Legionella E-news | 17
January 2002 |
Responding to a Legionnaires' Disease Outbreak in an Industrial Plant: A Case Study
by Matthew Freije and Scott Burgoon
Editor’s note: In his Master’s thesis, “Legionnaires' Disease: Lessons for Industry,” Scott Burgoon, Senior Industrial Hygienist with General Physics Corp., details incidents in five industrial plants--a meat packing plant, a power plant, and three plastic injection molding plants--in which exposure to Legionella was either suspected or confirmed. This article focuses on one of the injection molding plant outbreaks, highlighting management’s response to the situation, and OSHA’s response to management. The information is based on Maryland Occupational Safety and Health Administration (MOSH) Case Files. Many thanks to Scott for sharing his work.
contamination had not been suspected in a plastic injection molding
plant in Maryland (USA) until one of the employees died of what was
reported as Legionnaires’ disease. On 2 October 1998, the very same
day the death was reported to the Baltimore City Health Department, the
plant management initiated an investigation. They hired a consultant and
sought help from Johns Hopkins Hospital.
days later, on 7 October, the Maryland Occupational Safety and Health
Administration (MOSH), acting in an advisory capacity to the Maryland
Department of Health and Mental Hygiene (DHMH), initiated its own
investigation. Around this time six additional cases of pneumonia were
diagnosed in plant employees, five of which were eventually confirmed as
Legionnaires’ disease. The plant management shut down the facility and
treated the water systems.
estimated that exposures occurred during the first half of September.
The epidemiologic investigation revealed no common exposures to
employees outside the plant, so the plant was considered the likely
source of contamination. However,
by the time Legionella was suspected, the patients had already
begun aggressive antibiotic treatment, so diagnostic tests were
inconclusive. Although Legionella
was found in environmental samples, the strains could not be linked
to the affected employees.
plant manufactures plastic enclosures (e.g., caps, lids) by the
injection molding process, which utilizes water to cool molds and
finished product. Although water systems that cool molds are technically
closed systems, exposure to water spray can occur when changing molds or
temperature control equipment. In
addition to the potable water system, the plant has six non-potable
systems that were used for injection molding and air conditioning. The
plant has two sections, East and West; the Legionnaires’ cases
occurred only in the East section.
DHMH collected 74 environmental samples from both potable and non-potable water systems. Three separate laboratories that initially analyzed the samples reported negative results for all 74 samples. Subsequently, however, 6 of the 74 samples were sent to a fourth laboratory that did find Legionella (LpSg's 1, 5, and 6). In fact, 5 of the 6 retested samples were positive.
All the positive samples were collected from the cooling systems. The concentrations ranged from 30 to 3,510 cfu/ml, but DHMH considered the counts unreliable because of the processing delay. The sixth retested sample, collected from a water mist machine, tested negative. No samples from potable systems were retested (in hindsight this would appear to be a mistake).
discovered that two sodium hypochlorite drums used for two cooling
systems had been empty for six weeks, ever since the water treatment
company’s last service call on 3 August 1998.
A chemical feed pump had apparently malfunctioned, emptying the
drums more quickly than normal.
investigators could not confirm the source of contamination but
suspected one of two scenarios. The first scenario was that cooling
water that dumps into an open sump had become aerosolized and then
distributed by the ventilation system.
was found in water collected from the sump at the high (but possibly
inaccurate due to extended holding time) concentration of 3,510 cfu/ml.
possibility, deemed less likely by investigators, was that Legionella-contaminated
aerosols were blown from the rooftop cooling tower down the side of the
building to the employee smoking area.
Legionella (80 cfu/ml)
was found in the cooling tower, and all infected employees were smokers
who worked in the East building.
made the following recommendations, which the plant implemented
1997, the US Department of Labor, Occupational Safety &
Health Administration (OSHA) fined a Cincinnati injection molding
facility following an investigation of three Legionnaires’ cases (no
deaths) among its employees. OSHA cited Section 5(a)(1) of the 1970
Occupational Safety and Health Act, commonly referred to as the
“General Duty Clause,” which is a catch-all standard requiring
employers to maintain a workplace free from recognized hazards that
could cause death or serious physical harm.
OSHA stated that the Cincinnati plant employees were exposed to
excessive levels of legionellae during injection mold setting and
changing, quality laboratory parts testing, and equipment repair or
maintenance, and that these exposures could have caused
contrast, the Maryland plant was not fined for the 1998 outbreak even
though it was more severe than the Cincinnati outbreak in terms of cases
and deaths. The agencies’ decisions to fine or not to fine were
apparently based in large part on plant managements’ prevention
efforts and cooperation. Before the outbreaks, the Maryland plant had
attempted to properly treat its cooling water systems and monitor
bacteria counts, but the Cincinnati plant had not done so even though
cases of respiratory illness had been reported among its employees three
years prior. After the illnesses were reported, the Maryland plant
voluntarily initiated its own investigation and closed the plant, but
the Cincinnati plant did not. Throughout the investigation, the Maryland
plant cooperated fully with health officials, implementing all
recommendations immediately, but the Cincinnati plant did not.
are specific factors considered by MOSH in not fining the Maryland
The company had an industry accepted water treatment program in
There was no indication of previous employee illnesses from the
The company took immediate action to protect its employees by
notifying local health and medical officials as soon as a problem was
suspected, and by hiring a consultant to assist in the evaluation.
The company voluntarily closed the suspected section of the
The company cooperated fully with health, medical, and regulatory
6. The company implemented measures that exceeded those typically recommended when dealing with a suspected Legionnaires’ outbreak.
The company increased the frequency of its biocide treatment and
changed to another biocide.
sum, although the Maryland plant did not take all appropriate
Legionella-preventive measures in its water systems, it attempted to
properly treat its cooling systems, and, after a case of Legionnaires’
was identified, it immediately initiated an investigation, took steps to
protect employees, and cooperated fully with health authorities. In
doing so the plant avoided regulatory citations. What we don’t know is
how the plant fared against lawsuits that may have been filed on behalf
of the employees who contracted Legionnaires’, claiming the illnesses
could have been prevented if the plant had made a reasonably diligent
effort to control legionellae in its systems and had tested the water to
see if its control measures were working.