SEATTLE -- That soap scum that forms on the shower curtain? It's really a biofilm loaded with more than a billion bacteria per cubic inch.
The moving belt on an escalator? When you put your hand there, you're dipping into a puddle of bacteria left by all those who went before.
Then there's the sponge you use to rinse dishes at the sink. Yep, loaded with bacteria.
If this makes you want to go relax in a hot tub, think again. The air wafting from the hot water is probably loaded with microbes, some of them able to give you a hacking cough.
It's a microbial world, says Norman P. Pace, a researcher at the University of Colorado at Boulder. Virtually everything you touch is coated with the little critters. You couldn't escape them if you wanted to because your skin is covered with about 100 million bacteria, says Pace.
Yet science knows little about environmental microbes, how they live, reproduce and thrive in the natural world. Most of what is known comes from germs cultured and studied in the lab.
"We live in a microbial world and I find it appalling that this is ignored by science," Pace said at the national meeting of the American Association for the Advancement of Science over the weekend.
He discovered the colonies of soap scum bacteria when, out of curiosity, he took a sample from his own shower curtain and examined it under a microscope.
"I was amazed," he said. Later studies of shower curtains from other homes found the same thing.
"When you step into a shower, you are enmeshed in a bio-aerosol," he said.
Most of the soap scum bacteria is harmless to the healthy. But for people with compromised immune systems, such as patients with AIDS or on chemotherapy or with open wounds, some of the germs can be deadly.
Pace recommends that shower curtains be cleaned weekly.
When he rides an escalator, Pace said he puts down only his knuckles because of the broth of bacteria that may be present.
The kitchen sink sponge, he said, "is a spectacular source of bacteria."
In his own home, he regularly wrings out the sponge and lets it dry, breaking up the wet, warm bacteria paradise.
Pace explored the microbial world of hot tubs after he was asked to investigate why some on the staff at a therapeutic swimming pool were developing "lifeguard lung," a nagging cough that plagues pool workers.
He found that the air above a heated, indoor pool or above a hot tub is enriched with microbes by about 60 percent. Persistent exposure to the air caused the "lifeguard lung" in sensitive people. The same thing can happen around a hot tub.
"These findings are a bit scary. The bottom line is people should be aware of the risk of swimming in indoor pools or sitting in indoor hot tubs," Pace said.
One hot tub and pool solution, he said, is to increase ventilation so the cloud of microbes are swept away. "Lifeguard lung" generally clears when the exposure is stopped.
But, Pace said, "I wouldn't get into a public hot tub, or even a private one for that matter."
Despite the scary image of bacteria everywhere, Pace said it's not reasonable to go into a "Howard Hughes mode." The late billionaire isolated himself and sterilized most things out of fear of germs.
Among microbes there are good guys and bad guys. Many bacteria are beneficial, helping to keep the harmful ones in check. Antibiotics can kill both the useful germs and the bad ones. That gives an advantage to bacteria that are resistant to antibiotics, some of which can be harmful.
Instead, Pace practices prudence.
People should wash their hands frequently, clean off soap scum often, dry out the kitchen sponge and avoid excessive exposure to indoor pools and hot tubs, he said.