Evaluating the potability and human health risk of sachet water in Wukari, Nigeria

Abstract This study assessed physiochemical and biological properties of sachet waters. In general, sachet waters were within standards for all parameters except lead in batch A & B, iron in batch E, and E. coli in all water brands. Human health risk showed the order of THI as NO3 - > Pb > F- > Fe for batch A & B samples and NO3 - > F- > Pb > Fe for batch C, D & E. This showed nitrate constituting over 50% of the THI while batch B water samples showed THI above the acceptable limit for all age groups. The THI for infants suggests moderate risk. This indicates infants are more likely to be impacted even though water parameters were within standards. Hence, there is a need to monitor sachet water companies to protect public health.


Introduction
The sachet water industry started in the 1990s and due to the recent improvement in treatment and packaging, it has become one of the fastest-growing industries in Nigeria and West Africa. 1 Sachet water refers to 50 cl sealed plastic sleeves of purified drinking water which is widely used in most countries in West Africa. [2][3][4] It is widely accepted due to its affordability and general perception of quality. The sachet water industry is aimed at providing potable drinking water to the public. More so, it is affordable and easily accessible to the general public 2,5 which is why it has been accepted as the most widely used drinking water.
However, the increase in sachet water packaging companies has resulted in poor regulation across most west African countries. 6,7 There have been reports of heavy metals, nonmetals, and ions, [8][9][10] and biological 1,3,4,[11][12][13] contamination in sachet water across many communities in Nigeria, Ghana, and other west African countries. Currently, water treatment facilities are either lacking or have been dilapidated as a result of poor maintenance. [14][15][16] This results in water consumers seeking alternative sources from water vendors which are often of poor quality. Water supply vendors are now one of the main suppliers of water particularly in rural and peri-urban cities. One of such is the packaging of water in 50 cl polythene bags and selling as sachet water (locally called pure water). Prior to water sold in sachets, water vendors often sold water in buckets with people using the same cups to drink directly from the buckets. This was considered unhygienic and was further transformed into the water being tied in plastic bags and sold to the public. This also raised questions, particularly about the source of the water and the hygienic conditions of the environment where it was being produced. 17,18 A more hygienic way was to package treated water using sealing machines which eventually gave rise to the sachet water industry.
The government's inability to provide access to potable drinking water has contributed to the widespread dependence on sachet water. Consequently, the National Agency for Food, Drug Administration and Control (NAFDAC), Standard Organization of Nigeria (SON), and other State regulating agencies have not been effective in monitoring and regulating sachet water companies. 19 For instance, most sachet water industries in rural and peri-urban areas hardly have a regulatory visit from these agencies, and this results in negligence in terms of adhering to drinking water guidelines. In addition, most studies on sachet water only report water quality in comparison to national and international guidelines and fail to assess health risks associated with the consumption of such water.
This necessitates the need to investigate both the quality of water and the non-carcinogenic health risk of sachet water produced and sold in Wukari. This study, therefore, aims to investigate water quality and its associated non-carcinogenic health risk of the top five most preferred sachet water. This will be achieved by assessing the quality of most consumed water and the health risk to adults, children, and infants and proposing recommendations to both government regulatory agencies and sachet water companies.

Survey design and administer of questionnaires
A survey was designed to collect information on the different sachet water sold, the preferred sachet water, and the quality perceptions of the consumers. The study adopted the survey procedures and practical guidelines for designing surveys from Ref. 20. The survey questions were designed in two parts: (1) the respondents' demographic data and (2) the perception/ preference of sachet water consumed. The questionnaire was tested through a pilot survey with a small number of participants in the department of biological sciences. The pilot test assisted in verifying the questions, viability, feasibility, and completion time of the questionnaire. The revised questionnaire was then used to sort for opinions from supervisors and experts before the final version was approved for the study.
The study sample size was calculated from Equation (1) 2 at a 95% confidence level and 5% margin of error with assumed water quality of water at 50%.
where n is the sample size, Z 2 (statistic) is taken as 1.96, P is the quality of water at 50% and d is the margin of error at 5%. With a statistical margin of error of ±5% at a 95% confidence level, a sample size of 384.2 was computed and with a 10% adjustment, a sample size of 424 participants was targeted. However, to account for errors from incomplete surveys, and unreturned forms, the sample size was adjusted to 600 targeted participants. A purposive sampling technique was used to achieve the minimum sample size, as described in related social research by Ref. 21. A total of 533 of the 600 questionnaires that were distributed were returned.
However, 89 of the 533 completed questionnaires were discarded from the study due to several missing pieces of information while 67 were not returned. The total number of questionnaires used in the analysis stands at 444 (74%). Participants targeted include students, staff, sachet water sellers, and residents around the institutions.

