PETITIONED HEALTH CONSULTATION
OGDEN MARTIN INCINERATOR COMPANY
BRISTOL, HARTFORD COUNTY, CONNECTICUT
A review of the annual emission rates for dioxin and metals indicate that the rates of emissions vary from year to year. To evaluate the potential for the compounds to reach levels of health concern, the following modeling approach [4] was used:
The table below summarizes the results.
| Table 1. SCREEN Values for Compounds Evaluated | |||
| Compound | Maximum Emission at Stack |
Modeled Downwind Concentration (annual average) |
Comparison Value |
| Dioxin | 0.278 ng/m3 | 8.1 x 10-9 ng/m3 | 4.2 x 10-5 ng/m3 CREGa |
| Arsenic | 2.7 ug/m3 | 0.000028 ug/m3 | 0.0002 ug/m3 CREG* |
| Cadmium | 5.4 ug/m3 | 0.00015 ug/m3 | 0.0006 ug/m3 CREG* 0.2 ug/m3 EMEG** (chronic) |
| Chromium (assumed 100% Chromium VI) |
4.2 ug/m3 | 0.00048 ug/m3 | 0.00008 ug/m3 CREG* |
| Lead | 50.3 ug/m3 | 0.0022 ug/m3 | 1.5 ug/m3 quarterly avg (NAAQS***) |
| Mercury | 127 ug/m3 | 0.37 ug/m3 | 0.014 ug/m3 EMEG** (chronic) |
The purpose of using comparison values is to screen out substances that are considered to be at safe levels for the general public. ATSDR selects contaminants of concern by comparing environmental concentrations to health-based comparison values. These comparison values are set at levels that can reasonably be regarded as harmless. If a substance is above the comparison value, it is further evaluated. Comparison values are not toxicity thresholds. Exceeding a comparison value does not necessarily imply that a substance will cause harmful health effects.
The modeled annual average downwind concentrations for dioxin, arsenic, cadmium, and lead were all below their respective health comparison values and therefore ruled out as contaminants of concern. However, screening of chromium and mercury resulted in modeled annual downwind concentrations that were close to or exceeded health comparison values. These compounds were further evaluated using a refined model.
Refined modeling is a less conservative approach than the SCREEN method (see Appendix, "Refined Modeling"). More meteorological data points are used with the refined method, producing greater variability in wind direction. If a contaminant is below comparison values with the screening method, it will also be lower using the refined method. For this reason, refined modeling is used for compounds that are borderline or above the comparison values.
When mercury was evaluated using the refined model, it generated a value of 0.0078 ug/m3, below the associated comparison value. ATSDR considers this level to be safe for the general public. The refined model chromium value resulted in a level of 0.000094 ug/m3, borderline with the CREG comparison value. However, a CREG assumes a lifetime exposure (70 years) of being exposed to a constant concentration 24 hours a day. Emissions from OMI vary from year to year and the modeling method assumes a worst case scenario (i.e. uses the highest emission rate measured). ATSDR believes that chromium can be ruled out as a public health hazard but warrants continued monitoring.
The table below gives the refined modeling numbers for all the compounds evaluated.
| Table 2. Refined Modeling Values for Compounds Evaluated | |||
| Compound | Maximum Emission at Stack |
Refined Average Annual Concentration |
Comparison Value |
| Dioxin | 0.278 ng/m3 | 1.6 x 10-10 ng/m3 | 4.2 x 10-5 ng/m3 CREGa |
| Arsenic | 2.7 ug/m3 | 0.0000056 ug/m3 | 0.0002 ug/m3 CREG* |
| Cadmium | 5.4 ug/m3 | 0.00003 ug/m3 | 0.0006 ug/m3 CREG* 0.2 ug/m3 EMEG** (chronic) |
| Chromium (assumed 100% Chromium VI) |
4.2 ug/m3 | 0.000094 ug/m3 | 0.00008 ug/m3 CREG* |
| Lead | 50.3 ug/m3 | 0.00043 ug/m3 | 1.5 ug/m3 quarterly avg (NAAQS***) |
| Mercury | 127 ug/m3 | 0.0078 ug/m3 | 0.014 ug/m3 EMEG** (chronic) |
Based upon the stack emissions, the variability in emission rates, and modeled downwind
concentrations, ATSDR concludes that there is no apparent health hazard from the OMI
emissions. Continued monitoring of the dioxins and heavy metal emissions is recommended.
Collection of ambient air samples in the community during stack sampling would also better support the modeling estimates.
ATSDR recognizes that children are different from adults when exposed to contamination in their water, soil, air, or food. Children are at greater risk than adults from certain kinds of exposure to hazardous substances emitted from waste sites and emergency events. They are more likely to be exposed for several reasons. First, children play outside more often than adults, increasing the likelihood that they will come into contact with chemicals in the environment. Because they are shorter than adults they breathe more dust, soil, and heavy vapors close to the ground. Children are also smaller, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain damage if toxic exposures occur during certain growth stages. ATSDR does not anticipate any increased risk to children from OMI emissions based upon the stack emissions, modeling performed, and review of the health comparison values.
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