Asbestos and pre-1990 adolescent exposure

A recent study reported that nearly half of almost 200 adults that were exposed to Libby amphibole asbestos as adolescents were subject to pleural thickening in their lungs later in life, a condition that’s most commonly associated with asbestos exposure.

“When you think of asbestos, you think of asbestosis and mesothelioma, and while it’s more common in Libby, they’re still very rare diseases,” Montana State University professor and one of the many project researchers Dr. Jean Pfau said. “[Pleural thickening] on the other hand, is much more common.”

While the rate of pleural lining for this group was almost 50 percent, the average rate for this diagnosis ranges from .2 to 6.5 percent in people with no known asbestos exposure — a seven to 250 times greater risk.

In 1899, the first reported case of lung scarring caused by asbestos was written by Dr. H. Montague Murray. He described the lung scars as “curious bodies.” These curious bodies are too-well known by the people of Libby who were continuously poisoned by the WR Grace Mine for many years.

Now, the effects of asbestos on the body are well known, but new data is still being continually studied and published in medical journals across the world.

In October of this year, a piece of the three-fold research project into the effects of Libby amphibole asbestos added to the bulk of research scientists and doctors have.

Research scientists from Idaho State University, Icahn School of Medicine at Mount Sinai and University of Montana, along with the Center for Asbestos Related diseases clinic reported their findings in the journal article, “The Pre-Adult Latency Study.”

This study evaluated lung findings among 198 otherwise healthy adults who attended primary or secondary school and lived in Libby prior to a certain age.

Of the 198 participants who averaged 50 years of age, pleural thickening, or thickening of the lungs’ outer lining, was found in 96 (48 percent). In almost half of these, it was of the lamellar (layered) type which is not generally seen in exposure to other asbestos, and was further shown in the article to lead to greater decrement in pulmonary function compared to circumscribed pleural thickening.

These adults had been environmentally exposed to Libby Amphibole only during childhood and adolescence through mostly non-occupational and low exposure, whom subsequently left the area after a certain age, some of which returned to Libby within the five years prior to their CT scan.

According to the article, as they were children, 92 had participated in recreational activities along Rainy Creek Road, 180 played in, or watched games at the largely contaminated downtown ballfield, 134 played in piles of vermiculite, 134 used the asbestos-lined Middle School Track outside of scheduled gym classes, 107 heated-up vermiculite ore in science classes, 121 gardened in soil that contained vermiculite and 171 burned asbestos-dust covered firewood in their homes.

Studies have been done before on children and adolescents exposed to asbestos, but the studies prior to “The Pre-Adult Latency Study” did not include chest CT scans, which are necessary to identify the progression of pleural scarring in Libby patients.

While a CT scan is necessary to be sure if a person has pleural thickening, the subjects also underwent a pulmonary function test. The test studies how deep the subject can inhale and how hard they can exhale.

People who have pleural thickening have a comparatively more difficult time breathing out and taking deep breaths than people with healthy lungs.

“One of the things that these people talk about is that they do fine walking around their house, but as soon as they walk up a flight of stairs, they have trouble,” Pfau said. “Once [they] try to exert [themselves], [they’re] just not getting enough air.”

The subjects Pfau, along with other researchers studied, followed a list of criteria:

• They lived in the Libby/Troy area for at least six months but left the area prior to age 21 years for females and 23 years for males.

• They had at least 15 years between the first potential exposure to Libby amphibole and the date of CT scan used in the study.

• They never worked directly for or as a contractor of the vermiculite mine in Libby.

• They had not returned to the area after the age limits as mentioned above, to live or work (this was their initial requirements, but later expanded their test-subjects to include those who returned five years prior to the CT scan).

“What we wanted to do was look at people who had lived there their whole life and compare it to people who had only limited exposure early on,” Dr. Jean Pfau said. “While we weren’t able to compare it within our study, we saw that the risk was just as high or higher than people who stayed. Any disease where you see that nearly half of the people who had low exposure have that disease — that’s astonishing.”

Those who lived there for more than two years prior to 1990 had a six to seven times greater likelihood of pleural thickening than those who lived in the area for less than two years.

The frequency (48 percent) of subjects who showed pleural thickening on CT scan exceeds the frequency of this finding in many occupationally exposed groups.

On top of these findings, they also found that subjects with pleural thickening were three times more likely to be male than female.

One of the criticisms of studies on pleural thickening in the past, is that 56 percent subjects were overweight — which is associated with pleural thickening. However, Dr. Pfau said that their subjects were on-average with the rest of the country, and the Body Mass Index of the patients did not affect the level of pleural thickening.

The research project began when the Agency for Toxic Substances and Disease Registry awarded a $5 million grant to the Icahn School of Medicine at Mount Sinai in 2009, in partnership with researchers at Idaho State University and Montana State University, to create the Libby Epidemiology Research Program, which had the mission of furthering research in long-term health effects of amphibole asbestos in Libby and the surrounding community. The three-fold research project included the Pre-Latency Study, CT Progression Study and Autoimmune Outcomes.

Obviously not all of the asbestos is gone from Libby, Pfau said, but a huge amount is gone. Therefore, children growing up in Libby at this time, she said, are at a much lower risk of exposure than children exposed before the EPA started cleaning.

Pfau noted that one of the purposes of the study was to help doctors diagnose people with pleural thickening who lived in Libby or areas like Libby. Most doctors may do an X-ray, but X-rays will only show a shadow, Pfau said, and even then, a doctor has to really look for it. If a doctor knows to do a CT scan, a procedure that is less commonly used due the radiation output, they will be able to see it. That way, she said, patients with pleural thickening don’t walk away from a doctor’s visit thinking it’s their fault that they can’t breathe.


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