http://www.cdc.gov/mmwr/preview/mmwrhtml/00051658.htm
On September 25,
1986, an elderly Virginia couple had their home fumigated by
a local pest extermination company for the control of wood-
boring insects. Two hundred and fifty pounds of sulfuryl fluoride
(SF), a colorless, odorless fumigant gas commonly used for this
purpose, was applied in the approximately 80,000-cubic-foot
home that day. Before fumigation, the house was vacated, tightly
sealed, and externally covered with a tarpaulin to maintain
high levels of the gas inside. During fumigation, electric fans
were used to circulate the pesticide. Entry into the house was
prohibited until approved by the exterminators, and a security
guard watched the house from 2 p.m. on September 25 until 7
a.m. on September 26.
At 9 a.m. on September
26, the exterminators removed the tarpaulin and opened the doors
and windows to ventilate the house. Afterward, they ran electric
fans for 21/2 hours to facilitate air circulation. Reentry was
approved at 2 p.m., and reports suggest that the couple returned
home between that time and 5 p.m., approximately 5 to 8 hours
after the ventilation procedures began. The couple left their
home to attend a football game at 7 p.m. and returned for the
night at approximately 10 or 11 p.m.
On September 27,
within 24 hours of their return, the wife experienced weakness,
nausea, and repeated vomiting, and her husband complained of
dyspnea and restlessness. By the morning of September 28, the
husband had developed severe dyspnea and cough. At 7:15 a.m.,
he experienced a generalized seizure followed by cardiopulmonary
arrest. He was transported to a local emergency room, but resuscitative
measures were unsuccessful. Death was presumed to be caused
by an acute myocardial infarction, and inhalation of a toxic
agent was not suspected.
On October 1, the
widow, who was complaining of severe weakness, dyspnea, intermittent
chills, and anorexia, consulted her family physician. She had
not left her home in 3 days and was unable to walk into the
physician's office. She was admitted to the hospital, where
a chest x-ray revealed severe hypoxemia and diffuse pulmonary
infiltrates. On October 2, ventricular fibrillation occurred,
and she died at approximately 11 p.m. Because both deaths occurred
within a short period of time and the wife's illness was compatible
with toxic gas inhalation, these deaths were then thought to
be related to the recent home fumigation.
Autopsy reports provided
by the Office of the Chief Medical Examiner revealed that both
decedents died of acute pulmonary edema from exposure to a toxic
agent. Toxicologic analysis of blood and other tissues could
not be performed on the husband, but analysis of serum obtained
from the wife on October 1 (6 days after fumigation) revealed
a plasma fluoride level of 0.5 mg/l. No fluoride was detected
(at the 1.0 mg/kg concentration) in other tissues, including
those from the kidneys, liver, and lungs. No other toxic agents
were detected. Although the couple became ill at similar times,
the differences in time from exposure till death suggest that
their levels of exposure to SF may have differed. Unfortunately,
the details of their activities upon reoccupying their home
are not known.
On October 6, the
district manager of the extermination company notified the Virginia
Department of Agriculture and Consumer Services of the deaths.
Investigation verified that the cylinders of pesticide contained
SF and had been manufactured prior to June 28, 1986. The amount
used (250 pounds) was determined to be appropriate, based on
the cubic footage of the house, the air temperature, and the
relative humidity.
Although the exterminators
removed the tarpaulin, opened the windows and doors, and used
fans to aerate the home, they failed to measure the air concentration
of SF inside the home. This step is necessary to determine the
appropriate time for reoccupancy. Air samples taken during the
investigationby state officials on October 8 revealed no detectable
levels of SF, but levels of this gas would have been expected
to have dissipated by that time.
Neither of the two
workers who removed the tarpaulin and ventilated the house was
licensed, but their supervisor, who had extensive experience
with SF, was certified. The presence of a certified applicator
was not required by the product labels on the cylinders used
during this fumigation, and none was on hand at the time.
