A study presented last week at the 18th Annual U.S. Psychiatric and Mental Health Congress in Las Vegas found a possible link between the sustained elevation of the suicide rate in a North Carolina county and releases of hydrogen sulfide and other airborne chemicals from a nearby paper mill and perhaps other industrial locations in the area.
This is not the first time that a link has been proposed between elevated suicide rates in a North Carolina community and exposure to industrial chemicals. In fact, many authors of the latest study also worked on previous research that showed a possible link between an elevated suicide rate in a Salisbury community and exposure to hydrogen sulfide and other potential neurotoxins released from local asphalt plants and petroleum remediation sites.
In the prior study, the researchers found that between 1994 and 2003, the annual suicide rate in two Salisbury neighborhoods was 38.4 per 100,000, which is around triple the North Carolina’s average.
Those findings were presented to the 17th Annual U.S. Psychiatric and Mental Health Congress in 2004 and at the National Institute of Mental Health New Clinical Drug Evaluation Unit meeting in June 2005.
The new study, which focused on CDC data regarding suicides in the rural North Carolina county of Haywood, found that the rate had nearly doubled from an age-adjusted 11.8 per 100,000 in 1990 to 1996 to around 21.1 per 100,000 in 1997 to 2002.
Salisbury’s age-adjusted suicide rate has now remained elevated since 1997, peaking at 29.7 per 100,000 in 2000. The statewide age-adjusted average suicide rate for 1997 to 2001, however, was only about 11.4 per 100,000 per year.
"We clearly know there have been increases in suicides during this time period when there were also operational changes at the paper mill," said Dr. Richard H. Weisler, lead study author. "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 Haywood County paper mill uses Bleach Filtrate Recycle, or BFR, to remove chlorine and other toxins from the waste discharged into the Pigeon River. Dr. Weisler and his team wonder whether dirtier air has been the price of a cleaner river.
According to Weisler: "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."
"Black liquor" is a wood and chemical waste byproduct produced in the manufacturing process of turning wood into paper pulp. The Haywood County mill, like many others, burns black liquor to produce electricity.
The Haywood County mill releases many chemicals such as carbon disulfide, dimethyl disulfide, dimethyl sulfide and methyl mercaptan. In 2003 alone, for example, it released more than 93,000 pounds of hydrogen sulfide.
Research has shown that exposure to occupational levels of hydrogen sulfide (10 parts per million for a 10-minute ceiling) can result in dementia, nervousness, mania, and violence. Hydrogen sulfide has been shown to be a neurotoxin in studies of animals. It alters levels of serotonin, norepinephrine, dopamine, aspartate, GABA and glutamate.
"We speculate that hydrogen sulfide may serve as a marker for other potentially neurotoxic compounds being released in this mountain valley," Weisler said.
Haywood County is located within a series of mountainous valleys that often have temperature inversions trapping colder, dense air in the valley. This has the potential for preventing pollutants from dispersing, and increasing air quality problems. Both studies noted complaints of odor and air quality problems. For this reason, formal studies are needed to trace the flow of air pollution from the plant while also monitoring the amounts of the various chemical pollutants released by the mill.
Weisler stated that he and the team "hope there will be relevant and sensitive air monitoring, as well as a whole reassessment of whether or not burning the black liquor and using Bleach Filtrate Recycle is really the best approach to clean up the Pigeon River.”
Co-author Dr. Jonathan R.T. Davidson believes it is very important for people to remember that effective treatments exist for suicidal depression. He also stated: "Given 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."