Fresh vegetables stored for a long time, rotten vegetables and placed over a long time of cooked vegetables, the original dish of nitrate in nitrate reducing bacteria under the action can be converted to nitrite.
The vegetables nitrate containing high is a global problem, all over the world appeared nitrate in vegetables containing high amounts of situation. Nitrate itself is not toxic. Prolonged storage of fresh vegetables, rotten vegetables and put long cooked vegetables, the original vegetable nitrate in nitrate reducing bacteria can be transformed into nitrite.
Saliva and stomach bacteria can also be the reduction of nitrate to nitrite. Nitrite may influence hemoglobin oxygen delivery ability. Most people due to consumption of nitrate and nitrite containing higher amounts of vegetables and suffering from "blue baby syndrome" opportunity is extremely small, in very few circumstances baby to eat the high nitrite content of vegetables, can cause "blue baby syndrome".
Nitrite to the adult lethal dose, different studies showed the results do not. Studies suggest that human intake of 0.2 ~ 0.5 grams can cause poisoning, 3 grams can be lethal.
Use nitrate tester to check your vegetable and fruits nitrate level, whether they are in a healthy amonut.