Sample collection
Water samples were collected from the 5 most consumed water (derived from the survey results). Samples were collected within 24 hours of supply and distribution to ensure changes as a result of the number of days each water spent do not affect the validity of the results. A total of 10 samples each were purchased from and around the two higher institutions in Wukari which makes a total of 20 samples per sachet water company. The top 5 sachet water companies were labeled batch A, batch B, batch C, batch D, and batch E. Sample bottles were pretreated by washing bottles with 0.05 M HCl and rinsing with distilled water, after which they were rinsed three times with water samples before transferring the samples into the bottles for easy transportation to the laboratory under 4 C. 22 Physiochemical and bacteriological analysis The temperature was measured in-situ using a mercury thermometer, pH using a calibrated pH meter, TDS using the gravimetric method by taking the water sample and evaporating it in an oven at 105 C. TDS was then computed by taking the difference between the mass of the dried beaker and that of the beaker containing the residue and expressed in mg/L as described by APHA. 23 In addition, color was determined using the Hazen method, nitrate using Hydrazine reduction and color intensity measurement with a spectrophotometer at an absorbance of 520 nm, lead was determined by subjecting its filtrate to atomic absorption spectroscopy using a spectrophotometer, and iron using flame absorption Spectrophotometry. 23 Coliform count and E. coli were determined using Eosin Methylene Blue Agar. 22 To ensure quality assurance and control, the possibility of background contamination was evaluated. This was done by using a blank sample after every five samples to ensure the accuracy of the data. Also, the analysis was performed in duplicates and the average was recorded as the final result. In terms of the survey, a pilot survey was used to test for clarity and completion time of the questionnaire.

Assessment of Health-Related risk
The human health risk assessment is a key tool in appraising water quality even when the concentration of contaminants is within stipulated standard limits. 24,25 It has been used as an important step to safeguard the water supply and protect public health. 26,27 Therefore, the oral pathway of consumption of noncarcinogenic contaminants in sachet water was assessed and computed according to Refs. 28, 29. Average daily intake (CDI) was computed using Equation 2.
where CDI is chronic daily intake (mg/kg/day), Cw is the concentration of a particular contaminant (mg/L), IR denotes ingestion rate with assigned values of 2.5 L, 0.78 L, and 0.3 L for adults, children, and infants. 30,31 ED represents exposure duration with values of 64, 12, and 1 years for an adult, children, and infants respectively, 24,25 EF denotes exposure frequency taken as 365 days, ABW represents average body weight taken as 68, 18, and 5 kg for adult children and infants, AET represents average exposure time taken as 23360, 4380, and 365 days for adult children and infants respectively.
Furthermore, the Hazard Quotient (HQ) was computed using Equation 3.
where HQ is the hazard quotient RfD is the reference dose of a specific contaminant (mg/kg/day).
RfD values for nitrate, fluoride, iron, and lead were taken as 1.6, 0.4, 0.7, and 0.0035 (mg/kg/day) respectively. 28,33 The hazard index (HI) was computed from Equation 4 as the sum of HQ values of each contaminant. The classification of chronic (noncarcinogenic) risk based on Ref. 29 is presented in Table 1 and subsequently used to assess the hazard index.

