Myth of a germ-free world: a closer look at antimicrobial products

November 16, 2010

Killing microorganisms has become a national obsession. A pair of antimicrobial compounds known as triclosan and triclocarban are lately the weapons of choice in our war of attrition against the microbial world. Both chemicals are found in an array of personal care products like antimicrobial soaps, and triclosan also is formulated into everyday items ranging from plastics and toys to articles of clothing.

But are these antimicrobial chemicals, as commonly used by people across the nation, really safe for human health and the environment? More pointedly, do they even work? According to associate professor Rolf Halden, of the Biodesign Institute at Arizona State University, the answer to these questions is an emphatic “No.” Download Full Image

A biologist and engineer, Halden is interested in chemicals produced in high volume for consumer use. “I follow the pathways of these substances and try to figure out what they do to the environment, what they do to us and how we can better manage them.”

The antimicrobial triclosan was patented in 1964, and began its use in clinical settings, where it was found to be a potent bacterial killer, useful before surgical procedures. Since then, industry’s drive to convince consumers of the need for antimicrobials has been aggressive and highly effective. Antimicrobials made their first appearance in commercial hand soaps in the 1980s and by 2001, 76 percent of liquid hand soaps contained the chemical.

Antimicrobials have become a billion dollar a year industry and these chemicals now pervade the environment and our bodies. Levels of triclosan in humans have increased by an average of 50 percent since 2004, according to newly updated data from the Centers for Disease Control and Prevention (CDC).Triclosan and triclocarban are present in 60 percent of all rivers and streams nationwide and analysis of lake sediments have shown a steady increase in triclosan since the 1960s. Antimicrobial chemicals appear in household dust where they may act as allergens, and alarmingly, 97 percent of all U.S. women show detectable levels of triclosan in their breast milk. Such unnecessary exposures carry risks which, at present, are ill-defined.

Halden and his team conducted a series of experiments aimed at tracking the environmental course of the active ingredients in personal care products. The disturbing results of their research indicate that triclosan and triclocarban first aggregate in wastewater sludge and are transferred to soils and natural water environments, where they were observed to persist for months or years.

The chemistry behind these compounds, which contain benzene ring structures that have been chlorinated, make them notoriously difficult to break down. Further, they are averse to water or hydrophobic, tending to stick to particles, which decreases their availability for breakdown processes and facilitates long-range transport in water and air. A recent study demonstrated the accumulation of triclosan in dolphins from contaminated coastal waters.

Earlier, the EPA had been provided with industry-funded studies of wastewater treatment plant effluent, seemingly indicating elimination of triclosan and triclocarban during the treatment process. But Halden speculated that these chemicals might in fact persist in the solid byproduct left over after treatment – the sewage sludge. The group’s suspicions were confirmed through an initial testing of a large wastewater treatment plant serving 1.3 million people, located in the Mid Atlantic region of the U.S.

In the first study of its kind, conducted by the team in 2006, it was determined that three quarters of the mass of triclocarban entering the wastewater treatment facility was simply moved from the water into the sludge. Similar tests confirmed the accumulation of triclosan in sludge with 50 percent efficiency.

“We make 13 billion pounds of dry sludge per year,” Halden notes. “That is equal to a railroad train filled with sludge stretching 750 miles from Phoenix to San Francisco.” One half of this sludge winds up on agricultural fields. The potential for these chemicals to migrate into food or leach into groundwater, has not received adequate consideration. It is likely that antimicrobials are capable of moving up the food chain, through a process known as biomagnification.

Both triclosan and triclocarban have been linked to endocrine disruption, with potential adverse impacts on sexual and neurological development. Further, the accumulation of these antimicrobials in the environment is exerting selective pressure on microorganisms exposed to them, thereby increasing the likelihood that a super-bug, resistant to the very antimicrobials developed to kill them, will emerge – with potentially dire consequences for human health.

On the positive side, Halden’s team identified specific microorganisms adapted to not only tolerate but also break down pervasive antimicrobials. The research is part of a wider effort aimed at alerting the public and regulatory agencies, including the EPA and FDA, of the dangers of these chemicals as well as developing effective remediation strategies.

As Halden explains, “these microbes have the dual advantage of being resistant to destruction by antimicrobials and being able to break down these chemicals. You could put them to use for example by adding them to high-strength industrial wastewater before it gets combined with the domestic sewage.”

