I was hoping to venture south along the Volcanic Legacy Scenic Byway and hike/summit the 14,162ft Mt. Shasta in California this past Sept. But in checking the Shasta-Trinity National Forest (NF) site for alerts (always a good thing to do), I came upon one, listed last, about “Serpentine and Naturally Occurring Asbestos (NOA)”. It clicked through to a page with a long list of info and maps but no top line info. How many would proceed to click through and read all the info embedded in that list I wondered? Well, knowing that asbestos is a carcinogen, I did – and glad I did. Mt. Shasta turned out to be a big pile of dirt. Plus, there were no NOA warning signs at the trailheads. So knowing what I’m about to share, I took a few pictures and left. As I drove away, my mind raced with questions: Why weren’t there any NOA warning signs? Are there cancer cases attributed to NOA? How harmful is NOA to visitors of national forests? What about us folks & park employees who practically live outdoors all summer? etc, etc…. I started looking online for answers. Seeing as Nov. is Lung Cancer Awareness month and most of the studies appear to have been undertaken in or around the last decade, I decided to share what I’ve learned so far. It’s just basic info (there’s plenty online for those wanting more technical, scientific info) but hopefully, this is enough for folks to get the gist of the issue, start a conversation and maybe do something about it.
Starting with the Shasta-Trinity site, there’s a 2008 “NOA Fact Sheet” that describes the landscape: “Naturally occurring asbestos…has been found to be present in the majority of counties in California. It is commonly found in ultramafic rock formations, including serpentine, and in the soils where these rock types are located. Serpentine, the California State Rock, is found widely throughout the state.” The U.S. Geological Survey and the California Geological Survey have confirmed that NOA can be found in at least 45 of CA’s 58 counties (8 other counties contain ultramafic rocks, serpentinite or fibrous amphibole suggesting the possible presence of NOA). The Fact Sheet indicates that when present, naturally occurring asbestos may pose health risks if released into the air or soil (by being crushed or broken through natural weathering or through human activities) and then inhaled or ingested.
Among the health risks referred to are lung cancer and mesothelioma (a cancer that affects the lungs, heart and abdominal cavity). Proof that NOA can cause mesothelioma was published by UC Davis researchers in 2005. In March 2009, the International Agency for Research on Cancer reconfirmed that all forms of asbestos can cause mesothelioma. However, the risk of developing it is dose dependent and, as the UC Davis team found, “directly related to residential proximity to a source of ultramafic rock”. In another study, the Environmental Protection Agency (EPA) went on to estimate the increased risk of cancer based on OHV/hiking scenarios and frequency of visits -e.g. up to 12 visits per year for recreational scenarios, and up to 120 visits per year for workers (which would include outdoor enthusiasts like us). That study took place at the Clear Creek Management Area (CCMA) in CA which has been closed to the public since May 2008. According to the EPA, the 75,000 acre CCMA in San Benito and Fresno counties includes a serpentinite rock body containing a 31,000 acre outcrop of NOA. It is the largest asbestos deposit in the U.S. The EPA found that at the CCMA, ”There was no combination of scenario, toxicity value, or visits per year that was below the lower end of EPA’s acceptable risk range, i.e. risks less than 1 in 1,000,000. Only…Day Use Hiking…had risk calculations within the acceptable range.” The International Environmental Research Foundation (IERF) has challenged many of those findings and concluded that riding in moist conditions was below EPA’s “virtually safe level”. However, they agreed that “motorcycle riding in dry condition at CCMA raises dust in excess of the asbestos permissible exposure limit”. The IERF review was commissioned by the CA State Parks’ Off-Highway Motor Vehicle Recreation Division (OHVD). We should note that both sides have come under additional scrutiny and criticism. Those who challenge the EPA and believe the area can be enjoyed safely have undertaken efforts to re-open the CCMA. We aren’t aware of any others studying risks associated with these types of recreational scenarios in national forests containing NOA. Would we be alone in wanting to see some?
With these risks in mind, here’s what the Fact Sheet advises: “National forest visitors wishing to reduce their potential exposure to naturally occurring asbestos should consult the maps produced by the Forest Service or the State of California which identify the currently known areas of ultramafic and serpentine rock and naturally occurring asbestos”. I did and found this could be quite time consuming so included some of them below (links are at the end). They indicate the presence of NOA and/or former asbestos mines in all of the following National Forests in CA: Angeles (only mines), Eldorado, Klamath, Lassen, Los Padres, Mendocino, Plumas, San Bernardino, Sequoia (only mines), Shasta-Trinity, Sierra (only mines), Six Rivers, Tahoe. We went back and forth between the maps and the NF websites and were troubled to see NOA alerts missing from websites for the individual NFs we just listed (except Mendocino’s whose link for the NOA Alert points to the wrong info as of today -we let them know so they can fix it). Only the Shasta-Trinity NF and USFS’ Pacific Southwest Region websites provide info on NOA insofar as national forest lands are concerned. Also, as noted before, if I had not checked these sites, there would have been no signs at Mt. Shasta warning me of the presence of NOA. Anyone know if other NFs with NOA have warning signs?