Statistical analysis
The study used descriptive and inferential statistics.
Descriptive statistics were used to analyze the survey results while a student T-Test using Mini-tab version 20.0 was used to assess the significant difference in parameters to national and international guidelines. The means of parameters that were considered statistically significant (P < 0.05) suggest poor water quality.

Survey results
The demographic representation of the participants indicates that 53.8% (male) and 46.2% (female). In addition, students constitute 71.4% of participants from the two universities, while 20.7%, 4.5%, and 3.4% were staff, business owners, and unemployed and residents respectively. Age distribution indicates that most (61.7%) of the participants were between 18-25 years, while a little over half (56.8%) were undergraduates with secondary school certificates. Additionally, 66% earned below the 18,000 Naira minimum wage which correlates with 65.3% of those who could only afford between 1 and 3 bags of sachet water per week. Only 14.2% can afford over 7bags per week, which shows that consumptions of sachet water are often dependent on affordability, especially among students. The preference for sachet water varied among 10 different water packaging companies, with the top 5 accounting for 86.5% of the water that is consumed ( Figure 1). They include RT-batch E (27.7%), NBbatch D (16.4%), SJ-batch C (15.1%), EB-batch B (14%), and FB-batch A (13.3%). When asked why participants choose their most preferred brands and why other brands were not appealing to them, perceived water quality appears to be the most important criteria, followed by whether or not the packaging companies were registered with the national regulating agency (NAFDAC) (Figure 2). Findings from Ref. 34 support this and also suggest this and reiterate the importance of registering sachet water companies with regulatory bodies. Compliance with NAFDAC here indicates to the consumers that the water has met all the stipulated standards for drinking water and hence becomes an important criterion in the selection process. Although this does not mean the waters were safe, but rather gives a certain level of assurance to the consumers. Interestingly, cost appears to have an insignificant impact on the choice of sachet water even though the majority of those who consumed it earn lower than the national minimum wage. This means that consumers are willing to pay to get quality water for consumption.

Water quality results
The normality and distribution of data were tested using p-values (P < 0.05), while the summary of analytical results and statistical measures such as the mean and standard deviation were computed and presented in Table 2. In general, the least sachet water temperature was recorded in batch C (19.5 C) while the highest was in batch E (24.8 C). This was expected as the batch E production plant is located out of Wukari town thereby increasing the likelihood of higher temperature during transportation. Sachet water was within the national stipulated range 32 of 6.5-8.5 for pH in all water samples. Overall, the water samples were within the national drinking water standards with exception of lead, iron, and E. coli across some of the water samples. Water from all the sachet water analyzed was within standard limits for temperature, pH, color, turbidity, TDS, total hardness, nitrate, fluoride, and total coliform count. The results support the findings from other studies on sachet water by Refs. 1, 8, 18, 19, 35. However, all samples showed bacteriological parameters significantly above the drinking water guidelines (Figure 3) which can likely lead to health risks if consumed over a long period. Similar findings were reported by Refs. 8, 18 which indicate that most sachet waters failed to meet bacteriological quality and can likely constitute health risk within rural and semi-urban settlements in Nigeria. Bacteriological contamination can often be attributed to improper disinfection, less frequent cleaning and poor maintenance of treatment facilities, use of contaminated sachets for packaging, and an unhygienic packaging environment. 8,18,36 Although total coliform count was present alongside E. coli, only E. coli was found to be significantly above the drinking water standards This was also consistent with findings from Refs. 37, 38. In addition to high levels of E. coli, batch A and B samples showed values of lead (0.02 mg/l and 0.015 mg/l) and batch E showed Iron (0.35 mg/l) significantly above the standards at p < 0.05 (Figures 4 and 5). The prevalence of lead within the study area is likely of natural origin. 16

