Boron Human Health Risk Assessment Relative to the … · 2012. 12. 29. · Boron Human Health Risk...

JKAU: Mar. Sci., Vol. 23, No. 2, pp: 41-55 (2012 A.D. / 1433 A.H.)

DOI : 10.4197/Mar. 23-2.3

41

Boron Human Health Risk Assessment Relative to the

Environmental Pollution of Lake Edku, Egypt

Abeer Ahmed Moneer, Manal Mohamed El-Sadawy,

Ghada Farouk El-Said and Ahmed A. Radwan

National Institute of Oceanography and Fisheries (NIOF)

Qyet Bay, El-Anfoushy, Alexandria, Egypt

[email protected]

Abstract: Lake Edku is one of the four north economically important

lakes in Egypt. It receives annually huge amounts of discharged water

containing different untreated contaminants of sewage, domestic and

agricultural wastes. Boron was selected as one of the contaminants

because of its effects on the human health. The study was directed to

detect its concentration in fish (Tilapia nilotica) tissues, water and

sediment of the lake and to evaluate its human health risk. Boron

concentration in Lake Edku water was good correlated with the

proximity to drainage water sources. Human ingestion of fish from the

lake didn’t form any risk, however, the hazard index for the flesh was

still below unity. Statistical analyses and human health risk

assessment for boron in lake water showed its more effects on child

than on adult. Meanwhile, no adverse effect was detected for the

dermal contact with the studied sediments to both child and adult, but,

boron showed a long term effect on human health.

Keywords: Boron. Human health risk assessment. Lake Edku. Egypt

Introduction

Boron is an inorganic dissolved element in water. In natural waters,

boron forms stable species and exists primarily as un-dissociated boric acid [B(OH)3] and complex poly-anions (e.g., B(OH)4

-) (WHO, 2003; CCME, 2009). Boron concentrations in fresh surface water are ranged from 0.001 to 7 mg/ L and seawater contains 4.4 mg/L (WHO, 2003). Meanwhile, the earth's crust contains10 ppm boron (Kazanci et al.,

42 Abeer Ahmed Moneer et al.

2006).The potential sources of boron contamination in water resources are either anthropogenic (sewage effluents and fertilizers) or natural (water rock interaction and seawater encroachment). Boron compounds are released to water in municipal sewage from perborates in detergents, and in waste waters from coal-burning power plants, copper smelters, glass manufacture, textile, ceramic industries, household cleaning products, etc. (HERA, 2005;. Draft Toxicological Profile for Boron, 2007; HERA, 2005; Koç, 2007). At higher levels (above 1 mg/L), boron is considered as a serious threat to the use of ground water in both drinking and agricultural purposes (Chaudhary et al., 2010). Boron accumulates in tissues of aquatic and semi-aquatic animals and therefore, transfers to humans through food chain (EPA, 2008; Emiroğlu et al., 2010). The accidental boron poisoning, which has been reported during the human ingestion may cause vomiting, diarrhea, indigestion, alopecia (loss of hair), anorexia and dermatitis symptoms (EPA, 1997; Halifax Harbour Solutions Project, 2001). Deficiency of boron intake can affect the cellular function and the activity of other nutrients. Boron may interact with vitamin D and calcium, influence estrogen metabolism and play a role in cognitive function (Draft Toxicological Profile for Boron, 2007).

Lake Edku is one of the four Northern Nile Delta Lakes in Egypt. It lies along the Mediterranean coast of Egypt, west of the Rosetta branch of the Nile, between latitudes 31°10′ and 31°18′ N, and longitudes 30°80′ and 30°22′ E. Its entire northern side is bordered by the coastline of Abu-Qir Bay, to which it is connected through El-Maadiya inlet at its western

extremity. The Lake covers a total area of about 126 km2 (El-Sarraf et

al., 2001; Badr and Hussein 2010). The lake is subjected to huge amounts

of drainage waters containing sewage, domestic, and agriculture wastes

from two main drains in eastern and southern sides. The first main drain, Kom Belag, in the eastern side, obtains its discharge water from three sub-drains; Bosily, Edku and El-Khairy. The second main drain, Berzik

discharges the drainage water at the southern part of the lake. The lake received an annual average drainage water of about 142 X 106 m3 in 2010

according to The Ministry of Water Resources and Irrigation Data, Egypt 2010.

