Health Risk Assessment Of Fluoride In Drinking Water – A Case Study From Poldasht City, Northwest Iran

7404ENG Advanced Water and Wastewater Engineering

Exposure Assessment

Safe drinking water should be available to all the human beings but due to of some chemicals like fluoride are present in the drinking water above a safe limit, the drinking water becomes harmful to the people. Fluoride has been listed as one of the most prioritized hazardous substance as identified by the US Agency for Toxic Substances and Disease Registry. The fluoride mainly enters the human body via drinking water (Yousefi, Ghoochani & Mahvi, 2018). Many researchers found that the human body absorbs almost 90% of the fluoride from the drinking water, whereas, only 30 to 40% of fluoride is absorbed from the food. While, tooth damage is prevented by a standard concentration of fluoride but an excessive concentration of fluoride can lead to several health diseases. The adverse effects in health include tooth decay at a level of 0.5 mg/L fluoride in drinking water. When the density of the fluoride in drinking water is between 1.5 to 5 mg/L fluorosis occurs and at a more higher level the skeleton fluorosis occurs when the fluoride concentration is between 5 to 40 mg/day. If the drinking water contains 10 mg of fluoride-exposed to a child from birth to adult stage then it can cause genu recurvate and other problems like hypertension, neurological problems, infertility, cancer, arthritis Alzheimer’s and thyroid (Bus et al., 2015). Also, as recommended by the World Health Organization the limit of fluoride concentration in water is about 0.5 to 1.5 mg/L which does not cause any harm to the body. The fluoride concentration is much more than the standard level in the Poldasht City of Northwest Iran as found by the early researches. Hence, the fluoride content in the drinking water of the 28 villages are analyzed in this research and the adverse effects with the risk associated with the current situation in the city are represented in the later stages.

In this part of the research the exposure of fluoride to the people of 28 villages in Poldasht city are analyzed. The study sample has been obtained from the springs and the wells of 28 villages of the Poldasht City. Initially a total of one hundred and twelve water samples were collected from the village in a period of 6 months from 2014 to 2016. The samples of the water are collected in containers made from plastic and then those are transported to the research laboratory to analyze the samples. Now, according to standard instruction the density of fluoride in the water was determined by the SPADNS method which is also known as Zirconium Lake Method (Ludwicki et al., 2015). The fluoride concentration in between the range 0.0625 to 1.75 mg/L are determined in this method and the higher concentrations are diluted and then measured (Arora, Kumar & Moss,2018). The concentration of the fluoride has been assessed by using the spectrophotometer and the determination limit is 0.12 ppm and the quantification limit is 0.37 ppm.

Adverse Effects Assessment

If the fluoride ion is consumed at a high level for a long duration then it can cause chronic toxicity that can lead to Fluorosis in dental or at skeletal level. By the research it has been found by one factor Analysis of Variance(ANOVA) of the sample data that fluoride exposure in significantly different in different regions (Yousefi, Ghoochani & Mahvi, 2018). The results show that only 11% of the sample received fluoride exposure less than the limit as identified by the WHO. This particular value prevents the cavity in the tooth. The exposure levels in different regions of the city are represented below. 

The safety limits of Fluoride exposure as defined by the WHO is 0.4 mg per day for the infants, 0.7 mg per day for the children and 4 mg per day for the adults.

Determination of the adverse health effects to the human body is the motive of the health risk characterization and the assessment process. Now, the health risk assessment of fluoride by consumption of the drinking water is assessed in the rural region of the Poldasht city. By collecting the water samples from the taps of the villages and then subdividing the population into four main groups based on the difference in psychology and behaviour (Guissouma et al., 2017). The four groups are infants who are less than 2 years, children in between 2 to less than 6 years, the teenagers in the range 6 to less than 16 years and finally the adults more than 16 years. The fluoride exposure has been calculated by using the following formula 

