Hi!
This was forwarded to me. It is worth reading

Brian Nelson 713-467-3025. I will put it on my web site.
Subject: Heating Water in a Microwave
 

I feel that the following is information that any one who uses a microwave oven to heat water should be made aware of.
About five days ago, my 26 year old son decided to have a cup of instant coffee.

 He took a cup of water and put it in the microwave to heat it up (something that he had done numerous times before). I am not sure how long he set the timer for but he told me he wanted to bring the water to a boil. When the timer shut the oven off, he removed the cup from the oven. As he looked into the cup he noted that the water was not boiling but instantly the water in the cup "blew up" into his face. The cup remained intact until he threw it out of his hand but all the water had flew out into his face due to the buildup of energy.

His whole face is blistered and he has 1st  and 2nd degree burns to his face which may leave scarring.
He also may have lost partial sight in his left eye.

 While at the hospital, the doctor who was attending to him stated that this a fairly common occurrence and water (alone) should never be heated in a microwave oven. If water is heated in this manner, something should be placed in the cup to diffuse the energy such as a wooden stir stick, tea bag, etc. It is however a much safer choice to boil the water in a tea kettle.

Here is what our science teacher has to say on the matter: "Thanks for the microwave warning.
I have seen this happen before. It is caused by a phenomenon known as super heating. It can occur anytime water is heated and will particularly occur if the vessel that the water is heated in is new.
What happens is that the water heats faster than the vapor bubbles can form.
 

 If the cup is very new then it is unlikely to have small surface scratches inside it that provide a place for the bubbles to form. As the bubbles cannot form and release some of the heat that has built up, the liquid does not boil, and the liquid continues to heat up well past its boiling point. What then usually happens is that the liquid is bumped or jarred, which is just enough of a shock to cause the bubbles to rapidly form and expel the hot liquid. The rapid formation of bubbles is also why a carbonated beverage spews when opened after having been shaken. "CALL Brian Nelson for questions 713-467-3025

Microwave Oven Radiation

• About Microwaves
• What is Microwave Radiation?
• Cooking with Microwaves
• Microwave Oven Safety Standard
• Microwave Ovens and Health
• Have Radiation Injuries Resulted from Microwave Ovens?
• Ovens and Pacemakers
• Checking Ovens For Leakage
• Tips on Safe Microwave Oven Operation
• Erupted Hot Water Phenomena in Microwave Oven
• What Can Consumers Do to Avoid Super-Heated Water?
• Other Tips for Microwave Oven Use

About Microwaves

Microwaves are used to detect speeding cars, to send telephone and television communications, and to treat muscle soreness. Industry uses microwaves to dry and cure plywood, to cure rubber and resins, to raise bread and doughnuts, and to cook potato chips. But the most common consumer use of microwave energy is in microwave ovens.

The Food and Drug Administration (FDA) has regulated the manufacture of microwave ovens since 1971. On the basis of current knowledge about microwave radiation, the Agency believes that ovens that meet the FDA standard and are used according to the manufacturer's instructions are safe for use.

What is Microwave Radiation?

Microwaves are a form of "electromagnetic" radiation; that is, they are waves of electrical and magnetic energy moving together through space. Electromagnetic radiation ranges from the energetic x-rays to the less energetic radio frequency waves used in broadcasting. Microwaves fall into the radio frequency band of electromagnetic radiation. Microwaves should not be confused with x-rays, which are more powerful.

Microwaves have three characteristics that allow them to be used in cooking: they are reflected by metal; they pass through glass, paper, plastic, and similar materials; and they are absorbed by foods.

Cooking with Microwaves

Microwaves are produced inside the oven by an electron tube called a magnetron. The microwaves are reflected within the metal interior of the oven where they are absorbed by food. Microwaves cause water molecules in food to vibrate, producing heat that cooks the food. That's why foods high in water content, like fresh vegetables, can be cooked more quickly than other foods. The microwave energy is changed to heat as it is absorbed by food, and does not make food “radioactive” or "contaminated."

