In November 2021, many news outlets carried the story of the landslide in Washington state that caused elevated asbestos levels by dumping sediment containing naturally occurring asbestos (NOA) into the waterways of Swift Creek downstream from Sumas Mountain. The state’s ecology department warned that it could be especially dangerous during the summertime when the sediment dried and asbestos could be aerosolized by winds and inhaled by people visiting the area.
The environment can impact people’s health in numerous ways. For example, the geological settings in a geographic area can influence the air quality that a local community breathes. Medical geology, an emerging interdisciplinary scientific field of study, brings together professionals from medicine, public health, geology, and community development to help understand the relationship between trace contaminants and bioavailability for naturally occurring materials. NOA is a common-occurring mineral in many geological settings.
Exposure to NOA – as opposed to asbestos found in commercial products, mining, or processing operations – usually occurs without public knowledge and may have adverse health effects. People with significant exposure to asbestos or naturally occurring asbestos are at risk for developing asbestosis, lung cancer or mesothelioma. The probability that mesothelioma occurs will increase as exposure to NOA is prolonged and inhaled fibers cannot be removed from a person’s lungs.
Where is NOA Found?
NOA is generally found in places where volcanic ash and rock have been weathered by alkaline waters. Forest workers, construction workers and firefighters are exposed to potentially hazardous NOA during landscaping maintenance activities, site excavation, mining operations, and forest fires. Deposits of NOA are predominately found in California, Arizona, Oregon, Nevada, North Carolina, Georgia, and Maryland; but presently, thirty-five U.S. states report NOA sites. NOA disturbance and exposure may occur through aggregate mining, road construction, timber harvesting, or recreational uses. NOA fibers can adhere to clothes and car interior upholstery/carpeting. These adherent fibers result in future exposure outside the NOA-containing soil areas. This second-hand, off-site exposure also increases the risk of mesothelioma.
Exposure to NOA
NOA exposure is mostly environmental, and it affects individuals that live in areas where a natural deposit of the mineral exists. Mesothelioma is a rare cancer and the most dreaded asbestos-related disease. It affects the lining of the chest cavity and is extremely debilitating and terminal. NOA exposures can begin at a very young age and typically occur at levels below the permissible exposure limit (PEL). Some people develop mesothelioma after exposure to minor amounts of mineral fibers; while others who are exposed to large amounts never develop the disease. Asbestos fibers are generally widespread in the environment and even a 70-year-old mesothelioma-free healthy lung may contain up to one million fibers per gram of lung tissue. Approximately 3,000 people die of mesothelioma in the United States each year.
Current Occupational Safety & Health Administration (OSHA) regulation for asbestos exposure includes a short-term permissible exposure known as Excursion Limit (EL) where exposure to the airborne concentration of asbestos is limited to one fiber per cubic centimeter (f/cc) for a maximum of 30 minutes and a PEL of 0.1 f/cc for an eight-hour work shift in all industries – including construction, shipyards, and asbestos abatement work. The PEL was set in 1971 originally at 10 f/cc.
Minimizing Exposure to NOA
NOA is generally considered safe if it is left undisturbed and covered by soil and/or vegetation. The key steps to minimizing worker exposure to NOA is to anticipate the risk of exposure to mineral fibers during soil disturbance. This is accomplished by collecting soil samples from the correct locations and in the correct amount and sending them to a laboratory that utilizes the correct analytical method. The NOA exposure level is then calculated using the U.S. Environmental Protection Agency (EPA) fugitive dust model.
By knowing the level of potential exposure, the best corrective/protective actions for workers can be properly selected – such as water misting during soil disturbance of NOA-containing soils and using negative pressure air purifying respirators and disposable clothing. Also, a plan of action should be made taking into consideration the general population living in the area, so nobody will be exposed to fugitive mineral dust.
NOA Exposure Monitoring and Prevention Services from HETI
HETI can help find mineral fibers in soil; map the areas where NOA was found; and provide a comprehensive investigation of the study site through geological investigation and chemical/morphological analysis of NOA fibers present in the soil. Our professional staff can assist in examining the potential risk of NOA exposure for workers and the community through modeling and calculations of cancer risks, along with developing a risk communication framework for interacting with the general public, employees, and visitors.
HETI’s Dr. Daniel Farcas (speaker) and Dr. Michael Henderson (moderator) will present “Measuring the Exposure Levels to Naturally Occurring Asbestos for Field Workers in Western U.S. in the Context of Global Climate Change” at the 2022 American Industrial Hygiene Conference & Exposition in Nashville, TN on May 25 at 1:00 PM. [Registration is required – through this link: https://ww2.aievolution.com/aih2201/index.cfm?do=ev.viewEv&ev=1242