Potential Risk of Lead Toxicity from Bottled Water in Uganda

ABSTRACT

Background: Lead toxicity has serious adverse effects on health including predisposition to kidney and central nervous system disorders especially in infants and children. A potential source of lead toxicity is the consumption of fluids with high concentrations of lead. The lack of evidence of the purity of bottled water with respect to the presence or absence of lead hence exposing Ugandans to lead toxicity necessitated this study. 

Objective: To assess the presence of lead metal in the bottled water brands sold in Kampala, Uganda. 

Methods: Atomic Absorption Spectrophotometry was used to measure the concentrations of lead in five randomly selected brands of bottled water. The results were analyzed and compared against the World Health Organization (WHO) Standards and Guidelines of drinking water. 

Results: The lead concentrations in water samples ranged from 0.00826 ├ö├ç├┤ 0.25260mg/L. Thirteen samples had their lead concentrations below the WHO guideline of 0.01mg/L whereas 17 samples had their concentrations of lead far higher than recommended. The mean and the median lead concentrations from the study were 0.0854 and 0.09091 respectively. 

 

Conclusions: Bottled water sold in Kampala contains lead levels far higher than the WHO recommended limits. This could predispose the population to adverse health effects

Key words:  Lead toxicity, Bottled water

Corresponding author: Andrew Samuel Semuyaba ├ö├ç├┤ Department of Pharmacy, Makerere University College of Health Sciences (MakCHS). Email samuelsemuyaba@gmail.com Tel +256(0)70 434 1301. Article Details: Received February 18, 2014 Reviewed March 4, 2014 Accepted March 29, 2014. 

Competing interests: The author has no competing interests to declare. 

Citation: Semuyaba Andrew Samuel, Segawa Ivan, Wamala Amir, Potential Risk Of Lead Toxicity From Bottled Water In Uganda (Original Research). MPJ 2014;12(1):e13-20.

 

 

INTRODUCTION 

The demand for quality water has been crucial to the human society dating way back to prehistoric times. Good quality drinking water can be consumed in any amount without adverse effects on health. Such water is referred to as ├ö├ç┬úpotable├ö├ç├ÿ because it is free of harmful levels of impurities such as bacteria, viruses, inorganic minerals and organic substances.  

Bottled water is ideally any potable water that is manufactured, distributed or offered for sale, which is sealed in food-grade bottles or other containers and intended for human consumption1. It is generally perceived as pure, clean, ├ö├ç┬úprotected├ö├ç├ÿ and of good quality2.  

Bottled water is from a variety of sources which include protected underground springs, wells and municipal supplies. The water is then filtered through multi-barrier sources like source protections, source monitoring, reverse osmosis and micron filtration. Further treatment may include exposure to ultraviolet light, distillation or ozonation. Water bottlers may use one or more of these processes3. 

The Ugandan market is arrayed with a wide variety of bottled water. The kinds include spring water, purified underground drinking water, naturally sparkling drinking water, mineral water and others. 

The global bottled water sales have increased dramatically over the past several decades reaching a valuation of over US$ 35 billion largely because of the public perception of purity, safety and the questionable quality of tap water as perceived by the general public4. Warburton5 reported wide usage of bottled water in infant preparations and reconstituting other foods, for cleaning contact lenses and for filling humidifiers. Consumption of bottled water in the developing countries is increasing rapidly especially among the middle and high income earners.  

Uganda has had an explosion of manufacturing industries for bottled water and small scale manufacturers that pack their water in plastic bags since the inception of the first company in 1993. In total 27 bottling companies had been certified by the Uganda National Bureau of Statistics by the end of September 2011 besides the applications of another 10 companies waiting in line6. 

However, bottled water has come under criticism in the recent years about water quality and the validity of some marketing claims. Studies conducted in Norway, Turkey and Saudi Arabia reveal that some water quality constituents in drinking water were in violation of action level parameters, especially some toxic trace elements7,8,9. In Portugal, during the cholera epidemic of 1974, bottled water was identified as one of the vehicles of transmission of vibrio cholera10. 

