Review: Drinking Water Nitrate and Human Health: An Updated Review Nitrate levels in water resources have increased globally due to agricultural practices. The regulatory limit for nitrate in drinking water was set to prevent infant methemoglobinemia but did not consider other health effects. Nitrate can form N-nitroso compounds (NOC), which are carcinogens and teratogens. Over 30 epidemiologic studies since 2005 have evaluated nitrate and health outcomes, with the strongest evidence linking nitrate to colorectal cancer, thyroid disease, and neural tube defects. Many studies found increased risk with nitrate levels below regulatory limits. Future studies should improve exposure assessment and consider individual factors affecting endogenous nitrosation. In the U.S., 45 million people used private wells, which are not regulated. Nitrate levels in groundwater were three times the national average. In Europe, the Nitrates Directive reduced agricultural nitrate pollution. Nitrate levels in groundwater in some countries have decreased, while others remain high. Nitrate levels in drinking water in Europe are generally low, with some areas exceeding the MCL. Exposure assessment in epidemiologic studies is challenging, especially for private well users. Advances in modeling and geographic-based approaches improve predictions of nitrate exposure. Nitrate is absorbed in the gastrointestinal tract and can form NOC in the oral cavity. Under acidic conditions, nitrite can form nitrous acid, leading to NO and NO2. NO is involved in various physiological processes, while NOC are potent carcinogens and teratogens. Endogenous nitrosation can be inhibited by dietary compounds like vitamin C and polyphenols. Nitrate intake from food and water can lead to NOC formation, increasing cancer and birth defect risks. Dietary nitrate intake is a key factor in NOC formation. Red and processed meat consumption increases NOC levels, contributing to colon cancer risk. Methemoglobinemia in infants is caused by nitrate in water used for formula. Nitrate levels in private wells can exceed the MCL, leading to methemoglobinemia. Studies have found elevated methemoglobin levels in infants exposed to high nitrate levels. Adverse pregnancy outcomes, including spontaneous abortion, preterm birth, and congenital malformations, are linked to nitrate exposure. Studies show increased risk of birth defects with higher nitrate levels. Nitrate levels in drinking water are associated with increased risk of congenital malformations, particularly in the central nervous system. Cancer risk is associated with nitrate exposure. Studies show increased risk of bladder, thyroid, and kidney cancer with higher nitrate levels. Nitrate levels in drinking water are linked to increased risk of colorectal cancer. Nitrate intake from food and water is a risk factor for cancer. Animal studies show that in utero exposure to nitrosamides can cause brain tumors. Nitrate and nitrite intake during pregnancy is linked to increased risk of childhood brainReview: Drinking Water Nitrate and Human Health: An Updated Review Nitrate levels in water resources have increased globally due to agricultural practices. The regulatory limit for nitrate in drinking water was set to prevent infant methemoglobinemia but did not consider other health effects. Nitrate can form N-nitroso compounds (NOC), which are carcinogens and teratogens. Over 30 epidemiologic studies since 2005 have evaluated nitrate and health outcomes, with the strongest evidence linking nitrate to colorectal cancer, thyroid disease, and neural tube defects. Many studies found increased risk with nitrate levels below regulatory limits. Future studies should improve exposure assessment and consider individual factors affecting endogenous nitrosation. In the U.S., 45 million people used private wells, which are not regulated. Nitrate levels in groundwater were three times the national average. In Europe, the Nitrates Directive reduced agricultural nitrate pollution. Nitrate levels in groundwater in some countries have decreased, while others remain high. Nitrate levels in drinking water in Europe are generally low, with some areas exceeding the MCL. Exposure assessment in epidemiologic studies is challenging, especially for private well users. Advances in modeling and geographic-based approaches improve predictions of nitrate exposure. Nitrate is absorbed in the gastrointestinal tract and can form NOC in the oral cavity. Under acidic conditions, nitrite can form nitrous acid, leading to NO and NO2. NO is involved in various physiological processes, while NOC are potent carcinogens and teratogens. Endogenous nitrosation can be inhibited by dietary compounds like vitamin C and polyphenols. Nitrate intake from food and water can lead to NOC formation, increasing cancer and birth defect risks. Dietary nitrate intake is a key factor in NOC formation. Red and processed meat consumption increases NOC levels, contributing to colon cancer risk. Methemoglobinemia in infants is caused by nitrate in water used for formula. Nitrate levels in private wells can exceed the MCL, leading to methemoglobinemia. Studies have found elevated methemoglobin levels in infants exposed to high nitrate levels. Adverse pregnancy outcomes, including spontaneous abortion, preterm birth, and congenital malformations, are linked to nitrate exposure. Studies show increased risk of birth defects with higher nitrate levels. Nitrate levels in drinking water are associated with increased risk of congenital malformations, particularly in the central nervous system. Cancer risk is associated with nitrate exposure. Studies show increased risk of bladder, thyroid, and kidney cancer with higher nitrate levels. Nitrate levels in drinking water are linked to increased risk of colorectal cancer. Nitrate intake from food and water is a risk factor for cancer. Animal studies show that in utero exposure to nitrosamides can cause brain tumors. Nitrate and nitrite intake during pregnancy is linked to increased risk of childhood brain