14 November 2005
Pollutants Linked To Suicide Rate?
by Kate Melville
Could neurotoxin pollutants be causing an elevated suicide rate in a North Carolina community? Sited next to a paper mill and other industrial plants, the community is suffering a sustained increase in suicides, which researchers think could be linked to the release of hydrogen sulfide and other airborne chemicals.
The study, carried out by a psychiatrist from the University of North Carolina, was presented at the 18th Annual U.S. Psychiatric and Mental Health Congress. It follows up on earlier research that proposed a possible link between increased suicide rates in Salisbury, North Carolina, and chemical exposures from nearby industry. That study found that for a ten year period from 1994, the suicide rate in two Salisbury neighborhoods was 38.4 per 100,000 individuals a year, roughly three times the statewide average. It was believed that the increased figures could be related to chronic low-level exposure to hydrogen sulfide and other potential neurotoxins released from nearby asphalt plants and petroleum remediation sites.
Research with animals has shown hydrogen sulfide to be a neurotoxin, altering levels of brain chemicals such as serotonin, norepinephrine, dopamine, aspartate, GABA and glutamate.
In the new study, the researchers looked at the suicide rate in another North Carolina area - rural Haywood County - which nearly doubled from a rate of 11.8 per 100,000 residents for 1990-1996, to about 21.1 per 100,000 residents for the period 1997-2002. The suicide rate has remained elevated since 1997, peaking at 29.7 per 100,000 in 2000.
"We clearly know there have been increases in suicides during this time period when there were also operational changes at the paper mill," said the study's lead author Dr. Richard H. Weisler. "The 1997 spike in suicides in Haywood County corresponded to a switch to Bleach Filtrate Recycle in late 1996. Whether there is a connection between the increased suicides and operational changes has yet to be determined."
The paper mill in Haywood County uses Bleach Filtrate Recycle (BFR), to help remove chlorine and other toxins from the waste discharged into the Pigeon River. But Weisler questions whether the cleaner river comes at the cost of dirtier air. "The burning of chlorinated compounds that BFR potentially entails, as well as a possible increase in plant volume, may have led to increased releases of dioxins and other harmful compounds into the air. The switch to BFR, which involves burning of black liquor, may have resulted in an increase in air quality problems," he explained.
Other related studies of asphalt plants, paper mills and sewage treatment plants have shown that exposure to occupational levels of hydrogen sulfide (10 parts per million for a 10-minute ceiling) can result in nervousness, mania, dementia and violence, according to the researchers. Weisler believes further studies should examine whether levels lower than those to which nearby residents are exposed could also influence brain chemistry.
Better air monitoring is also needed, according to Weisler, as well as a reassessment of using Bleach Filtrate Recycle. Study co-author Dr. Jonathan R.T. Davidson, from Duke University, concluded that: "The findings of this study may suggest another potential risk factor for suicide, but this needs to be confirmed in future studies."
Source: University of North Carolina School of Medicine