In the group’s recent studies, appearing in Water Research and The Journal of Hazardous Materials, levels of triclosan and triclocarban were measured, to determine the degree to which these chemicals, along with other antimicrobials, become concentrated in sludge, and what happens to them thereafter. Triclosan and triclocarban account for two-thirds of the mass of all the antimicrobials in sludge, Halden found, based on a survey of 72 chemicals entering the wastewater treatment stream. Further, massive bioaccumulation of antimicrobial chemicals has been observed in various species. Earthworms exposed to triclosan, for example, showed accumulation of the chemical by a factor of 2700 percent.

Halden notes the impact these persistent chemicals can have on other life forms in the environment that are not their intended target. The thresholds for killing microbes are much higher than those for other, more fragile life forms, like algae, crustaceans and fish.

“This explains why residual concentrations of antimicrobials found in aquatic environments are still sufficiently harmful to wipe out the small and sensitive crustaceans, which are critical to the aquatic life cycle and food web,” Halden says.

For certain, chemicals like triclosan and triclocarban have their place in public health, particularly in clinical settings, among people who are trained in their proper use. However, in 2005, the FDA put together an expert panel to review all the available information on these chemicals. Halden was among the voting members of this committee, which concluded that regular use of antimicrobial products by the general public was no more effective than traditional methods of proper hygiene – simply washing thoroughly with regular soap and water.

Society, Halden insists, is participating in a grand experiment in which we are all guinea pigs. While effective regulation of these chemicals is badly needed, Halden says that the inertia of regulatory agencies is a formidable obstacle. In the meantime, the best hope is for consumers to avoid triclosan and triclocarban containing products.

“The culture of fear leads people to make impulsive decisions and buy a lot of antimicrobial products that are not really needed,” Halden says. “It's a profitable market to be in, but not one that is ultimately sustainable or a good idea.”

In addition to Halden’s appointment at the Biodesign Institute, at Arizona State University, he holds the title of associate professor in the School of Sustainable Engineering and the Built Environment, at the Ira. A. Fulton School of Engineering, ASU.

Richard Harth, richard.harth">">

Science Writer

Biodesign Institute at ASU

Lisa Robbins

Assistant Director, Media Relations and Strategic Communications


2 research projects up for Governor's Innovation Awards

November 16, 2010

Two ASU projects – one that develops wearable environmental sensors and another which has developed novel brain stimulation methods – are among the finalists for the 2010 Innovator of the Year Award for Academia, which is given out as part of the annual Arizona Governor’s Celebration of Innovation.

The first project goal is to develop sensitive, wearable and wireless chemical sensors to quickly and reliably detect toxic chemicals in the air that are critically important for health risk assessment, disease prevention and environmental monitoring. The project is led by Nongjian (N.J.) Tao, a professor of electrical engineering and director of the Biodesign Institute’s Center for Bioelectronics and Biosensors, as well as fellow researchers Erica Forzani, Francis Tsow and Rodrigo Iglesias.

The second project involves development of methods and devices for implementing transcranial pulsed ultrasound in the noninvasive stimulation of intact brain circuits. This project, led by William (Jamie) Tyler, an assistant professor of neurobiology and bioimaging in the School of Life Sciencs in ASU’s College of Liberal Arts and Sciences, has been focused on providing solutions for overcoming limitations held by other brain stimulation methods including electrical, photonic, magnetic, and pharmacological ones.

Tuning into innovation

Tao’s technology is built upon a novel microfabricated tuning fork array sensor platform (Biodesign Insitute) and wireless sensor technology (Motorola). The team has validated and demonstrated applications of the technology for indoor and outdoor air quality, occupational safety and health, and asthma prevention.

The sensor system has been successfully tested to map air quality in Phoenix (with the Arizona Department of Environmental Quality), studied traffic pollution-related health risks in Los Angeles (with the Keck School of Medicine at University of Southern California and California EPA), protected firefighters and arson investigators (with Phoenix Fire Department), and monitored the environmental effects of the BP oil spill in the Gulf of Mexico (with the University of New Orleans). Download Full Image

The sensor has been presented by National Institutes of Health Director, Francis Collins, to the U.S. Congress as an example of successful translational university technology; and by the NIH to the World Health Organization (Geneva, Switzerland), and UK Biobank. The Biodesign Institute team, working together with collaborators at the University of Arizona, Motorola, and the Arizona Division of Occupational Safety & Health, continue to refine and broaden the applications of their invention.

