September 8, 2011

Entry #2: September 5-9, 2011

Nitrogen: nutrient and contaminant

          This week in class, we examined how environmental nutrients can have an impact on human health. Specifically, we discussed the ways in which nitrogen in the form nitrogen oxides can influence body. Although the element nitrogen is a key building block for living matter, in certain molecular forms, it can also tear life apart.

          In its elemental form, nitrogen is a colorless, odorless, harmless gas that composes roughly 78% by mass of the air in earth’s atmosphere. However, when nitrogen becomes fixed – combines with other elements – it forms more reactive molecules that can influence human health. One such group of reactive, nitrogen containing molecules is nitrogen oxides, which include nitrates, nitrites, and nitrogen dioxide. For human beings, the excessive consumption of or exposure to nitrogen oxides can prove to be detrimental to ones health.

          Nitrogen oxides are formed naturally in the atmosphere with the help of lightning. The electrical energy from lightening causes diatomic oxygen and nitrogen molecules to disassociate. The newly freed oxygen and nitrogen atoms are then able to interact with each other and form nitric oxide and nitrogen dioxide. Nitrogen dioxide then combines with water vapor in the atmosphere to make nitric acid, which falls to the earth in the form of acid rain, where it enters the soil. Once in the soil, the weakly acidic nitric acid solution is neutralized and the nitrogen eventually takes the molecular form of nitrate (Nitrogen (N), 2011). As much as 25% of the total amount of nitrate in the environment is comes from the atmosphere (Gupta et al., 2008).

          Nitrogen oxides also enter the environment through anthropogenic processes like excessive application of chemical fertilizers in the agricultural process. Nitrates in the fertilizer enter the soil, interact with water, and end up contaminating the ground water of the immediate area. Developing countries like India are especially likely to utilize nitrate-containing fertilizers on their crops. The irrigated soils of developing countries located in humid, tropical environments facilitate the infiltration of nitrates into the ground water (Singh et al., 1995). Another anthropogenic means by which nitrogen oxides are introduced into the environment is through the combustion of fossil fuels.

          Regardless of the mechanism by which the nitrogen oxides were made, or whether they were ingested through drinking water, eating food, or inhaling air, once the nitrogen oxides find their way into one’s body, they begin to wreak havoc at the molecular level and cause numerous health problems. The primary mechanism by which nitrogen oxides cause health problems is through the ingestion of nitrates. Symptoms of methemoglobinemia are expressed after the consumption of water with high levels of nitrate. Methemoglobinemia occurs when nitrate is reduced to nitrate by saliva microflora and forms methemoglobin via the oxidation of the ferrous ion of hemoglobin into the ferric state (Gupta et al., 2008). This disease reduces the ability of red blood cells to carry oxygen throughout the body (Methemoglobinemia, 2011). Unfortunately, infants are most susceptible to this ailment do to their small body size, which means that they end up consuming more water per unit weight than an adult. Additionally, the fluid in the stomach of infants is less acidic than that of most adults, which results in better living conditions for the nitrate reducing microflora (Gupta et al., 2008).

          Nitrate ingestion can also result in respiratory problems like asthmatic attacks, cause hypertension in the cardiovascular system, foul-up the bowels by inducing diarrhea, lead to type-1 diabetes, and cause goiter. Sadly, infants are not excluded from these nitrate-induced ailments and are also at risk of having a low birth weight, and struggling to gain weight. However, children sometimes do not live to suffer these ailments since nitrate consumption of the mother can lead to stillbirth and spontaneous abortion. Nitrates also function as procarcinogens since they form carcinogenic compounds when they react with other molecules like amines and amides (Gupta et al., 2008).

          Developing countries are especially at risk for nitrogen oxide contamination of the atmosphere. More than half of the populations of developing countries are forced to meet their domestic energy needs through the utilization of coal, wood, and dung. Frequently, these fuels are burned on rudimentary and primitive stoves in the rural households, which results in incomplete combustion and contaminates the air in the household. This phenomenon is known as indoor air pollution and contaminates the atmosphere with many different harmful molecules including nitrogen oxides, which lead to the horrendous health problems described above (Bruce et al., 2000).

          The ingestion of nitrate is clearly a problem, not just in developing countries like India, but also in nations all around the world. Fortunately, measures can be taken to prevent unnecessary suffering from these pernicious nitrogen oxides. The ultimate solution is to purify all of the water for consumptive and agricultural use through the use of the denitrification processes. Unfortunately, this method is very costly and cannot be implemented on a large scale (Gupta et al, 2008). There are other, less expensive alternatives to preventing nitrate health issues. Farmers can fertilize their fields more conservatively and not inject copious amounts of nitrates into the environment. Women also can prevent health problems in their children by breast-feeding until the children are at least six months old. This would limit the child to nitrate exposure in the drinking water used to mix baby formula, and improve the overall health of the child since natural milk contains nutrients and antibodies important for developing a healthy body.

         

References

Bruce, N., Perez-Padilla, R., & Abalak, R. (2000). Indoor air pollution in developing countries: a

     major environmental and public health challenge. Bulletin of the World Health Organization, 78(9), 1078-1092.

Gupta, S.K., Gupta, R.C., Chhabra, S.K., Eskiocak, S., Gupta, A. B., &Gupta, R. (2008). Health issues related to N pollution in water and air. Current Science, 94(11), 1460-1477.

Methemoglobinemia. (2011). In Encyclopedia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/378362/methemoglobinemia

Nitrogen (N). (2011). In Encyclopedia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/416180/nitrogen

Singh, B., Singh, Y., & Sekhon, G. S. (1995). Fertilizer-N use efficiency and nitrate pollution of groundwater in developing countries. Journal of Contaminant Hydrology, 20(3-4), 167-184.