Is Your Kitchen Microwave Safe?
Most of us have experienced it. Whether it’s smelling that burnt popcorn cooked 30 seconds too long, searing your tongue on coffee that has been "warmed up," or watching in horror as that plastic container holding your leftover lasagna starts to warp and melt, we all have undergone mishaps with that modern convenience called a microwave oven. The device was discovered accidentally when the chocolate bar of a scientist experimenting with microwaves melted in his pocket. How safe are they?
How Do They Work?
Microwave ovens are one of many household appliances that generate an electromagnetic field. That is, they employ waves of electrical and magnetic energy moving together through space. "Microwaves" are short (one to 20 centimeters) waves of electromagnetic energy and are used in cellular telephones, radar detectors and other technology.
In a microwave oven, the emitted microwaves cause water molecules to oscillate at an extremely high rate, thereby creating heat. The food is cooked from the inside out. As Louis Slesin, editor of Microwave News, explains, this phenomenon results in uneven heating of the food—what he calls the "jelly doughnut effect." Says Slesin, "The food with the highest water content heats up the quickest, so a jelly doughnut that feels slightly warm to the touch has scalding hot jelly inside." It is possible for cold spots to harbor harmful bacteria such as salmonella, which is a particular concern for baby bottles.
Popular holistic health expert Dr. Andrew Weil has written, "There may be dangers associated with microwaving food… there is a question as to whether microwaving alters protein chemistry in ways that might be harmful." Dr. Fumio Watanabe of Japan’s Kochi Women’s University studied the effects of microwaving milk. Heating samples for six minutes degenerated 30 to 40 percent of the milk’s vitamin B12. This breakdown occurs with conventional heating methods but at a much slower rate, after approximately 25 minutes of boiling.
A 1992 Stanford Medical School study reported a "marked decrease in activity of all anti-infective factors" in microwaved human breast milk, which would imply that the milk lost its immune-fighting properties. The study concluded that "microwaving appears to be contraindicated at high temperatures, and questions regarding its safety exist even at low temperatures."
In the late 1980s scientists Hans Hertel and Bernard Blanc of the Swiss Institute of Technology tested blood from subjects both before and after eating microwave-cooked food. They reported that the subjects had a decrease in all hemoglobin values as well as increases in white blood cells and cholesterol.
Hertel and Blanc concluded, "Food prepared in microwave ovens is dangerous to health and may lead to pathological changes in the blood that indicate the beginning of a cancerous process." The scientists were taken to court by the Swiss appliance industry and were convicted in 1993 of interfering with commerce. This ruling was later reversed.
For decades, the common perception has been to assume that non-ionizing radiation—which includes the spectrum of visible light, infrared rays, radio frequencies and microwaves—is harmless. Ionizing radiation, in contrast, is known to destroy molecular bonds, and is the more dangerous type associated with x-rays and gamma rays. While it is clear that within close proximity both microwaves and radio frequencies can damage tissue through heating, the potential of damage from non-thermal effects is a growing area of concern, especially with devices being used for extended periods of time.
According to Norbert Hankin of the Environmental Protection Agency (EPA)’s Center for Science and Risk Assessment, "We don’t have a solid position on the possible health risks from exposure to microwaves due to inconclusive research." He concludes, "The real question remains whether there could be cumulative effects."
Microwave ovens are in 84 percent of America’s homes, and industry spokespeople claim they are completely safe. Industry standards are enforced by the Food and Drug Administration (FDA), which allows some leakage of microwaves from these ovens (which the industry calls negligible). Exposure is greatest within two inches of the oven.
Even so, experts advise consumers to have their microwave ovens checked annually by reputable technicians. The FDA cautions people to move away from a microwave oven while it’s in use, and not to look into the chamber, since the eye is the most permeable organ to microwave radiation. Says the agency, "Exposure to high levels of microwaves can cause cataracts." This is especially important for children, whose eyes are still developing. If anything is impeding the tightness of the door’s seal, you may have additional leakage. Use only "microwave-safe" glassware or packaging, and avoid the use of plastic wrap.
A body of evidence suggests that the leaching of toxic chemicals from plastics, adhesives, inks and browning trays may be occurring in the super-heating within a microwave oven. Some of these chemicals may mimic hormones, thereby disrupting the endocrine system. FDA tests done in 1988 found that the microwaveable "heat-susceptor" packaging used to brown such foods as pizzas and waffles can release chemicals into the food in as few as three minutes of cooking.
Les Borodinsky, an FDA chemist who worked on the study, noted that the "functional barrier" packaging of these microwaveable products did not seem to effectively prevent chemical leaching. This worries some experts, who note that traces of carcinogens have been found in microwaveable packaging.
The industry doesn’t deny some chemicals migrate, but says there is no health hazard, and points to studies that have affirmed the technology’s safety. Critics complain that many of the studies were financed by the industry itself.
The FDA recommends that only plastic labeled "microwave safe" come into contact with food in a microwave. However, Lisa Y. Lefferts and Stephen Schmidt of the Center for Science in the Public Interest argue that even some "microwave-safe" containers may be a cause for concern. "So far it’s been up to the manufacturers to test their own products, and to decide what is and isn’t safe for use in the microwave," they wrote.
Feeling the Heat, or Not?
Carl Blackman of the Cellular Toxicology Branch of the EPA says, "No theory yet explains the potential biological changes from exposure to non-thermal radiation. It may be innocuous, but we don’t know." In Europe, the accepted standards are lower than in the U.S.
FDA scientist Howard Bassen argues, "The only changes that occur in microwaved food are those that would happen with any other form of heat." He says, "[Electromagnetic] radiation exposure from a microwave is absolutely minimal, and is much less than that from other devices, such as cellular and cordless phones."
Clearly more studies are needed before consumers can truly feel confident when they push the b
utton to "nuke" their food.
KIMBERLY JORDAN ALLEN is a freelance writer who doesn’t own a microwave.