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assessing and communicating risk:
a partnership to evaluate a superfund site on leech lake tribal lands

View the Cass Lake, MN Superfund Site Report

Why was this project needed?
The Leech Lake Tribal Council was concerned that the former wood preserving facility located along Pike Bay in Cass Lake, MN, had not been studied well enough to know whether or not the clean up actions taken by the company that owned the site were successful. They were concerned about whether there were still chemical contaminants on and near the site that might harm the health of local people and the environment.

What is the partnership?
In 1997, the University of Minnesota’s Natural Resources Research Institute and Sea Grant Program teamed up with the Leech Lake Tribal Council to submit a grant proposal to the U.S. Environmental Protection Agency Environmental Justice Program. The proposal was funded and began in 1998.

What was proposed in the grant?
To address the tribal council’s concerns, the University agreed to bring together experts to review the available scientific data from the site and try to determine whether the site was being cleaned up effectively. The experts were also asked to make recommendations for future work on the site, including additional data that should be collected. The University also agreed to share the conclusions of the experts with the Leech Lake Tribal Council and local community. Three groups of experts were brought together. The first group reviewed groundwater data (Groundwater Panel), the second reviewed human health data (Human Health Panel), and the third group reviewed ecological data (Ecological Panel). As part of the project, scientists from the University collected additional biological and geological data.

What were the general conclusions of the three expert panels?

The site at Cass Lake continues to be contaminated with chemicals at levels considered harmful to humans and wildlife. The chemicals are commonly found at wood preserving industries and are related either to actual preserving activities or to general facility maintenance. Some of the chemicals can cause cancer. Known contaminants of concern (COCs) include:

•Semi-volatile organic compounds (SVOCs), including Polycyclic aromatic hydrocarbons (PAHs)
•Pentachlorophenol (PCP)
•Dioxins and polychlorinated biphenyls (PCBs)
•Certain heavy metals

The site and surrounding area have not been sampled well enough to know how far the contamination has spread. There is not enough information to know how likely it is that additional contaminants will move off of the site into the surrounding area in the future. It is not clear how great the risk is now or will be in the future to environmental and human health. More groundwater, ecological, and human health data are needed.

Although a number of steps have been taken to clean up the contamination, those efforts have not been fully successful. The panels of experts found evidence to suggest that some contaminants are moving off of the site to areas that could cause human and ecological health risks.

The panels of experts also found evidence that people living or working near the site are probably being exposed to toxic chemicals at levels higher than what is considered protective of human health. This is especially important for children who live and play near the site.

What were the general recommendations of the three panels?
Steps should be taken as soon as possible to reduce health risks to children and other people exposed to the site. For example, there are high levels of dioxins and furans in the soils on the site. Until these contaminants are cleaned up, the site should be fenced off to keep people away.

It is important for scientists to learn more about the amount and location of the contaminants that were released when the plant was in operation, where the contaminants are currently distributed, as well as how much and where the contaminants are moving.

Work needs to be done to have a better understanding of all the different ways that humans, plants, and wildlife are currently being exposed to the contaminants. These efforts need to consider how local people use natural resources in their day-to-day lives.

The health of local people who have been exposed to the site and the health of the local environment, including plants and wildlife, should be evaluated carefully. This will help scientists do a better job of estimating how much of a risk the site is to human and ecological health.

Standard methods of determining the health risks of a contaminated site do not always look at special circumstances, such as traditional tribal uses of natural resources. The methods used to determine risks should be designed to include traditional tribal practices and should consider the possibility that people might be exposed to contaminants in a number of ways as they live, work, and play near the site.

The Groundwater, Human Health and Ecological Panel Reports, and other Superfund Site related information can be found at the Web Site below.



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 www.seagrant.umn.edu/water/leech.html modified February 14, 2017