Ohio EPA and EPA have established a 560 ppb screening value for n-butyl acrylate based on the ATSDR Provisional Health Guidance Value (HGV). All of the hits (positive detections) within the Ohio River are well below this number, around 12.5 ppb at it's peak approximately 0.2 miles from the release site. The majority are between 1-2 ppb farther away from the site, just above laboratory detection limits.

https://epa.ohio.gov/static/Portals/47/citizen/response/East-Palestine-Ohio-River-Sampling-Data.pdf