Activity-Based Air Monitoring

For several reasons, the District does not believe that activity-based monitoring by the District is necessary at this time. Currently, the U.S. Environmental Protection Agency (EPA) does not plan to conduct monitoring of this type in Placer County.

The activity-based air monitoring conducted at Oak Ridge High School in El Dorado Hills by the U.S. EPA and Agency for Toxic Substances and Disease Registry (ATSDR) was intended to determine if activities (such as playing baseball, playing soccer, and jogging), and the associated disturbance of dust while performing the activities, increased exposure to asbestos fibers over background reference sampling. The area is known to have Naturally Occurring Asbestos (NOA) containing materials and NOA deposits. The results from the sampling indicate that the disturbance of dust-containing asbestos fibers will result in increased air concentrations of up to 43 times that of fiber counts for reference samples taken without activities occurring.

Community Health Assessment

The U.S. EPA has stated that it is not currently possible to accurately assess the health risk for El Dorado Hills’ residents from the types of exposures that were observed in its study. Furthermore, the U.S. EPA has stated that a health assessment was not the purpose of the studies, but the results are of concern because of the potential for long-term development of asbestos-related diseases. Because the ATSDR's study was restricted to assessing the potential health risks contingent on activity-based sampling for NOA at Oak Ridge High School, in El Dorado Hills, the ATSDR was subsequently prompted by members of the El Dorado Hills community to determine what this finding meant to their health, and what they should do to protect their health.

Study Results

To answer these questions for the community as a whole, the ATSDR used the EPA sampling results to estimate how much NOA an El Dorado Hills resident might breathe in throughout life. Several different risk assessment calculation methods were then compared to get a general sense of the risk of developing asbestos-related cancers from these exposures. Finally, results of additional studies on NOA in the El Dorado Hills area were examined.

The ATSDR concluded that while the predicted risks were high enough to warrant preventive measures, the risk of disease from asbestos exposure was difficult to predict. The ATSDR reached two important conclusions in the recently issued Health Consultation:

  • Conclusion 1: Breathing in naturally occurring asbestos (NOA) in the El Dorado Hills area, over a lifetime, has the potential to harm people’s health.
  • Conclusion 2: A health study of the community of El Dorado Hills would not provide helpful information at this time.


The ATSDR recommends that El Dorado County continue to enforce state and local dust regulations to limit people's potential exposure to asbestos and that the county continue to provide the community information about where naturally-occurring asbestos is found so that people can avoid it or minimize their exposure during normal activities. The ATSDR also recommends that the state of California continue to monitor asbestos-related cancer incidence rates in the area in the event an increase should occur. View the ATSDR Health Consultation for Public Comment, El Dorado Hills, California.

District Conclusion

Consideration of the findings of the U.S. EPA and ATSDR from the air sampling studies conducted in El Dorado Hills, has led the District to the following conclusion regarding the need for activity-based sampling: In areas where NOA is known to be present in the soil and in surrounding areas, activity-based sampling would likely indicate an increase in exposures due to dust and soil being disturbed. However, as there are no means to evaluate the increased health risk from such increased exposures, little would be gained by the performance of such sampling. It is simpler and more direct for the assumption to be made that asbestos fibers may be present in dust and soil in areas where NOA is known to be present or more likely to be found, and to direct efforts and available resources toward reducing potential exposures to the fibers.

Air sampling conducted by the California Air Resources Board (CARB) in 1999 found low, but detectable, asbestos fiber concentrations at locations in Foresthill and Auburn. While paving of McKeon-Ponderosa Way, in Foresthill, has undoubtedly reduced dust disturbance, the results supports the District's reasonable conclusion that where NOA is found you are likely to find some asbestos fibers in the air. There is no level at which exposure to asbestos fibers is deemed to be free of risk. Since activities that disturb dust and soil that potentially contains NOA fibers will likely increase the concentration of fibers in the air, precautions should be taken to either minimize participation in the activity or to minimize dust disturbance for the activity, or both.

Additional Information

  • For further information, visit the U.S. EPA Studies in El Dorado Hills website.
  • Information on the ATSDR's studies in El Dorado Hills is available at the link El Dorado County Air Quality Management District.
  • For information regarding asbestos concentrations view Air Monitoring for NOA in Placer County. (Note: The PCAPCD has moved since the sampling was conducted. The location of the sampling was at 11464 "B" Avenue, Auburn, California.)