Although heat is produced directly in the food, microwave ovens do not cook food from the "inside out." When thick foods are cooked, the outer layers are heated and cooked primarily by microwaves while the inside is cooked mainly by the conduction of heat from the hot outer layers.

Microwave cooking can be more energy efficient than conventional cooking because foods cook faster and the energy heats only the food, not the whole oven compartment. Microwave cooking does not reduce the nutritional value of foods any more than conventional cooking. In fact, foods cooked in a microwave oven may keep more of their vitamins and minerals, because microwave ovens can cook more quickly and without adding water.

Glass, paper, ceramic, or plastic containers are used in microwave cooking because microwaves pass through these materials. Although such containers can not be heated by microwaves, they can become hot from the heat of the food cooking inside. Some plastic containers should not be used in a microwave oven because they can be melted by the heat of the food inside. Generally, metal pans or aluminum foil should also not be used in a microwave oven, as the microwaves are reflected off these materials causing the food to cook unevenly and possibly damaging the oven. The instructions that come with each microwave oven indicate the kinds of containers to use. They also cover how to test containers to see whether or not they can be used in microwave ovens.

FDA recommends that microwave ovens not be used in home canning. It is believed that neither microwave ovens nor conventional ovens produce or maintain temperatures high enough to kill the harmful bacteria that occur in some foods while canning.

Microwave Oven Safety Standard

The Food and Drug Administration (FDA) has the responsibility for carrying out an electronic product radiation control program mandated by the Electronic Product Radiation Control provisions of the Food Drug and Cosmetic Act. Through it's Center for Devices and Radiological Health, FDA sets and enforces standards of performance for electronic products to assure that radiation emissions do not pose a hazard to public health.

A Federal standard limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface. This limit is far below the level known to harm people. Microwave energy also decreases dramatically as you move away from the source of radiation. A measurement made 20 inches from an oven would be approximately one one-hundredth of value measured at 2 inches.

The standard also requires all ovens to have two independent interlock systems that stop the production of microwaves the moment the latch is released or the door opened. In addition, a monitoring system stops oven operation in case one or both of the interlock systems fail. The noise that many ovens continue to make after the door is open is usually the fan. The noise does not mean that microwaves are being produced. There is no residual radiation remaining after microwave production has stopped. In this regard a microwave oven is much like an electric light that stops glowing when it is turned off.

All ovens must have a label stating that they meet the safety standard. In addition, FDA requires that all ovens have a label explaining precautions for use. This requirement may be dropped if the manufacturer has proven that the oven will not exceed the allowable leakage limit even if used under the conditions cautioned against on the label.

To make sure the standard is met, FDA tests microwave ovens in commercial establishments, dealer and distributor premises, manufacturing plants, and its own laboratories. FDA also evaluates manufacturers' radiation testing and quality control programs.

Although FDA believes the standard assures that microwave ovens do not present any radiation hazard, the Agency continues to reassess its adequacy as new information becomes available.

Microwave Ovens and Health

Much research is under way on microwaves and how they might affect the human body. It is known that microwave radiation can heat body tissue the same way it heats food. Exposure to high levels of microwaves can cause a painful burn. The lens of the eye is particularly sensitive to intense heat, and exposure to high levels of microwaves can cause cataracts. Likewise, the testes are very sensitive to changes in temperature. Accidental exposure to high levels of microwave energy can alter or kill sperm, producing temporary sterility. But these types of injuries - burns, cataracts, temporary sterility - can only be caused by exposure to large amounts of microwave radiation, much more than the 5mW limit for microwave oven leakage.

Less is known about what happens to people exposed to low levels of microwaves. Controlled, long-term studies involving large numbers of people have not been conducted to assess the impact of low level microwave energy on humans. Much research has been done with experimental animals, but it is difficult to translate the effects of microwaves on animals to possible effects on humans. For one thing, there are differences in the way animals and humans absorb microwaves. For another, experimental conditions can't exactly simulate the conditions under which people use microwave ovens. However, these studies do help us better understand the possible effects of radiation.

The fact that many scientific questions about exposure to low-levels of microwaves are not yet answered require FDA to continue to enforcement of radiation protection requirements. Consumers to take certain common sense precautions.

