In addition to its use as a laundry additive, bleach’s antimicrobial activities have seen widespread use in cleaning up houses flooded by hurricanes or tropical storms.
This fall along the Eastern Seaboard in the aftermath of Hurricane Irene and Tropical Storm Lee, bleach was almost as valuable a commodity as bottled water and batteries. Because large storms and flooding disrupt municipal water purification systems, potable drinking water was sometimes unavailable even after all the electricity was restored. Bleach’s first role was to treat water to kill bacteria to make the water safe to drink. In cleaning up flooded basements, bleach also played an essential role in disinfecting floors, walls, and furniture touched by the flood waters, since anything that could not be disinfected had to be disposed of to avoid the growth of mold and bacteria.
Household chlorine bleach contains approximately 3-6 percent sodium hypochlorite, although that percentage drops over time leading to a weaker solution. In the laundry, bleach removes stains and makes white clothes brighter because it is an oxidizing agent that breaks bonds in the chromophore of a molecule – the chromophore is the part of any molecule responsible for indicating color. Thus, breaking these bonds makes clothes look whiter.
But its strength as an oxidizing agent is not the reason why bleach is an important chemical compound for disinfecting surfaces. As an anti-microbial agent, bleach kills microbes by unfolding or denaturing their proteins, which then clump together and no longer function, killing the microbe. The anti-microbial activity is actually not attributed to bleach’s oxidizing capacity. To understand this difference, compare bleach to hydrogen peroxide, another strong oxidizing agent. But as hydrogen peroxide doesn’t denature the proteins in microbes, it doesn’t disinfect a floor or kitchen counter as well as bleach does.
Another area where bleach has played an important role is with respect to the AIDS epidemic. Early on, one of the most important transmission routes for passing HIV from one person to another was among drug users who shared syringes and needles. Before needle exchange programs were established, bleach proved to be an effective and immediately available stopgap measure. Treating syringes and needles treated with bleach before they were passed to someone else greatly reduced the spread of HIV.
We don’t often think of that ubiquitous white bottle of Clorox beyond its use in laundry, but bleach is an important agent in maintaining our health.
For more information, go to http://www.biologynews.net/archives/2008/11/13/how_household_bleach_works_to_kill_bacteria.html or http://www.kingcounty.gov/healthservices/health/communicable/hiv/publications/infograms/bleach.aspx