A Validated Approach for Assessing Exposure to Asbestos in Soil

JONATHAN THORNBURG (1)

(1) RTI International

     Abstract Number: 237
     Last modified: April 30, 2010

Abstract
Exposure to naturally occurring asbestos or asbestos containing materials at brownfield sites is becoming a significant public health threat. Naturally occurring asbestos is found in residential areas of all 50 states of the USA, Turkey, and South Korea. Asbestos contaminated industrial sites are also common, especially as these sites are re-developed for other uses. This research presents an approach to assess the public’s potential exposure to asbestos found at these sites.

The Releasable Asbestos Field Sampler (RAFS) was designed to quantify asbestos emission rates from soil with less than 0.1% asbestos. The asbestos emission rate data is then input into an aerosol physics and fluid dynamics based model to predict the corresponding breathing zone concentration. This approach is an alternative to activity-based sampling (ABS), currently the only method to obtain inhalation exposure estimates. Collocated, simultaneous RAFS and ABS tests at 12 locations in the USA provided data to validate the RAFS-Model approach.

Asbestos emission rates generated by the RAFS are highly correlated with ABS measured concentrations (R2 = 0.98), but over-predict exposure (slope = 14) because of the RAFS measured asbestos emissions at the soil surface. RAFS measured concentrations vary from 2 fibers per cc to 0.001 fibers per cc. The breathing zone model accurately predicted actual exposure concentrations measured by ABS. Breathing zone concentrations ranged from 1 fiber per cc to less than 0.0001 fibers per cc. Regression statistics showed the slope equaled unity, intercept was zero, and the R2 was still greater than 0.90.

The research conclusions support the RAFS-Model approach as an accurate, reliable and economical alternative to ABS for assessing the public health risk from asbestos exposure at contaminated sites. Further research will associate chronic, low-level asbestos exposure to one's lifetime risk of developing cancer.