In the present work, the levels of boron concentration in the water,

fish and sediment of Lake Edku are determined. Health risk assessment can be deduced from these results.

Boron Human Health Risk Assessment Relative to theEnvironmental … 43

Materials and Methods

Fourteen sampling locations were selected to represent the different regions of Lake Edku, Fig.(1). Stations 1-3, 6, and 11 were located near the entering of Abu-Qir seawater from El-Boughaz region. Regions 4-5 and 7 were affected by the different sources of drainage water containing domestic, sewage and agricultural wastes that were received from the two main drains (Kom Belag and Berzik) in eastern and southern areas. Locations 12-14 described the drainage sources of the main drains before flowing into the lake area. The surface water samples were collected seasonally during January-November 2010 from each chosen location and the sediment samples were collected during January 2010. 0.2 g of each finely powdered sediment sample was digested by adding a mixture of HNO3, HClO4 and HF acids (3: 2: 1) and preserved in clean PVC bottles for analysis. A total of 100 fresh fish samples of Tilapia nilotica species that are commonly distributed in Lake Edku and edible of approximately similar size (total length=11.58±0.51 cm) and weight (total weight = 29.46±4.68 g) were collectedduring January, Augustand November 2010. The fish samples were placed into plastic bags and transported to the laboratory during the same day. Flesh, liver, gills, bone, skin, brain, gonads, and heart tissues for each individual fish were homogenized to form composite samples. Five-tenth gram (0.5 g) of each wet composite samples were completely digested (triplicate for each sample) with concentrated nitric acid (Merck, Germany) and stored in polyethylene bottles.

Boron was determined in the fish tissues, water and sediment samples using the curcumin colorimetric technique (APHA-AWWA-WPCF, 1999). Chloride was determined in water and the first portion of

sediment samples following Mohr's method (Manual of Methods of

Foods, 2005; APHA-AWWA-WPCF, 1999). Water chlorinity values were calculated based on the use of salinity values as follows (Strickland and Parsons, 1965):

Salinity = 0.03 + (1.8050 X Chlorinity)


Fig. 1 Sampling locations for Lake Edku during 2010.

Where: The red and yellow stars represent the outside and the inside Lake Edku locations,

respectively.

The human risk assessment for the flesh tissue of fish, water and

sedimentcalculations were done following the equations (Albering et al., 1999):

For lake fish:

��ℎ �� = ��

Where:

CF = concentration of the contaminant in fish [mg kg−1

fresh weight (fw)].

IRf = ingestion rate of fish (kg fw day−1) [0.015 and 0.055 kg fw day−1 for child and adult, respectively].

FI = fraction contaminated (unit less) [0.5 for both child and

adult]; AF = absorption factor (unit less) [1 for both child and adult].


BW = body weight (kg) [15 and 70 kg for a child and adult, respectively].

Daily exposure averaged over a lifetime (e.g., 70 years) was calculated as followed:

�� = 6��ℎ��

70!+

64��ℎ��7

! "�

For lake water:

��#�$�� %�� =

��$�&�� '�

Where: Cw = concentration of heavy metals contaminant in surface water

(mg/L). IRw = ingestion rate of surface water (0.05 liter/exposure day for

both child and adult). EF = exposure frequency (30/365 days for both child and adult). AF = absorption factor (1 for both child and adult) and BW = Body

weight (15 and 70 kg for child and adult respectively).

��#��#�$��ℎ#��#�$�� %��

�� = ��%�$��%$�&��&�$�� (�

�%$ = 5000�(0.038 + 0.153�) �

5000 + (0.038 + 0.153�) �

! � exp(−0.016�*1.5

! Where:

SAw = dermal surface area for exposure in surface water (0.95 and 1.8 m2 for child and adult respectively).

ASw = dermal absorption rate for exposure in surface water [(mg/m2)/(mg/L)/hr].

EDW = exposure duration from dermal exposure to surface water(2 and 1 hr/day for child and adult, respectively).


KOW = octanol/water partition coefficient, and M = molecular weight (g/mol).