Reported by: JG Nuckolls,
MD, Galax; DC Smith, MD, Mount Rogers Health Dist, Marion; WE
Walls, Virginia Dept of Agriculture and Consumer Svcs; DW Oxley,
MD, Office of the Chief Medical Examiner, Roanoke; RL Hackler,
RK Tripathi, PhD, CW Armstrong, MD, GB Miller, MD, State Epidemiologist,
Virginia Dept of Health. Div of Environmental Hazards and Health
Effects, Center for Environmental Health and Injury Control;
Div of Field Svcs, Epidemiology Program Office, CDC.
Editorial Note
Editorial Note: SF
(chemical formula F202S) was first introduced in 1957 as an
insecticide and has been widely used to exterminate wood-boring
insects in buildings. It is applied by fumigation techniques
that require the building to be tightly sealed to allow a high
concentration to penetrate the wood. In 1986, approximately
200 to 500 homes in Virginia were fumigated with SF (Dow Chemical
Company, unpublished data). It is, however, more widely used
in other areas of the United States, such as Florida and California.
Background plasma
fluoride levels for humans have been reported to be approximately
0.01 mg/l. While peak concentrations of 0.06 to 0.4 mg/l have
been noted 30 minutes after ingestion of 10 mg of fluoride,
these levels have been noted to decrease to 0.2 mg/l within
2-9 hours (1). Thus, the concentration of 0.5 mg/l found in
serum obtained from the wife 6 days after fumigation suggests
that she had experienced acute exposure to an elevated concentration
of fluoride.
In short-term toxicologic
experiments, inhalation of 1,000 parts per million (ppm) of
SF for 3 hours or 15,000 ppm for 6 minutes was fatal to less
than 5% of experimental animals (2). However, these studies
also indicate that higher concentrations of SF cause respiratory
irritation and central nervous system depression, which may
be followed by excitation, convulsions, and respiratory arrest
(2,3). Animals exposed to low but unspecified doses of SF first
had parasympathetic stimulation with vomiting, diarrhea, lacrimation,
salivation, and abdominal colic (3). This stage was followed
by cardiovascular collapse and pulmonary edema. Similar observations
were noted in the two cases reported here.
The scientific literature
reports at least four deaths from exposure to SF since its wide
usage began 10 to 15 years ago (3-5). However, these two fatalities
in Virginia are the first in which the residents had not reentered
the structure under unusual or prohibited circumstances. In
this situation, there had not been appropriate air monitoring
during aeration and before clearance for reoccupancy was given.
These precautions are clearly required by the product label.
The product labels
on all cylinders manufactured since June 28, 1986, require that
two persons trained in the use of SF be present at all times
during fumigant introduction, testing, and aeration procedures.
After fumigation, the house is to be aerated until the level
of SF is less than or equal to5 ppm, as measured by a Miran*
gas analyzer. Measurements should be taken before reoccupancy
because the kinetics of SF dissipation depends on many variables
including the amount of fumigant applied, the quality of the
tarpaulin, the ambient temperature, and the wind speed. No one
should enter the house without a self-contained breathing apparatus
if the level of SF is greater than 5 ppm. The Occupational Safety
and Health Administration's current permissible exposure limit
and the American Conference of Governmental Industrial Hygienists'
(ACGIH) threshold limit value for SF are 5 ppm (6). The ACGIH
short-term exposure limit is 10 ppm. The level considered immediately
dangerous to life and health is 1,000 ppm, and persons exposed
at this level must use a supplied-air respirator with a full
facepiece, helmet, or hood.
The difference in
time of death for the couple was striking, but data are not
sufficient for interpretation. The only known host factor that
may account for this difference is age, since neither the husband
nor wife had a prior history of cardiopulmonary disease. The
husband was 8 years older than the wife, but it is doubtful
that this small age difference could account for the large time
difference between their deaths.
Persons who develop
illness that may be related to SF exposure require consultation
by a physician. Health-care workers should be aware that exposure
to highly toxic substances such as SF may occur without warning
or detection and may involve persons other than the individual
patient. The initial symptoms of illness from SF exposure can
be nonspecific and may resemble other common illnesses, even
when the dose has been in the lethal range. Early clinical recognition
of illness, timely investigation of the source, and appropriate
environmental intervention may help prevent fatalities from
this type of exposure.
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