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Human Health Assessment Shows Information Gaps
August, 2000

 

Overview

Although dated June 1999 the Glynn Environmental Coalition (GEC) only recently received the Final Baseline Risk Assessment for Human Health. This document contains information on how dangerous the site is to people. The Environmental Protection Agency (EPA) uses computer modeling to determine if chemicals at the site are dangerous.

There are concerns that the present site conditions may be very different than those described in this document. Many of these studies remain  incomplete. Very little can be concluded from this Risk Assessment, except that a considerable amount of work remains to be done before EPA can select a remedy.

The Human Baseline Risk Assessment

Risk assessments are used to decide what chemicals need to be cleaned up, where the site needs treatment, and the type of cleanup methods that will be used. There are two basic kinds of assessments, the Human Health Assessment and the Ecological Assessment. The Human Health Assessment looks only at the danger to people; the Ecological Assessment considers the threat to plants, fish, insects, birds and other wildlife.

The risk assessment study looks at what kinds of chemicals are at the site, where they occur within the site, how they occur—in topsoil, underground, in ponds or streams, or in groundwater. The study also looks for “pathways”—for instance, if the chemical is in groundwater, will anyone actually drink water from the site. Finally, the study looks at the type of injury the chemical can cause. Chemicals that cause cancer are studied differently than chemicals that are poisons.

Site History

Located in western Glynn County, the Brunswick Wood Preserving Superfund Site treated wood products with oils and minerals. Many of the chemicals used in the treatment processes contained toxins or carcinogens (“cancer-causers”). When the company closed down, these chemicals were left untreated. The company had very poor containment practices and the chemicals can be found offsite as groundwater plumes and in the sediments of nearby Burnett Creek.

The EPA Emergency Response Branch did perform a partial removal of contaminated materials. Also, the State of Georgia Environmental Protection Division (EPD) removed a considerable amount of contamination. EPA documents designate the site area as 84 acres. Because the site has never been fully stabilized, it continues to pollute nearby streams and groundwater. The full extent of the waste and the exact positions of offsite plumes are still not known.

Contaminants of Concern

The main toxins came from wood treatment by combinations of pentachlorophenol, oil (creosote), or copper-chromium-arsenate (CCA). This resulted in contamination from arsenic, PCP, dioxins, PAH, and other chemicals. The toxic effects range from long-term threat of cancer to short-term poisoning.

Areas of Concern

There are no safe areas on this site. The levels of contaminates are high enough that safety is “relative” to how long a person is exposed. A person visiting the site for a few hours could be injured in some areas, but not in others. However, since all areas have some amount of contamination there can be no long-term use of the site. There may be offsite areas that are unsafe as well. Much of the information in the Risk Assessment is based on early studies during the emergency cleanup. The purpose of that work was to stabilize the site and remove the most dangerous material. Offsite and perimeter areas were not well characterized.

All “media” show toxins on the site, including topsoil, buried soil, groundwater, surface water and sediments. There are at least two groundwater plumes that are carrying toxins offsite. Plumes are high concentrations of chemicals that flow away from a source. The toxins most likely to move in groundwater are carcinogens (cancer-causing chemicals) such as PAH (aromatic hydrocarbons) and PCP (chlorinated phenol). EPA says the chemicals are moving in groundwater to Burnett Creek; however there has been no modeling study to prove this theory. So far there is no study showing a hydraulic connection between the groundwater and the creek.

Exposure pathways

There is a difference between risk and threat of risk. It is generally accepted that, if there is no “pathway” to exposure, then there is no risk. So if a chemical is completely bound up and isolated away from people then the chemical has no actual risk. Risk “threat” comes from concern that chemicals which are not stabilized or protected in some way may move from the site into neighborhoods, or into homes from contaminated tap water.

Each chemical also has unique effects. Some dissolve in water, some will move in air. Each chemical usually damages only one type of organ in the body—skin or liver for example. Not only the proximity of the chemical to a person but the type of exposure—skin, eating, drinking or breathing—is taken into consideration when a risk assessment is done.

