Increased Suicide Rate is Possibly Linked to Chemicals Released from Nearby Asphalt Plants
DURHAM, N.C. -- Exposure to low levels of hydrogen sulfide and
possibly other airborne chemicals from nearby asphalt plants may have
contributed to an increased suicide rate in a North Carolina community,
a study suggests for the first time.
In 2003, the suicide rate in
two Salisbury, N.C., neighborhoods was found to be 128 per 100,000
individuals a year, roughly 10 times the statewide average, as stated
in community reports confirmed by death certificates for that year by
the Blue Ridge Environmental Defense League (BREDL).
lead author is Dr. Richard H. Weisler, adjunct professor of psychiatry
at the University of North Carolina at Chapel Hill School of Medicine,
adjunct assistant professor of psychiatry at Duke University Medical
Center and BREDL volunteer.
Other collaborators in this research
were Dr. Jonathan R.T. Davidson, professor of psychiatry at Duke
University Medical Center; Dr. Lynn Crosby, a toxicologist with BREDL;
Lou Zeller, BREDL director; Hope Taylor-Guevera, director of Clean
Water for North Carolina; Sheila Singleton, executive director of the
N.C. Depression and Bipolar Support Alliance; and Melissa Fiffer and
Stacy Tsougas, undergraduates at Duke University's Nicholas School of
the Environment and BREDL summer interns.
comprising two U.S. census tract block groups contained a total of
1,561 residents who were living immediately downwind from a liquid
asphalt terminal; an asphalt hot-mix plant, which also contained a
former N.C. Department of Transportation solvent-contaminated cleanup
site where the DOT had previously dumped solvents used for testing
asphalt; and a contaminated former petroleum tank farm.
1994 and 2003, death certificate evaluations for the two Salisbury
neighborhoods showed a 3-fold statistically significant increase in the
suicide rate, the study found. Four deaths by suicide in adults were
reported from the 687 residents in the census tract block group 1. Two
deaths by suicide in adults were reported among the 874 residents of
census tract block group 2. Only two deaths by suicide would be
expected for this population over a 10-year period, but six suicides
"For example, here in the block group 1
neighborhood in the mid-90s, we found one death by suicide for about
every 230 people during the worst 12-month period, versus an average of
one death by suicide for every 8,621 people in the rest of North
Carolina," Weisler said. "When we saw this data it gave us pause."
said of hydrogen sulfide, "The odor was frequently apparent when I
lived there as a child and later when I visited my mother, who lived in
the neighborhood from 1962 until her death in 2001."
(2001), the N.C. Department of Environment and Natural Resources
(NCDENR) estimated the average maximum hydrogen sulfide level in a
large part of the affected area at 215 parts per billion (pbb), while
some sections of the neighborhoods were reported as low as 30 ppb.
Moreover, based on their own air modeling study, the NCDENR estimated
that historical releases of hydrogen sulfide reached average maximum
levels of 860 ppb in a few residences very near the asphalt facilities.
comparison, the World Health Organization has a 10-minute exposure
standard of five ppb. The California one-hour standard is 30 ppb. The
newly revised, but not yet implemented, North Carolina 24-hour hydrogen
sulfide standard is 86.2 ppb.
These exposures accompanied 574 formal complaints to the City of Salisbury
from March 11, 1999, to Oct. 15, 2004, for noxious odors and associated
respiratory problems, which are still occurring – though at a reduced
rate – said Weisler.
In addition to suggestions of an increased
suicide rate, the incidence rate of primary brain cancers in these
neighborhoods from 1995 to 2000 showed an increase about 6.4 times
greater than expected for the population, possibly due to benzene and
other solvent exposures, Weisler said.
Several studies have shown
increased rates of lung and brain cancer among workers with long-term
exposure to asphalt emissions, the researchers said.
his study team made a hypothetical link between hydrogen sulfide and
suicides due to biological plausibility. They noted that hydrogen
sulfide affects brain neurochemistry as a direct gaseous neuromodulator
that potentially affects mood states and the psychological stress
response. In animal studies, it has been shown to alter the
neurotransmitters serotonin, norepinephrine, dopamine, aspartate and
Hydrogen sulfide also affects the hypothalamic pituitary adrenal axis and corticotropin releasing factor in animal studies, the report said.
is the part of the brain involved in the stress response, and we think
it's also involved in psychological resiliency, how people deal with
stressors," Weisler said. "It's frequently associated with mood
disorders, and there are suggestions that resiliency is impaired when
people are suicidal."
The study team reported that additional
neurotoxic compounds such as benzene, chlorinated solvents and carbon
disulfide, among others, were released in unknown quantities by the
asphalt terminal and hot-mix asphalt plant. Carbon disulfide, also a
neurotoxin, has been linked to personality changes, mood disorders and
suicides in occupational settings, the researchers said.
addition, "Some research suggests that highway workers exposed to
asphalt-solvent fumes show an increase of suicide rates and brain
A full characterization of the types of chemicals and
the levels of releases at the liquid asphalt terminal is needed, said
Also needed, he added, is the retrospective ground water
contamination modeling study called for in 2002 by the N.C. Department
of Health and Human Services to more completely understand the possible
causes of health problems in the affected neighborhoods.
not know if ground water modeling would help us understand the
suicides, but since there were exposures it would be quite useful to
have that modeling information. The same modeling would certainly help
with interpreting the cancer data as people with brain, lung, blood,
pancreatic, breast, and colon cancers had been or may have been using
solvent contaminated well water for extended periods," Weisler said.
Davidson said the most important point for people to remember is that effective treatments exist for suicidal depression.
that suicide can be a tragic consequence to depression, people who are
experiencing persistent symptoms of depression should contact their
health-care provider for a professional evaluation," he said. "The
findings of this study may suggest another potential risk factor for
suicide, but this needs to be confirmed in future studies."
most common symptoms of depression include loss of interest in
activities once considered pleasurable, social withdrawal, changes in
appetite, low mood, inability to function effectively in work or family
situations and, often, a feeling of hopelessness and despair. "It is
the hopelessness that can lead to suicidal thoughts or actions,"
A person with a family history of suicide
attempts or substance abuse may be at greater risk than others, he
said, adding that the study findings may eventually suggest yet another
risk factor for suicide – making further study all the more important.
and Davidson both emphasized the need to educate residents of the
affected areas about mood and anxiety disorders as well as substance
use disorders and their treatments.
City of Salisbury and Rowan
County Health and Mental Health officials are working with suicide and
chemical exposure experts at the U.S. Centers for Disease Control and
Prevention to implement a psychoeducation and referral program for area
residents, as well as educational programs for area health and mental
health providers, Weisler said.
Formal health studies of the two
neighborhoods and other potential sites with chemical exposures are
being planned in further collaboration with the CDC and UNC's School of
The health status of residents who died by suicide
will be investigated further in a study involving Dr. Steven B. Wing,
associate professor of epidemiology, and others at UNC's School of
Significant steps have already been taken, said
Weisler, but reducing potentially toxic exposures from the industrial
plants and safe cleanup of the solvent and petroleum contaminated area
sites will be crucial.
"We do not know with scientific certainty
that the area suicides are linked to hazardous chemical exposures, but
we know enough to recommend that it is not worth taking any more
chances on the potential association."
Weisler presented the findings Nov. 19 to the 17th Annual U.S. Psychiatric and Mental Health Congress in San Diego.