BACKGROUND AND STATEMENT OF ISSUES
The Agency for Toxic Substances and Disease Registry (ATSDR) prepared this health consultation in response to petitions from the Nebraska Department of Environmental Quality (NDEQ) and a private citizen in 1995 for a public health assessment of the Omni Engineering Asphalt Plant. An explanation of terms appearing in italics may be found in Appendix C. The petition letters from the NDEQ and the private citizen state that residents in the area suffer from headaches, nausea, eye irritation, and respiratory irritation.
The Omni Engineering site is located at 14012 Giles Road in Sarpy County, Nebraska approximately 15 miles south of Omaha. The facility is situated in a small valley and is bordered by the Stony Brook subdivision to the north and the Meadows subdivision to the south (Appendix A, Figure 1). The Stony Brook subdivision contains approximately 200 single, upper-middle- income homes. Meadows is a smaller subdivision that contains middle-income homes and was built in 1974 when Omni Engineering began operations. Approximately 6,805 people live within a 1-mile radius of the facility .
Omni Engineering is a permanent hot-mix asphalt plant that produces and recycles asphalt. The process involves drying sand, gravel, and coarse aggregate with a rotary drying kiln. Emissions may arise when liquid asphalt is added to this dry mixture (Appendix A, Figure 2). Currently, the only emission control is a fabric baghouse that captures particulates. Plant operations occur between April and late fall.
On October 6, 1995, the NDEQ petitioned ATSDR to perform a public health assessment of the Omni Engineering facility . The NDEQ also requested that ATSDR conduct a literature search for a listing of potential emissions from asphalt plants. On December 28, 1995, a community member petitioned ATSDR for a public health assessment of the Omni Engineering facility citing that the emissions from the facility caused severe eye irritation, respiratory irritation, headaches, and vomiting .
In March 1996, the ATSDR regional representative, the ATSDR Exposure Investigations and Consultation Branch, and the ATSDR Division of Toxicology provided the NDEQ with a listing of potential constituents of emissions from asphalt plants (Appendix B, Table 8.1-5, ).
From May 28-29, 1996, ATSDR staff met with representatives from the NDEQ, area residents, a Sarpy County commissioner, and a state senator to document health concerns and to receive input on additional air sampling. ATSDR staff toured the perimeter of the facility. Following this site visit, the U.S. Environmental Protection Agency (EPA), Region 7 agreed to perform air sampling near the Omni Engineering facility.
In the spring of 1997, the EPA finalized plans to monitor sulfur dioxide (SO2) levels near the Omni Engineering facility for a twelve month period . EPA's decision to monitor for sulfur dioxide was based on the following: 1) sulfur dioxide was the contaminant most likely to be present  and would be an indicator of other compounds present (please refer to Appendix B), 2) the residents' complaints indicated that the problems were transient in nature that were driven by meteorological conditions , and 3) due to the types of health complaints reported by residents .
The objective of the monitoring program was "to conduct a special purpose monitoring study to measure sulfur dioxide concentrations in the ambient air" and to provide information of the sulfur dioxide concentrations typically occurring in the residential area near the Omni facility. . The monitoring site was in close proximity to a residential area to the northwest of the Omni facility. Sulfur dioxide ambient air concentrations were measured at this location from April 15, 1997 through October 15, 1997 . The EPA discontinued monitoring operations at the Omni Engineering plant in October 1997 and did not complete sampling for a twelve month period as planned because: 1) the facility does not operate during the cold months of the year, and 2) the data indicated that the level of sulfur dioxide was insignificant and did not exceed the standards discussed below.
ATSDR evaluated the sulfur dioxide ambient air data to determine if adverse health effects were likely following human exposure to sulfur dioxide levels near the Omni Engineering site. In addition, ATSDR compared the measured sulfur dioxide ambient air concentrations to the US EPA sulfur dioxide National Ambient Air Quality Standard (NAAQS) to determine if measured concentrations exceeded the NAAQS.
ATSDR concurs with the EPA that sulfur dioxide ambient air concentrations measured from April 15, 1997 through October 15, 1997 were below the EPA NAAQS of 0.50 parts per million (ppm), 3-hour arithmetic mean (secondary standard) and 0.14 ppm, 24-hour arithmetic mean (primary standard) . In addition, the levels of sulfur dioxide detected at the ambient air monitoring site near the Omni Engineering plant were below levels known to cause adverse health effects in humans. This includes asthmatics who may be sensitive to low levels (0.25 ppm) of sulfur dioxide while exercising. Sulfur dioxide's odor threshold ranges from 0.7 ppm to approximately 5 ppm and becomes irritating at approximately 2 ppm .
Child Health Considerations
ATSDR recognizes that infants and children may be more vulnerable to exposures than adults in communities faced with contamination of their air, water, soil, or food  . This vulnerability is a result of the following factors:
- Children are more likely to play outdoors and bring food into contaminated areas .
- Children are shorter, resulting in a greater likelihood to breathe dust, soil, and heavy vapors close to the ground.
- Children are smaller, resulting in higher doses of chemical exposure per body weight.
- The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages.
Because children depend completely on adults for risk identification and management decisions, ATSDR is committed to evaluating their special interests for the Omni Engineering facility, as part of the ATSDR Child Health Initiative.
Children who are the most likely to be exposed to environmental media at the Omni Engineering facility site include the children living in nearby homes.
As indicated in the discussion above, the concentrations of sulfur dioxide in ambient air are not at levels of health concern for area residents, including children.
- The ambient air concentrations of sulfur dioxide detected at the monitoring
site near the Omni Engineering Asphalt plant between April 15, 1997 and October
15, 1997 represent a no
apparent public health hazard. ATSDR uses this category for sites
where human exposure to contaminated media is occurring or has occurred in
the past but the exposure is below a level of health concern .
ATSDR concurs with the US EPA that sulfur dioxide ambient air concentrations
measured from April 15, 1997 through October 15, 1997 at this site were below
the EPA NAAQS of 0.50 parts per million (ppm), 3-hour arithmetic mean (secondary
standard) and 0.14 ppm, 24-hour arithmetic mean (primary standard), .
- The levels of sulfur dioxide detected at the Omni Engineering plant are below levels known to cause adverse health effects in humans. This includes children and those with asthma who may be sensitive to low levels (0.25 ppm) of sulfur dioxide while exercising .
ATSDR offers no additional recommendations at this time. If additional information becomes available for the Omni Engineering site, ATSDR will update this health consultation as necessary.