Cancer Risk

Risk for cancer is reported as probability of cancer in a range of “one in one-million” to “one in one-thousand” chance. These numbers are interpreted the same way as “lotto” or other games of chance.  If an average person is exposed to site chemicals their “odds” of getting cancer sometime during their lifetime increase by “one in one-million” to “one in-one-thousand” depending on the amount of chemical. “One in one-million” is considered to be absolutely no chance of getting cancer from this exposure. However, “one in one-thousand” is considered very risky.

Toxic Risk

Toxicity—how poisonous a chemical is—is calculated differently than cancer risk. Since toxicity is usually short-term there is often information on the effects of a chemical on animals that can be used to estimate danger to people. All of the toxic effects are added up and a “Hazard Index” (or “HI”) calculated for all non-cancer risk. If the HI is greater than 1 then site chemicals are dangerous and the levels unacceptable. HI’s lower than 1 are acceptable.

Study Findings

EPA considered two risk models: the Current Use model and the Future Use models. The Current Use model only looked at “industrial” site use; however Future Use was further broken down to future residential and future commercial/industrial use.  When forming the models EPA uses different exposure standards for residential or commercial uses. For example, the number of days in a year a child would be exposed under commercial standard is 250 days (about 8 months and 3 weeks), while the same child would be exposed under a residential standard for 350 days/year (about l1 months and 2 weeks).

nder the Current Use model the EPA claims there is no risk for cancer or toxicity. However, the cancer risk model gave the value of “one in ten-thousand” chance, which is just barely passing. If EPA’s guidelines are even slightly off there could be a high cancer risk under the Current Use model. The site would not pass using residential standards.

For the Future Use model the site does fail under the residential standards. Cancer risk is within the level of a “one in one-thousand” chance, which exceeds safety guidelines. Further, the groundwater plumes fail under residential standards, and these plumes may extend offsite. Also, the Hazard Index is higher than 1 for site chemicals, and was especially high for children.

Actual Site Conditions May Not Match Models

Risk models are only as good as the numbers used in the math calculations. Poor or incomplete studies result in models that have no usefulness.

¨         These models have not taken into consideration the possibility that local fisherman may be exposed from catching and eating fish from the polluted creek.

¨      The groundwater studies are incomplete. There is no information provided on direction and rate of plume movement.

¨      Subsurface soil data was not considered. Sediments in impoundments and ditches were not considered, even though it is known that some ponds dry out. 

¨      The soil data is based on grid sampling that is very widely separated. According to Figure 2.1 in the Report some of the more contaminated areas were sampled at 300-foot intervals, this can bias the data into concluding that the site is safer than shown.

Conclusions

The EPA has modeled the Brunswick Wood Preserving Site to show very little risk to the public. There were very few samples taken during the Remedial Investigation. These were scattered over a wide area. During the Risk Assessment modeling, some potential pathways were not used.

 EPA’s models assume that no one can enter the site or stay for any length of time without EPA’s permission.

The models assume that no fish are contaminated from Burnett Creek and no one eats them if they are.

The studies assume that no one drinks or uses groundwater from the site.

EPA assumes they have found the highest chemical concentrations.

Further, the EPA assumes that all chemicals occur within areas defined by fences and ditches, although residents say that clouds of toxic fumes often covered the site.

Unfortunately, the public cannot assume the site is safe based on this Risk Assessment.

 Written by R. Kevin Pegg, Ph.D.; edited by Dr. Mary S. Saunders. Copies of the newsletter are available from the GEC, at the Glynn County library, or at www.NucleicAssays.com/tags  on the Internet.

"This project has been funded wholly or partly by the U.S. Environmental Protection Agency under Assistance Agreement Number 1984482-98-0 to The Glynn Environmental Coalition, Inc. The contents of this document do not necessarily reflect the views and policies of the U.S. Environmental Protection agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use."

 

 
   
   
 

Understanding Cancer Risk Models

Chance of new cancers

EPA

Abbreviations

Risk

“one in one-million”

1/1,000,000;

1 x 10-6

No Risk of cancer

“one in

 one-hundred thousand”

1/100,000;

1 x 10-5

More risk, but acceptable

“one in ten-thousand”

1/10,000;

1 x 10-4

Some risk, but allowable

“one in one-thousand”

1/1,000;

1 x 10-3

High Risk of cancer

 

 

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