Water quality health and hazard risk assessment on Drinking Water Sources

XUE Lianqinq WU Chunling Geng Fuming State Key Laboratory of Hydrology-Water Resources and

Hydraulic Engineering Hohai University, Nanjing 210098 China

e-mail lqxue@hhu.edu.cn

WU Yifeng Environment engineering departmant

Southeast University Nanjing 210096 China

e-mail shinfun@163.com

Abstract—A mathematical assessment method on water quality health and hazard risk in drinking water sources is established to calculate risk values caused by chemical carcinogens, radioactive pollutants, as well as non carcinogenic pollutants. And the assessment model is applied to analyze and assess the contaminated groundwater health status and hazard risk level. The results showed that the health risk values caused by chemical carcinogens are higher than the standard recommended maximum acceptable by the International Commission on Radiological Protection (ICRP), and far greater than the non carcinogen-induced Degree of risk. The ranking of risk values due to chemical carcinogen by drinking water is Cr+6>As>Cd, and the ranking of risk values due to non-carcinogen pollutants by drinking water is Pb>F->CN-> hydroxyl benzene>NH3-N. Chemical carcinogens are primary and should be removed possibly. The results also provide important information for groundwater quality management.

Keywords- water quality; risk; assessment model; pollutants

I. INTRODUCTION Water environment pollution has become a growing

problem in recent years. Especially in some drinking source region, there is a serious threat to the water sources quality security, which certainly will seriously affect people's lives and health. At present, 90 percent of human cancers are caused by chemical carcinogens [1], with the increase of water supply sources polluted, health-hazards assessment can not merely describe whether the pollution is serious, but should quantify the severity of the pollution. Water environmental health risk assessment is becoming a new research field, the study mainly adopts risk value as evaluation index to quantitatively describe the magnitude and possibility of health hazards caused by pollutants [1,2]. More water supply sources are suffering from contamination, at the critical moment, it is necessary to directly obtain the synthetic quality conclusions of the sources with the water quality health-hazard risk assessment in order to determine the major water pollutant.

II. HEALTH-HAZARD ASSESSMENT MODEL

A. Research Background In the environmental health risk assessment system applied

at home and abroad, the classification of pollutants is mainly

based on the standard, followed by evaluation. According to the classification system compiled by the International Agency for Research on Cancer (IARC) through a comprehensive carcinogenic reliability assessment of the chemical toxic substances, the pollutants can be divided into gene toxic substances and non-gene toxic substances, and the former include chemical carcinogens belonging to Group 1 and Group 2A and the radioactive pollutants, the latter are non-carcinogen chemical substances. Based on the health-hazard effect of pollutants, as well as a large number of studies on the risk due to toxic substances via drinking water during decades, the health-hazard assessment models in different nature were established [1-3, 6].

B. RiskModel of Chemical Carcinogens The calculation models of the mean individual health risk

value caused by chemical carcinogens via drinking water are[1-3].

( )1 exp / 70c cig ig igR D q⎡ ⎤= − −⎣ ⎦ (1) c c

igi

R R=∑ (2)

2.2 / 70cig iD C= (3)

Where cigR is the mean individual health risk value caused

by chemical carcinogen i, a-1; cR is comprehensive risk value,

a-1; cigD is exposure dose per weight of chemical carcinogen i

via drinking water, mg/(kg*d); igq is carcinogenic coefficient of chemical carcinogen i via drinking water, mg/(kg*d); 70 in (1)is the average age of people, a; 2.2 in (3) is the mean drinking amount per day for adult, L; Ci is the concentration of chemical carcinogen I, mg/L; 70 in (3) is the mean weight of adult, kg.

C. Risk Model of Radioactive Substances The calculation models of the mean individual health risk

value caused by radioactive substances via drinking water are showed as the following.

rig

rig DR 21025.1 −×= (4)

This paper is funded by the Natural Science Fund Project (No. 50609006 & No.40830639)

978-1-4244-2902-8/09/$25.00 ©2009 IEEE 1

ag

awi

rig gUCD = (5)

Where rigR is the mean individual health risk value caused

by nuclides via drinking water, a-1; 21025.1 −× is death probability coefficient of cancer induced by radiation, 1/Sv; Ci is the concentration of pollutant, mg/L; a

wU is the individual

drinking amount of age group a, L/a; agg is the transformation

factor of intake dose via drinking water for group A.

