Presence of Asbestos Fibers in Drinking Water

Posted on Behalf of  Mark Maddaloni

Historical estimates of background asbestos exposure have often focused on the ambient (outdoor) environment. These data are useful, but provide incomplete information regarding an individual’s total lifetime background asbestos exposure because 1) Americans spend a large majority (approximately 87%) of their time indoors (https://indoor.lbl.gov/sites/all/files/lbnl-47713.pdf); and 2) the presence of indoor sources typically results in asbestos concentrations in indoor settings having a greater concentration than paired outdoor samples (Lee et al., 1992).

One potential indoor exposure, asbestos in drinking water, is often overlooked and remains a poorly characterized source. The major sources of asbestos in drinking water are asbestos cement water main decay and natural deposit erosion. The U.S. Environmental Protection Agency’s (EPA) Maximum Contaminant Level (MCL) for asbestos in drinking water is 7 million fibers per liter (MFL). While the MCL is based on ingested asbestos, the potential for asbestos fibers to become airborne and be inhaled during activities such as showering exists. This potential source of inhalable asbestos fibers in the indoor environment has been difficult to study because of the numerous variables and uncertainties associated with the exposure scenario, including water-borne fiber concentration, fiber aerosolization/deposition rates, shower/bathroom characteristics, and possible re-entrainment of residual fibers on bathroom surfaces from evaporated water.

The few studies that have investigated the relationship between asbestos concentration in water and indoor air during and after showering have shown disparate results. More research is needed to better understand this relationship and should focus on the aforementioned variables and uncertainties.

Cardno ChemRisk has years of experience studying potential exposure to asbestos fibers. In addition to investigating the sources of exposure, we also focus on understanding how fiber type and size can affect potency. In summary, indoor asbestos exposure from potable water is under-studied, and more research is needed to understand the factors that influence potential exposure scenarios.

To learn more about our capabilities, or if you have any questions regarding this topic, please contact Mark Maddaloni.