The level of concern for lead in drinking water is defined by an action level of 15 ppb under the Lead and Copper Rule. This means that when lead concentrations exceed 15 parts per billion in a significant portion of taps, the water system must take steps to reduce lead exposure, such as optimizing corrosion control, public education, and lead service line replacement. For water, 15 ppb is the same as 15 µg/L, since 1 ppb roughly equals 1 µg/L in dilute solutions. So, 15 ppb (or 15 µg/L) is the threshold that triggers required protective actions. Other values are not the EPA action level used to determine when those steps are needed.

Lead in soil mainly comes from older uses of lead-containing products, particularly lead-based paint and leaded gasoline. When exterior paint on homes chips or flakes, the lead in that paint can shed dust and chips that settle into the surrounding soil. Historically, gasoline with tetraethyl lead released lead into the air, and that lead settled into soils along streets, driveways, and near homes. New mulch doesn’t introduce lead, and gravel doesn’t inherently add lead to soil; moisture in soil isn’t a source of lead itself, it only affects how lead moves once it’s in the soil. So the statement that chipped paint and gas are sources best captures the common, historical ways lead gets into soil.

EBL stands for Elevated Blood Lead. This label is used in EPA guidance to indicate that a child has lead in their blood at a higher-than-normal level and requires follow-up. The form Elevated Blood Lead Level would typically be abbreviated EBLL, which is why the acronym EBL corresponds to Elevated Blood Lead rather than including the word “Level.”

Lead exposure depends on the situation, but for adults working with lead, the air around them becomes the main route of exposure. When lead is released as dust or fumes in industrial settings, inhaling those particles or vapors delivers lead directly into the bloodstream through the lungs, often giving a larger and faster dose than swallowing lead-contaminated material. The lungs absorb a significant portion of inhaled lead, which is why inhalation in the workplace is the dominant exposure pathway for active workers. Other routes exist but are typically less important in this context. Skin absorption of lead is minimal, since intact skin is a poor entry point. In the general population outside of work—through contaminated dust, soil, water, or food—ingestion becomes more relevant, but among adults with occupational exposure, inhalation in the workplace is the primary route.