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Antimicrobials Alter Stream Communities and Lead to Resistance, Study Finds

(Beyond Pesticides, August 12, 2013) A recent study on triclosan, an antibacterial pesticide found in soaps, deodorants, toothpastes, cosmetics, fabrics, plastics, and toys, finds that exposure changes the composition of bacterial communities in streams and also increases bacterial resistance. The study contributes to continually mounting evidence demonstrating that triclosan is toxic to human health and the environment, even as the U.S. Environmental Protection Agency (EPA) gets ready to review the registration of the chemical.

In May, EPA initiated the registration review of triclosan, an antibacterial pesticide that has been heavily scrutinized by concerned groups, including Beyond Pesticides, as well as members of Congress. Under pressure after its 2008 review, EPA announced that it would again review triclosan in 2013, five years earlier than scheduled. Over the last few years, as a direct result of pressure from consumer groups and the media regarding the need for triclosan in consumer products and the mounting scientific evidence documenting adverse health effects, including impacts to the thyroid hormone, major manufacturers have begun to quietly reformulate their products without triclosan.

This study, published in the journal Environmental Science and Technology, took several field and artificial stream surveys, to identify the effects of triclosan on bacterial communities located on the stream beds. Antibacterial chemicals  enter streams, rivers, and lakes largely through household waste water. While municipal wastewater treatment plants remove the majority of triclosan from wastewater, low levels of the chemical still enter aquatic ecosystems. Overflowing sewage during rainy periods and sewage from old, leaking sewer pipes are other sources of triclosan that can contaminate waterways.

With these considerations in mind, researchers sought to determine how exposure to triclosan affected bacterial communities in the Chicago area. Researchers found that exposure to triclosan caused severe declines in the diversity of bacteria along the stream floor and changes to the overall community. Additionally, researchers found triclosan changed abundance of cyanobacterial sequence by almost six times, resulting in a “dramatic die off of algae.”

“It seems that algae are a lot more sensitive to triclosan than we previously thought,” said co-author John J. Kelly, PhD., at the Department of Biology at Loyola University Chicago. The findings raise concern because, as Dr. Kelly says, “They are being used in a very high amount and little is known what its impacts are on the environment.”

These bottom dwelling bacteria are, in fact, integral to ecosystem functioning as they drive the initial degradation of organic material that is required for transforming nutrients available to plants and algae, known as “nutrient cycling.” Thus, changes to bottom-dwelling bacteria due to the contamination of antibacterials have much broader impacts to the aquatic food web.

The study provides important information on the impact of triclosan on benthic communities, particularly as a model for water systems contaminated with triclosan. Researchers in the study used a concentration that represented 15% of the highest sediment triclosan concentration ever reported in literature, which was in Baltimore. Surprisingly, “While we did use high doses and the bacteria responded pretty well: they didn’t all die,” said Dr. Kelly. “Instead they seem to be able develop high levels of resistance,” he said.

Previous research has shown that cultured bacteria develops triclosan resistance, however, this study represents the first of its kind to link triclosan exposure and bacterial resistance in the field, raising concerns about the broad adverse impacts of antibacterials over the long term. Researchers found that, “Over the course of the five week study, the [triclosan] resistance level climbed to a maximum of 14%, suggesting that resistance levels in the field might also continue to rise if [triclosan] concentrations increase.”

When introduced to the market in 1972, triclosan was confined to hospital and health care settings. However, it has since exploded across the consumer marketplace, despite increasing research that it causes harm to human health and the environment. As an endocrine disruptor, triclosan has been shown to affect male and female reproductive hormones and possibly fetal development, and is also shown to alter thyroid function. Triclosan is not only an endocrine disruptor found at increasing concentrations in human urine and breast milk, but also contaminates waterways and possibly even drinking water. The Centers for Disease Control and Prevention (CDC) also has found that triclosan is present in the urine of 75% of the U.S. population, with concentrations that have increased by 42% since 2004. Despite industry claims, triclosan research has raised questions about its efficacy against harmful bacteria, including those found in hospitals.

Beyond Pesticides in 2004 began voicing concern about the dangers of triclosan and in 2009 and 2010 submitted petitions to the U.S. Food and Drug Administration (FDA) and EPA, calling for the removal of triclosan from consumer products on the basis that those uses violate numerous federal statutes. Since then, many major companies are quietly removing triclosan from their products. Colgate-Palmolive, makers of SoftSoap, and GlaxoSmithKline, makers of Aquafresh and Sensodyne toothpastes,have reformulated these products to exclude triclosan, according to media reports. Others, including Johnson & Johnson, L’Oreal, The Body Shop, and Staples, have started phasing it out of products.

Notably, Rep. Ed Markey (D-MA) also submitted letters of concern on the issue of triclosan to both EPA and the Food and Drug Administration (FDA). In FDA’s response, the agency acknowledged that soaps containing triclosan offer no additional benefit over regular soap and water. FDA stated that, “Existing data raise valid concerns about the [health] effects of repetitive daily human exposure to these antiseptic ingredients” and announced plans to address the use of triclosan in cosmetics or other products. FDA also expressed concern about the development of antibiotic resistance from using antibacterial products and about triclosan’s potential long-term health effects. Additionally, Rep. Louise M. Slaughter (D-NY) and two colleagues asked FDA to ban triclosan in 2010 due to the hazards that the chemical poses, including antibiotic resistance and potential health problems leading to higher health care costs.

Join the ban triclosan campaign and sign the pledge to stop using triclosan today. Encourage your local schools, government agencies, and local businesses to use their buying power to go triclosan-free. Urge your municipality and workplace to adopt the model resolution that commits to not procuring or using products containing triclosan.

Source: Environmental Science and Technology

All unattributed positions and opinions in this piece are those of Beyond Pesticides.


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