Metal Contamination of Drinking Water from Corrosion of Distribution Pipes

Environmental Pollution 57 (1989) 167-178

Ibrahim A. Alam & Muhammad Sadiq

Water Resources and Environment Division, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

(Received 24 February 1988; revised version received 22 September 1988; accepted 26 September 1988)

A BS TRA C T

The objectives of th& study were to evaluate metal contamination of drinking water resulting from the corrosion of distribution pipes and its significance to human health. A community in Dhahran, which is served from its own desalination facilities, was chosen for this study. About 150 drinking water samples were collected and analyzed for metal concentrations using an inductively coupled argon plasma analyzer. It wasjbund that copper, iron and zinc in the drinking water increased during its transportation from the desalination plant to the consumers. This increase was related to the length and material of distribution pipes. Concentrations of copper and zinc were increased during overnight storage of water in the appliances. Metal concentrations found in this study are discussed with reference to human health.

INTRODUCTION

Drinking water in Saudi Arabia is mainly obtained by desalting seawater or ground water. After desalination, the finished water is generally mixed with ground water, disinfected, pH adjusted, and transported through the distribution network to the consumers. Drinking water supplies contain variable amounts of metals (Bostrom & Wester, 1967; Durum, 1974; Andermann & Shapir, 1975). Several of these 167 Environ. Pollut. 0269-7491/89/$03'50 O 1989 Elsevier Science Publishers Ltd, England. Printed in Great Britain 168 lbrahim A. Alam, Muhammad Sadiq metals are essential for normal functioning of the human body, whereas others are non-essential (Underwood, 1971; WHO, 1973). Essential as well as non-essential metals can be toxic to humans if present above threshold levels (Baccini & Roberts, 1976). The sources of metals in-drinking water are associated either with natural processes or man's activities (NRC, 1977). Generally, desalination removes most of these metals (Andermann & Shapir, 1975). However, during mixing with ground water, disinfection, fluoridation, and pH adjustment, metals are reintroduced into the finished water. The occurrence of corrosion in the distribution system may also add metals to the finished water before it reaches the consumers (Semple et al., 1960; Harris & Elsea, 1967; Dangel, 1975; Moore et al., 1975). Therefore, corrosion of distribution pipes could be the major source of toxic metal contamination of drinking water supplies in Saudi Arabia. Information on the contribution of pipe corrosion to the concentrations of metals in the drinking water supplies is scanty. The objectives of this study were to investigate corrosion of the distribution pipes as a source of metal contamination, and to evaluate probable human health effects associated with the corrosion products in the drinking water.

MATERIALS AND METHODS

A population of over 4000 in Dhahran, Saudi Arabia, was selected for this study. The study area had three desalination plants which were supplied with raw water from nine groundwater wells within 1 km of the desalination facilities. The casings of the groundwater wells were of cast iron. Groundwater from these wells was transported through corrugated cement pipes to the storage tank. During treatment in the desalination facilities, a predetermined portion of the salt was removed from the groundwater. The desalinated water was chlorinated, using sodium hypochlorite, and pH was adjusted by adding soda ash. The desalinated and treated water was pumped through main distribution pipes to the inlet for each building. The type and material quality of the pipes within different buildings were variable. Information on the type of material, age, and length of the supply pipes of the mains, as well as from the main to the sampling points, is listed in Table 1. Similar information on faucets and appliances was not available. About 150 drinking water samples were collected from 32 randomly selected locations within the study area. To evaluate the effect of overnight storage in the faucets and appliances, 50 ml of water were taken before using drinking water early in the morning. This water sample was designated as SO. To have a uniform residence time, all the office and school locations were flushed for 20 min between 8 and 9 pm on the previous evening. The average Metal contamination of drinking water from pipe corrosion 169

