Nitrate contamination invegetables grown inPunjab: An imminenthuman health risk Muhammad Mubashir, Saeed A.Malik,Tariq M. Ansari and Aleem A. Khan
All living systems need nitrogen for the production of complexorganic molecules, such as proteins, nucleic acids, vitamins,hormones and enzymes. Due to the intense use of syntheticnitrogen fertilizers and livestock manure in modern dayagriculture, food (particularly vegetables) and drinking water maycontain higher concentrations of nitrate than in the past. Themean intake of nitrate per person in Europe is about 50-140 mg/dayand in the US about 40-100 mg/day. In the proximal small intestine,nitrate is rapidly and almost completely absorbed (bio-availabilityat least 92%). In humans, approximately, 25% of the nitrateingested is secreted in saliva, where some 20% (about 5-8% of thenitrate intake) is converted to nitrite by commensal bacteria. Thenitrite so formed is then absorbed primarily in the small intestine(Bartikiavichiute et al., 1991).Nitrogen is a vitally important plant nutrient, the supply of whichcan be controlled by man. Plants primarily in the form of nitratesabsorb it through smaller amount of other forms can be absorbedincluding the ammonium N using the energy provided byphotosynthesis. When nitrogen supplies are adequate andconditions are favorable for growth. Proteins are formed from themanufactured carbohydrates when plants are deficient in nitrogen.They become stunted and yellow in appearance (Bernstein, 1964).
Researchers have studied the link between nitrate rich fruit andvegetable and gullet cancer which claims the lives of more than30,000 people in the UK every year in reported cases of cancer,which affects the three times, as many men, as women have treblein the last 20 years (Barker et al., 1979).Elevated levels of nitrate in drinking water and eatable plants havethe negative impact on human health (Niecko et al., 2001).Nitrates have also been linked to miscarriages in women and anincreased risk of non-Hodgkin’s lymphoma (Jasa et al., 1988) andbladder and ovarian cancers (Townsend et al., 2003; Ward et al.,2005).Nitrate had been found to react with amines and amides to formnitrosamines and nitrosamides, which have been found to inducecancer in rodents. There is no other group of carcinogens knownthat have the ability to induce such a wide variety of tumors inorgans, ranging from lung, oral, brain, skin, leukemia, and bladder(Tannehill et al., 1996).During an epidemiological survey, a high percentage (41%) ofgoiter was prevalent among the children aged 6-14 years in thevillages with nitrate contamination (Gatseva et al., 1998).
Collection & Analysis of vegetable samplesVegetable samples were taken from selected sites and wereimmediately transported to laboratory in proper leather labeledpaper bags that allow for transpiration; this reduces the possibilityof rooting.Summer and winter vegetables were collected from all 35 districtsin Punjab, Pakistan.In each district, a sum of nine, market based and agricultural fieldswere selected to collect seasonal vegetable samples for nitrateassessment.The samples include, Carrot, Eggplant, Okra, Onion, Potato,Radish, Spinach, Squash, Tomato, and Turnip.Total number of vegetable samples = 35 x 9 x 2 = 630Multivariate statistics were performed as, mean and standarderror of mean, Analysis of variance, Repeated analysis and Duncanmultiple range test (DMRT).
Research Rationale and Hypothesis.Nitrate contamination is a growing concern with the initiativesfollowing green revolution in agricultural development. The fastgrowing world human population means more and more foodrequired, in a scenario of frequently changing global climatepattern and weather regimes. In order to cope with the prolificdemand for food, in the wake of global warming phenomena, hasput great burden on the present agricultural practices to enhancecrop yield per acre. There is dire and ever growing demand to getmultiple crops from the same patch of land and with high cropyielding ratio.The bioecological system is unable to provide ample organicbased fertilizers to cope with the prolific food demand of the worldpopulation, which almost approaching 7 billion people, as we talk,hence requires to supplement the use of chemical fertilizers totackle the issue. Consequently, the application of nitrogenfertilizers is on the inexhaustible increase. There have been a fewstudies done on assessment of the use of nitrogen and itsprobable effects on human health, in particular, and on thebiodiversity and bioecological systems, in general.Thereby, a study was designed to assess the nitrates levels, invegetables being grown and sold in different markets.
Conclusion.The population of Pakistan is expandingat the rate of more than 3% per annumnecessitating demand for more food andsubsequent increase in the use offertilizers. There is a need for propereducation of the framers regarding thejudicious use of fertilizers and they mustbe made aware of the detrimentaleffects, before using such fertilizers (a)whether there is any deficiency in thesoil and (b) the requirement of the cropto be raised.
Precautions and Preventions.Nitrate-nitrogen accumulates from sunset to sunrise and is reduced fromsunrise until late in day. Effective control of the nitrate-nitrogen content ofvegetable products can be achieved simply by adjusting the time of harvestat the afternoon hours. The temperature effects the nitrate accumulationbecause it affects the processes of absorption, translocation andassimilation and varies from species to species (Wiebe, 1993; Nedwell,1994).Vegetables are the primary dietary source of nitrate; however, when theyare taken with vitamin C and other nitrosation inhibitors (Bartsch andFrank, 1996) and, therefore, high intakes may not result in high rates offormation of N-nitroso compounds.Leafy green vegetables and some root crops assimilate nitrate naturally.Fertilizer applied in excess may result in the accumulation of large amountof nitrate in some vegetables. Eating these vegetables contribute to thedaily ingest of nitrate.