Hand blenders, sometimes called immersion blenders, are incredibly convenient — They let you puree food inside of a pot or bowl, instead of making you pour the food into a blender and back out again. But a report from Stockholm University finds that they can also transfer toxic chemicals into food.

Eight of the twelve models tested leaked chemicals called chlorinated paraffins. Chlorinated paraffins (CPs) have many industrial uses. They're mainly used as a coolant and lubricant in metalworking and as a plasticizer or flame retardant in rubber, leather, glue and plastics.

Short chain CPs are stored in the body in a manner similar to PCBs. And they are suspected of causing long-term harm.

Like motor oil, most preparations of CPs are mixtures of chemicals of many different sizes. Studies on the health effects of CPs have focused on the smaller ones, sometimes called short-chain chlorinated paraffins or SCCPs.

SCCPs are toxic to fish and many other types of aquatic life, and they remain in the environment a long time. They aren't known to cause short-term harm to people, but they are stored in the body in a manner similar to PCBs. And they are suspected of causing long-term harm.

The International Agency for Research on Cancer (IARC) classes SCCPs as a possible human carcinogen, while the U.S. National Toxicology Program classes them as "reasonably anticipated to be a human carcinogen." The Environmental Protection Agency lists SCCPs among their “Chemicals of Concern,” a short list of troubling (but unregulated) chemicals.

Blenders leaked both short and medium-chain CPs. The leak appears to be coming from the blender hood, the part located just above the rotating blade. A hole drilled into the hood of the blenders confirmed that CPs were present there.

The eight models of immersion blenders that leaked are listed below in order of how much chlorinated paraffin they leaked, with the top model leaking the most and the bottom model the least:

  • OBH Nordica Kitchen Quickprep 500 Model 7701
  • Russel Hobbs Model 18274-56
  • Coline Model LW-3318
  • OBH Nordica Kitchen Quickmix Model 6705
  • Electrolux Ultramix Pro Model ESTM 6400
  • Matsui Model M24HBW09E
  • Braun Multiquick 3 Model 4162
  • Voltage Model HM-918

The four models that didn't leak CPs were:

  • Bosch Model MSM6B100
  • OBH Nordica Model 6707 (Chili)
  • Philips ProMix Model HR 1607/08
  • OBH Nordica Model 6712 (Indigo)

What's the take-home lesson here? Even though further study is needed, the researchers believe the results clearly indicate that certain hand blenders can expose people, particularly small children, to harmful substances.

More information, including photos of all 12 blenders, can be found in the University's report.