D. Risk Model of Non-CarcinogenPollutants The calculation models of the mean individual health risk

value caused by non-carcinogen pollutants via drinking water are [2]:

70/10 6−×=ig

ignig RfD

DR (6)

∑=i

nig

n RR (7)

Where nigR is the mean individual health risk value caused

by non-carcinogen pollutants i via drinking water, a-1; nR is comprehensive risk value, a-1; igD is daily mean exposure dose per weight of non-carcinogen pollutants i via drinking water, mg/(kg*d), calculated by (2); igRfD is the reference dose of non-carcinogen pollutants i via drinking water, mg/(kg*d); 70 is the mean age of people, a.

The above calculation models of the mean individual health risk value due to pollutants of drinking sources are the basic form of health risk assessment, and should be improved appropriately in practical applications according to the type and concentration of pollutants, as well as local living standard, thereby evaluating the quality of water supply sources.

III. APPLICATION OF MODEL Based on the distribution of underground water wells in a

city of Shandong Province and the principle of uniformity, there are ten monitoring points arranged in the city : 1# City Kindergarten, 2# Canning Factory, 3# Woolen Mill, 4# Mining Machinery Plant, 5# Welfare Institute, 6# Paper Mill, 7# General Brewary, 8# Agricultural College, 9# Cotton Mill, 10# Water Works Well[4]. The health risk models were applied to analyze the quality data monitored at the ten points of groundwater source in this city [4], in order to explore the risk caused by various pollutants and the quality safety of groundwater, water quality monitoring data were given in Tab.1.

A. Water Quality Analysis For the items in table 1, the toxic substances harmful to

human health are as follows. Chemical carcinogens are hexavalent chromium (Cr+6), arsenic (As), cadmium (Cd), and non-carcinogen pollutants mainly include lead (Pb), cyanide (CN-), fluoride (F-), ammonia (HN3-N) and volatile phenol [4]. Radioactive pollutants have not been detected, the concrete

name of organic pollutants has also not been obtained. Therefore, only the health risk values of chemical carcinogens and non-carcinogen pollutants were calculated. However, the health hazard due to organic pollutants of sources, especially trace organic compounds can not be ignored.

TABLE I. GROUNDWATER QUALITY MONITORING DATA OF A CITY

Value (mg/L)

Monitoring Number 1# 2# 3# 4# 5#

pH 6.94 6.98 7.02 6.82 6.86 Total hardness 280.6 271.6 389.7 459.8 377.6 Volatile phenol 0.001 0.001 0.002 0.001 0.002

CN- 0.002 0.002 0.002 0.004 0.002 Fluoride 0.30 0.25 0.29 0.23 0.12

Cr+6 0.002 0.002 0.002 0.002 0.002 NH3-N 0.020 0.020 0.018 0.032 0.020 NO3--N 14.03 9.32 16.35 28.23 24.66 NO2--N 0.015 0.012 0.018 0.016 0.001

As 0.010 0.004 0.006 0.004 0.007 Pb 0.010 0.010 0.016 0.014 0.010 Cd - - - - 0.0006

Permanganate 0.72 1.03 0.82 0.84 1.13 Value (mg/L) 6# 7# 8# 9# 10#

pH 6.89 6.70 6.79 7.10 7.57 Total hardness 451.2 544.3 426.5 153.0 302.1 Volatile phenol 0.001 0.001 0.002 0.001 0.001

CN- 0.002 0.002 0.002 0.002 0.002 Fluoride 0.20 0.22 0.26 0.24 0.33

Cr+6 0.003 0.004 0.009 0.002 0.003 NH3-N 0.020 0.040 0.050 0.020 0.033 NO3--N 19.70 27.03 18.73 3.54 9.41 NO2--N 0.001 0.001 0.002 0.002 0.002

As 0.004 0.004 0.006 0.004 0.005 Pb 0.010 0.014 0.014 0.010 0.010 Cd - 0.006 - - -

Permanganate 0.76 0.44 0.64 1.26 0.96

The carcinogenic coefficient of pollutants and the reference dose via drinking water can be found in the data offered by U.S. EPA [6-8], and the carcinogenic coefficients of chromium, arsenic and cadmium are shown in table 1. For non carcinogenic pollutants, the reference dose of lead [1-3], cyanide, fluoride, nitrogen and phenol via drinking water can be seen in table 2. Other parameters of the model, namely concentration of pollutants, the mean drinking amount for adult,

2

adult weight and the mean weight, should be determined according to the situation of study area.

