The Minnesota Pollution Control Agency will be testing water quality along the entirety of the Mississippi River within the state’s borders in 2024, the agency announced this week.

The MPCA typically only tests portions of the river in any given year, and this year’s effort to sample over 50 locations from Bemidji to the Iowa border represents a first for the agency in what could be read as increasing concern about emerging threats to water quality, including 3M-manufactured chemical compounds known as PFAS.

Water quality within Minnesota’s stretch of the river has improved dramatically over the past four decades, according to a fact sheet from the Metropolitan Council. But levels of some contaminants — including nitrogen from excessive fertilizer use and chloride from road salt — are rising.