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Epidemiologic Notes and Reports
Fatalities Attributed to Methane Asphyxiain
Manure Waste Pits -- Ohio, Michigan, 1989
In June and July 1989, a total of seven farm workers in two
separate
incidents died after they were asphyxiated by methane gas in manure
pits. Brief reports follow.
Ohio. On June 26, 1989, a 31-year-old male dairy farmer and his
33-year-old brother died after entering a 25-foot-square by
4-foot-deep
manure pit inside a building on their farm. A pump intake pipe in
the
pit had clogged, and the farmer descended into the pit to clear the
obstruction. While in the pit, he was overcome by lack of oxygen
and
collapsed. His brother apparently saw him collapse and entered the
pit
in an attempt to rescue him. The brother, too, was overcome and
collapsed inside the pit. Four hours later, another family member
discovered the two men, and the local fire department was called to
rescue them. The coroner's report attributed the cause of death in
both
cases to drowning, secondary to loss of consciousness from methane
asphyxia.
Michigan. On July 26, 1989, five farm workers in one family died
after
consecutively entering an outdoor manure pit on a farm. The pit
measured 20 feet by 24 feet by 10 feet deep. The victims were a
65-year-old male dairy farmer, his two sons (aged 37 and 28 years),
a
15-year-old grandson, and a 63-year-old nephew. The index victim,
the
37-year-old son, initially entered the pit by ladder to replace a
shear
pin on an agitator shaft. While attempting to climb out of the pit,
he
was overcome and fell to the bottom of the pit. The grandson then
entered the pit to attempt rescue. He, too, was overcome and
collapsed.
One by one, the nephew, the younger son, and the dairy farmer
entered
the pit in attempts to rescue the others, were overcome by lack of
oxygen, and collapsed. A carpet installer working at the farm then
entered the pit as a rescuer and was overcome; however, he was
rescued
by his assistant and subsequently recovered. Finally, the owner of
a
nearby business arrived with two additional workers and, using a
rope,
extricated the five victims from the pit. When paramedics arrived,
they
began cardiopulmonary resuscitation. The nephew was pronounced dead
at
the scene, and the other four victims were transported to the
emergency
room of a nearby hospital. The dairy farmer and his younger son
were
pronounced dead on arrival at the hospital; the 37-year-old son
died 1
hour after reaching the emergency room. The grandson was
transferred by
helicopter to a major trauma center but died within 6 hours of his
removal from the pit. For the four older victims, the medical
examiner
attributed the cause of death to methane asphyxia. Assignment of
the
official cause of death for the grandson awaits completion of the
autopsy report.
Reported by: Industrial Commission of Ohio, Columbus. Water
Pollution
Control Federation, Washington, DC. Div of Safety Research,
National
Institute for Occupational Safety and Health, CDC. Editorial Note
Editorial Note: Acute traumatic occupational deaths* in the United
States are monitored by the Division of Safety Research, National
Institute for Occupational Safety and Health (NIOSH), CDC, through
the
National Traumatic Occupational Fatalities (NTOF) file (1). For
1980
through 1985, the NTOF data file includes 16 work-related deaths
that
involved asphyxiation of workers in manure pits (or similar waste
tanks) on farms. These deaths resulted from nine separate incidents
in
nine different states (Figure 1). Five of these episodes resulted
in
multiple fatalities. Because NTOF only includes deaths of workers
greater than or equal to 16 years of age that are clearly
identified as
work-related, these 16 deaths represent the minimum number of
asphyxiation fatalities that occurred during this period among U.S.
farmers, farm family members, farm workers, and others working in
manure pits.
A farm manure waste pit is a confined space, defined by NIOSH (2)
as a
space that "by design has limited openings for entry and exit;
unfavorable natural ventilation which could contain or produce
dangerous air contaminants; and which is not intended for
continuous
worker occupancy." Manure pits are fermentation tanks where raw
animal
wastes undergo anaerobic bacterial decay. This bacterial action
generates methane, hydrogen sulfide, and other gases. Methane is a
colorless, odorless, and flammable gaseous hydrocarbon. It can
displace
oxygen in confined areas, resulting in an oxygen-deficient
atmosphere.
Hydrogen sulfide is a highly toxic, colorless gas that at
concentrations of greater than or equal to 300 ppm can cause
unconsciousness, respiratory failure, and sudden death (3). If
these
gases are not properly vented from a tank or other confined space,
an
oxygen-deficient or toxic atmosphere may be created. In industrial
settings, the Occupational Safety and Health Administration (OSHA)
limits permissible peak exposures to hydrogen sulfide to a ceiling
of
50 ppm (for less than or equal to 10 minutes); NIOSH recommends a
ceiling of 10 ppm (for less than or equal to 10 minutes) (4). There
is
no OSHA permissible exposure limit for methane. OSHA exposure
standards
are not enforceable on farms with less than or equal to 10
employees.
The apparent tendency for episodes such as those described here
to
result in multiple fatalities is of major concern. Fatal incidents
resulting from entry into manure pits often involve more than one
victim; the deaths of any additional workers occur during rescue
attempts conducted without use of appropriate equipment and safety
precautions. Investigations performed by NIOSH as part of the Fatal
Accident Circumstances and Epidemiology Project show that
approximately
43% of confined-space-related deaths involved co-workers or other
persons who were attempting to rescue the initial victim(s) (NIOSH,
unpublished data). The hazards of confined spaces and improper
rescue
methods have been addressed in previous NIOSH publications,
including a
guide to safe work practices in confined spaces (2,5,6).
In the two events reported here, hot humid weather may have
contributed to the generation of methane gas and increased the
amount
of gas in the manure pits. The possible connection between hot
weather
and increased gas accumulation in manure tanks is also suggested by
the
NTOF data (Figure 2). All 16 deaths identified in the NTOF file
occurred in April through September, with the highest number
occurring
in August. Farmers should be made aware of the particular hazards
of
entering manure pits during the summer months.
NIOSH is preparing information for farm operators on the hazards
of
manure pits and recommendations for safely evaluating, ventilating,
and
entering (when absolutely necessary) manure pits. Recommendations
will
also be provided for the safe conduct of rescue operations in
circumstances such as those described in this report. NIOSH will
disseminate this information during the fall.
References
National Institute for Occupational Safety and Health. National
Traumatic Occupational Fatalities: 1980-1985. Morgantown, West
Virginia: US Department of Health and Human Services, Public Health
Service, 1989.
National Institute for Occupational Safety and Health. Criteria
for
a recommended standard . . . working in confined spaces.
Cincinnati,
Ohio: US Department of Health, Education, and Welfare, Public
Health
Service, 1979; DHEW publication no. (NIOSH)80-106.
National Institute for Occupational Safety and Health. Pocket
guide
to chemical hazards. Cincinnati, Ohio: US Department of Health and
Human Services, Public Health Service, 1985; DHHS publication no.
(NIOSH)85-114.
CDC. NIOSH recommendations for occupational safety and health
standards, 1988. MMWR 1988;37(no. S-7).
National Institute for Occupational Safety and Health. Alert . .
.
request for assistance in preventing occupational fatalities in
confined spaces. Cincinnati, Ohio: US Department of Health and
Human
Services, Public Health Service, 1986; DHHS publication no.
(NIOSH)86-110.
National Institute for Occupational Safety and Health. A guide
to
safety in . . . confined spaces. Morgantown, West Virginia: US
Department of Health and Human Services, Public Health Service,
1987;
DHHS publication no. (NIOSH)87-113.
*International Classification of Diseases, Ninth Revision,
E800-E999.
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