Brain tweaking

Novel treatments of brain disorders and injury represent some of the most significant and unmet needs in modern medicine. Tyler's development of ultrasonic neuromodulation offers hope for new brain stimulation therapies used in treating a broad range of brain disorders, without requiring surgery and with a spatial resolution several times better than other noninvasive approaches like transcranial magnetic stimulation. Tyler's group has shown that his method is safe, reliable, and precise. Their recent translational breakthroughs demonstrate how ultrasonic neuromodulation can be used to terminate epileptic seizure activity or to modulate learning and memory processes in animal models. The group is working on establishing human studies over the coming year.

Ultrasonic neuromodulation represents a paradigm-shifting platform around which many new neurotechnologies utilizing brain stimulation will emerge. These include use in current therapeutic brain stimulation procedures for replacing surgically invasive devices such as deep-brain stimulating electrodes or in near future brain-machine interfaces where brain stimulation will connect us to information clouds and social network highways. Tyler has filed three patent applications, built two prototype devices and co-founded a start-up medical device company (SynSonix, LLC; SynSonix is further developing brain-machine interfaces, some of which are designed for treating neurological disorders and others designated for entertainment purposes, such as video gaming. The innovative research and development activities of Tyler’s group offers a new area for biotechnology growth in Arizona, in addition to expanding the burgeoning neuroscience program and ongoing world-class biomedical research at Arizona State University and in the Valley. 

An innovative tradition

The 2010 honors represent the sixth year in a row that ASU has been a finalist for the Innovation Award for Academia. In 2009, Milton Sommerfeld and Qiang Hu, both ASU Polytechnic Campus professors of applied science and mathematics, were honored with the top award. Sommerfeld and Hu have developed a process that can convert algae into aviation or jet fuel. They also recently won the Arizona Bioindustry Association’s top research award for 2010 and Time magazine named the process one of the top innovations in 2008. The Biodesign Institute’s director of the Center for Evolutionary Functional Genomics, Sudhir Kumar, a professor in the School of Life Sciences, was also chosen as an award finalist in 2009.

In 2007, Roy Curtiss III, director of the Biodesign Institute’s Center for Infectious

Diseases and Vaccinology and professor in the School of Life Sciences, was selected as a finalist for his research team’s efforts to develop new vaccines against disease targets including pneumonia, hepatitis, tuberculosis, plague and human and avian flu.

In 2006, Biodesign researcher and life sciences professor Bert Jacobs and his team, also in the institute’s Center for Infectious Diseases and Vaccinology, won the award for a project to create a vaccine that can cure smallpox infections in their early stages and also provide a powerful tool for fighting a host of other viral pathogens, including a new project directed at HIV.

In 2005, the Biodesign Insitute’s Center for Infectious Diseases and Vaccinology won the Innovator of the Year award again for a project led by researchers Charles Arnzten and Tsafrir Mor, who are also professors in the School of Life Sciences, involving a multi-pronged research effort to prevent HIV infection.

In 2004, the Ira A. Fulton School of Engineering’s Center for Cognitive Ubiquitous Computing (CUbiC) was also bestowed with top honors for their iCARE research project, which has developed several projects to help people who are visually impaired recognize text, people and environments.

Winners will be announced during the awards ceremony Nov. 18 at the Phoenix Convention Center in downtown Phoenix. The event commemorates the top technological and business achievements of the year. The Governor’s Celebration of Innovation has become a premier community gathering in Arizona. The Governor's Innovation Awards, Arizona’s highest honor for technology innovation, is presented annually by the Arizona Technology Council and the Arizona Department of Commerce.

The Arizona Technology Council, in partnership with the Arizona Department of Commerce, chose the finalists for the Governor’s Celebration of Innovation in their respected categories. The award recipients were selected by an independent selection committee comprised of local business and academic leaders, based on their contribution to the business and technology community and their technological innovation. One company, within each category, will be announced as the winner on the night of the awards gala.

Britt Lewis

Communications Specialist, ASU Library