The report found that some of the areas people considered most likely to be contaminated, like microwave keypads, were not, while some they had never thought of, like refrigerator water dispensers and the rubber gasket on most blenders, were among the worst.
The findings suggest that many people who try to keep a tidy kitchen may be overlooking some of the more problematic areas, said Lisa Yakas, a microbiologist with NSF International, a nonprofit public health group that published the report. The goal of the study, Ms. Yakas said, was not to frighten the public, but to provide some insight on the best ways to reduce the spread of food-borne illness in the kitchen.
"What we really wanted to do was to just make them more aware of these places that they might not have even thought of," Ms. Yakas said.
Research suggests that the kitchen is a particularly important place to practice good hygiene. Nearly 10 million cases of food poisoning occur in the United States every year, and according to the Centers for Disease Control and Prevention, one in five outbreaks of food-borne illness are caused by food that people eat in their homes. Leafy vegetables and other plants are responsible for more than half of all cases, and about a third of all the fatal cases are caused by contaminated poultry.
Most healthy adults can fight off such infections. But the elderly, the very young and people who are pregnant or have compromised immune systems have a higher risk of complications.
"Any one of these populations could be represented in your home at some time, so it's important to protect them," Ms. Yakas said. "As a mom with two little kids at home, it's something that I worry about."
For the new study, the researchers took swabs of a variety of common kitchen items in the homes of 20 families living in the suburbs of Detroit and Ann Arbor, Mich. They also asked people in the homes to rate the items that they thought were most likely to be contaminated and most in need of regular cleaning.
The microwave keypad was the area they considered the dirtiest. But it was not. Instead, the researchers found that refrigerator ice and water dispensers, spatulas, blender gaskets – the rubber seal at the base of the blender that helps prevent leaks – and refrigerator meat and vegetable compartments had the highest germ counts.
Water and ice dispensers, which provide moist environments that can breed micro-organisms, were often found to contain yeast and mold. That can be a particular hazard for people with allergies.
Image: Refrigerator water dispenser, via Shutterstock