Often enforcement and monitoring of water quality is uneven and irregular for both tap water and bottled water because tap water contamination incidents must be reported promptly to the public and the same is true for bottled water. While contamination does occur, many instances have never received public notice. 

Contaminated drinking water can increase health risks, causing illness and death. Providing low quality drinking water would vitiate the intent behind the right to water therefore drinking water must be safe, free from microorganisms, chemical substances and radiological hazards that constitute a threat to a person├ö├ç├ûs health11. 

Studies done on lead intoxication in the United States and Britain plus other parts of the world have confirmed an association between high lead levels and serious disorders in the kidney, heart, bone marrow, gastrointestinal and central nervous systems especially in infants and children12. The assessment of presence of toxic metals in drinking water can therefore prompt the development of measures to protect consumers from lead poisoning. 

Bottled water confers a higher social status on the consumer and is frequently used in place of tap water due to convenience, pleasant taste and perceived purity 13. Whereas majority of people in Ugandan towns are increasingly using bottled water for drinking, the presence or absence to lead was unknown. The public therefore deserves assurance of the safety of the bottled water. 

METHODS

Study design and setting

The study was a cross sectional study assessing lead concentration in bottled water brands in Kampala central division. Kampala is the capital city of Uganda. It is therefore the largest business center in Uganda with over 55% of the bottled companies.

Study materials and sampling procedure

The study materials included branded certified bottled water. Expired water and that which had been tampered with were not included in the study.

Five brands of bottled water were selected at random. Six samples of each brand were bought from groceries, supermarkets and street vendors totaling up 30 samples. These were clearly marked for identification.

The clearly marked samples were taken to the Geology Department Teaching Laboratory, Faculty of Science at Makerere University for analysis. The samples were kept and transported in a cooling box. A data sheet was assigned to each collected sample and it contained information about each individual sample. A sticker was attached to each bottle containing the sample bearing a number identical to that on the data sheet assigned to that sample.

Sample analysis

Analysis of the samples was done using a Perkin-Elmer 2380 Atomic Absorption Spectrophotometre. A multi-step procedure was used for analyzing metals.

Step 1: The water samples in their original package bottles were acidified with 1ml Concentrated Nitric acid and left to stand for 24 hours to rule out possibility of contamination from laboratory containers.

Step 2: Pure lead samples were dissolved in de-ionized water to prepare lead standards. Serial dilutions of 0.2, 0.5, 1.0, 2.0 and 5.0 parts per million were made

Step 3: Involved measurement of analytical conditions which include current, wavelength, lighting mode (Pure lead Cathode lamp) and fuel gas flow specific for lead metal.

Step 4: The standards were aspirated into the Atomic Absorption Spectrophotometre each at a time and the absorbance for each was read from the machine. These values of absorbance were used to draw a calibration curve. Each aspiration of a sample was followed by aspiration of the machine with de-ionized water to prevent contamination of the following samples.

The acidified water samples were also aspirated from into the spectrophotometer each at a time and its absorbance was read from a screen on the machine. The machine was zeroed with de-ionized water after every aspiration. The aspiration of the samples was in duplicate and an average value of absorbance was determined. The concentration of lead in water samples was obtained from the calibration curve drawn in Microsoft Excel.

Data Management and analysis

The analysis results in terms of absorbance were recorded in the sample data forms. Data was entered and stored in a computer using Microsoft Excel. Percentages were calculated for samples that had concentrations of heavy metals below and above acceptable limits. The maximum acceptable level of lead was 0.01mg. The samples that had concentrations above normal levels were also compared to ascertain the brand with the highest level of heavy metals.

Ethical considerations

Permission to carry out the study was sought from the Department of Pharmacy, College of Health Sciences. The project was reviewed by the Internal Review Board and approval was granted by the Makerere University College of Health Sciences Research Ethics Committee.