Health risk assessment
There has been limited information regarding the health risk of sachet water in Nigeria. Therefore, the non-carcinogenic health risk posed by ingestion of the different sachet water for three groups of humans (adults, children, and infants) was assessed. The mean values for the health quotient (HQ) of chemical contaminants in the different sachet waters are presented in Table 3. Based on the HQ values computed for sachet water sources and human groups (adults, children, and infants), the risk order was as follows nitrate > lead > fluoride > iron for batch A and B water samples and for all the human group classification. While the order for batches C, D, and E was nitrate > fluoride > lead > iron for adults, children and infants respectively. In both orders, HQ-nitrate accounts for over 50% of the total non-carcinogenic health risk in all the water samples and across all human groups assessed. These findings are consistent with findings from Refs. 39-43 for HQ-nitrate -HQ-fluoride and HQ-lead -HQ-iron, respectively. In addition, batch B water samples indicate moderate risk with THI values greater than 1 (see Table  1). Consequently, water samples from batches A, C, D & E reveal low health risk to adults and children whereas all water samples show moderate health risk to infants. This suggests a likelihood of health risk, particularly for babies under one. Nitrate is known to cause blue baby syndrome in infants 44 ; therefore, it becomes imperative to restrict infants from the consumption of these sachet waters. Although findings from Ref. 45 were not in agreement with the study findings, spatial and temporal factors including susceptibility to contamination within the packaging plant could likely explain the disparities in the findings. Overall, THI exceeding the standard (1) for infants ( Figure 6) is of serious concern and requires urgent attention.   Although some of the parameters were within national standards for drinking water, the THI shows moderate risk which agrees with Refs. 24, 25, 46 and further recapitulate that water quality parameters can be within stipulated standards and at the same time, pose a long-term health impact. There is therefore the need to incorporate the THI in assessing water quality, particularly for the different groups (adults, children, and infants). More so, there is abundant room for further progress by assessing the risk for women separately from men. This is because women are likely to have less weight than men and also have a slightly less ingestion rate compared to men.

The implication of findings and sachet water management
The implication of the study result is that sachet water although considered vital to meeting water requirements is not of sufficient quality to guarantee public health despite most of the variables meeting drinking water standards. Findings suggest that lead, Iron and E. coli are the variables of concern. However, non-carcinogenic health risk suggests that despite most variables meeting stipulated guidelines, they can likely result in long-term impact, particularly on children and infants. Currently, the water treatment plant in Ibi/Wukari is not efficient in supplying drinking water of sufficient quality 14,16 therefore it is safe to say that water management within Wukari is ineffective in addressing the challenges. Monitoring of water supply systems needs to be intensified to effectively address private and public water supply. 38,47 Main water supply systems within Wukari need   to be protected from agricultural activities, improper waste management, open defecation, and recently, climate change. This is imperative particularly because most private water vendors supply water directly from borehole sources which are likely affected by both natural and anthropogenic factors.

Conclusion
The measurement of physicochemical and biological parameters in sachet drinking water in Wukari indicates that parameters such as lead, iron, and E. coli have concentrations above acceptable limits in some packaged water. This suggests a risk to public health particularly due to the high dependence and consumption of sachet water in rural and semi-urban communities in Nigeria. The non-carcinogenic human health risk assessment further indicates that nitrate is the most effective parameter in inducing the total hazard index (THI). Furthermore, the THI for adults and children appears to be within the low-risk point but was at the same time at moderate risk for infants. Therefore, it can be concluded that sachet water within the study area can likely pose health concerns for infants compared to adults and children. It is recommended that water regulating agencies continuously monitor sachet water companies and ensure their operations are within acceptable guidelines to protect public health across the nation. In addition, there is an opportunity for improvement in assessing drinking water sources within Wukari. The inclusion of other variables would have likely indicated an overview of a wide range of variables that this study failed to cover. Additionally, sachet water samples were purchased from shops and the time it might have stayed in shops (shell life) before collecting could likely affect the results of some variables. Furthermore, there is the likelihood of carcinogenic health risks and the presence of fungi in drinking water, which is of great importance, because of their mycotoxin production, resistance to chlorination, and absence in monitoring parameters is an important area for further study.