For sediment

��#�� %� ��=

�%��&�� +�

��#��#�$��ℎ#�� %� ��=

�%�%��%��*��&��&�� ,�

�� = 6��

70! +

64��7

! -�

Where: CS = concentration of heavy metals contaminant in sediment (mg

kg-1dw). IRS = ingestion rate of sediment (0.001 and 0.00035 kg dw/day for

child and adult, respectively). EF = exposure frequency (30 for both child and adult). AF = absorption factor (1 for both child and adult). SAS = dermal surface area for sediment exposure (0.17 and 0.28

m2 for child and adult, respectively).

AD = dermal adherence rate for sediment (0.51 and 3.75 mg cm-2 for child and adult respectively).

ASS = dermal absorption rate (0.01 and 0.005 L/hr for child and

adult, respectively). Mf = matrix factor (0.15 for both child and adult). EDS = exposure duration to sediment (8 hr day-1 for both child and

adult). BW = body weight (15 and 70 kg for child and adult, respectively).

The hazard index refers to the ratio between calculated daily exposure and tolerable daily intake [TDI]. Where, TDI refers to reference dose of boron that can be taken in daily without identifiable risk at

lifetime exposure (Equation 8).


Hazard index= lifetime daily exposure (fish or sediment) ÷ tolerable daily intake (TDI) (8)

Correlation matrices and multiple regression analyses were performed using Statistica computer software version 5. These analyses were applied with significance level of 0.05 to determine the relation among all the determined parameters in the different water and sediment samples.

Results and Discussion

The seasonal and annual boron distribution in the different tissues in Tilapia nilotica species is illustrated in Table 1. The annual results show variation in boron accumulation along the different fish tissues in the descending order of: Brain> bone> liver> skin> flesh> gills> gonads> heart. This variation possibly is accompanied with many factors including, temperature, pH value, feeding rate and physiological condition of fish (CCME, 2009). The flesh tissues in lake fish show smaller boron concentrations than those recorded for both Niagara River and Neosho River Basin in Kansas (0.92-6.89 μg/g and 2–4 μg/g, respectively; Draft Toxicological Profile for Boron, 2007). The higher boron accumulation is detected in the brain, bone and liver tissues possibly accompanies its bioactivity character in cell system that causes mental disorders, osteoporosis, and heart disease (Nielsen, 2009).

Table 1. Seasonal and average annual boron distribution (µg/g) in the different tissues of Tilapia nilotica.

Tissue Winter Spring Autumn Average S.D.

Flesh 0.123 0.101 0.090 0.104 0.017

Liver 0.352 0.172 0.178 0.234 0.102

Gills 0.116 0.080 0.071 0.089 0.023

Bone 0.494 0.238 0.272 0.334 0.139

Skin 0.159 0.136 0.072 0.122 0.045

Brain 1.744 0.873 0.061 0.893 0.842

Gonads 0.081 0.080 0.059 0.073 0.013

Heart 0.098 0.024 0.018 0.047 0.045

The annual water distribution of boron in Lake Edku gives an

average of 3.64±0.88 mg/L (Table 2). The maximum average boron content (5.31 mg/L) is recorded at location 2, meanwhile the minimum one (1.95 mg/L) is determined at location 8. The high average concentrations (4.84, 5.31, 3.59, 4.55 and 4.77 mg/L) are detected in sites


1-3, 6, and 11 near the seawater entering from El-Boughaz region. However, seawater has high boron concentration of 4.5 mg/L (Butterwick et al., 1989). Also, the Alexandria coastal seawater of Egypt showed average boron concentrations varied from 3.92 to 5.22 mg/L with an average concentration of 4.62± 0.35 mg/L (Youssef, 2003). Additionally, lower contents for the rest locations are affected by the drainage waters that cover the lake. However, stations 4-5 and 7 (3.02, 3.31 and 3.22 mg/L) show concentrations relatively similar to those in the drainage sources at locations 12-14 (3.14, 3.68 and 3.12 mg/L). The drainage discharge water contains wastes including; sewage, domestic and agricultural wastes (Youssef, 2003). The present boron data show higher values than those previously recorded in Lake Edku, Kom Belag and Berzik during 2000 (0.59 ±0.04 - 0.38±0.08 and 0.049–0.097 mg/L, respectively). The elevation in boron concentration may refer to many factors, including, temperature, pH, chloride content, amount and the type of boron contaminants that deposited into the lake (El-Said, 2005; Koç, 2007; and El-Said et al., 2010). However, boron is an inorganic element and does not biodegrade in the water body or sediments of marine and freshwater environments (Schoderboeck et al., 2011). Amongst the boron contamination sources that can contribute to its presence in lake area are fertilizers, herbicides, soap and detergents (ATSDR, 1992; and EPA, 2008). The British Columbia Water Protection Section of the Ministry of Water, Land and Air Protection Canada recommended boron concentration in fresh water of < 1.2 mg/L for protection of aquatic life (Moss and Nagpal, 2003). On the other hand,

