The challenges of applying an Activity-Based Sampling methodology to estimate the cancer risk associated with asbestos contaminated landfilled zones

Our plain-English summary of The challenges of applying an Activity-Based Sampling methodology to estimate the cancer risk associated with asbestos contaminated landfilled zones, by M.F. Cely-García, B. Lysaniuk, R. Pasetto, et al (Environmental Research, 2020).

The study

• Authors: M.F. Cely-García, B. Lysaniuk, R. Pasetto, J.P. Ramos-Bonilla
• Journal: Environmental Research
• Published: 2020;181:108893
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Inhabitants of Sibaté (Colombia) report that between approximately 1975 and 1985 asbestos-containing materials (ACM) were dumped at different locations in the urban area of the municipality. Starting in around 1986, the dumping of materials resulted in landfilled zones, on top of which different facilities were then constructed. In a previous study, an underground friable asbestos layer was discovered in these landfilled zones. However, potential exposure to asbestos on the surface of landfilled zones in Sibaté has not been determined. In the current study, the U.S. EPA Activity-Based Sampling (ABS) methodology was adapted and applied in three scenarios located on potential landfilled areas in Sibaté, to estimate the current risk of exposure to asbestos through inhalation, and the resulting excess lifetime cancer risk (ELCR). For this purpose, generic ABS in a football stadium, and specific ABS in both a public playground and a school courtyard were conducted. Personal, area and blank samples were collected and analyzed using phase contrast microscopy (PCM) and transmission electron microscopy (TEM) following NIOSH 7400 and ISO 13794 methods, respectively. Exposure point concentrations were determined and compared against the action level for asbestos in air (ALAA), and were also used to calculate the ELCR of each scenario. A total of 25 airborne asbestos samples were collected, and 22 of these (12 personal samples, 7 area samples and 3 blank samples) were analyzed using PCM. Eighteen of these samples (12 personal, 3 area samples and 3 blank samples) were analyzed using TEM. The total asbestos structures concentration of personal samples ranged from non-detected to 0.326 S/cc (i.e., total asbestos structures counts ranged from 0 to 12). All samples had PCM-Equivalent asbestos structures concentrations below analytical sensitivity. Of the 22 samples analyzed, 18 were overloaded with particles. Although chrysotile and actinolite were identified in some personal samples, suggesting a potential risk of asbestos exposure, the ELCR was at U.S. EPA acceptable risk levels. Since the ABS methodology was applied in a limited number of scenarios and a small number of samples were collected, these results should be interpreted with caution and additional sampling campaigns are required to fully understand the risk of asbestos exposure in Sibaté. Methodological and analytical challenges encountered in the current study are discussed in detail, which could inform future ABS studies, not only in Sibaté, but also in other areas with asbestos-contaminated soils.

Copyright © 2019 Elsevier Inc. All rights reserved.

