Risk Assessment

Background

A human health and ecological risk assessment is the process of estimating the probability of harm (if any) to human health or the environment that might occur because of air emissions during normal, day-to-day operation of a combustion facility, and during unusual ("upset") conditions that are not catastrophic in nature. (Operating conditions sometimes occur during the burning process that can momentarily upset the balance of the incineration system resulting in temporarily increased emissions.) The results are used to ensure that permit conditions for a facility are sufficiently protective of human health and the environment. The Pre-Trial Burn Human Health and Ecological Risk Assessment ("Pre-RA") was conducted in 1996 by Ecology and Environment, Inc. of Seattle on behalf of the Oregon Department of Environmental Quality (DEQ).

The Pre-RA was conducted using general guidelines from the federal Environmental Protection Agency (EPA), modified as necessary to meet Oregon regulatory requirements. The Pre-RA used site-specific topographical and meteorological data from the Umatilla Chemical Depot (UMCD) and the surrounding area. Because the Umatilla Chemical Demilitarization Facility (UMCDF) had not yet been constructed it was necessary to use emissions data from the Army's Johnston Atoll chemical weapons incinerator, the only other chemical demilitarization facility in operation at the time. A workplan for the Post-Trial Burn Health and Ecological Risk Assessment (Post-RA) was completed in 2003. The Post-RA is scheduled to be completed once results from the first agent trial burn on the first furnace are compiled and site-specific emissions data are available. s data are available. This will be called the Post-Trial Burn Risk Assessment, or "Post-RA."

Human Health Risk Assessment Process

The four basic steps in a human health risk assessment are:

1. Hazard Identification: (Is there a hazard? If so, what is it?)
2. Dose-Response Assessment: (How much is harmful? What are the harmful effects?)
3. Exposure Assessment: (How could a person be exposed? Through eating? Drinking? Breathing? Skin contact?)
4. Risk Characterization: (What are the possible harmful effects? What is the likelihood that harmful effects will occur?)

Hazard Identification determines whether exposure to a substance causes a harmful health or environmental effect and the nature of the effect. Hazardous chemicals are identified by chemically analyzing the wastes that will be fed into the incinerators to determine what kind of air pollutants might be produced during the burning process. The available information on each type of potential pollutant is then reviewed to determine if the chemical has been identified as harmful, and what type of harm it might cause. Hazard identification also helps the DEQ decide what types of pollutants should be measured during the trial burns of the incinerators.

Dose-Response Assessment looks at the relationship between the dose (amount) received and the harm or injury that it causes. Generally, as the dose of a harmful chemical increases, so does the amount of harm it can cause. For example, pregnant women, children, or the elderly, might be more sensitive to a chemical than others.

Exposure Assessment involves describing the nature and size of the population and area exposed and the amount and length of time of the exposure. Exposure assessment uses a variety of exposure "scenarios" to account for people's different lifestyles. For example, someone who lives close to the incinerators and grows their own food and raises animals might be exposed to stack emissions not only through breathing, but also from eating plants or animal products that have also been exposed. Another scenario assesses exposure of small children because children breathe faster than adults and are more likely to come in contact with soil that has been exposed to stack emissions.

Risk Characterization combines the information collected during the first three steps and determines the likelihood that humans or animals will experience any of the health effects associated with a substance, or that the environment will be harmed. Characterizing risks usually involves assigning a value to a risk, such as "there is a one in 100,000 chance that someone who lives near the site might get cancer." But some risks cannot be assigned a number value, and the methods applied to develop risk estimates use assumptions about how people and the environment could be exposed to the stack emissions.

Results of the Umatilla Pre-Trial Burn Human Health Risk Assessment

The Pre-RA evaluated risks posed to human health for a variety of "receptors, " including adult and child residents, subsistence farmers, and subsistence fishers. One of the ways that effects on hypothetical "receptors" were evaluated was to assume a receptor was going to live in areas where the heaviest deposition of emissions from incinerator stacks were likely to occur (as determined by computer modeling).

In making its conclusions as conservative as possible, the study assumed that people would be directly exposed to stack emissions for the 3.2 years the facility is expected to be open, and indirectly exposed for a total of 30 years. In the case of cancer-causing chemicals, it assumed that people would be directly or indirectly exposed for 70 years. In actuality, the facility will be incinerating hazardous wastes for only about one year of the 3.2 years it is expected to be operating. The rest of the time will be spent on maintenance and re-configuring the facility to process different munition types.

The only "receptor" that was identified with a cancer risk that exceeded regulatory standards was a subsistence farmer living at what was identified as the highest impact location (about 328 feet northeast of the facility's common stack location). Ingestion of beef and dairy products from cattle raised at this location contributed the most to these elevated risk estimates, with dioxin as the main concern. Non-cancer health effects at the high impact location were above regulatory standards for adult and child residents and subsistence farmers, due to inhalation risks. The computer model found unburned mustard gas, dioxin, thallium, and manganese would be threats to human health, with manganese as the main contaminant of concern for this pathway. (Manganese is a naturally occurring element that is essential to humans, but short or long term illnesses may result from inhalation of manganese dust.)

Of course, no one actually lives or farms in this area or would be expected to do so during the plant's operation. (The Pre-RA does not address exposures to incineration plant workers and the results don't apply to them. Workers would wear protective clothing and take other precautions.) Evaluations of the effects on receptors living and farming at more likely locations (such as right outside the fenceline of the Umatilla Chemical Depot) showed that there should not be any adverse health effects from the operation of the Umatilla Chemical Agent Disposal Facility (UMCDF).

Ecological Risk Assessment

The ecological risk assessment provides an evaluation of potential impacts to such resources as fish and wildlife habitat and endangered species. The same type of process is involved in placing hypothetical ecological "receptors" in areas identified as potentially "high impact" locations. The ecological risk assessment concluded that it was unlikely that adverse ecological effects would occur at any area, with the exception of the highest impact point located several hundred feet from the UMCDF stack.
 

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