There is no identified risk-free threshold exposure to asbestos. Based on epidemiology and toxicology, asbestos fiber dimensions have been implicated in causing asbestos-related diseases. Phase-contrast microscopy provides only a limited index of exposure to fiber dimensions implicated in mesothelioma induction. Installed asbestos-containing materials (ACMs) create an ongoing risk of intense exposure during natural disasters and remodeling, along with low-level exposure arising from the continual emission of airborne asbestos into the environment arising from weathering of installed ACM. Epidemiological studies have demonstrated a risk of disease associated with proximity to asbestos cement roofing (ACR), while ongoing environmental emissions of asbestos from installed ACR have also been demonstrated. Owing to the limitations of the available data, a precautionary approach is warranted; asbestos-free roofing materials should be used in new construction and existing ACR should be removed at the earliest opportunity.