Just about every day we zap coffee, make a cup of tea, or heat up soup in the microwave. Likely you've been using ceramicware — we've all heard plenty at this point about the dangers of reheating in plastics — many of which claim to be "microwave safe." With reports of lead in everything from water to jewelry to toys, at the Good Housekeeping Research Institute (GHRI) we wondered if there could be lead or other toxic substances in the ceramic mugs, bowls, and plates we use for nuking, and that exploration led to an even bigger question: What does it mean to be truly microwave safe?
What we discovered is that there is no true universal definition. To some it might mean that heavy metals don't leach into foods while, to others, it might involve ceramicware not getting so hot as to burn you when you remove it from the microwave. So we examined ceramicware from major manufacturers to see just how safe it truly is to use in your home.
Read on to find out the , and .
At the outset, we were most concerned about toxic chemicals in ceramicware. To find out if substances like lead and mercury were present and could be leaching into food when the vessels were heated, the Kitchen Appliances & Technology Lab at GHRI purchased samples of eight brightly colored mugs from leading brands or retailers and sent them to an independent lab to be tested.
First, we tested according to a standard procedure to see if they contained any lead, cadmium, arsenic, and mercury. Lead was found in at least one sample of each mug, arsenic in all of them, and in a few, cadmium. None of the mugs were found to contain mercury.
Once we determined that, yes, there were heavy metals in the mugs, our next question was, "Do they leach into food?" We tested two additional samples according to the standard method used by dinnerware manufacturers. This procedure calls for allowing an acetic solution (water with acid added) stand in the ceramicware overnight and then testing it for toxins. Before dinnerware is sold in the US, it must be tested according to this method and found to not have more than the low levels of heavy metals allowed by the United States Department of Agriculture (USDA). Our results: None of the test mugs leached lead, cadmium, or arsenic.
But we weren't satisfied and here's why. When this standard test method is performed by manufacturers, they use new mugs and acetic solution that is at room temperature. We wondered if mugs that have been aged by repeated microwave heating and dishwasher cleaning, and, second of all, using boiling solution in the test procedure could give different results. After all, consumers typically boil liquid in microwave dinnerware, so it's important to know if heavy metals leach under these circumstances.
We "aged" samples of our mugs by putting them through a month's worth of microwaving and washing in the dishwasher. Then we retested our aged samples as well as two new samples, using them to bring acetic solution to a boil in the in the microwave. This time we found that one of our test mugs, Pfaltzgraff Artisan Red, did leach lead, although in amounts lower than those allowed by the FDA.
When it comes to "microwave-safe" mugs, it's not just toxic substances we were concerned about. Another discovery we made while testing ceramicware: All, our mugs were labeled as microwave safe and yet some of them got so hot in the microwave that if we weren't careful there was a risk we'd be burned. We dug around, speaking to microwave and ceramicware experts and found out there's no standardized definition for the term "microwave safe". But a standard test method for determining if ceramics get too hot to handle does exist. However, it's not mandatory for manufacturers to perform the test and determine that their products stay cool enough for safe handling before claiming they're microwave safe.
We once again aged mugs and tested them, as well as new mugs, according to the standard procedure to find out just how hot they get when they're used to bring water to a boil, as they might be if you were making a cup of tea or cocoa. Temps above 140°F, are generally considered too hot to handle and hot enough to cause burns, depending on how long they're in your hand. We found both aged and new samples of several mugs got hotter than allowed by the standard. However aged samples were more likely to get hot and to reach even higher temperatures than new samples.
Right here on GoodHousekeeping.com, we conducted a survey of 2,000 consumers to find out how often you use your microwave and what you think "microwave safe" means. We heard from over a thousand of you. Here's what you told us.
- 49% of you told us that "microwave safe" means that a product will not break, crack, shatter, or become damaged in some way when it's heated in the microwave oven. "I figure it means that the dish won't break into a million pieces!" "You can use it in the microwave without fear of it blowing up."
- 36% of you think that "microwave safe" means that a product is safe for use in the microwave but can't say what that specifically means.
- 32% of you think "microwave safe" means a product won't leach harmful or toxic chemicals or substances into food.
- Only 15% of you consider "microwave safe" to mean that a product won't get hot when heated in the microwave. "That you won't burn your hand getting it out!!" "It lets the microwaves go to the food and doesn't heat."
All this confusion despite the fact that 63.6% of you said you use your microwave ovens several times a day and 98% of you look for microwave safe ceramicware when you're out shopping. We advocate that the Consumer Product Safety Commission (CPSC) create a standard definition of "microwave safe" and make it mandatory that products labeled "microwave safe" meet a version of ASTM Standard C1607, revised to call for testing pieces that have been aged by subjecting them to repeated microwave and dishwashing cycles before testing.
What You Can Do:
- Don't take it for granted that dinnerware labeled microwave safe won't get too hot when heated in the microwave. When you're out shopping for microwave-safe dinnerware, purchase just one piece and test it out by using it in the microwave before springing for an entire set.
- Be careful when you're removing an item with hot liquid or food from the microwave oven. Keep pot holders nearby where they're easy to find and use.
- Don't allow children to use the microwave unsupervised. If kids aren't old enough to use the stove or the toaster, they shouldn't be using the microwave.