TABLE 1 Type, Age and Size of Distribution Pipes in the Study Area

S. no. Location Pipe age Main pipe Distribution pipe~ (year) Length Material Size Length Material Size (m) (em) (m) (em)

1 House 1978 1 900 A/C 10 20 Gav. iron 2"5 2 House 1979 1600 A/C 10 20 Gav. iron 2'5 3 House 1979 1 550 A/C 10 20 Gav. iron 2"5 4 House 1983 2390 A/C, PVC 10 20 PVC 2"5 5 House 1980 2000 A/C 10 20 PVC 2-5 6 House 1980 2 100 A/C 10 10 + 10 PVC, Copper 2.5 7 House 1980 2400 A/C 10 10 + 10 PVC, Copper 2-5 8 House 1970 1 150 A/C 10 50 PVC 10 9 House 10 House 1 550 A/C 10 400 PVC 5-0 11 House -- -- 12 Office building 1970 250 CPVC 10 5 PVC 1"3 13 Office building 1973 260 CPVC 10 20 PVC 2.5 14 Office building 1974 800 CPVC 10 50 Gav. iron 1-9 15 Office building 1976 600 CPVC 10 20 Copper 2"5 16 Office building 1978 700 CPVC 10 10 Copper 1"3 17 Office building 1983 840 CPVC 10 20 Copper 3-8 18 Office building 1983 1060 CPVC 10 150 + 20 PVC, Copper 5-0 19 School I 1984 350 Gay. iron 7"6 50 Copper 2-5 20 School 1 1984 380 Gay. iron 7-6 50 Copper 2"5 21 School 1 1984 400 Gay. iron 7-6 50 Copper 2"5 22 School 1 1984 400 Gay. iron 7.6 50 Copper 2"5 23 School 2 1984 430 Gay. iron 7-6 50 Copper 2.5 24 School 2 1984 430 Gay. iron 7-6 50 Copper 2"5 25 School 2 1984 430 Gay. iron 7.6 50 Copper 2.5 26 School 3 1984 450 Gay. won 7.6 50 Copper 2:5 27 School 3 1984 450 Gay. iron 7.6 50 Copper 2.5 28 School 3 1984 450 Gay. iron 7-6 50 Copper 2"5 29 Community center 1984 1 520 A/C 10 30 Cafeteria 1974 750 CPVC 10 20 Gay. iron 3.8 31 Cafeteria 1980 250 A/C 10 -- -- 32 Stadium 1980 2100 A/C 10 --

A/C: asbestos/cement; Gay. iron: galvanized iron; CPVC: hard PVC. a Represents pipe length between main line and the point where utilities are connected, i.e. service pipes. residence time for SO samples from these locations was 12 h. The residence time of SO samples from the houses varied between 7 and 9 h. Subsequent water samples from the same points were taken after draining the faucets for 5 and 15 min without allowing the freshwater to stand in contact with the pipes. The second and the third water samples were designated as S 1 and $2, respectively. The groundwater, and the finished or product water samples after all treatments, were collected from the desalination facilities. The collected water samples were divided into two parts: one for pH measurements and the other for metal determinations. The portion for metal determination was preserved using ultrex grade nitric acid. The concentrations of aluminum, barium, cadmium, chromium, cobalt, copper, 170 lbrahim A. Alam, Muhammad Sadiq calcium, iron, magnesium, manganese, nickel, potassium, lead, sodium, vanadium, titanium, strontium and zinc in the water samples were determined using an inductively coupled argon plasma analyzer (ICAP). The measurements were repeated five times and a mean and standard deviation of these observations were computed. To ensure high quality of the analytical results of this investigation, Standard Reference Material--a water sample (SRM 1643a) obtained from the United States Bureau of Standards (USNBS)--was analyzed along with the collected water samples.

RESULTS AND DISCUSSION

A comparison of metal concentrations in samples S1 and $2 using a t-test revealed that the chemical compositions of these samples were not significantly different (P < 0"05). Similar concentrations of metals in S1 and $2 samples suggest that freshwater from the mains had reached the sampling points. Therefore, the mean concentrations of metals in the collected water S1 and $2 samples are given in Table 2. Concentrations of metals in SO water samples are also included in Table 2. To evaluate water quality, the maximum permissible and highest desirable concentrations of each metal in drinking water, as suggested by WHO (1971), are given in Table 2. The mean copper concentrations in the S 1 and $2 water samples ranged from below the ICAP detection limit (<0-01) to 3.00#g m1-1. The concentrations of copper in the finished water from the treatment plants and groundwater wells were below the ICAP detection limit. As the drinking water was being transported through the distribution pipes, copper

