The chemical industry has helped fortify our homes against microbial invasion. But is our fear of germs making us even sicker?

The "vomiting virus" now sweeping across Britain may be headed our way. At the same time, San Francisco is being hit with a new strain of the nasty bacterium known as MRSA (methicillin resistant Staphylococcus aureus) -- this one responsible for "flesh-eating pneumonia."

Meanwhile, four patients were recently isolated in the University of Maryland Medical Center, infected with a multidrug resistant bacterium called Acinetobacter baumannii, which has attacked a number of Afghanistan war veterans. As one doctor said of the that bug, "When these people get infected ... you sort of say this is the last straw."

Those new menaces, and more, are joining the usual biological villains that lurk everywhere in midwinter.

Even more than in past years, we're turning to the chemical industry for help in fortifying the American home against microbial invasion. Few go as far as Jacques Niemand, a reclusive Briton who was killed last May by fumes rising from vast quantities of disinfectant that he kept in open buckets around his house to ward off infection. But lower-intensity chemical warfare on our invisible housemates is in full swing.

Many hospital patients and people with compromised immune systems depend for their very survival on large quantities of not-entirely-benign antimicrobial products. However, there appears to be widespread scientific consensus that for most routine home uses, thorough washing with soap provides sufficient protection.

In domestic use, there's the possibility that some antimicrobial products could induce disease-causing bacteria to evolve antibiotic resistance. Then, as they flow down the drain into sewers and beyond, significant tonnages can accumulate in the tissues of wildlife and people with potentially toxic consequences. And it could be that dramatic increases in asthma and allergy rates are related to immune-system distortion that comes from living in microbe-poor bubbles.

Homeland sterility enforcement

Brian Sansoni, vice president for communication and membership with the Soap and Detergent Association, cites a body of research showing that antibacterial soaps reduce the numbers of harmful bacteria on the skin or other surfaces and are especially useful when you're caring for elderly or immunosuppressed people, dealing with an infectious illness in the house, or preparing food.

"The bottom line," says Sansoni, "is that consumers can continue to safely use antibacterial soaps and hygiene products with confidence - as they already do in homes, schools, offices, hospitals and health care centers, day care centers and nursing homes - every single day."

Among family members who do most of the housecleaning, 71 percent say they prefer to use antibacterial products when available. And germ-killing products are more widely available than ever. As of 2001, 76 percent of liquid hand soaps and 29 percent of bar soaps contained antibacterial chemicals. Mintel's Global New Products Database has seen introductions of new antimicrobial products grow from fewer than 200 in 2003 to more than 1600 last year.

Once you've strategically placed chemical hand cleaners in the kitchen, bedroom, car, and office, you can stock up on antimicrobial toothpaste, cosmetics, kitchen counter wipes, cutting boards, knives, chopsticks, dishrags, gloves, underwear, bath towels, computer keyboards, toys, dog ear wipes, laundry detergent, and paint. The Amana Corporation is promoting a washing machine whose drum is impregnated with an antimicrobial chemical, and several manufacturers offer vacuum cleaners that are chemically resistant to bacteria or bathe your carpet in germ-killing ultraviolet light. And, if you're intent on leaving no bug unturned, you can subscribe to an antibacterial garbage can-cleaning service.

The Environmental Protection Agency (EPA) has registered 8,000 disinfectant products to date. That's required, because the law says they're pesticides. Whether it's referred to as "disinfectant" or "antibacterial" or "antimicrobial" or even the somewhat disturbing term "biocidal," each compound kills a range or organisms -- bacteria, fungi, yeast, or even the viruses that cause colds and flu -- but none fully eradicates them.

The most popular of these weapons are still products of pre-1970 "better living through chemistry." There are standbys like ammonia, pine oil, and chlorine bleach, as well as types of germ-killing super-detergents called quaternary ammonium compounds; most prominent in that latter class is benzalkonium chloride, the active ingredient in many disinfectant wipes and sprays.

The compound drawing the most recent attention has been triclosan, along with its cousin triclocarban. Those chemicals, 1960s-era spinoffs from weed-killer research, are considered safe enough to come into very close contact with the human body: in food preparation, bathing, and even for cleaning sex toys.

Chemical weapons can backfire

Triclosan regularly makes the news because of suspicions that it might select for populations of bacteria resistant to pharmaceutical antibiotics. That's because triclosan and some antibiotic drugs attack bacteria through similar mechanisms, and resistant bacteria use similar means to rid themselves of both types of (what are to them) toxins.

A 2003 study funded by Proctor & Gamble Company allayed concerns about washing dishes with antibacterial detergent, finding that genetic resistance did not increase in bacterial cultures exposed to triclosan for several months. At the time the paper was published, one of its authors, a scientist at a British university, told the press that Proctor & Gamble "does not produce a liquid dishwashing detergent that contains triclosan" -- implying that the company therefore had no conflict of interest. P&G did, however, make a range of other products containing the chemical, and soon after, began marketing triclosan-fortified dishwashing liquids as well.