In plain English

This study tested whether asbestos becomes airborne from the surface of zones in Sibaté, Colombia, where residents report asbestos-containing materials were dumped and built over. In late 2018, three researchers in protective gear adapted a U.S. EPA method called Activity-Based Sampling. They raked soil at a football stadium and simulated a child playing in the dirt at a playground and a school courtyard while wearing air samplers. Of 25 air samples, 22 were read by light microscopy and 18 by electron microscopy. All light-microscopy results were below the detection limit. Electron microscopy found chrysotile in 9 samples and chrysotile plus actinolite in 1. Personal samples reached up to 0.326 structures per cubic centimeter, though the article's table says that sample should not be considered because pump flow drifted over 5%. No structures meeting the 'PCM-equivalent' definition used in the EPA risk calculation were counted, so the estimated excess lifetime cancer risk was at U.S. EPA acceptable levels. Most filters were overloaded with dust and missed the recommended sensitivity. The authors cautioned that, with few scenarios and samples, it should not be concluded that there is no current risk.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Field air-sampling study adapting the U.S. EPA Activity-Based Sampling method, with excess lifetime cancer risk calculations; described by the authors as an initial effort
• Who was studied: Three sampling scenarios on or near potential asbestos-landfilled zones in Sibaté, Colombia (an area within a football stadium, a children's playground near the stadium, and a courtyard in a public school), sampled on November 23 and December 11, 2018. Researchers performed the activities; no human subjects were studied.
• Exposure: Airborne asbestos released by disturbing surface soil. At the stadium, researchers raked the soil vigorously (generic sampling). At the playground and school courtyard, they simulated a child playing in the dirt with shovels and buckets (specific sampling).
• Main results:
  • Of the 25 air samples collected, 22 were analyzed by phase contrast microscopy (PCM) and 18 by transmission electron microscopy (TEM): 12 personal, 3 area and 3 blank samples.
  • All PCM concentrations were below the limit of detection; the number of fibers counted per sample ranged from 0 to 4.
  • By TEM, no structures were detected in 8 of 18 samples (including the 3 blanks). One sample had both chrysotile and actinolite structures, and the other 9 had chrysotile structures.
  • Four personal samples had no asbestos structures detected. In the other personal samples, 1 to 12 total asbestos structures were counted, with total asbestos structure concentrations of 0.006 to 0.326 S/cc.
  • In Table 2, the sample with the highest total asbestos concentration (Specific CY P5, 0.326 S/cc) carries a footnote stating that it is reported but should not be considered, because sampling flow drift exceeded 5%.
  • In all samples, 0 PCM-Equivalent asbestos structures were counted, so 0 S/cc was used as the exposure concentration for the risk calculations.
  • In all three scenarios, the exposure concentration was below the action level for asbestos in air, and the excess lifetime cancer risk was at U.S. EPA acceptable risk levels.
  • All samples except 4 (1 area sample and the 3 blanks) were overloaded with particles.
  • Surface soil samples from the bare patches in the school courtyard were reported as non-detected.
  • Soil samples from municipal pipeline excavation holes near the stadium showed a friable asbestos layer in 3 of 4 samples, so the excavations disturbed the asbestos layer. However, the four 24-hour air samples taken near the excavations were below the PCM limit of detection.
• The authors' conclusion: The authors concluded that the results should be interpreted with caution and that it should not be concluded from these preliminary results that there is currently no risk of asbestos exposure from the landfilled zones; they called for additional sampling.
• Limitations the authors state:
  • Small number of scenarios and samples, so the results cannot be generalized.
  • Sampling was done only at one time of year.
  • Filter overloading introduced uncertainty into the results.
  • Because sampling times were shortened, the recommended analytical sensitivity was not reached.
  • Overloading caused pressure drop, and 8 samples had a flow drift above 5%.
  • The indirect TEM preparation may break bundles and clusters into shorter fibers, which may push PCM-equivalent concentrations below the analytical sensitivity; the authors say this could have happened here and could lead to underestimation.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM), Friable, phase contrast microscopy (PCM), Transmission Electron Microscopy (TEM), NIOSH Method 7400, ISO 13794, Personal Breathing Zone Sample, Analytical Sensitivity.

Related studies

• Where are the landfilled zones? Use of historical geographic information and local spatial knowledge to determine the location of underground asbestos contamination in Sibaté (Colombia) — B. Lysaniuk, M.F. Cely-García, et al. (2020)
• Using GIS to Estimate Population at Risk Because of Residence Proximity to Asbestos Processing Facilities in Colombia — B. Lysaniuk, M.F. Cely-García, et al. (2021)
• Estimation of personal exposure to asbestos of brake repair workers — M.F. Cely-García, F.C. Curriero, et al. (2017)
• Cumulative Retrospective Exposure Assessment (REA) as a predictor of amphibole asbestos lung burden: validation procedures and results for industrial hygiene and pathology estimates — J.O. Rasmuson, V.L. Roggli, et al. (2014)
• Heavy equipment maintenance exposure assessment: using a time-activity model to estimate surrogate values for replacement of missing data — F.W. Boelter, J.W. Spencer, et al. (2007)
• Exposure of UK industrial plumbers to asbestos, Part II: Awareness and responses of plumbers to working with asbestos during a survey in parallel with personal sampling — D. Bard, G. Burdett (2007)

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