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Nitrate and Nitrite Levels of Potable Water Supply in Warri, Nigeria: A Public Health Concern? Professor Orish Ebere ORISAKWE PhD,ERT,MRSC Dept of Clinical Pharmacy Faculty of Pharmacy University of Port HARCOURT Rivers State, Nigeria.


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Health implications of exposure to NO3 in drinking water were first reported by Comly in 1945 after observing cyanosis in infants, where well water was used in formula preparation (Comly 1945 ). In the literature survey by Walton (1951), Roe (1933) is credited with being the first to associate nitrate exposure with fatal infant Met-Hb.

SOURCES OF NITRATE Nitrate occurs naturally in soil. containing nitrogen-fixing bacteria, decaying plants, septic system effluent, and animal manure.

Other sources of nitrate include nitrogenous fertilizers and airborne nitrogen compounds emitted by industry and automobiles [U.S. Geological Survey (USGS) 1996c].

LONGEVITY OF NO3 IN GROUND WATER. Nitrate penetrates through soil and remains in groundwater for decades (Spalding and Exner 1993; USGS 1999).

FACTORS AFFECTING NO3 IN DRINKING WATER. Water from shallow wells (< 100 feet below land surface) in areas with well-drained soils and high N2 inputs (e.g., close proximity to agricultural areas) have an increased risk of exposure to NO3-rich groundwater. Agricultural activities are the largest non-point sources of NO3 contamination of groundwater because of greater use of N2 fertilizer on crops and the trend toward concentrated animal farming (Spalding and Exner 1993; USGS 1996b). Private wells are shallower and closer to sources of NO3 contamination, public supply wells are in deeper groundwater aquifers where contamination is less likely (USGS 1996a).

MAXIMUM CONTAMINANT LIMIT (MCL) World Health Organization (WHO) and European Union maximum admissible concentration standards is 50 mg/l nitrate ion. The U.S. Environmental Protection Agency [EPA] drinking water standard is 10 mg/l as nitratenitrogen, roughly equivalent to 45 mg/l nitrate ion. The MCL for nitrate in drinking water was set at 10 mg/L nitrateâ&#x20AC;&#x201C;nitrogen (NO3â&#x20AC;&#x201C;N) or 45 mg/L nitrate (NO3).

NITRATE TOXICITY Nitrate toxicity is related primarily to the in vivo conversion to nitrite after ingestion [(NAS) 1977; Swann 1975]. NO3 NO2 OXIDISE Hb to [Met Hb] overwhelms the reduction capacity of the cells (Jaffe 1981; Swann 1975 (Bruning-Fann & Kaneene, 1993).

HEALTH EFFECTS OF NITRATES Some reports have suggested an association between exposure to NO3 in drinking water and spontaneous abortions, intrauterine growth restriction, and various birth defects (CDC, 1996; Croen et al, 2001). Coss et al (2004), suggest that chronic exposure to drinking water NO3 at levels below the MCL NO3 -N (10 mg/liter) is not associated with pancreatic cancer.

HEALTH EFFECTS OF NITRATES CONTINUED Turkdogan et al. investigated NO3 â&#x20AC;&#x201C; NO2 levels in some drinking water in Van, an endemic upper gastrointestinal (esophageal and gastric) cancer region of Eastern Turkey (2003). Found that NO3 â&#x20AC;&#x201C; NO2 is significant in the development of endemic upper gastrointestinal (esophageal and gastric) cancers in the Van region of Turkey.

Nitrate exposure can lead to hypertrophy of the thyroid due to inhibition of uptake of iodine by the thyroid. van Maanen et al 2002 observed this effect at drinking water nitrate concentrations above the guideline value of 50 mg/L, whereas a German study demonstrated this effect at nitrate levels as low as 22.5 mg/L.

CONTROVERSY ON THE HEALTH EFFECTS OF NITRATES Although the role of NO3 in drinking water as a risk for cancer is controversial, high levels of NO3 and nitrosamines in drinking water have been associated with increased mortality (Cantor, 1997) and increased incidence of some cancers and lesions (Gulis et al, 2002).

