Inland Northwest residents worried about Mount St. Helens spewing volcanic ash can probably breathe easier, University of Idaho geologist Mickey Gunter said.
Gunter, a professor of geology and specialist in the health effects of mineral dusts, studied sampling data for very small airborne dust particles collected near Moscow and elsewhere in Idaho after Mount St. Helens erupted in 1980.
“The vast majority of ash is material that has never been shown to be harmful,” he said.
Health records showed no elevated levels of lung cancer among the region’s residents, Gunter and co-author Michael R. Norton reported in the scientific journal American Mineralogist in 1999.
Health records did show higher levels of chronic obstructive pulmonary diseases, Gunter said, mainly among farmers in the state’s most dusty areas. But even those levels were less than urban residents face.
The greatest frequency of both lung cancer and chronic obstructive pulmonary lung diseases occurs among urban residents, Gunter said. Research shows air pollution by diesel engines, which produce the very fine soot particles that penetrate deeply into lungs, is a major factor.
Asthma sufferers and others with chronic respiratory problems may need to take short-term measures if the volcano were to spread ash across the region, Gunter said.
The long-term implications of a regional ashfall are minor, however, he said. Volcanologists recently lowered the alert level to reflect reduced prospects of an eruption.
Gunter hoped the study would help clear the air about the health risks of volcanic ash. “We felt that information might alleviate a lot of that fear,” he said.
In his study, Gunter analyzed data from air samplers monitoring airborne particles smaller than 10 microns in diameter – known as PM10 for particulate matter smaller than 10 microns. The particles are about a tenth the diameter of a human hair and smaller. The smallest particles penetrate deepest into the lung and so pose the greatest health hazards.
The samples showed that quartz, the most dangerous mineral in our air according to government regulators, normally comprises 10 to 15 percent of the PM10 samples collected throughout the state routinely.
The volcano’s big blast 24 years ago clouded the region’s atmosphere with dust for months. Mount St. Helens ash collected after the massive 1980 eruption contained less than 1 percent quartz and only a fraction of that was 10 microns or smaller.
An international health organization now classifies quartz as a cause of cancer, Gunter said, although in 1980 it was labeled only a probable cause. But Gunter finds it strange that the most abundant mineral on the Earth is considered carcinogenic.
Research suggests that crystalline silica, and specifically quartz, causes disease because it is insoluble and the body’s normal processes cannot get rid of it, but only when inhaled in large amounts. Also freshly broken quartz appears to be more harmful.
The health data Gunter analyzed was collected from 1969 to 1994. It showed Idahoans, and particularly Idaho farmers, were at greater risk of chronic obstructive pulmonary lung diseases, although at lower risk of lung cancer, even after the data were adjusted for the state’s smaller population of smokers.
The chronic obstructive pulmonary disease reflects years of exposure to dusty conditions, Gunter said. It would make sense that farmers exposed during the 1940s, ‘50s and ‘60s were most at risk because tractors then did not have the air-conditioned cabs common today.
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