Page 11: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Ammonia
Part II. Science and Technical Considerations - Continued
Ammonia is formed endogenously and is present in the human body at concentrations significantly higher than those typically found in drinking water. Ammonia is also efficiently metabolized by the body, and little information concerning the toxicity of ammonia through the ingestion route of exposure was found in the literature.
There are no validated data available regarding carcinogenic effects of ammonia or ammonium compounds in humans following oral exposure. Ammonia has not been classified by IARC according to its carcinogenicity.
In humans, most health effects reported as a result of ammonia exposure are associated with exposure through inhalation, which is not a relevant mode of action in the consideration of toxicity associated with drinking water. Although ingestion of concentrated ammonia causes irritation and damage to the mouth, throat and gastrointestinal tract, these effects are unlikely to occur at the concentrations of ammonia found in drinking water (Klendshoj and Rejent, 1966; Klein et al., 1985; Lopez et al., 1988).
In animals, acute and short-term exposure studies suggest that the respiratory tract is the most sensitive target of toxicity. Available scientific evidence does not suggest that ammonia is carcinogenic in animals. However, well-designed studies have not been conducted, and the relevance of the available data to assess the cancer risk of oral exposure to ammonia is uncertain.
Based on the lack of an appropriate endpoint from the ingestion of ammonia, the lack of sufficient evidence of systemic effects in humans, as well as limited relevant studies in experimental animals, no health-based guideline can be derived for ammonia in drinking water.
The World Health Organization has assessed the toxicity of ammonia in drinking water and concluded that a guideline value need not be established, based on the absence of health effects at the concentrations to be expected in drinking water (WHO, 2003).
The U.S. EPA has not established a regulatory limit for the presence of ammonia in drinking water. In Australia, an aesthetic limit (based on the corrosion of copper pipes and fittings) has been established at 0.5 mg/L, measured as ammonia. No health-based guideline value has been established for ammonia (NHMRC, 2004).
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