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DISCUSSION

Using current emissions, the model results indicate that formaldehyde concentration is slightly above the draft HRV two hundred meters from the plant. However, given the imprecision of cancer risk estimates at these very low air concentrations, MDH does not consider this estimated formaldehyde concentration to be significantly different from the draft HRV. Therefore, the estimated concentration is very small and does not results in a significant increase in cancer risk.

If potential emissions are realized all three contaminants are estimated by the model to be at levels of concern at 200 meters. Acrolein and formaldehyde are estimated to be at levels of concern at 700 meters. These results indicate a need for more refined analysis in order to better determine the accuracy of the screening model. Furthermore, modeling is needed to determine a less than 3 month average concentration for acrolein. Generally, model results have indicated 13 week average concentrations to be about 1.5 times modeled annual concentrations. Therefore, this conversion would be expected to decrease the screening guideline for acrolein by a factor of 1.5.

Particulate Matter

If the MPCA were evaluating this facility for the criteria pollutant PM10, background concentrations of PM10 would have to measured to determine whether the plant emissions, when added to background levels, exceeded the health standard (MDH 1998b). It should also be noted that the USEPA is currently considering establishing a more stringent particulate matter standard based on particulate matter less than 2.5 microns (PM2.5). PM2.5 emissions from the Plant are currently unknown.

It is important to note that Georgia Pacific staff believe that even the most recent potential maximum emissions data for PM10 which was submitted to MDH are unrealistically high. However, MDH reran the model (not shown) using what Georgia Pacific staff verbally told MDH staff to be a more reasonable upper estimates of PM10 emissions from the plant, and results for PM10 were still estimated to be above the 24 hour standard (160 µ/m3 at 200 meters) (MDH 1998c).

The Geogia Pacific plant will be required to conduct more extensive analysis of PM10 emissions from its facility as part of its permit application. This process is not expected be completed for several years.

Formaldehyde and Acrolein

The health standards for acrolein and formaldehyde are MDH draft Health Risk Values (HRVs). The formaldehyde standard is currently under review by the Toxicology Excellence for Risk Assessment (TERA), a non-profit corporation (TERA 1997). MDH will most likely increase the draft HRV for formaldehyde based upon the conclusions of TERA's study. MDH is not aware of any work currently underway that would affect the draft HRV for acrolein.

The MPCA is currently considering how they will apply the draft HRVs when regulating industry. In situations where screening guidelines indicate HRVs may be exceeded at or beyond the industry's property line, the MPCA is considering requiring the industry to conduct more analysis, reduce emissions, or otherwise address the situation (MPCA 1997b). The MPCA is proposing that maximum emission rates be applied during these investigations since the company may legally emit this amount in the future. In a situation like this, Georgia Pacific would typically be required to conduct more refined analysis in order to determine whether formaldehyde and acrolein are above the HRVs beyond their property line as a result of plant emissions. Currently, Georgia Pacific is not legally required to do this.

Agency for Toxic Substance and Disease Registry (ATSDR) Child Health Initiative

ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of their water, soil, air, or food. Children are at greater risk than adults from certain kinds of exposures to hazardous substances. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. Children are also smaller, resulting in higher doses of chemical exposure per body weight. The developing organ systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decisions, and access to medical care. The draft HRVs are meant to protect sensitive sub-populations, including children who may live near the facility.

CONCLUSIONS

MDH, with the assistance of MPCA staff, have analyzed the potential impact of air emissions from the Georgia Pacific Hardboard plant on a nearby residential area. MDH used plant emissions data provided by Georgia Pacific with an EPA screening model. MDH notes that there may be some uncertainty in the actual reported emissions given the limited stack testing, but that modeling was performed using the best available data. The results indicate formaldehyde concentrations 200 meters from the plant are currently similar to health based standards. Given the imprecision of cancer risk estimates at these very low air concentrations, MDH does not consider the estimated formaldehyde concentration to be significantly different from the draft HRV. Therefore, the estimated concentration does not result in a significant increase in cancer risk and poses no apparent public health hazard.

MDH conducted the evaluation at the request of the Bemidji public school system, which had been planning to construct a new elementary school near the plant. Plans to build the school have since been abandoned, partially on the basis of this evaluation.

If the plant were to increase emission levels to the potential maximum levels reported by Georgia Pacific, then formaldehyde, acrolein and PM10 could pose a public health hazard to individuals living near the plant. Only further analysis will determine if the screening model results are accurate. If the air concentration levels of formaldehyde and acrolein predicted by the model were reached, the likelihood of individual health effects would be small. Nevertheless, MDH could not, with confidence, rule out the possibility of adverse health effects on exposed populations. PM10 air concentrations near the facility were predicted to be above its 24 hour average health based standard using potential maximum levels emitted from the facility. If levels exceeded the criteria standard for PM10 near the facility, health effects may occur in people exposed.

RECOMMENDATIONS

  • The Georgia Pacific Air Permit should require acquisition of data necessary to identify potential exposures to emitted compounds above health-based standards. This may include further characterization of emissions as well as site-specific meteorological conditions and topographic characteristics.

  • Georgia Pacific should conduct a more thorough investigation of emissions from the entire facility and resubmit to the MPCA accurate emission estimates from the plant.
  • Further characterization of the stack emissions should be performed to assure that the mean of the three samples taken is representative of the average annual emissions.

  • All emissions from the plant should be considered during this analysis.
  • If further analysis concludes that potential maximum emissions may be of health concern, then MDH might recommend measures be taken (e.g. more controls on permit conditions).

  • MDH recommends that data also be acquired on PM2.5 emissions, and that modeled air concentrations be compared to proposed air standards.

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