“EWG rated big city (population over 250,000) water utilities based on three factors: the total number of chemicals detected since 2004; the percentage of chemicals found of those tested; and the highest average level for an individual pollutant, relative to legal limits or national average amounts, including for the most common pollutants (disinfection byproducts, nitrate and arsenic).”
Source: How Clean is City Water? View EWG’s Big City Water Ratings via Environmental Working Group (via horizonwatching)
