Estimated five-day biochemical oxygen demand (BOD₅) and chemical oxygen demand (COD) concentrations attributed to aircraft and pavement deicer freezing point depressants (FPDs) in samples from monitoring sites near Milwaukee Mitchell International Airport, 2005–2022, and percent of measured BOD₅ and COD concentrations. The contribution of non-FPD (“other”) compounds at each site was calculated by subtracting the sum of BOD₅ or COD contributed by all FPDs from the measured BOD₅ or COD. The dashed line represents values that were not detected and are assumed to be zero. If other contributions to BOD₅ or COD were negative, these values were set to zero to represent their minimal influence to BOD₅ and COD. Formate was not included in estimates for BOD₅ because toxicity to bacteria in the formate-containing product prevented measurements of BOD₅. The number of samples apportioned for each site were as follows: infall, n = 25; primary outfall, n = 63; secondary outfall, n = 43; receiving stream, n = 51; tertiary outfall, n = 27. Two outliers for % COD contributed and 11 outliers for % BOD₅ contributed (greater than 150%) were included in boxplot calculations but were excluded by scale limits to provide easier interpretation of most of the data. PG = propylene glycol; EG = ethylene glycol; Ac = acetate; For = formate. Boxes, 25^th to 75^th percentiles; dark line, median; whiskers, data within 1.5 times the interquartile range (IQR); circles, values outside 1.5× the IQR.