As the first map above shows, CA isn’t alone in this. NOA has been found in more than 2 dozen U.S. states including the Pacific NW. Focusing on WA, we did a search and didn’t come across any NOA Alerts for our national forests. However, on Asbestos.com where you can search by state, they show NOA in WA’s northeast above Spokane in the Okanogan highlands and central Cascades around Wenatchee and Ellensburg (where chrysotile asbestos is present in serpentine rock deposits in mountainous areas). Asbestos was also once mined in WA at two sites in Lyman, Skagit County and near Alta Lake, Okanogan County. Lastly, we found WA state and Whatcom County Dept. of Health advisories for NOA resulting from the Sumas Mountain landslide (near the headwaters of Swift Creek) releasing NOA-containing sediment into that creek and into
the Sumas River near the town of Nooksack, past the town of Sumas and into Canada. The zone is west-northwest of one of our favorites, Mt. Baker. So note to self: close car windows and vents and don’t stop to play in the pretty white stuff that’s asbestos on the shores of Swift Creek and Sumas River if we ever drive through that zone on the way to Mt. Baker. Hopefully, there are warning signs there to remind us.
As we read about the Pacific NW, we began to wonder if hiking our beloved volcanoes and breathing volcanic ash and dust could pose risks. Well, we found a Centers for Disease Control and Prevention blog about Erionite, “a naturally occurring mineral that belongs to a group of silicate minerals called zeolites…[and is] found in volcanic ash that has been altered by weathering and ground water….Disturbance of this material can generate airborne fibers with physical properties and health effects similar to asbestos. For example, it has long been known that residents of some Turkish villages where erionite-containing rock was used to construct homes have a remarkably high risk for development of malignant mesothelioma. Until recently, erionite was not generally considered to be a potential hazard in North America, in part because relatively little risk for exposure was seen. However, evidence has slowly accumulated linking exposure to erionite with serious adverse health effects in North America.” Erionite is classified as a Group 1 carcinogen, labeling it as a cancer-causing agent too. Like NOA, deposits are present in many Western states (see map image above). However, the most talked about areas are N. Dakota where gravel dug from pits containing erionite were used to pave roads since the ’80s and caused lung damage, and UT, Mexico and Turkey where there have been instances of erionite-related illnesses. After that map was released, erionite was also found in WA. However, I haven’t been able to find any sources confirming it’s in Cascades volcanic ash. If you know of any, we’d like to hear from you. We hope future research doesn’t link it to our volcanoes because the National Institute of Environmental Health Sciences reported that “erionite is much more potent than asbestos in causing malignant mesothelioma”. As for other effects of breathing volcanic ash, there is a published study: The respiratory health hazards of volcanic ash: a review for volcanic risk mitigation.
So here are tips from the Fact Sheet for reducing your exposure to NOA (and erionite):
-Be aware of windy conditions and avoid dusty conditions to reduce exposure
-Limit dust generating activities, such as riding offroad vehicles, riding bicycles, running or hiking, riding horses or moving livestock, etc.
-Avoid handling or disturbing loose asbestos containing rock types
-Drive slowly over unpaved roads, with windows and vents closed, to minimize dust generation (California Air Resources Board recommends that vehicle speeds not exceed 15 miles per hour on unpaved roads where asbestos is present)
-Avoid or minimize the tracking of dust into vehicles [and homes]
-Do not use compressed air for cleaning your vehicles after your visit. Use a wet rag to clean the interior” and, as other sources suggest, a High Efficiency Particulate Air (HEPA) filter vacuum.
We all know that kicking up dust is unavoidable when hiking dry trails. So, when conditions are like that, we’re going to take the NF Alert about a “potential for exposure to asbestos fibers on your visit to national forests in California” very seriously. We will simply designate NOA zones on dry days as no hike zones given the large number of days we hike (or add a HEPA filter mask to our safety gear list?). We wonder how many people who visit these areas know about NOA. Prior to this, we did not. We thought about the countless, long backcountry trips on dusty trails that we and other outdoor enthusiasts take and grew concerned. Could it be that our frequent exposures to NOA are sufficiently low level to be considered safe? -problem is: we just don’t know. We hope by writing this, others can become aware of the issue. We’d like to hear from you if this concerns you too. Also, since we’re new to this, we’d welcome experts and others who have useful info to chime in and educate us further: please comment here or email us to add/correct info. In the meantime, let’s all pray for snow – seems to be the safest way to enjoy these areas: when these natural risks are buried deep under snow. Live to ski another day!
To continuing reading about NOA, here are our sources and some additional links:
- the U.S. Geological Survey for maps (they’re working to identify and map reported natural asbestos occurrences in the U.S.)
- more maps and “Data files” with gps location info here
- 2012 publication about Washington’s Swift Creek which contains a lot of history, other info and resources and raises some interesting legal issues