The daily average drinking water consumption, density of Fluoride in the drinking water and weight of the body gives the Estimated Daily Intake of the fluoride as given in the above formula (Craig et al., 2015). The expression of EDI is mg per kg of the bodyweight in each day. The consumption of fluoride data and the weight of the body were predicted based on the responses of the groups (Waghmare et al., 2015). The response statistics was the mean amount of water consumption of different groups named as, children, teenagers, infants and the adults are,0.85, 2, 0.08 and 2.5 L/day respectively (Peckham, Lowery, & Spencer, 2015). Similarly, the body weights of the target groups are 10 for infants, 15 for children, 50 for teenager and 78 kg for the adults. The hazard quotient represents the non-carcinogenic risk of fluoride that is given by, 

Risk Characterization

The dose of the reference as used in the assessment of risk is given by the daily limit of exposure to the human population. The reference doses of the fluoride are 0.06 mg/kg/day which are found from Integrated Risk Information System database (Nishimuro et al., 2015). If the HQ value is less than one then this means that there is lower chance of experiencing adverse health effects (Choi et al., 2015). If the HQ value is more than 1 then that means the risk is more than the acceptable level and there is a chance of health issues.

The density of fluoride in drinking water taps are represented with mean and tolerance in Poldasht city. 

Table 1: The density of fluoride in drinking water of Poldasht City as expressed by means ± sd

Village	Mean ± sd(mg/L)	Min (mg/L)	Max(mg/L)
Pomak	2.44±0.72	1.95	3.21
Ghoulish lanamish	2.24±0.52	1.58	2.87
Moradlo vasati	1.73±0.34	1.44	1.91
Nazok sofla	0.63±0.02	0.58	0.62
Gharghlogh sofla	1.95±0.52	1.55	2.4
Ghir kendi	1.62±0.09	1.54	1.67
Nazok olyia	0.8±0.20	0.57	1.01
Shiblo olia	0.84±0.27	0.48	1.16
Divankhane	1.25±1.16	0.42	2.04
Ghare jalo	1.68±0.03	1.67	1.6
Shahrak aras	0.69±0.21	0.46	0.81
Moradlo olia	2.46±0.76	1.93	3.01
Eshg abad	1.84±0.20	1.68	2.07

The hazard quotient as calculated in different regions and for different age groups as presented below.

Conclusion:

Hence, the identified water pollutant Fluoride has several impacts on health as found from the research article which was conducted in Poldasht city of Northwest Iran. It has been found from the research that the concentration level of fluoride in the different Poldasht city villages was 0.27 to 10.3 mg/L and the sample average was 1.70 mg/L. As analysed from the collected sample 57% of the drinking water samples crossed the set limit of fluoride in the drinking water. Hence, some tools of rapid decision-making are needed to decrease the health problems by reducing the density of fluoride in drinking water. Also, it was found in the city that mostly the young, teenagers and children are exposed by the fluoride. The drinking water contaminated by the fluoride also higher than the HQ level of 1 for all the age groups in Sarioo region. Hence, it is recommended that to take suitable measures for reducing the density of fluoride in drinking water and then to control the fluorosis. Suitable actions needed be implemented for enhancing the fluoride monitoring levels for avoiding the risk associated with the population.

Reference list:

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Craig, L., Lutz, A., Berry, K. A., & Yang, W. (2015). Recommendations for fluoride limits in drinking water based on estimated daily fluoride intake in the Upper East Region, Ghana. Science of the Total Environment, 532, 127-137.

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Waghmare, S. S., Arfin, T., Manwar, N., Lataye, D. H., Labhsetwar, N., & Rayalu, S. (2015). Preparation and characterization of polyalthia longifolia based alumina as a novel adsorbent for removing fluoride from drinking water. Asian J. Adv. Basic Sci, 4(1), 12-24.

Yousefi, M., Ghoochani, M., & Mahvi, A. H. (2018). Health risk assessment to fluoride in drinking water of rural residents living in the Poldasht city, Northwest of Iran. Ecotoxicology and environmental safety, 148, 426-430.