TABLE 2 Mean Metal Concentrations in the Collected Water Samples

S. no. Location Sample Metal concentration (#g ml - 1) type Ca Cu Fe K Mg Na Sr Zn pH

1 House S1 +$2 49.66 0-000 0-128 6.86 15.41 183 1.25 0-042 8.07 SO 49.10 0.000 0-090 7.08 15.75 183 1.37 1.000 8.01 2 House S1 +$2 58-66 0.000 0.051 7.39 16.73 184 1.32 0.772 7.96 SO 59.67 0-004 0-102 7.37 17.26 183 1.34 0.723 7.96 3 House SI +$2 22.33 0.000 0-031 4.32 15.71 183 0.52 0.122 7.44 SO 24.60 0.498 0-019 4.36 13.60 183 0.55 1.581 7.89 4 House S1 + $2 39.82 0.042 0-031 6.12 10-99 207 0.88 0-11 7.41 SO 37.29 0.067 1.139 6-88 11.0 202 1.37 2.374 7.73 5 House SI +$2 40.49 0.044 0-034 7.20 11.99 184 0.95 0.025 7.83 SO 58.39 0.908 0"016 7.56 17.23 186 1.39 1.780 7"44 6 House SI +$2 45.75 0.131 0.032 7.53 13.52 183 1.09 0'028 7'26 SO 47.50 1.380 0.007 7.25 18-04 182 1.14 0-356 7.74 Metal contamination of drinking water from pipe corrosion 171

TABLE 2--contd.

S. no. Location Sample Metal concentration (#g ml- 1) type Ca Cu Fe K Mg Na Sr Zn pH

7 House S1 +$2 60.89 0-071 0.022 7.59 17.68 185 1.42 0-021 7.61 SO 60.90 1.124 0.013 7.71 17.48 190 1.42 5-554 7"81 8 House S1 + $2 25.61 0.000 0.141 5.32 7.89 220 0.58 0-234 7.38 SO 26.79 0.005 1.825 6.04 8-18 260 0-63 1.560 7.46 9 House SI +$2 32.19 0.000 0-073 7.53 11.08 208 0.81 0.007 7-89 10 House S1 +$2 27.89 0.431 0-099 6.90 9.41 184 0.58 0.110 7-29 11 House S1 + $2 29-21 0.000 0-009 6.73 9.56 184 0.64 0.000 7.65 12 Office building SI + $2 38.22 0.738 0.024 6.25 11.22 183 0.92 0.401 7.42 SO 38.83 1.413 0.032 6.09 11'22 182' 0.94 1.539 7.40 13 Office building S1 +$2 34.08 0.195 0.072 5.34 t0.98 183 0.83 0-441 7.41 SO 38.24 0.682 0.127 5.38 10.78 183 0-92 1.906 7.37 14 Office building S1 +$2 33"82 0.355 0-028 5.41 10.71 189 0-82 0.139 7.41 SO 33.83 1-409 0.018 5.34 10.73 183 0.83 0.095 7.42 15 Office building SI +$2 34.76 2"256 0.050 5.67 11.02 183 0.88 0.048 7.26 SO 34.72 1.754 0.011 5.29 10-99 186 0.85 0-096 7.35 16 Office building SI +$2 35.99 1.434 0.038 5-56 11.34 187 0-95 0.452 7.35 SO 35.02 1.135 1.971 5.39 11-33 189 0.91 0.542 7.69 17 Office building SI +$2 34.96 2'976 0.224 5.49 11.04 183 0'93 0.153 7.38 SO 35.79 1.965 0.028 5.74 11.44 186 0.95 0-298 7.53 18 Office building SI +$2 37.18 0.060 0.056 5.49 11.89 187 1.00 0.050 7.52 SO 35.54 6'834 0.272 5.28 10'98 183 0'92 0.112 7.56 19 School 1 S1 +$2 55-67 2.783 0.071 7.19 17.34 188 1.40 0-019 7.72 SO 55.19 2.328 0-058 17.15 17.19 184 1.39 0-823 7.74 20 School 1 S1 + $2 56-03 2'484 0.168 6.99 17.33 187 1.40 0.055 7.76 SO 55.59 1"921 0.080 7'12 17.33 187 1-39 0.633 7.79 21 School 1 SI +$2 21.46 2.016 0.287 7.34 7.11 220 0.54 0.071 7-41 22 School 1 SI +$2 21.68 2'082 0.130 7.41 7.40 220 0.54 0.099 7.51 23 School 2 SI +$2 55.81 1.070 0.300 7.04 17.27 186 1.41 0.007 7-88 SO 54-92 0.043 0-087 6.93 17.10 184 1.39 0.128 7.61 24 School 2 SI +$2 28.96 1.459 0-489 8.83 9.57 223 0-73 0.059 7.41 25 School 2 S1 + $2 21-76 1.597 0.522 7-42 7.21 219 0.54 0.033 7.48 26 School 3 S1 +$2 54.81 1-432 0.765 6.62 16.82 185 1.37 0.014 7.82 SO 54.92 0"032 0.068 5.74 15.89 186 1.12 0.259 7"54 27 School 3 S1 +$2 22.90 1.641 0.515 7-88 7.42 200 0.55 0.075 7.69 28 School 3 SI +$2 21.76 1.560 0.119 6.59 6.29 204 0.39 0.139 7.94 29 Community center S1 + $2 53.60 0'530 0.169 6-37 16-09 230 1.30 0.076 7-54 30 Cafeteria S1 + $2 26.1l 0.000 0.032 4.18 8-33 198 0.69 0.050 6.98 31 Cafeteria S1 + $2 25.82 0.376 0.036 5.97 9-16 208 0.63 0.033 7.41 32 Stadium S1 + $2 51-93 0-302 0'102 6.80 11"02 233 1.24 0.072 8.05 33 Treatment plant S1 + $2 22'58 0.000 0.000 5.64 7.41 207 0.61 0.000 7.52 34 Treatment plant SI + $2 21.72 0.000 0.000 3.86 6.67 187 0.56 0.010 7.53 35 Treatment plant S1 + $2 25.84 0.000 0.000 6.63 9.34 t86 0.65 0.017 7.48 36 Groundwater well S1 +$2 257-66 0.000 0.021 21.7 88.26 587 7.34 0-045 7.59

