University study outlines dust risks
Two University of Montana professors revealed the results of the North Fork Road Dust Study to Flathead County commissioners Monday morning.
The conclusion: Airborne particulate matter along the road during summer months is often twice the nationally accepted amounts, which could lead to significant health problems.
The Environmental Protection Agency has a baseline standard of 150 micrograms per day for particulates that are about one-sixth the diameter of a human hair.
Airborne matter that size on the North Fork Road peaked at 350 micrograms on July 26, 2007.
During the study, which ran from the middle of July until the end of August last year, monitoring devices showed that dust levels dipped below the baseline level only twice. The average number for one site, located about five miles north of Polebridge near Red Meadow Road, was 211.
"By definition, it does exceed national air standards," professor Tony Ward said.
Rain in August helped push the number down to the 150 baseline.
Two other monitoring locations south of Polebridge also showed elevated levels of dust.
Every three days, the monitors would activate at midnight and run for 24 hours. The machines also would record 60-second averages so one logging truck couldn't skew the numbers.
A typical day showed that road dust problems began a little after sunrise and peaked from 8 to 9 p.m.
The study measured two sizes of particulates in the air.
The larger size, called PM10, is about one-sixth the diameter of a human hair. These particles are generally caused by the crushing and grinding of car tires over gravel roads. This larger dust settles quickly, but it still is a breathing hazard because it is small enough to bypass the body's defenses and deposit in the lungs.
The second size, PM2.5, is about 1/25th the diameter of a human hair and remains in the air much longer. These particles are capable of traveling for miles and pose a significant health risk by worsening asthma and other cardiovascular problems. Children in particular are susceptible to the fine dust.
The EPA has a baseline of 35 micrograms per day for the PM2.5 matter. Along the North Fork Road, the average was 73.
Ward called the numbers "substantial."
Dust from the study was collected and sent to a lab in Portland, Ore., which found aluminum, silicon, potassium, calcium and iron in the dust samples.
When Andrij Holian, the director of the University of Montana's Center for Environmental Health and Sciences, heard of the results, he decided to run a health study. Holian lives on a gravel road and wanted to know what harm road dust could cause.
Because of silica's well-documented ability to damage the lungs, Holian had a hunch that road dust would prove to be a problem.
He was correct.
Holian exposed mice to varying levels of road dust for four weeks. His study showed that large doses of road dust each week - 400 micrograms and 1 milligram - led to damaged lungs and the beginning stages of emphysema.
The pathology of repeated exposure to road dust was similar to problems caused by cigarette smoke.
Holian said two years of traveling the North Fork Road would equate to the toxic amounts of road dust introduced to the mice.
"So during a lifetime of exposure - maybe 70 years - you would accumulate 20 times as much as we put in these mice over a short period of time," Holian said.
How far the risk exists off the road is still unknown. The dust monitors were placed 30 to 40 feet from the road, but the study also included sensors inside vehicles.
Even with vehicle windows rolled up, passengers still were exposed to significant levels of PM10 dust. One car, traveling behind two logging trucks, showed a PM10 level of 5,620 - more than 37 times the accepted limit.
Traffic counts during the study show that the North Fork Road carries close to 400 vehicles per day, but other county roads such as Mennonite Church Road, McMannamy Draw and KM Ranch Road have similar numbers.
Reporter Michael Richeson may be reached at 758-4459 or by e-mail at mricheson@dailyinterlake.com