TABLE II. THE CARCINOGENIC COEFFICIENT OF CHEMICAL CARCINOGENS VIA DRINKING WATER

Carcinogens Assessment Factor (mg/(kg*d))

Cr+6 As Cd igq 41 15 6.1

TABLE III. THE REFERENCE DOSE OF NON-CARCINOGENIC POLLUTANTS VIA DRINKING WATER

Non-carcinogenic

pollutants

Assessment Factor( mg /(kg*d))

Pb CN- F- HN3-N Phenol

igRfD 0.0014 0.037 0.06 0.97 0.1

TABLE IV. THE HEALTH RISK VALUES OF CHEMICAL CARCINOGENS VIA DRINKING WATER

Risk Value ×E-05 (a-1)

Monitoring Number 1# 2# 3# 4# 5#

Cr+6 3.68 3.68 3.68 3.68 3.68 As 6.72 2.69 4.04 2.69 4.71 Cd - - - - 0.16

Total risk 10.4 6.37 7.71 6.37 8.55 Risk Value ×E-05 (a-1) 6# 7# 8# 9# 10#

Cr+6 5.51 7.34 16.5 3.68 5.51 As 2.69 2.69 4.04 2.69 3.36 Cd - 1.64 - - -

Total risk 8.20 11.7 20.5 6.37 8.88

TABLE V. THE HEALTH RISK VALUES OF NON-CARCINOGENIC POLLUTANTS VIA DRINKING WATER

Risk Value ×E-9 (a-1)

Monitoring Number 1# 2# 3# 4# 5#

Pb 3.21 3.21 5.13 4.49 3.21

CN- 0.0243 0.0243 0.0243 0.0485 0.0243

F- 2.24 1.87 2.17 1.72 0.898

HN3-N 0.0069 0.0056 0.0083 0.0074 0.0046

Phenol 0.0045 0.0045 0.0089 0.0045 0.0089

Total risk 5.49 5.11 7.34 6.27 4.14 Risk Value ×E-9 (a-1) 6# 7# 8# 9# 10#

Pb 3.21 4.49 4.49 3.21 3.21

CN- 0.0243 0.0243 0.0243 0.0243 0.0243

F- 1.50 1.65 1.95 1.80 2.47

HN3-N 0.00046 0.00046 0.00093 0.00093 0.00093

Phenol 0.0045 0.0045 0.0089 0.0045 0.0045 Total risk 4.73 6.17 6.47 5.03 5.71

B. Calculation of Health Hazard Risk

The health risk values caused by chemical carcinogens and non-carcinogenic pollutants of groundwater sources, namely the mean individual annual risk, were calculated in Tab. 4 -5.

C. WaterQuality Health Hazard Risk Aassessment

From Tab.4-5, it can be concluded that the health risk values caused by chemical carcinogens are 4 to 5 orders of magnitude higher than those due to non-carcinogenic pollutants for groundwater in this city, meaning that the chemical carcinogens need to be controlled preferentially for groundwater supply sources and must be removed before consumption to reduce risk. For a more intuitive health risk value of chromium, arsenic, and cadmium, the results are plotted into histogram, as shown in Fig.1.

In Tab.4 and Fig.1 the analysis results of 10 monitoring points in a city are shown. And the health risk values calculated due to chemical carcinogens are in the range of 6.37×10-5a-1-2.05×10-4a-1, all higher than the standard recommended by ICRP, that is 5.0×10-5a-1 which means there should be less than 500 persons endangered or died from pollutants in drinking water for every ten million people each year. Where the largest health risk value can be obtained at 8# monitoring point, and the total risk value is 2.05×10-4a-1, 4.1 times more than the standard recommended by ICRP, while 205 times more than the standard of 1.0×10-6a-1[1-2] recommended by the Swedish Environmental Protection Agency and the Netherlands Construction and Environment Agency. The total risk values at 2#, 4#, 9# monitoring points are smaller, namely 6.37×10-5a-1. For groundwater sources in the city, the ranking of risk values due to chemical carcinogen by drinking water is Cr+6>As>Cd, meaning groundwater sources in the region have been seriously polluted by chromium and arsenic, and drinking safety is at risk. It is necessary for water treatment plants using groundwater to take appropriate technical means to remove such pollutants and then reduce the risk of drinking water, finally improve the drinking safety.

