Healthy Indoors Magazine - USA Edition

Legionella Continued from previous page Healthy Indoors 33 these damaged infrastructure assets increase a community's risk of Legionnaires disease. The biofilm and settled debris and scale that line the interior surfaces of water mains and other distribution pipes often contain Legionella. When these are disturbed by a pipe break or construction repair efforts, large quantities of Legionella bacteria can be released into a com- munity's drinking water supply. A more chronic and sinister potential impact of aging water lines is the rapid consumption of the protective chlo- rine disinfectants added to the water supply. As more organic debris and scale are deposited in the water distribution lines over time, they tend to react with the chlorine disinfectants. This has two consequences. First, the disinfectants are no longer available to prevent Legionella and other bacteria from colonizing and amplify- ing in water lines or the building water systems they supply. Second, these reactions between chlorine disinfectants and organic debris cre- ate a group of disinfection by-products called trihalomethanes (THMs). The US EPA has determined that these by-products are carcino- genic and have implemented rules to reduce their levels in drinking water supplies. The end result of this situation is that many water supply systems contain lower levels of chlorine than they once did. Often we find that levels of chlo- rine disinfectant are well below concentrations needed to control Legionella. During outbreak investigations it is common to find no detectable chlorine in the water supply of a building, leav- ing its water system wide open to colonization and amplification of Legionella. Aging increases your risk of LD. It seems the only thing worse than getting old is the alterna- tive. One of the major risk factors of contracting LD is progressing past 50 years old. While it is likely due to the multitude of other age-related physical ailments and maladies that the elderly are most susceptible to LD, we can use in- creased age itself as a reliable surrogate for risk in this case. Other factors that may increase the elderly's risk of exposure to LD are traveling and the increased likelihood of visiting a hotel, resort or cruise ship that happens to be harbor- ing Legionella. Higher rates of hospitalization and living in assisted care facilities, where outbreaks seem to occur with all too common frequency, may also factor into the higher incidence of LD among the elderly. When we firmly recognize that aging increases everyone's chance of contracting LD we need only to look at the "baby boomers" and realize that some associated increase in LD cases will probably impact them. The percent of the US population aged 65 and above will rise from 13% in 2010 to 16.1% in 2020. That reflects an increase of over 14.5 million Americans aged 65 and older. (4) As we see a disproportionate increase in persons over the age of 65 we should anticipate an increased number of LD cases. As this group continues to age and transitions to assisted living facilities and skilled nursing care, their susceptibility to respiratory infections increases. Ironically, those who maintain better health, mobility, and indepen- dence may also have an increased risk of expo- sure to Legionella. Instead of retiring and staying home, traveling to resorts and foreign countries may actually increase their likelihood of contract- ing travel-associated LD. Economic Drivers The green revolution and widespread efforts to reduce energy usage in the United States may be necessary to the sustained survival of our soci- ety, but it is also likely to have some unintended consequences. Efforts to reduce energy con- sumption often translate into lowering hot water temperatures in home and commercial plumbing systems. All other conditions being equal, lower- ing hot water temperatures from 140F to 120F is likely to increase the probability of Legionella colonization and amplification. Aging water heat- ers tend to have more sediment and scale, which creates a comfortable home for Legionella to grow. We have seen well-intended efforts to re- duce energy result in Legionella amplification. Efforts to reduce water usage by installing low- flow fixtures can result in stagnation of water, chlorine dissipation, and habitats that are more

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