Cases of substandard water that were found had their results reported to the Uganda National Bureau of Statistics.

RESULTS

The concentrations of lead determined in the 30 samples of 5 brands of bottled water bought from different outlets in Kampala divisions are summarized Table 1 with 0.00826 mg/ml as the minimum and 0.25260 mg/ml as the maximum concentration.

About 56.7 %( n=17) of the samples had a lead concentration above the WHO limit of acceptable levels of lead.

The mean and the median lead concentrations from the study were 0.0854 and 0.09091 respectively, both above the recommended WHO guideline. The means of the concentrations from the respective outlet are summarized in table 3.


DISCUSSION

Poor adherence to good manufacturing practices could have contributed to the contamination of the water in the case of this study. The PET bottles used for packaging could be thought to contribute to the contamination of the water by leaching materials into it but they do not leach lead14,15. The results from this study hence imply that water is either not purified well or gets contaminated during transit from the source to the manufacturing plant or is not purified at all before packaging. The high concentrations of lead measured are due to presence of lead in water and these results are valid. Even if the samples used in the study had been packaged in glass bottles that leach lead into the water15, the release rate of this metal is slow and does not pose a health concern. This effect can only be considered for a sound understanding of natural levels of lead in uncontaminated waters16,17,18,19.

From tables 1 and 2, 9 samples (30%) and 5 samples (16.67%) contained lead concentrations of 0.09091mg/l and 0.17355mg/l respectively. The results compare with a study to assess the levels of lead in domestic water for consumption in Kawempe Division in which water samples from springs and taps from various access points within the division were analyzed for lead by the same method of flame absorption atomic spectrophotometry. All the water samples had lead concentrations in the range of 0.0582 ÔÇô 0.1193mg/L20.

 The grocery samples were the majority of the samples with concentrations below 0.01 while the street vendor had the majority of the samples with concentrations above 0.01.               

These results suggest that some manufacturers could be bottling water from these sources without proper treatment and purification. Inference can also be made into lack of surveillance by UNBS to be a contributing factor in the production of substandard water coupled with its unclear specifications and regulations for bottled water. In another survey to determine the chemical purity of commercial bottled water in Egypt where the main source of the water is the Nile, brands of bottled water included in the study contained lead though the concentrations were still below the WHO guideline of 0.01mg/L21. They noted that filtration of water through charcoal filters lowered the lead level significantly. The lack of proper treatment methods by our manufacturers could therefore be another cause of the high concentration of lead in the bottled water. Lead is present in tap water to some extent as a result of its dissolution from natural sources. In addition PVC pipes used to transport water from the Nile contain lead compounds that could leach into the water resulting in high lead concentrations in drinking water21.

According to Schock22,23 the amount of lead dissolved from plumbing systems depends on several factors, including presence of chloride and dissolved oxygen, pH, temperature, water hardness and standing time of water.

From Table 2, three sample from every brand in the study conformed to the WHO guideline while others did not. From table 2, also all the three outlets (supermarkets, grocery shops and street vendors) at least sold substandard water. Two of the three samples with the highest concentration of lead were bought from the supermarkets, which people believe to obtain their products from the right manufacturers of bottled water. Whether contamination of bottled water occurs during batch production processes or variation in the quality personnel and treatment technologies employed by bottlers or counterfeiting of products to explain this observation cannot be confirmed.

 Dabeka et al20 conducted a survey of bottled waters sold in Canada and compared their findings against the WHO and Canadian guidelines of 0.01mg/L for lead in drinking water. Only one of the 199 bottled mineral water samples analyzed contained a lead concentration (0.015mg/L) exceeding the guideline value. In contrast to findings of this study, 13 samples contained a lead concentration of 0.00826mg/L well below the guideline while 17 samples contained a lead concentration far exceeding the guideline. The question about inconsistency in concentration levels of lead in bottled water products from the same manufacturer as noted above may be answered by further research.

