Monthly Round Up of Important Ideas and Standards in
Industrial Hygiene and Safety
IN THIS ISSUE: Legionnaires’ Disease
Legionnaires’ disease, a type of pneumonia, has been in the news due to a series of recent outbreaks in Brooklyn, New York. The lung disease is a concern in factories, office buildings, and other confined workplaces. However, with proper maintenance and design of water systems, the bacterium that causes the disease can be effectively controlled.
Legionnaires’ disease, caused by Legionella bacterium, got its name after a 1976 outbreak during an American Legion convention. Although this type of bacterium was around before 1976, more illness from Legionnaires’ disease is now being detected. Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires’ disease in the U.S. However, many infections are not diagnosed or reported, so this number may be higher. More illness is usually found in the summer and early fall, but it can happen any time of year. Most people with Legionnaires’ disease have pneumonia (lung infection) since the Legionella bacteria grow and thrive in the lungs. Legionella bacteria are found naturally in the environment, usually in warm water. People get Legionnaires’ disease when they breathe in a mist or vapor (small droplets of water in the air) that has been contaminated with Legionella bacteria. It is not transmitted from person to person.
Severity of the disease ranges from a mild cough and low fever to rapidly progressive pneumonia and coma. Early symptoms include malaise, muscle aches, and slight headache. Later symptoms include high fever (up to 105°F), a dry cough, and shortness of breath. Gastrointestinal symptoms including vomiting, diarrhea, nausea, and abdominal pain are common. The disease is treated antibiotics. It most frequently attacks individuals who have an underlying illness or weakened immune system. The most susceptible include persons who are elderly, smokers, and immunosuppressed. Individuals with chronic obstructive pulmonary disease (COPD), organ transplant patients, and persons taking corticosteroid therapy are also at elevated risk.
In the workplace, cooling towers, evaporative condensers, and fluid coolers that use evaporation to reject heat are the most likely source of a Legionnaires’ disease outbreak. Since these systems use a fan to move air through a recirculated water system, a considerable amount of water vapor is introduced into the surroundings despite the presence of drift eliminators designed to limit vapor release. In addition, this water may be in the ideal temperature range for Legionella growth, 20° – 50°C, 68° – 122°F.
- Visual inspection, periodic maintenance of the system, and twice yearly cleaning are the best ways to control growth of Legionella and related organisms in these systems.
- Properly monitoring and maintenance to prevent buildup of scale and sediment.
- Use of oxidizing chemicals to control the growth of Legionella.
Domestic hot-water systems with water heaters that operate below 60°C (140°F) and deliver water to taps below 50°C (122°F) may also be an issue.
- Store hot water at a minimum of 60°C (140°F), and deliver at a minimum of 50°C (122°F) to all outlets.
- Drain hot-water tank periodically to remove scale and sediment and cleaned with chlorine solution if possible. The tank must be thoroughly rinsed to remove excess chlorine before reuse.
- Eliminate areas in system where water may stagnate when possible, or install heat tracing to maintain 50°C (122°F) in the lines.
- Rubber or silicone gaskets provide nutrients for the bacteria, and removing them will help control growth of the organism.
- Flushing lines frequently to reduce growth.
- Domestic hot-water recirculation pumps should run continuously and should be excluded from energy conservation measures.
- Periodic chlorination of the system is another means of control. Since chlorine is quite corrosive and will shorten the service life of metal plumbing, control of the pH is extremely important to ensure that there is adequate residual chlorine in the system.
If a problem is suspected in any water system, both the air and water can be tested. If the bacterium is found and problems persist, redesign may be necessary. See CDC website for further information at http://www.cdc.gov/legionella/index.html
For more information on this topic and to discuss your company’s safety and industrial hygiene needs call OccuSafe at (214) 662-6005 or contact us at email@example.com
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