It is obvious in table 5 that the health risk values caused by non carcinogenic pollutants are in the range of [4.14×10-9a-1，7.34×10-9 a-1], namely less than 10 persons endangered or died from pollutants in drinking water for every ten million people

0.00E+00

5.00E-05

1.00E-04

1.50E-04

2.00E-04

2.50E-04

1 2 3 4 5 6 7 8 9 10

CrAsCdTatal risk

Figure 1. Health risk values for chemical carcinogens

3

each year. 5# monitoring point is subjected to slight pollution, with the risk value of 4.14×10-9a-1. While the risk value at 3# monitoring point is 7.34×10-9a-1 which refers to the most serious contamination suffered. Take 3# monitoring point with the highest risk as a example, the ranking of risk values due to non-carcinogen pollutants by drinking water is Pb> fluoride > cyanide > volatile phenol >NH3-N, showing that lead pollution is more serious in this region, and lead waste and garbage in the city should be given safe disposal.

IV. CONCLUSIONS More and more water supply sources are suffering from

contamination, the type of chemical pollutants is also increasing year by year, and it is difficult for the conventional water purification process to remove trace organic pollutants which will have significant influences on human health. It is feasible to directly obtain the synthetic quality conclusions of the supply sources showed by risk value through water quality health-hazard risk assessment on water supply sources, thus determining the major water pollutant and the management priority.

The water environmental quality and the health risk for public can be quantitatively described by calculating the health risk due to pollutants of groundwater sources. The results show that the health risk values caused by chemical carcinogens are higher than the standard recommended by ICRP, that is 5.0×10-

5a-1, and their effect is much greater than that of those non-carcinogen contaminations.

The ranking of risk values due to chemical carcinogen by drinking water is Cr+6>As>Cd, therefore the contamination from hexavalent chromium and arsenic should be given special attention in the groundwater management of this city. Especially, the direct exploitation of groundwater for drinking ought to be improved in the rural areas and suburds, and it is necessary to achieve central water supply between the village and town. Hexavalent chromium, arsenic, and some other pollutants should be removed by use of relevant techniques to reduce the risk caused by groundwater pollution. The ranking of risk values caused by non-carcinogen pollutants is Pb> fluoride > cyanide > volatile phenol >NH3-N, despite the risk value is still lower, but should be of great importance for management. Lead Pollutants, in particular waste battery, should be disposed properly to prevent groundwater pollution. For the health management of groundwater sources, prevention is more effective than treatment.

This study adopted the health risk assessment methods on drinking water proposed by U.S. EPA, and only considered one exposure pathway, that is, the mean water intake. Moreover, risk values calculated did not include the risk due to trace organic pollutants which have caused enough attention in recent years, therefore the risk values obtained from calculation are less than the real environmental status.

ACKNOWLEDGMENT This paper is funded by the Natural Science Fund Project

(No. 50609006 and No.40830639). The basic monitoring data

is from the following references and the paper author would like to give thanks to them.

REFERENCES

[1] QIAN Jia-zhong,LI Ru-zhong, WANG Jia-quan etc, “Environmental health risk assessment for urban water supply source”, Journal of Hydraulic Engineering , 2004; (8), pp:90-93.

[2] ZENG Guang-ming, ZHUO Li, ZHONG Zheng-lin etc. “Assessment models for water environmental health risk analysis”, Advances in Water Science 1998; 9(3),pp: 212-217.

[3] HU Er-bang. “Practical techniques and methords of environmental risk assessment”, Beijing: China Environmental Science Press 2000; 6, pp:467-482.

[4] WANG Yu-jun, LI Guang-de, LIU Gui-hua. “Assessment of the quality of the groundwater in Taian city”, Journal of Shandong Agricultural University 1999; 30(3), pp:213-218.

[5] http://www.ep.net.cn/msds/epa/epa02-1.htm[S] [6] Gao,J, Zhang LP. Preliminary health risk assessment of heavy metals in

water in Beijing. Environmental Science, 2004.25 (2), pp: 47-50. [7] Beynon M. A mathematical analysis: an understanding of uncertainty.

European Journal of Operational Research, 2002,140(1):pp:148-164. [8] GAO Ji-jun, ZHANG Li-ping, HUANG Sheng-biao etc. “Preliminary

health risk assessment of heavy metals in drinking waters in Beijing”, Environmental Science 2004; 25(2),pp: 47-50

4