Have Radiation Injuries Resulted from Microwave Ovens?

There have been allegations of radiation injury from microwave ovens, but none as a direct result of microwave exposure. The injuries known to FDA have been injuries that could have happened with any oven or cooking surface. For example, many people have been burned by the hot food, splattering grease, or steam from food cooked in a microwave oven.

Ovens and Pacemakers

At one time there was concern that leakage from microwave ovens could interfere with certain electronic cardiac pacemakers. Similar concerns were raised about pacemaker interference from electric shavers, auto ignition systems, and other electronic products. FDA does not specifically require microwave ovens to carry warnings for people with pacemakers. The problem has been largely resolved because pacemakers are now designed to be shielded against such electrical interference. However, patients with pacemakers may wish to consult their physicians if they have concerns.

Checking Ovens For Leakage

There is little cause for concern about excess microwaves leaking from ovens unless the door hinges, latch, or seals are damaged. In FDA's experience, most ovens tested show little or no detectable microwave leakage. If there is some problem and you believe your oven might be leaking excessive microwaves, contact the oven manufacturer, a microwave oven service organization, your state health department, or the nearest FDA office.

A word of caution about the microwave testing devices being sold to consumers: FDA has tested a number of these devices and found them generally inaccurate and unreliable. If used, they should be relied on only for a very approximate reading. The sophisticated testing devices used by public health authorities to measure oven leakage are far more accurate and are periodically tested and calibrated.

Tips on Safe Microwave Oven Operation

• Follow the manufacturer's instruction manual for recommended operating procedures and safety precautions for your oven model.
• Don't operate an oven if the door does not close firmly or is bent, warped, or otherwise damaged.
• Never operate an oven if you have reason to believe it will continue to operate with the door open.
• As an added safety precaution, don't stand directly against an oven (and don't allow children to do this) for long periods of time while it is operating.
• Users should not heat water or liquids in the microwave oven for excessive amounts of time.

Erupted Hot Water Phenomena in Microwave Ovens

The FDA received reports in the past of serious skin burns or scalding injuries around people's hands and faces as a result of hot water erupting out of a cup after it had been over-heated in a microwave oven. Over-heating of water in a cup can result in superheated water (water heated past its boiling temperature), which does not appear to be boiling.

This type of phenomena occurs if water is heated in a clean cup. If foreign materials such as instant coffee or sugar are added before heating, the risk is greatly reduced. If superheating has occurred, a slight disturbance or movement such as picking up the cup, or pouring in a spoon full of instant coffee, may result in a violent eruption with the boiling water exploding out of the cup.

What Can Consumers Do to Avoid Super-Heated Water?

Users should follow the precautions and recommendations found in the microwave oven instruction manuals, specifically the heating time. Users should not use excessive amounts of time when heating water or liquids in the microwave oven. Determine the best time setting to heat the water to the desired temperature and use that time setting regularly.

Other Tips for Microwave Oven Use

• Some ovens should not be operated when empty. Refer to the instruction manual for your oven.
• Clean the oven cavity, the outer edge of the cavity, and the door with water and a mild detergent. A special microwave oven cleaner is not necessary. Do not use scouring pads, steel wool, or other abrasives.

For more consumer information on microwave oven radiation, you can contact the Consumer Staff of the Division of Small Manufacturers, International and Consumer Assistance (DSMICA) by electronic mail at DSMICA@cdrh.fda.gov , or use this link: www.fda.gov/cdrh/comment4.html .

2. Answer B is the best practice; give yourself two points if you picked it. Hot foods should be refrigerated as soon as possible within two hours after cooking. But don't keep the food if it's been standing out for more than two hours. Don't taste test it, either. Even a small amount of contaminated food can cause illness. Date leftovers so they can be used within a safe time. Generally, they remain safe when refrigerated for three to five days. If in doubt, throw it out.

