Airborne metals including chromium do not present a health hazard for Dundee neighborhood residents. Samples are appropriate for long term assessment and peak exposures are less of a concern.

RECOMMENDATION

Consider short term sampling for naphthalene and phenol in the Dundee neighborhood to evaluate peak exposures.

PREPARERS OF REPORT

Frank Schnell, Ph.D, DABT
Senior Toxicologist
Exposure Investigations and Consultation Branch
Division of Health Assessment and Consultation

Reviewed by

Gregory M. Zarus
Atmospheric Scientist
Exposure Investigations and Consultation Branch
Division of Health Assessment and Consultation

Sue Casteel
Region VII Representative
Office of Regional Operations

Shawn Blackshear
Region VII Representative
Office of Regional Operations

REFERENCES

1. American Conference of Governmental Industrial Hygienists; 1998, location Threshold Limit Values and Biological Exposure Indices.
2. IRIS
3. ATSDR's Tox Profiles for chromium, naphthalene, and phenol.
4. U.S. E.P.A. (1986). Guidelines for carcinogenic risk assessment. Fed. Reg., 51: 33992-34006, September 24, pg. 33997-8.

APPENDIX: ANALYTICAL DATA

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