Map of Nigeria in Africa showing the nine states of the Niger Delta

LOCATION OF NIGER DELTA The Niger Delta is located in Atlantic Coast of southern Nigeria where River Niger divides into numerous tributaries. 2nd largest delta in the world with a coastline spanning about 450 Km terminating at the Imo River entrance. The region spans over 20,000 square Km and it has been described as the largest wetland in Africa and among the three largest in the world. About 2,370 square Km of the Niger Delta area consist of rivers, creeks and estuaries and while stagnant swamp covers about 8600 square Km.

The major drainage systems of the Niger Delta include those of; a) the Niger River, b) the Ase River, c) the Ethiope River, d) the Warri River, e) the Orashi River, f) the Sombreiro River, and g) the Imo River.


Flooding in one of the major cities n the Niger Delta. This can have negative impact on hand dug wells and other surface water resources.





River bank: Notice the refuse dumpsite

Typical living condition in rural Niger Delta.

Just for the sake of water

Niger Delta women and children head home after fetching water from the river

Children carry water near gas flares in Niger Delta

Water everywhere but little to drink

Water â&#x20AC;&#x153;big issueâ&#x20AC;? in the Niger Delta

Seeing pipe borne water for the first time

Harvesting rain water.

Rainwater to the rescue of majority of the local Niger Delta

HEALTH PROBLEMS IN THE NIGER DELTA Spontaneous abortion , ectopic pregnancy (Gbaroro & Igbafe, 2002), malignant lymphomas (Omoti, 2006 Omoti & Halim, 2005), soft tissues sarcomas (Seleye-Fubara et al 2005) have been reported in Niger Delta of Nigeria.


So where is the train heading now

AIMS AND OBJECTIVES â&#x20AC;˘ The present work is aimed at investigating the impact of industrialization on the nitrate and nitrite burden of potable water supply in Warri.


A total of 30 water samples were divided into two subsets of 15, 5 each of surface water shallow well and borehole from INDUSTRIAL AREAS and 15, 5 each of surface water, shallow well and borehole from MARKET AREAS were collected. Hand dug-wells are between 16-45m deep . Boreholes (150 – 200m) situated in unconfined sedimentary.

NO3 and NO2 assay NO3 with Bruccine colorimetric method of the Association of Official Analytical Chemists (1980). NO2 was spectrophotometrically determined according to the Greiss method of Montgomery and Dymock (1961)

Table 1: Nitrates and Nitrites in water samples from industrialized area Location of sampling point

Nitrate mg/l

Nitrite mg/l

Ekpan River Ekpan well Ekpan borehole

1.43 1.18 2.63

0.18 0.12 0.03

Ubeji River Ubeji Well Ubeji borehole

4.28 1.12 0.18

1.34 0.14 0.03

NPA River NPA well NPA borehole

1.08 1.48 1.13

0.42 0.32 0.08

Aladja River Aladja well Aladja borehole

0.70 1.82 1.20

0.25 0.15 0.03

Otokutu River Otokutu well Otokutu borehole

0.40 1.42 1.10

0.30 0.08 0.06

Table 2: Nitrate and Nitrite in water samples from market area Location of sampling point

Nitrate mg/l

Nitrite mg/l

Agbarho River Agbarho well Agbarho borehole

0.93 2.40 1.18

0.12 0.18 0.02

Udu River Udu well Udu borehole

8.36 2.17 1.35

1.12 1.14 0.10

Marcava River Marcava well Marcava borehole

0.22 2.20 1.40

0.16 0.14 0.08

Pessu River Pessu well

4.29 2.28 1.27

0.62 0.60 0.06

4.65 2.19 1.38

0.64 1.10 0.05

Pessu borehole Enerhem River Enerhem well Enerhem borehole

RESULT: NO3 and NO2 industrialized area Table 1 shows the nitrate and nitrite level in water samples from the industrialized area of the city. Surface water from Ubeji had highest level of nitrate and nitrite 4.28 and 1.34 mg/l respectively whereas Ubeji borehole had lowest level of nitrate 0.18 mg/l. Aladja and Ubeji bore holes showed lowest levels of nitrite of 0.03mg/.

