Excessive consumption of nitrogen chemical fertilizers by farmers can contaminate agricultural crops and groundwater and/ or drinking water with nitrate. In the case of agricultural crops, vegetables and fruits are the main sources of nitrate, which account for more than 80% of the average nitrate entering the human body. In general, according to the path of nitrate movement, the use of leaves, stems and roots of the agricultural crops contain more nitrate respectively, and those agricultural crops whose fruits are consumed have less nitrate.
It is noteworthy that the residual nitrate in some cases in vegetables, especially spinach and lettuce is more than sausages. In addition to the amount of fertilizer, plant cultivar, type of cultivation, climatic conditions, harvest time and post-harvest storage are effective in nitrate accumulation in plants.
Moreover, the nitrate accumulation in plants is indirectly related to the activity of reductase enzyme so that with the decrease in the enzyme activity, the rate of nitrate accumulation would increase. In addition to environmental conditions such as the light intensity, the activity of this enzyme is also dependent on the presence of some elements such as molybdenum and manganese, and deficiency of such elements would reduce this enzyme activity. The mechanism of action of the enzyme requires that in the first stage, nitrate to reduce to nitrite by nitrate reductase enzyme and then nitrite is reduced to ammonium by nitrite reductase enzyme and enters the amino acid production pathways through a process.
According to studies on ground- and drinking waters, the amount of nitrate in some drinking water sources in different cities of Iran is higher than the permissible limit. Therefore, controlling the nitrate concentration in water is important as one of the dangerous factors involved in carcinogenesis (colon, ovary, kidney and bladder).
Harmful effects of nitrate on human health
According to the World Health Organization (WHO), the acceptable and safe daily intake of nitrate is 0-3.7 mg / kg body weight for adults.
Nitrate entering the human body is converted to nitrite through processes, following of which the nitrite is combined with amines to form nitrosamine, a carcinogen.
During the storage of canned food with high levels of nitrate, the tin used to cover the cans is released and after entering the food and human consumption, it causes eye irritation, headache, abdominal pain, dizziness as well as breathing disorders.
If the infant formula milk is made using drinking water containing a higher level of nitrate than 50 mg / l, which is the permissible level as prescribed by the Iranian Standards Institute, there would be the risk of infants developing methemoglobinemia or bruised neonatal syndrome.
Recommendations to decrease the nitrate entering the body
Because nitrate entry through food and drinking water is unavoidable, the best solution is to prevent the nitrate from entering the body at higher than the permissible levels.
Solutions at farms
• Planting cultivars that absorb less nitrate.
• Proper management of nitrogen fertilizers, so that in addition to avoiding overdosing, the time of fertilizer application is also considered. Nitrate accumulation is higher in cold seasons due to reduced light intensity, shorter day length and reduced reductase activity.
• Supply of elements such as molybdenum and manganese because the lack of these elements causes the nitrate accumulation in plants.
• Harvesting crops, especially leafy vegetables, in the afternoon. This allows the enzyme reductase to function throughout the day resulting in reduced nitrate accumulation.
Solutions at home
• Rinsing agricultural products and placing them in 20% vinegar solution for 10 minutes will lead to significant reduction in the amount of nitrate.
• Reducing the nitrate levels by boiling the agricultural products instead of frying them.
• Brushing and using mouthwash as this will reduce the conversion of nitrate to nitrite by reducing the microbial load present in the mouth.