It has been claimed that water heated in a microwave oven kills plants, proving that the appliances are unsafe. Today we'll investigate the veracity of this claim.
The claim is unproven.
The origin of this popularly-cited assertion is that of a science fair project by a girl in secondary school in the UK back in 2006. That project showed a series of photos in which the plant using microwaved water died, while the plant receiving purified water thrived.
The description of the experiment read:
Below is a science fair project that my granddaughter did for 2006. In it she took filered water and divided it into two parts. The first part she heated to boiling in a pan on the stove, and the second part she heated to boiling in a microwave. Then after cooling she used the water to water two identical plants to see if there would be any difference in the growth between the normal boiled water and the water boiled in a microwave. She was thinking that the structure or energy of the water may be compromised by microwave. As it turned out, even she was amazed at the difference.
The website for the original project is no longer available, but it can still be seen in a web archive. The student’s grandparent, who originally posted the experiment online, conceded that the student had an agenda regarding this experiment. “On top of that she was wanting the microwaved ones to do poorly, and although most scientists would dismiss the idea, it is possible that her thoughts toward each plant had an effect as well.”
While the photos of the experiment are convincing, the test was not performed under scientific conditions. There are a variety of reasons why the school experiment could have yielded different results between the two plants. These may include differences among the containers, infestation, contaminants in the container in which water was heated, soil quality, the handling of the plants, or any other variety of factors. Such factors would be more controlled in a scientific setting in order to isolate the microwaved water as a true variable.
Researchers have not found any difference between microwaved food or liquids and those heated by other methods. Cancer Research notes that “Microwaves heat food, but do not make any changes to it that aren’t made in any other cooking method.” Discussion of this experiment have led to the larger discussion about the suggested dangers of microwave ovens.
Many individuals have attempted to duplicate the results of this test without success as shown in the videos below:
We performed our own non-scientific version of the microwaved water experiment in 2013, and our results matched those of the videos above. After 10 days of watering two plants with purified water and microwaved water, we found no discernible difference between plants watered with water and those receiving microwaved water.
There is no scientific evidence that microwaved water is harmful to plants, and the results of the science 2006 fair project have proven difficult to duplicate. Further, our own tests have shown virtually no difference between plants watered with filtered water or microwaved water.
The student’s grandparent perhaps best summarized the debate regarding this experiment, stating, “But this was a simple 6th grade science fair project, and was never intended to be anything more than that.”