South African water quality guideline established irrigation guidelines

for boron of 0-5.0 mg/L (Republic of South Africa, 1996). According to these water quality guidelines for fresh and irrigation water, it can be concluded that the studied lake area is still safe.

Boron distribution along sediments of Lake Edku is attributed to

the different water sources that feed this area (Table 2). Boron concentration in Lake Edku sediment samples varies between 0.30 and 0.91 mg/g in sites 2 and 4, respectively, with an average of 0.52± 0.17

mg/g. B in the middle of the lake region (stations 5-8 and 10), exposed to the drainage waters shows higher values (0.54, 0.49, 0.73, 0.57 and 0.50 mg/g, respectively). In addition, locations 12-14, outside the lake, give approximately similar values (0.70, 0.46 and 0.59 mg/g) to those in the middle area. In contrast, nearby regions (sites 1-3) to the El-Boughaz are


of lower boron contents (0.45, 0.30 and 0.38 mg/g, respectively). These values are approximately lower than that detected for marine sediments 0.5 mg/g; (Eisler, 1990). Additionally, the present boron data near El-Boughaz area appears to be lower than those recorded for eastern and western sides of Egyptian coastal Mediterranean Sea area (0.84±0.30 and 0.74±0.26 mg/g, respectively). In contrast, the Lake Edku sediments nearby the seawater have higher values than those determined for El-Max and Abu Qir Bays during 2007, 0.18± 0.48 and 0.19±0.51 mg/g, respectively; (Faragallah et al., 2010). This possibly refers to many factors such as: sediment type, pH, presence of some interfering ions, temperature, and sediment water interface exchange as well as the anthropogenic boron sources (El-Said et al., 2010; and McDonald et al., 2010).

Table 2. Average annual distribution of boron in Lake Edku water (mg/L) and sediment (mg/g) during 2010.

The human risk assessment calculations for flesh tissue of fish, water and sediment of Lake Edku are performed following equations 1-8.The average seasonal boron ingestion by child, adult and the daily

exposure are of small values (less than unit). The average daily exposure of the present work is smaller than those reported for the dietary human boron intake (Rainey et al., 1999). This indicates that the flesh of the common distributed edible species, Tilapia nilotica is still safe for human

Station number Water Sediment

Inside the lake area

1 4.84 0.45

2 5.31 0.30

3 3.59 0.38

4 3.02 0.91

5 3.31 0.54

6 4.55 0.49

7 3.22 0.73

8 1.95 0.57

9 3.39 0.45

10 3.04 0.50

11 4.77 0.41

Average 3.73 0.52

S.D. 1.01 0.17

Outside the lake area (drain sources)

12 3.14 0.70

13 3.68 0.46

14 3.12 0.59


nutrition. Winter has the largest daily exposure. The tolerable daily intake [TDI] for boron is 0.137 mg kg

-1 day-1 (EGVM, 2003). Accordingly, the hazard index for the flesh samples of Tilapia nilotica is <1. The largest daily exposure recorded in winter may attribute to the direct contact of the fish species to the lake sediment during their burial in this cold season (Masoud et al., 2006). Child ingestion gave higher values than adult ones. However, child’s exposure may differ from an adult’s exposure in many ways (Draft Toxicological Profile for Boron, 2007).

