ABSTRACT
Nitrate occurs as a contaminant in drinking water primarily from groundwater and wells, and in high concentrations it has harmful biological effects. There are many sources of nitrogen, both natural and anthropogenic (i.e. caused by human kind), that could potentially lead to the pollution of groundwater with nitrates. However, the anthropogenic sources can give rise to dangerous levels of nitrate. Waste materials are key anthropogenic sources of nitrate contamination of groundwater. For example, fertilized agricultural lands, industrial waste water, animal feedlots, some septic tanks and urban drainage are well known sources of nitrates. In terms of food production, the anti-microbial activities of nitrate and nitrite have been recognized for centuries and are still used for the preservation of meat produce (Deng-sheng et al. 2006; Wayne et al. 1991; King et al. 2000). Nitrate itself is not carcinogenic, but instead acts as a procarcinogen, meaning that it reacts with other chemicals to form carcinogenic compounds via a multiple step process. Nitrate is converted into nitrite after consumption and the nitrite reacts with natural or synthetic organic compounds known as secondary amines or amides in food or water to form new combinations of either nitrosamines or nitrosamides, many of which are carcinogens (Mirvish 1991). However, two of the well known conditions associated with inadvertent and excessive nitrate ingestion are the development of methemoglobinemia and goitre, as described in detail below.