WHO water quality 75 R 0"05 R0-1 R -- 30R -- -- 5R 7-8R standards 200P 1.0 P 1.0P 150P 15 P 6-9P

Ca: calcium, Mg: magnesium, Fe: iron, K: potassium, Cu: copper, Zn: zinc, Sr: strontium, Na: sodium. --: no data available. R: highest desirable concentration. P: maximum permissible concentration. 172 lbrahim A. Alam, Muhammad Sadiq concentrations increased to as high as 3 #g ml- ~ in water samples collected from location 17. Evaluating the results of copper analyses in the light of information listed in Table 1, it was revealed that higher copper concentrations were found in water samples collected from locations with copper pipes in the branch lines. It is obvious that corrosion of the copper distribution pipes was responsible for the build-up of copper in these samples. In the study area, all the houses were single storey with short lengths of copper pipes and hence water samples collected from residential locations contained lower levels of copper than those from the office or school buildings. The office buildings were multistoried and thus the drinking water was exposed to longer lengths of pipes and probably for longer periods of time, which resulted in higher copper levels. The main pipes from the water treatment plant to schools 1, 2 and 3 were of galvanized iron. The branch pipes were of copper. This is probably the reason that water samples from these locations exhibited very high copper concentrations. The results of this study show that copper build-up in the drinking water results from the corrosion of branch distribution pipes. The pH of the drinking water may affect corrosion, but data from this study are inconclusive regarding this. The chloride concentrations in the drinking water samples were high (> 400 #g ml- 1) and this might have contributed to the corrosion of copper pipes. To further verify the role of pipe corrosion in copper contamination of the drinking water, sampling location 16, which has six floors and branch pipes of copper, was selected. Water samples were collected from the drinking water fountains located at the same position at each floor. Copper concentrations found in the water samples are plotted in Fig. 1, together with the lengths of copper pipes up to the sampling locations. It is evident that, in response to an increase in copper pipe lengths, the concentrations of copper in the water samples increased gradually from level 1 to level 6. This clearly demonstrates that corrosion of the distribution pipes was responsible for copper build-up in the drinking water. Dependence of copper contamination of drinking water on the length of copper lines in the distribution system can also be seen on Fig. 2, which depicts copper concentrations in various water samples along with copper pipe lengths. Copper is a gastrointestinal tract irritant and can be highly toxic (NRC, 1977). There are reports of infant mortality and an outbreak of copper poisoning associated with contaminated drinking water (Semple et al., 1960; Walker-Smith & Blomfield, 1973). Some of the high copper concentrations in the collected water samples are plotted on Fig. 2. A majority of the water samples contained copper higher than the highest desirable limit and many above the maximum permissible limit suggested by WHO (1971). Metal contamination of drinking water from pipe corrosion 173

