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Detecting Environmental Risks

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Making Lab Data Sing

Published December 3, 2024

In environmental science, the accurate interpretation of data is essential—especially when it comes to incidents involving spills or accidents. If liquids have spilled, if a canister has cracked, or if soil has been contaminated, there’s one step you can be sure of: someone will eventually ask for data to confirm what happened. This data might be used to validate an insurance claim, or more hopefully, to understand how to remediate the site to prevent future incidents.

Two key issues though must be understood when working with environmental data: 1) the process of sample testing; and then, the interpretation of the results. These elements come into play once soil or groundwater testing is performed, and they help us make sense of what the data is telling us.

Sample Testing: A Common Approach

Most chemical laboratories will provide test results that are accompanied by information about the legally permissible concentration of specific chemicals. This applies to both soil and groundwater tests. For example, consider PCE (tetrachloroethylene) a toxic and hazardous solvent commonly used in dry cleaning. In groundwater, the federal regulatory limit for PCE is 5 parts per billion (ppb). When you receive a laboratory report, you will typically see the results of the testing alongside this concentration limit, helping you quickly determine whether a public health contamination problem exists that needs attention.

This is usually straightforward: if the level of contamination exceeds the permissible limit, further action will be necessary. Many reports may highlight whether immediate action is required, often using bold or distinct fonts to make this clear.

The Mystery of “ND” (Non-Detect)

But what happens if the test results include the term ND, which stands for “Non-Detect”? Does this mean the chemical was not present at all?

The short answer: not necessarily.

ND doesn’t mean that the chemical isn’t there; rather, it means that the testing equipment used by the lab couldn’t detect the chemical in the sample, even if it was present in some small amount. The equipment may simply have been unable to identify the chemical because it was below the detection threshold of the lab’s instruments. It’s important to note that the equipment may not be faulty; it’s just that the chemical concentration was too low for the technology to detect.

In these cases, ND is not an outright confirmation of absence—it simply means that, with the tools available, the chemical could not be found. The results don’t rule out the possibility that it was there; they just reflect the limitations of the detection methods used.

The Bottom Line

Environmental data is a powerful tool for understanding the impact of accidents or spills, but it’s important to interpret the results correctly. Understanding terms like “Non-Detect” and knowing how to read laboratory results can help ensure that you take the proper steps in response to found contamination. Whether you’re investigating the source of a spill, validating an insurance claim, or planning remediation efforts, the data can provide invaluable insights—if you know how to read and understand the data properly.

In short, environmental data is often more nuanced than it may first appear, and careful interpretation is key to making informed decisions.

Any questions? …just contact me.