 

Table 1: Lead concentrations of the samples with the respective outlets

Sample number

Sample code

Type of outlet

Lead concentration (mg/ml)

1

A1

Grocery

0.00826

2

A2

Supermarket

0.00826

3

A3

Street Vendor

0.17355

4

A4

Supermarket

0.00826

5

A5

Street Vendor

0.09091

6

A6

Grocery

0.09091

7

B1

Street Vendor

0.00826

8

B2

Street Vendor

0.09091

9

B3

Grocery

0.09091

10

B4

Grocery

0.00826

11

B5

Supermarket

0.09091

12

B6

Supermarket

0.00826

13

C1

Street Vendor

0.09091

14

C2

Street Vendor

0.00826

15

C3

Grocery

0.25620

16

C4

Grocery

0.17355

17

C5

Supermarket

0.00826

18

C6

Supermarket

0.25620

19

D1

Street Vendor

0.00826

20

D2

Street Vendor

0.17355

21

D3

Grocery

0.00826

22

D4

Grocery

0.00826

23

D5

Supermarket

0.17355

24

D6

Supermarket

0.09091

25

E1

Street Vendor

0.00826

26

E2

Street Vendor

0.09091

27

E3

Supermarket

0.25620

28

E4

Supermarket

0.09091

29

E5

Grocery

0.00826

30

E6

Grocery

0.17355

Samples with the same letter of the sample code were of the same brand.

Table 2: A table summarizing the number of samples below and above the recommended WHO limit per outlet

 

Below recommended WHO limit

Above recommended WHO limit

Grocery

5

5

Supermarket

4

6

Street vendor

4

6

Total

13

17

The recommended WHO limit is 0.01mg/ml


Table 3: The mean concentrations of the respective outlets

Type of outlet

Mean concentrations (mg/ml)

Grocery

0.08210

Supermarket

0.09845

Street Vendor

0.07437

 

LIMITATIONS

The initial study design was to determine the levels of both lead and arsenic metals in bottled waters. However an extensive survey of all laboratories around Kampala right from UNBS, Government facilities, only half of the Analytical Lab, NCRL, Uganda Industrial Research Institute and Chemiphar laboratories revealed that they lacked the necessary analytical equipment for arsenic. This led to implementation of only half of the objectives.

Over 37 brands of bottled water are sold in Kampala, but only five of them were randomly selected for the study due to financial constraints.

The study was restricted to a few divisions in Kampala and a few brands were studied and therefore not representative of the other brands of bottled water in the whole country.

CONCLUSIONS

More than half of the samples had lead concentrations exceeding the WHO drinking water standard. These samples may not be suitable for human consumption. Bottled drinking water therefore, may be a potential source of lead exposure depending on the volume of water consumed by an individual over a sustained period of time.

Consumers who doubt the safety of tap water more frequently substitute it with bottled water. The notion that bottled water is pure, clean and safe may be wrong based on the findings of this study. Many other toxic elements may be present in these waters due to pollution effects on aquifers and artesian wells.

RECOMMENDATIONS

This research puts forward baseline information about one of the important public health aspects that has been ignored. The following suggestions may be of help to address gaps that have been found out by this study;

Further research is required to extensively and rigorously evaluate the chemical purity of all bottled water sold in Kampala and Uganda as a whole. Consideration should be given to increasing metal elements that will be studied in in future studies on bottled water quality.

Surveillance of bottled water is also required for the continued compliance to standards by manufacturers.

Well-designed epidemiological studies need to be carried out to correlate current levels of lead in bottled drinking water and the related morbidities to establish the actual risk of lead poisoning suggested by this study.

Manufacturers of bottled water should institute testing programs for the presence of heavy metals in finished products and sources of water and in addition set up a monitoring frequency to ensure consistency in concentrations of toxic elements.

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