The human risk assessment calculations for lake water using equations (3 and 4) show that the dermal contact with contaminated surface water in Lake Edku for child (DCCSW) C are of higher values than those calculated for adult. Child can be more affected by boron content variation in lake water than adult. Also, lower values (<1) for adult are almost detected in stations (3-11), inside the lake area with an average 0.460±0.430. However, most higher values (>1), for child and adult are determined in the regions proximity to seawater and drainage water sources.

The correlation matrix for boron, water chlorinity, (DCCSW)C and (DCCSW)A contents shows that the average annual boron content in lake water is related to water chlorinity value (r = 0.2678; p<0.046). Also, very high correlation coefficient (r = 1.000; p< 0.000) between (DCCSW)C and (DCCSW)A is detected.

Additionally, the multiple regression equation for the different

variables in lake water using (DCCSW)C as a dependent parameter is

represented as follows:

(DCCSW)C = 0.001 + 1.000 (DCCSW)A+ 0.002 B - 0.0002 Chlorinity

(n= 56; R= 0.99999; p<0.0000)

Correlation matrix and multiple regression analyses for different parameters in lake water (B, Chlorinity, (DCCSW)C and (DCCSW)A) confirm the effect of the different feeding drainage water sources on boron content and the water dermal contact for both child and adult and the long term accumulation of boron in human body.

All the calculations for the dermal contact with the studied sediment samples for child and adult give values less than unity. This


indicates that the lake sediments are still safe for human dermal contact. Sediments of both drain sources (locations 12-14; outside lake) and those in the middle of the lake show higher dermal contact values than that of locations proximate to seawater source (sites 1-3). Additionally, the dermal contact for adult shows higher values than that of child. Accordingly, boron dermal contact has a long term effect on human. Lake Edku sediments seems to be safe for boron ingestion from sediment (ICS) and total boron exposure level for both child and adult, however, they are of values less than unity. Accordingly, in the future, boron can cause human health risk due to its continuous elevation in the lake environment. Additionally, the comparison of lifetime daily exposure values (CLTDE) with the tolerable daily intake (TDI) ones shows that the hazard index values are still below 1.

The correlation matrix of different calculated parameters (Dermal, ICS, daily exposure and CLTDE) child and adult show high positive relations ranges between r = 0.8277 and r = 1.000. In contrast, boron content in the sediment gives a negative neglected relation with all the pervious calculated parameters.

Multiple regression for the different variables in lake sediment are given as follows:

CLTDE = - 5.78 X 10-9 + 1.00 daily exposure (Child) + 2.402 X 10-7

Chlorinity + 2.117 × 10-7 ICS (Adult)

(n= 14; R = 1.0000; p<0.0000)

Interestingly, the statistical analyses for lake sediments show high positive correlations between the different calculated parameters (Dermal, ICS, daily exposure and CLTDE) for child and adult.

Additionally, these analyses confirm the adverse effect of the

accumulated boron in the sediment inside the lake area on human health.

Conclusions

Risk assessment based on two datasets: Human exposure and effects/hazard assessment was studied in Lake Edku, Egypt. In this work

the effects assessment was addressed by evaluating existing data from studies on boron toxicity. In order to describe environmental risks typically human health risk was calculated for child and adult. Boron


variability in lake water was affected by the type of feeding water sources (seawater and drainage water). The high average annual boron concentrations in lake water were recorded at the sites near El-Boughaz region that enters the Abu-Qir Bay seawater. The relative similar boron values recorded in both inside and outside the lake stations (main drains) may accompany their proximity to the discharged wastes including; sewage, domestic and agricultural wastes. Additionally, boron content in lake water was directly affected by the feeding water sources (seawater, and drainage waters). In contrast, lake sediments accumulated boron more than those near seawater inlet and main drains. Furthermore, the human risk assessment calculations for lake water confirmed the effective role of the different boron sources in the north western, eastern and southern parts of the studied area on human health. Also, child could be more affected by boron content variation in lake water than adult. The dermal sediment contact calculations for child and adult gave values less than unity. Accordingly, the results indicated that water and sediment of Lake Edku are still safe for dermal contact and ingestion of human and have a long term effect on human. Additionally, the ingestion of commonly distributed fish species, Tilapia nilotica in Lake Edku doesn’t pose any human health hazards.

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