3. If answer A best describes your household's practice, give yourself two points. Give yourself one point if you chose B. The kitchen sink drain, disposal and connecting pipe are often overlooked, but they should be sanitized periodically by pouring down the sink a solution of 1 teaspoon (5 milliliters) of chlorine bleach in 1 quart (about 1 liter) of water or a solution of commercial kitchen cleaning agent made according to product directions. Food particles get trapped in the drain and disposal and, along with the moistness, create an ideal environment for bacterial growth.

4. If answer C best describes your household's practice, give yourself two points. Washing with soap and hot water and then sanitizing with a mild bleach solution is the safest practice. If you picked A, you're violating an important food safety rule: Never allow raw meat, poultry and fish to come in contact with other foods. Answer B isn't good, either. Improper washing, such as with a damp cloth, will not remove bacteria.

5. Give yourself two points if you picked answer C. The safest way to eat hamburgers is to cook them until they are no longer red in the middle and the juices run clear. That doesn't happen with rare-cooked meats, and it may not happen with medium-cooked ones. Cooking food, including ground meat patties, to an internal temperature of at least 160 F (71 C) usually protects against food-borne illness. Well-done meats reach that temperature. To be on the safe side, check cooked meat, fish and poultry with a meat thermometer to ensure that they have reached a safe internal temperature. For microwaved food, follow directions, including the standing time, either in or out of the microwave, after cooking. Microwave cooking creates pockets of heat in the food, but allowing the food to stand before eating allows the heat to spread to the rest of the food.

6. If you answered A, you may be putting yourself at risk for infection with Salmonella enteritidis, a bacterium that can be in shell eggs. Cooking the egg or egg-containing food product to at least 140 F (60 C) kills the bacteria. So answer C--eating the baked product--will earn you two points. You'll get two points for answer B, also. Foods containing raw eggs, such as homemade ice cream, cake batter, mayonnaise, and eggnog, carry a Salmonella risk, but their commercial counterparts don't. Commercial products are made with pasteurized eggs; that is, eggs that have been heated sufficiently to kill bacteria, and also may contain an acidifying agent that kills the bacteria. Commercial preparations of cookie dough are not a food hazard. If you want to sample homemade dough or batter or eat other foods with raw-egg-containing products, consider substituting pasteurized eggs for raw eggs. Pasteurized eggs are usually sold in the grocer's refrigerated dairy case.

7. Answers C or D will earn you two points each; answer B, one point. Bleach and commercial kitchen cleaning agents are the best sanitizers--provided they're diluted according to product directions. They're the most effective at getting rid of bacteria. Hot water and soap does a good job, too, but may not kill all strains of bacteria. Water may get rid of visible dirt, but not bacteria. Also, be sure to keep dishcloths and sponges clean because, when wet, these materials harbor bacteria and may promote their growth.

8. Answers A and C are worth two points each. There are potential problems with B and D. When you let dishes sit in water for a long time, it creates a "soup." The food left on the dish contributes nutrients for bacteria, so the bacteria will multiply." When washing dishes by hand, he said, it's best to wash them all within two hours. Also, it's best to air-dry them so you don't handle them while they're wet.

9. The only correct practice is answer C. Give yourself two points if you picked it. Wash hands with warm water and soap for at least 20 seconds before and after handling food, especially raw meat, poultry and fish. If you have an infection or cut on your hands, wear rubber or plastic gloves. Wash gloved hands just as often as bare hands because the gloves can pick up bacteria. (However, when washing gloved hands, you don't need to take off your gloves and wash your bare hands, too.)

10. Give yourself two points if you picked B or C. Food safety experts recommend thawing foods in the refrigerator or the microwave oven or putting the package in a water-tight plastic bag submerged in cold water and changing the water every 30 minutes. Changing the water ensures that the food is kept cold, an important factor for slowing bacterial growth that may occur on the outer thawed portions while the inner areas are still thawing. When microwaving, follow package directions. Leave about 2 inches (about 5 centimeters) between the food and the inside surface of the microwave to allow heat to circulate. Smaller items will defrost more evenly than larger pieces of food. Foods defrosted in the microwave oven should be cooked immediately after thawing. Do not thaw meat, poultry and fish products on the counter or in the sink without cold water; bacteria can multiply rapidly at room temperature.