Blue-green algal blooms like the one pictured here (Lake Erie, 2009) produce toxic microcystins that threaten human health. Source: NOAA – NASAWithout naming the brands used in their testing, scientists from Ohio State University discovered that some of the water-filter pitchers created to remove harmful contaminants from drinking water don’t necessarily accomplish what they were designed for.

Looking at three unnamed pitchers — all of which claim to filter harmful contaminants from tap water — scientists discovered that only one of the pitchers performed as advertised, removing a toxic byproduct of harmful agal blooms (HABs) called microcystins.

Of the three, the pitcher made exclusively of coconut-based activated carbon filtered water in the shortest amount of time, only removing roughly 50 percent of microcystins from the water. The pitcher made up of a blend of active carbon and that filtered water at the slowest rate successfully removed all detectable traces of microcystins from the drinking water.

“Because drinking-water treatment plants also use activated carbon, I figured that these home filters might also remove some microcystins, but I wasn’t expecting results this good and such big differences among the pitchers,” said Justin Chaffin, the study’s lead author and a senior researcher and research coordinator at Ohio State’s Stone Laboratory.

Considered a global threat to drinking water, HABs produce toxins — with the most common among them being microcystins — that can be both harmful to animals and humans alike.

While they don’t name the pitcher brand, the team did drop hints to suggest which brands consumers might want to avoid.

“In general, the cheaper the pitcher, the worse job it did filtering out the toxins,” Chaffin said.