Legionella
EPA Designation Regulated
EPA Classification Microorganisms
EPA Levels 1,2 zero MCLG (mg/L)
TT3 MCLG (mg/L)
Alternative Names none
Sources Found naturally in water; multiplies in heating systems
A genus of bacteria, some species of which have caused a type of pneumonia called Legionnaires Disease.

Overview

Legionella bacteria are found naturally in the environment, usually in water. The bacteria grow best in warm water, like the kind found in hot tubs, cooling towers, hot water tanks, large plumbing systems, or parts of the air-conditioning systems of large buildings.3 Legionella bacteria in water are a health risk if the bacteria are aerosolized (e.g., in an air conditioning system or a shower) and then inhaled. Inhalation can result in a type of pneumonia known as Legionnaires disease.

Health Effects

Legionnaire's Disease, a type of pneumonia

EPA Data Source: Legionella

EPA Definitions:

1Maximum Contaminant Level Goal (MCLG) - The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.

Maximum Contaminant Level (MCL) - The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.

Maximum Residual Disinfectant Level Goal (MRDLG) - The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.

(TT) Treatment Technique - A required process intended to reduce the level of a contaminant in drinking water.

Maximum Residual Disinfectant Level (MRDL) - The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.