Interpreting data
About our sampling
What types of samples are we taking?
We are collecting water, sediment, and soil samples in the Duwamish Valley.
When will samples be collected?
We plan to sample quarterly and also opportunistically after large storm events to capture pulses of contaminants that could be entering waterways.
Where will samples be collected?
We will focus on areas that have been identified by community partners as areas of concern, access points, near combined sewer overflows (CSOs), and at known outflow points. We are also looking for community feedback on your areas of concern! If you have places you think should be sampled, please get in touch using the "Getting involved" tab or click HERE.
What contaminants are you looking for?
Key contaminants include cement kiln dust (CKD), carcinogenic polycyclic aromatic hydrocarbons (cPAHs), polychlorinated biphenyls (PCBs), heavy metals (including arsenic, cadmium, mercury, and lead), and dioxins and furans, all of which are listed as contaminants of concern (COCs) in the Lower Duwamish Superfund. Concentrations found in our samples will be compared to local, regional, and national screening levels as appropriate.
Photo below: Dr. Melanie Malone demonstrating sediment sampling (courtesy of the University of Washington).
Screening level FAQs
What are screening levels used for?
Screening levels (SLs) represent concentrations of contaminants that should not be exceeded, because certain concentrations may pose harm to human and ecological health. Because each contaminant is different, there are different SLs. Generally, SLs are used to determine if a site with contamination needs to be cleaned up, or if a site with contamination has the potential to create adverse health effects (e.g. cancer, developmental delays).
Do all contaminants have SLs?
Not all contaminants currently have SLs. Additionally, while contaminants may have SLs, they might not fully represent the contaminant's impact on human health.
What does it mean if a sample result exceeds an SL?
It depends on the particular scenario. Some sites undergoing investigation by a government agency may be required to clean up contamination. Some sites are not being regulated, and the owner of the site may just want to lower contamination levels and may seek guidance from experts on risk.
What is risk assessment?
Risk assessment, the process by which scientists determine what concentrations of contaminants cause harm, is very complicated. SLs developed in risk assessment may vary even between different agencies within the same state. Sometimes SL exceedance means that there is potential for harm to health; sometimes it means that cleanup is required. If you have concerns about concentrations of contaminants in your community, you should speak with an expert in risk assessment, or with our team if you're in the Duwamish Valley. It is important to speak with a risk assessor who values community input and can respond to community concerns about concentrations of contaminants and SLs.
Understanding and using data
When we receive data from the lab, it undergoes analysis and interpretation by our team before being shared as reports with our community partners. When it comes to understanding these data, there a few key pieces of the process that provide the most insight into site qualities.
Let's walk through an example
Below is an example of a screening table used for contaminants. Although this table only shows mercury levels, our tests include multiple other contaminants.
Test results for each sample are under "Concentrations Detected" in columns according to their contaminant type. In the example, this column shows the concentrations of mercury in milligrams per kilogram (mg/kg) for soil samples. For water samples, concentrations would be shown in milligrams per liter (mg/L).
On the right (under the green columns), test results are compared to screening levels (SLs). The SL can be found in the green headers. If a sample exceeded a SL, there is a "Y" for yes. If the sample did not exceed the screening level, there is an "N" for no. In some cases, you may see "N/A" under an SL; this could be that either the usual screening level does not apply based on the type of sample, or that the agency that developed the screening levels does not currently have a SL for that particular contaminant.
In the example below, soil sample EXS-4 has a mercury concentration of 2.1 mg/kg. This soil sample exceeds multiple SLs, so "Y" is written for WA DOE Cleanup Level (SL limit 2 mg/kg) and Background Mercury Puget Sound in King County, WA (SL limit 0.04 mg/kg). The EPA does not currently have carcinogenic screening levels for ingested or dermal exposure for mercury, so those are marked with "N/A." There currently is no ECO-SSL for mercury, so that is also marked with "N/A."
What is a soil background?
A soil background is like a soil’s “family history”; it focuses on the concentrations of contaminants that are either naturally occurring or were a result of historical human activity that are not influenced by that area’s current use. In the case of mercury, the background concentration is 0.04 mg/kg in the Puget Sound.
So what recommendations would we provide for data like this?
Since this soil exceeded SLs for mercury, we would advise that people working in the soil wear gloves, long sleeves, and pants to prevent dermal exposure, peel or wash well any vegetables grown in the area, remove contaminated or dirty clothing and shoes before entering your home, wash your hands and face, and carefully supervise children to avoid any consumption of the soil (while still encouraging lots of outdoor fun!). Depending on the location, use, and access to these sites, we would also provide more specific recommendations to limit exposure. For general tips on limiting exposure, see HERE.
Sharing information
Across all research activities, we will continuously engage community groups and Tribes to review project goals and findings using the principles of free, prior, and informed consent. Along the way, we will develop appropriate documentation and data sharing tools that prioritize community data ownership. We will specifically identify how best to: document and provide instructional manuals for collecting and inputting contaminant data into a shared repository; present and store water quality and soils data so they are accessible and actionable to each community group; identify policy priorities and levers the data may support; establish pathways for advocacy and direct remediation action; and provide opportunities to scale this type of community-driven inquiry to other institutions and sites (e.g., through open source toolkits). We will use surveys and interactive workshops to evaluate which tools are most legible and useful to different groups. These tools will be made available through this website as they become available and shared with our community partners for dissemination.
Sources
https://www.epa.gov/risk/regional-screening-levels-frequent-questions
https://kingcounty.gov/services/environment/wastewater/duwamish-waterway/superfund-cleanup/staying-safe