SECTION: Section F; Column 1; Health & Fitness; ESSAY; Pg. 6

LENGTH: 889 words

HEADLINE: Germs, Germs Everywhere. Are You Worried? Get Over It.

BYLINE: By MARY ROACH.

Mary Roach is the author of ''Stiff: The Curious Lives of Human Cadavers.''

BODY:


I saw a television advertisement recently for a new product called an air sanitizer. A woman stood in her kitchen, spraying the empty space in front of her as though using Mace against an imaginary assailant. She appeared very determined. Where others are satisfied with antibacterial-laced sponges, dish soaps, hand sanitizers and telephone wipes, here was a woman who sought to sterilize the air itself.

As a casual student of microbiology, I find it hard to escape the absurdity here. This woman is, like any human being, home to hundreds of trillions of bacteria. Bacteria make up a solid third, by weight, of the contents of her intestines.

If you were to sneak into her bathroom while she was showering -- and based on my general impression of this woman from the advertisement, I don't recommend this -- and secret away a teaspoon of the water at her feet, you would find some 820 billion bacteria. Bacteria are unavoidably, inevitably -- and, usually, utterly benignly -- a part of our world. (Statistics courtesy of a University of Arizona microbiologist, Dr. Charles P. Gerba, a man who gave his son the middle name Escherichia, the E in E. coli.)

The fantasy of a germ-free home is not only absurd, but it is also largely pointless. Unless you share your home with someone very old, very young (under 6 months) or very ill, the few hundred bacteria on a countertop, doorknob or spoon pose no threat. The bacteria that cause food poisoning, the only significant rational bacterial worry in the average home, need to multiply into the thousands or millions before they can overwhelm your immune system and cause symptoms.

The only way common food poisoning bacteria can manage this is to spend four or five hours reproducing at room temperature in something moist that you then eat. If you are worried about food poisoning, the best defense is the refrigerator. If you don't make a habit of eating perishable food that has been left out too long, don't worry about bacteria.

Viruses are slightly different. You need only pick up a few virus particles to infect yourself with a cold or flu, and virus particles can survive on surfaces for days. So disinfecting the surfaces in the home should, in theory, reduce the chances of picking up a bug. (Some antibacterial products also kill viruses.)

In practice, the issue is less clear. A study by Dr. Elaine Larson at the Columbia School of Nursing called into question the usefulness of antibacterial products for the home. In New York, 224 households, each with at least one preschooler, were randomly assigned to two groups. One group used antibacterial cleaning, laundry and hand-washing products. The other used ordinary products.

For 48 weeks, the groups were monitored for seven symptoms of colds, flu and food poisoning -- and found to be essentially the same. According to Dr. Gerba's research, an active adult touches an average of 300 surfaces every 30 minutes. You cannot win at this. You will become obsessive-compulsive. Just wash your hands with soap and water a few times a day, and leave it at that.

I suspect that a minority of the Americans who buy antigerm wipes and sanitizers are motivated by concerns over food poisoning or colds and the flu. Their behavior is a product not so much of prudence, but of phobia. Phobias are irrational fears, wrought of the union of dread and misunderstanding. People see a headline -- an outbreak of E. coli O157:H7 at a hamburger chain, say -- and they start to worry.

In the case of bacteria, they cannot see the source of their worry, and they do not know much about it, so they go overboard. They add a few more ''wiping events,'' as the cleanser market researchers say, to their daily routines. Where there is an irrational fear, there is a product-development team to fan it and feed it and exploit it.

According to the research firm Mintel International, 11 new home antibacterial products have appeared on the market this year, more than twice the number in 2003. It is the biggest marketing coup since bottled water.

The makers of antibacterial products are fond of the word ''germs.'' It is purposefully vague. Do they mean bacteria? Viruses? Both? Neither? Because the idea is simply to connote contamination. These products are as much about cooties as they are about viruses or bacteria.

Contamination is in many ways a psychological construct. It is the notion that our belongings or our loved ones can become unclean by the mere touch of a stranger. Nothing is actually transferred by the touch. The contamination is symbolic, magical, irrational. It makes sense that the extravagantly rich -- Howard Hughes or Donald Trump, for instance -- are our most notorious germphobics, people made uncomfortable by the thought of shaking a stranger's hand.

The higher you rise and the better sequestered you are from the ''unwashed masses,'' the smaller and dirtier the average Joe must begin to seem. Other human beings become our germs.

A plea, then, for a little calm, a little rationality. Try to look upon bacteria as did their discoverer, Antoni van Leeuwenhoek, ''For me, this was among all the marvels that I discovered in nature the most marvelous of all, and I must say, that for my part, no more pleasant sight has met my eye than this of so many thousand living creatures in one small drop of water.''