NO3 and NO2 from market area Nitrate and nitrite in water samples from market area is shown in table 2. Udu River had highest nitrate level of 8.36 mg/l while lowest nitrate was found in Marcava River 0.22 mg/l. Highest level of nitrite was seen in Udu river 1.12 mg/land lowest level of nitrite was found in Agbarho borehore 0.02mg/l.

DISCUSSION According to Rim-Rukeh et al 2007 hand dug wells nitrate levels in Niger Delta ranged from 11.3 ±1.31 to 23.0 ±1.46 (mg/l) Rim-Rukeh et al 2007 river water nitrate levels in Niger Delta ranged from 20.3 ±1.18 to 28.0 ±1.52 (mg/l)

DISCUSSION Parameters RW DRY 51 – 54 ± 52.4 14.62 RAINY 20.3

39 – 50 ± 46.6

Rainwater (RW) Open-well water (OWW) Borehole water (BHW)

• Efe et al 2005

OWW BHW 51 – 53 ± 52

50.0 – 51.1 ± 50.8

Nitrate, mg/L N 12.1 – 16.0 ±

14.0 – 20.6 ±

NO3 (mg/l) of Rain water in Warri between April – October 2005 Period

NO3 (mg/L)

April-June 2005

1.50 ± 0.007 (17.76 ± 0.322)

July – August 2005

1.81 ± 0.006 (23.31± 0.000)

Sept-Oct 2005

1.13 ± 0.011 (23.16 ± 0.003)

NO3 (mg/l) of Rain water in Warri between April – October 2006 Period

NO3 (mg/L)

April-June 2006

2.14 ± 0.006 (11.13 ± 0.003)

July – August 2006

1.50 ± 0.000 (8.91 ± 0.175)

Sept-Oct 2006

1.86 ± 0.029 (6.60 ± 0.013)

Nitrate (mg/L) in packaged water in the Niger Delta


mean ÂąSEM 0.62 Âą 0.06

Range 0.0267-1.477

Rivers Ubeji and NPA had highest levels of total coliform count. Coliform pollution was least in the borehole samples.

Total Coliform Count of potable water in W arri.

80 70

Ekpan riv er Ekpan w ell Ekpan borehole Ubeji river Ubeji w ell Ubeji bor ehole Agbar ho riv er Agbar ho w ell Agbar ho borehole NPA riv er NPA w ell NPA borehole UDU riv er UDU w ell UDU borehole Markav a river Markav a w ell Markav a bor ehole Aladja riv er Aladja w ell Aladja borehole Otokutu riv er Otokutu w ell Otokutu borehole

60 50 40 30 20 10 0

Loc ation/Sampling Points.

CONCLUDING REMARKS Water samples from the market area of Warri showed higher levels of NO3 and NO2 than samples from the industrialized area Surface water and borehole water in Warri, Niger Delta seem not to contain NO3 and NO2 that exceed the US EPA or the FMEnv MCL of 10mg/l NO3- N. Satchet or packaged water in this Region also had nitrate levels lower than the MCL. Other sources of potable water like rain water from elsewhere in Niger Delta but not Warri contain NO3 levels that exceed the MCL

CONCLUDING REMARKS CONTD contrary to the claims of many, the poor health conditions of the Niger Delta people may not be completely blamed on oil producing activities since lower NO3 and NO2 were seen in the industrialized parts of Warri. indiscriminate disposal of waste and poor sanitation may be additional contributing factor of NO3 and NO2 pollution of water supply in the Niger Delta of Nigeria.

RECOMMENDATIONS need for health workers to educate the local populace on the implication of nitrate pollution and help ensure improved sanitation by disposing municipal wastes and sewages so that runoff waters will not pollute the potable waterways.

Acknowledgements: Nduka John my PhD student. Photographers who took the shots used in this presentations.

Nitrate and Nitrite Levels of Potable Water Supply in Warri Nigeria  
Nitrate and Nitrite Levels of Potable Water Supply in Warri Nigeria  

Orish Ebere Orisakwe - Nitrate and Nitrite Levels of Potable Water Supply in Warri Nigeria