Dish soap, detergent, shampoo, toothpaste, deodorants, facial tissues and antiseptics—they all kill germs. Rolf Halden, professor at Biodesign Institute of Arizona State University in USA, explains to Salonie Chawla how the pervasive use of sanitisers is polluting the environment, affecting health and giving rise to resistant bacteria
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How do sanitisers harm the environment?
Antimicrobial household and personal care products mostly depend on two chemicals—triclosan and triclocarban. As we use the products, the chemicals are washed down the drain. Even after treatment, 50 to 70 per cent of the compounds remain in municipal biosolids.
Less than 3 per cent gets discharged through treated effluent, which is sufficient to contaminate the environment because the compounds persist for long. Our recent study of US sewage sludge, published in the latest issue of the Journal of Hazardous Materials, showed triclocarban and triclosan account for over 60 per cent of the total mass of pharmaceutical and personal care products detected in the sludge.
How do these compounds affect the food web?
Microbes, algae and crustaceans are sensitive to the chemicals. As they get exposed to water polluted with raw or treated sewage, the chemicals accumulate in their tissues and contaminate the food web. The movement of the chemicals through the food web is yet to be studied in detail. However, traces of triclosan and its transformation product, methyl-triclosan, have been detected in worms, snails, fish and dolphins. Milk of European and US women also contains detectable quantities of triclosan, presumably due to use of antimicrobial personal care products.
How does overuse of antimicrobial products lead to loss of their effectiveness and result in resistant bacteria?
Triclosan, when used in low concentration, inhibits bacterial growth and disinfects or kills bacteria when used in high concentration. But studies have shown certain bacteria, such as E coli, Staphylococcus aureus, and Salmonella enterica, when exposed to sub-lethal concentration of triclosan, develop resistance towards important antibiotics.
What should one do?
A panel convened by the US Food and Drug Administration in 2005 concluded there is no proven benefit of the use of antimicrobial detergent. The compounds play an important role in clinical settings. But when used in households, for instance, washing hands with antimicrobial soap, we expose germs to the chemicals just for a few seconds. This does not provide the sought after benefit. In fact, antimicrobial soap offers no proven benefit over regular soap.
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