Moss Landing Soil: Did EPA use X-ray fluorescence (XRF) to test soil on and around the site?

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Monterey County is overseeing the soil sampling in the community to assess exposure, while EPA remains focused on overseeing the battery removal work at the site.

X-ray fluorescence (XRF) is a screening tool used to detect metals in soil. Screening tools are helpful to assess where additional sampling may be needed.

• Results can help assess potential contamination levels but require soil sampling and laboratory analysis for confirmation.

Soil Sample Accuracy for Community Sampling

As part of Monterey County’s community soil sampling effort, Vistra sampled soil around the Moss Landing community. The samples were collected to support a human health risk assessment. Monterey County collected “split samples” with Vistra. This means the county took samples from the same locations and times as Vistra.

• These samples are sent to different, independent labs.
• The results are compared to each other for quality control.

Find more information about community sampling efforts on Monterey County’s Moss Landing website.

How Are Air Results Evaluated?

We calculate whether an air result is hazardous by comparing how much is in the air (the concentration) with how long you may have contacted it.

• Exposure to fire events like Moss Landing are short-term, acute exposures.
• Long-term exposure (months to years) are considered chronic exposures.

Acute and chronic exposures each have their own threshold (called a “screening level”) for what is considered potentially hazardous.

So, if you were exposed to a contaminant for a short period of time, the concentration of the contaminant would have to be higher for it to potentially have a health impact than the same concentration over a longer period.

Further, each contaminant has a different toxicity. This means the screening levels for each are different.

• We take these differences into consideration when we are evaluating your data.
• When no screening level exists, experts assess and use the most health protective value.

Lastly, safety margins are built into creating these screening levels. The levels are conservative and are based on protecting the most sensitive community members. This means that, if there was data showing a level had been exceeded, it does not mean all could expect health effects.