Nitrate contamination in vegetables grown

in Punjab: An imminent human

health risk

Muhammad Mubashir, Saeed A. Malik, Tariq M.

Ansari and Aleem A. Khan

All living systems need nitrogen for the production of complex organic molecules, such as proteins, nucleic acids, vitamins, hormones and enzymes. Due to the intense use of synthetic nitrogen fertilizers and livestock manure in modern day agriculture, food (particularly vegetables) and drinking water may contain higher concentrations of nitrate than in the past. The mean intake of nitrate per person in Europe is about 50-140 mg/day and in the US about 40-100 mg/day. In the proximal small intestine, nitrate is rapidly and almost completely absorbed (bio-availability at least 92%). In humans, approximately, 25% of the nitrate ingested is secreted in saliva, where some 20% (about 5-8% of the nitrate intake) is converted to nitrite by commensal bacteria. The nitrite so formed is then absorbed primarily in the small intestine (Bartikiavichiute et al., 1991).

Nitrogen is a vitally important plant nutrient, the supply of which can be controlled by man. Plants primarily in the form of nitrates absorb it through smaller amount of other forms can be absorbed including the ammonium N using the energy provided by photosynthesis. When nitrogen supplies are adequate and conditions are favorable for growth. Proteins are formed from the manufactured 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 and vegetable and gullet cancer which claims the lives of more than 30,000 people in the UK every year in reported cases of cancer, which affects the three times, as many men, as women have treble in the last 20 years (Barker et al., 1979).

Elevated levels of nitrate in drinking water and eatable plants have the negative impact on human health (Niecko et al., 2001).

Nitrates have also been linked to miscarriages in women and an increased risk of non-Hodgkin’s lymphoma (Jasa et al., 1988) and bladder and ovarian cancers (Townsend et al., 2003; Ward et al., 2005).

Nitrate had been found to react with amines and amides to form nitrosamines and nitrosamides, which have been found to induce cancer in rodents. There is no other group of carcinogens known that have the ability to induce such a wide variety of tumors in organs, ranging from lung, oral, brain, skin, leukemia, and bladder (Tannehill et al., 1996).

During an epidemiological survey, a high percentage (41%) of goiter was prevalent among the children aged 6-14 years in the villages with nitrate contamination (Gatseva et al., 1998).

Collection & Analysis of vegetable samples Vegetable samples were taken from selected sites and were immediately transported to laboratory in proper leather labeled paper bags that allow for transpiration; this reduces the possibility of rooting.

Summer and winter vegetables were collected from all 35 districts in Punjab, Pakistan.

In each district, a sum of nine, market based and agricultural fields were selected to collect seasonal vegetable samples for nitrate assessment.

The samples include, Carrot, Eggplant, Okra, Onion, Potato, Radish, Spinach, Squash, Tomato, and Turnip.

Total number of vegetable samples = 35 x 9 x 2 = 630

Multivariate statistics were performed as, mean and standard error of mean, Analysis of variance, Repeated analysis and Duncan multiple range test (DMRT).

 

Research Rationale and Hypothesis.Nitrate contamination is a growing concern with the initiatives following green revolution in agricultural development. The fast growing world human population means more and more food required, in a scenario of frequently changing global climate pattern and weather regimes. In order to cope with the prolific demand for food, in the wake of global warming phenomena, has put great burden on the present agricultural practices to enhance crop yield per acre. There is dire and ever growing demand to get multiple crops from the same patch of land and with high crop yielding ratio. The bioecological system is unable to provide ample organic based fertilizers to cope with the prolific food demand of the world population, which almost approaching 7 billion people, as we talk, hence requires to supplement the use of chemical fertilizers to tackle the issue. Consequently, the application of nitrogen fertilizers is on the inexhaustible increase. There have been a few studies done on assessment of the use of nitrogen and its probable effects on human health, in particular, and on the biodiversity and bioecological systems, in general.

Thereby, a study was designed to assess the nitrates levels, in vegetables being grown and sold in different markets.

Nitrate Concentration(ppm) In Winter Vegetables Of Punjab Province

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D. Spinich

H. Spinich

B.Pur B.NagrRykhn DgkhnLayh M.garhR.pur F.abadJhang NkanaT.T.sing G.walaGujrat H.abadMbdin Nr.walS.kot KasurLahore OkaraSh.pura K.walLodhran MultanPakpat S.walVehari AttockCk.wal JehlumR.pindi BakharKhushab M.waliSargodha

Conclusion.  The population of Pakistan is expanding at the rate of more than 3% per annum necessitating demand for more food and subsequent increase in the use of fertilizers. There is a need for proper education of the framers regarding the judicious use of fertilizers and they must be made aware of the detrimental effects, before using such fertilizers (a) whether there is any deficiency in the soil and (b) the requirement of the crop to be raised.

Precautions and Preventions.Nitrate-nitrogen accumulates from sunset to sunrise and is reduced from sunrise until late in day. Effective control of the nitrate-nitrogen content of vegetable products can be achieved simply by adjusting the time of harvest at the afternoon hours. The temperature effects the nitrate accumulation because it affects the processes of absorption, translocation and assimilation and varies from species to species (Wiebe, 1993; Nedwell, 1994).

Vegetables are the primary dietary source of nitrate; however, when they are taken with vitamin C and other nitrosation inhibitors (Bartsch and Frank, 1996) and, therefore, high intakes may not result in high rates of formation 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 amount of nitrate in some vegetables. Eating these vegetables contribute to the daily ingest of nitrate.