Abstract:
Bromide (Br-) concentrations (mg/L) in groundwater range from no observed adverse effect levels
(NOAEL), which is considered safe, and increase to constituent of concern (COC) when the concentrations
approach the recommended maximum levels for safety, and to potentially hazardous chemical constituent
when the concentrations exceed the recommended safe levels. The default recommended NOAEL of less
than or equal to 0.01 mg/L was validated with the highly sensitive chicken embryo model. Chronic and acute
exposure to Br- in groundwater can induce negative consequences, which include hypothyroidism, reduced
production and Br- accumulation in organs and secretion in milk, depending on the type of livestock and their
physiological state, and potential interactions with environmental factors. Bromide competes with chloride
(Cl-) and infiltrates the Cl- space, has a relatively long half-life in proportion to the ingestion rate, and a low
renal clearance rate of approximately 5% of ingestion, leading to an accumulation in the body. The most
vulnerable livestock are neonatal and suckling animals, those with a high water intake, such as during
lactation, or in an adverse environment, and because of chronic exposure. The recommendation is to include
Br- in chemical analysis of water quality and to assess the potential risk to livestock.
