February 17, 2000

This report provides a preliminary summary and review of the Baseline Human Health Risk Assessment report, which was performed by Short Elliot Henderson (SEH) on the Ashland Lakefront property. The review is provided by the Technical Outreach Services for Communities (TOSC) program with the assistance of faculty advisors at Michigan State University. The lead reviewer is Dr. Karen Chou, Associate Professor of Toxicology, at Michigan State.

Overview of Risk Assessment Report

The goal of the report is to determine the potential adverse health effects caused by environmental contaminants at the Ashland site. Its intent is to provide information for making decisions about cleaning up the site. The report provides population-based probabilities—they apply to groups, not individuals. The conclusions are useful as a predictor of current or future exposures, but not exposures that have already occurred. The report is reviewed based on the site history, the chemical and biological properties of the identified contaminants, and information provided in the report. Additional explanation of the risk assessment process is provided in the TOSC Information Brief, "Human Health Risk Assessment."

Widespread volatile organic compounds and semi-volatile organic compounds contamination were identified on the Ashland Lakefront site, along with high concentrations of polycyclic aromatic hydrocarbons (PAHs) in a "tar dump" at the base of the bluff. The contamination extends into the shallow groundwater aquifer and into the Copper Falls aquifer beneath the location of the old manufactured gas plant. The contamination has also been found in a filled ravine area in the bluff, in a groundwater seep located at the base of the bluff, as well as in the nearshore Lake Superior sediments. Elevated concentrations of inorganic chemicals including lead, zinc, iron, and chromium, have also been identified in the groundwater, surface soil and subsurface soil samples.

The study area of the report is limited to approximately 10 acres of Kreher Park and approximately 10 acres of nearshore sediments. It considers the upper shallow groundwater table, site soils, nearshore sediments, and lake water. The report does not include evaluation of the contamination located in the filled ravine, in the Copper Falls groundwater aquifer, adjacent residential properties or on the NSP property.

Carcinogenic risk and non-carcinogenic assessments were performed for chemicals that exceeded background concentrations and for which there are regulatory toxicity values. For coal tar and lead, a description of toxicity was provided. The risks were analyzed for five groups based on likelihood of exposure: city workers, recreational adult, recreational child, recreational adolescent and trespassing adolescent (Table 1). The report followed government assumptions as to average weight, amount of dust possibly inhaled, how much water might be swallowed, etc. Most of the input variables for exposure assessment were obtained from U.S. EPA; variables not available from EPA at the time of publication were determined with professional judgment developed in consultation with the Wisconsin Department of Health and Family Services. The possible routes of exposure are shown in Table 1.

Preliminary findings of Human Health Risk Assessment review

The highest level of risk in all five groups is associated with dermal (skin) exposure to seep water and contaminated sediments. Other prominent risks are associated with the ingestion (eating) of surface soil for children and the ingestion of, and dermal exposure to, contaminants in the site subsurface soil, the seep water and the ground water.

The SEH risk assessors identified many uncertainties. The majority of the uncertainties are caused by the limited number of samples collected and analyzed, assumptions of variables, such as default values for calculating exposure, and the incomplete knowledge of the chemical and biological properties of the contaminants. Those uncertainties, however numerous, are an inherent part of the risk assessment. In reviewing the Ashland report, TOSC did not have complete data, and therefore the level of uncertainty is not completely understood. We are attempting to gather the data and will provide comments at a future date.

While information is lacking for a complete review of the report (because TOSC is still obtaining some documents), the approach to the risk assessment appears appropriate. It provides a set of preliminary information for setting priorities to address the contamination. However, it is important to point out that the report does not include the Northern States Power property, the Copper Falls aquifer or the filled ravine. Nor does it include the population and the activities in the residential area, the church and the school.

To evaluate the conclusions of the report in depth, the TOSC reviewers need additional information, including:

• additional analytical data not included in the report, and
• calculation formulas for exposure assessment for each scenario and sub-populations

TOSC will append final comments to this review when additional documentation is provided.

Summary

1. The approach of the Human Health Risk Assessment is acceptable, but TOSC reviewers did not have sufficient data to reach a final conclusion.
2. The highest risk associated with the site, for all groups studied, is direct skin contact with seep water.
3. City workers and children have significant risk of exposure through incidental ingestion of soil and water.
4. Adolescents are at significant risk of exposure through trespassing onto the site.
5. TOSC reviewers recommend that additional risk assessment work be conducted, including of the NSP property and adjacent residential properties.