An independent 2004 evaluation of bacterial cultures collected from hands in more than 200 upper-Manhattan households did not find a relationship between resistance to triclosan and resistance to antibiotics (pdf). The lead author on that study was Dr. Allison Aiello, now assistant professor of epidemiology at the University of Michigan. She believes too little research that has been done to date, and much of what has been done was funded by industry.

Says Aiello, "There is still a big gap in surveillance and research on the ground." Now that lab research has made clearer the potential mechanisms by which triclosan might help breed bacteria resistant to clinical antibiotics, she says, "We need rigorous, independent, long-term studies on household use to fill the gaps in our knowledge."

Brian Sansoni also welcomes more research, but he says it shouldn't matter who pays for it: "The fact is, it's industry's responsibility to undertake and/or fund research on the ingredients they produce or are used in their products. It's a part of good product stewardship."

Back in the laboratory, there are hints of trouble. Research has shown, for example, that lab-selected strains of the disease-causing bacteria Salmonella enterica and Escherichia coli O157 resistant to triclosan or benzalkonium chloride also showed increased resistance to antibiotic drugs. Such "cross resistance" has been associated with use of other disinfectants as well, including pine oil, which is the natural active ingredient of Pine Sol.

Aiello points to another potential worry: "The triclosan concentrations used in medical settings are quite high, and are effective. But my work shows that the concentration in household soaps and detergents [only a tenth to a half of one percent, which is diluted further in cleaning] is too low to be very effective in reducing illness." On the other hand, she says, that lighter exposure may be just right for leaving behind genetically adapted bacteria.

To Sansoni, the threat of bacterial resistance is "suburban mythology." Pointing to the research of Aiello and others, he says, "The studies and the research to-date have shown there is no real world evidence linking the use of antibacterial products to antibiotic resistance."

"It is a shame," he adds, "that a few loud voices are trying to equate use of antibacterial products in the same breath with the known contributor to the antibiotic resistance problem: the over-prescription of antibiotic drugs by the medical community. It's like trying to compare an anthill to Mount Everest."

The associate director of the Clinical Microbiology Laboratory at the University of Nebraska Medical Center in Omaha, Dr. Paul Fey, says he would be concerned if, as some studies indicate, the molecular "pumps" that resistant bacteria use to rid themselves of triclosan could also flush out medically important antibiotics. "That's another good reason why triclosan and other antibiotics should not be used in soaps, plastics, etc. And it's unnecessary. Plain soap itself is one of the best antimicrobials there is."

Sansoni cites an issue brief his group provided a US Food and Drug Administration (FDA) advisory committee in 2005, describing the benefits of antimicrobial bars, liquids, gels and wipes. In the end, that committee issued a nonbinding statement saying that in routine use, antibacterial soaps are no better at fending off illness than is regular soap, and that they might contribute to antibiotic resistance in bacteria. FDA took no action in response to the panel's recommendation.

Beyond the kitchen sink

Proctor & Gamble Company scientists have published studies showing that sewage treatment can break down triclosan. But, says Dr. Rebecca Sutton, staff scientist at the Oakland, Calif. office of the Environmental Working Group (EWG), "Our current water-treatment processes are not designed to deal with it, and they aren't dealing with it." She points to numerous studies finding triclosan and triclocarban througout the environment, including the waters of San Francisco Bay.

The US Geological Survey reported in 2002 on a wide range of potential pollutants found in stream across the country. Triclosan was identified in 58 percent of the samples. Out of 95 chemicals surveyed, triclosan was one of the most commonly detected, outstripped by only three others: caffeine, cholesterol, and a metabolite of nicotine.

As far back as 1998, the people of Sweden were spitting out two tons of triclosan per year in their antibacterial toothpastes alone. In 2002, the chemical was detected in the country's municipal wastewaters, fish, and human breast milk.

Triclocarban, of which 1.7 million pounds are produced in the US each year -- check that rusty orange label on your bar soap -- was found at high levels downstream from three sewage-treatment plants out of nine surveyed across nine states. But it was in the treated solids -- sludge -- where the chemical built up to more than a million times the concentration flowing into the plants.

Triclosan behaves similarly. Speaking to Scientific American, Rolf Halden of the Johns Hopkins Bloomberg School of Public Health explained that their buildup in bacteria-laden sewage solids is of particular concern because sludge is used to fertilize food crops. That, he said, "could be a recipe for breeding antimicrobial resistance."

And along with resistant bacteria, there are the prospects of dead algae, ailing fish and amphibians, and even sick humans. In a 2003 Japanese study, triclosan was acutely toxic to very young fish and caused liver damage in older males. And triclocarban can amplify the action of testosterone in humans and rats.

In other recent experiments, triclosan disrupted the functioning of frogs' thyroid glands. That is especially worrisome, says Sutton, because "the effects occurred even at concentrations less that are found in many of the country's streams, and the human and frog thyroid systems are very similar."

The Fear Factor

To declare war on household bacteria is to lose -- inevitably. You've probably seen the slogan many times on Lysol products (manufactured by Reckitt Benckiser PLC): "Kills 99.9% of germs in 30 seconds." And who's to doubt it? But under good conditions, the much-feared bacterium Staphylococcus aureus, for example, doubles its numbers every 30 minutes through cell division. So once the Lysol has worn off and the surviving bacteria go back to multiplying, the population could grow to its pre-Lysol size in as little as 5 hours.

Rather than stockpile buckets of disinfectant and spray every surface in the house every few hours, most independent researchers recommend that we settle for a stalemate in the war on microbes. But the home-products industry has other ideas.

Along with nursing and family groups, Clorox cosponsors a "Say Boo to the Flu" campaign, which, along with videos on handwashing and vaccination, features microbiologist Dr. Kelly Reynolds of the University of Arizona advising parents to be sure the cleaning products they buy are labeled "disinfecting" or that they contain chlorine bleach or quaternary ammonium compounds -- both of which are made by Clorox.

(A well-publicized 2002 study conducted by Dr. Reynolds's Arizona colleagues -- and funded by Clorox -- found that the average office desk is populated with 400 times as many bacteria as the average toilet seat. That sounds terrifying until you remember that neither desks nor toilet seats are significant causes of any kind of illness.)

WebMD's Flu Prevention page, sponsored by Lysol, features straightforward articles like one on the universally recommended practice of handwashing with plain soap and water. Alongside that are "Flu tips for parents," in which a Dr. Jim Sears recommends that "one of the most important ways to protect your family and stop viruses dead in their tracks is to disinfect commonly touched surfaces with a disinfectant spray or wipe, such as those made by Lysol®."

The Dial Corporation, which kicked off combat against skin-borne microbes with a deodorant in the 1940s, boosted sales of its antibacterial soaps in 2003 with a series of less-than-subtle TV ads. Featuring a range of scenarios -- a kid urinating in a swimming pool, a man using someone else's sweat-drenched towel in a gym, a nudist group riding a bus -- the commercials fed buyers' germ-phobia.

One of the company's vice presidents told USA Today, "We had been talking to focus groups, and consumers were coming back and saying, 'I'm clean enough.' We were stuck with this dilemma. But we turned it around and came up with [the ads'] premise: 'You're not as clean as you think you are.'"

Antibacterial compounds in bar soap or shoe insoles are there to make you smell better, not to keep you healthy. Used in mop handles, computer mouses, or telephones, they are intended to protect the object, not you, against degradation by run-of-the-mill bacteria and fungi. And bathing with antibacterial soap offers no protection when you swallow pee-laced pool-water.

But paranoia sells.

The Reactionary Principle

A commentary last year in the journal Occupational and Environmental Medicine urged adoption of the well-known "Precautionary Principle" -- that when a substance or technology is suspected of being harmful, "precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically." Instead, said the article, current research operates under the "Reactionary Principle." The author explained:
Under this system, anyone is free to introduce a new hazard into the environment, and governments must wait until an overwhelming body of evidence is accumulated before intervening. Each new regulatory action is challenged with the objective of slowing down or stopping public oversight ... We can see reactionary principle inaction in the unconscionable delays in regulating a long list of hazards whose risks were clear long before effective actions were taken to control them: asbestos, benzene, dioxins and PCBs. While these are "old" hazards, a reactionary approach is evident as well in many current controversies in our field, including the potential health risks from hexavalent chromium, artificial butter flavouring, and the antimicrobial agent triclosan.
Even if, displaying full trust in the safety of antimicrobials, you could manage to eliminate those 99.9 perecent of bacteria and viruses from your doorknobs, your computer keyboard, and the change in your pocket, you would still be carrying in and on yourself a community of microorganisms outnumbering -- ten times over -- the cells of your own body. Almost all of those creatures are either neutral or beneficial to you.

But the modern arsenal of purifying products, including not only disinfectants but also regular detergents, medications, vegetable washes, ozone blowers, ultraviolet gizmos, filtered and bottled drinking water, air conditioning, and year-round-sealed windows may be reducing contact between people -- especially children -- and organisms with which we've evolved and which our bodies need for healthy development. Not being "smart weapons", antimicrobial products can wreak collateral damage on harmless and friendly microbes.

The now 30-year-old "hygiene hypothesis" says that skyrocketing rates of allergy and asthma in Western societies may result from human immune systems being driven haywire by excessively sterile home environments. It's a hard thing to demonstrate, the biological mechanisms are highly complex, and there are still plenty of doubters, but patterns continue to fit fairly well. (For an excellent discussion of the hypothesis, see Garry Hamilton's 2005 article in the British magazine New Scientist. Unfortunately, it's not free online).

"We have to find a healthy balance in hygiene," says Allison Aiello. "For example, right now on your hands there are millions of beneficial Staphylococcus bacteria that help maintain the health of your skin." In fact, in her work she has seen disease-conscious people scrub their hands too enthusiastically, creating dry-skin cracks that other, more dangerous bacterial species can infect.

To Paul Fey, putting antimicrobial chemicals into cleaners and toys is "just crazy -- The only reason it's there is to keep parents from worrying." But, he thinks, maybe it's the products themselves they should be worrying about: "This constant search for a totally sterile environment may be hurting our health, and especially children's health."

Stan Cox is a plant breeder and writer in Salina, Kansas. His book, Sick Planet: Corporate Food and Medicine, will be published by Pluto Press in April.