1.00 ] -//////// 0.90 1 =7 0.00 1 == 0.70 1

0.60 -'~ ~/////.,//

0.50 - "HHHH

LJ o.~o- ~ "/////~ ~//////~ o.~o ,1///111/~/////~ '.,:.744k44 ~///M//, 1/11////~ C.J V///////~ "/'/))))2)) .1111111, /i/i/i/i/ 0.20 V//////~ ,///////, ~////////~ ~//.////~d Y//////~ 0.10 ¢HHHH ,HHH~, ~/////h ~iii////1 /

Iron in the finished water at the treatment plants was not detectable ( < 0.01/~g ml - ~) and its concentration in the groundwater was 0"02/tg ml - During transportation through the distribution pipes, iron levels built-up to between 0.02 to 0.77/tg ml - ~. If the mean concentrations of iron in the water samples S1 and $2 are seen in the light of information given in Table 1, it can be concluded that iron build-up was higher in the samples where water flows

3.00 - 2.00 - 7 I 2.60 - / / 240 / 7 - / =n :,. / 2.20 - / / / g 2.00 ¢77 1.80 == 1.60 1.~0 ¢ S == 1.20 1.00 0.80 ' ¢ o,o 0.4.0 - 15 555 0.20 -

o.oo 7-,Ii i !,,5,',! 6 ;o 12 1'3 ;4 34. 36 Sampling Locations 10 .... 20 25 50 10 50 50 50 50 30 30 30 30 4.0 40 .... Length of Copper Pipes (m) Fig. 2. Distribution of copper in drinking water samples (mean of S1 and $2 samples). 174 Ibrahim A. Alam, Muhammad Sadiq through the galvanized iron pipes. Therefore, iron build-up could be attributed to the corrosion of such pipes. The highest desirable and the maximum permissible limits of iron in drinking water have been proposed by WHO (1971) as 0.1 and 1 #g ml- 1, respectively. The maximum limit of iron in drinking water is based on its objectionable taste rather than its toxicity. All the water samples analyzed in this study contained less iron than the maximum permissible limit; however, many of the samples exceeded the highest desirable limit. Calcium and magnesium concentrations in the water samples ranged between 21 and 61, and 7 and 17 #g ml- 1 as compared with 275 and 88 #g ml-1, respectively, in the groundwater sample. Potassium and strontium concentrations in the analyzed drinking water samples were found to be < 8 and 2 #g ml- 1, respectively. It was found that the concentrations of calcium, magnesium, potassium and strontium varied significantly from day to day and from treatment plant to plant. However, their relative ratios with respect to each other remained almost unchanged, suggesting that there was no input from the corrosion of the distribution pipes. The variations in the above elements might be a result of salt removal in different proportions during desalination of groundwater. WHO (1971) has proposed 75 and 200pg ml-1 for calcium, and 30 and 150/~g ml-1 for magnesium as the highest desirable and the maximum permissible limits in drinking water. All the water samples analyzed in this study were below the highest desirable concentrations. No desirable or permissible limits for potassium and strontium have been proposed by WHO (1971). Calcium and magnesium are essential for normal human growth. It has been found in several epidemiological investigations in the USA and European countries that drinking water hardness, i.e. concentrations of calcium and magnesium, is inversely associated to cardiovascular mortality in particular, and adult mortality in general (Schroeder, 1960; Crawford et al., 1968; CEC, 1976; Sonneborne et al., 1983). These investigations have pointed out that the presence of calcium and magnesium in the drinking supplies might prove beneficial to humans. All the drinking water samples contained sodium higher than 180#g ml-x. Sodium concentration in the groundwater sample was about 600 #g ml- 1. The reasons for high sodium in the drinking water samples was not pipe corrosion but the groundwater used for blending, chlorination with sodium hypochlorite, and the pH adjustment process which uses soda ash. There are no proposed drinking water quality standards for sodium. High concentrations of sodium have been implicated in hypertension (Sakaki, 1964; Shaper et al., 1969; WHO, 1978a). In Europe, sodium content in drinking water was reported to range from 4 to 125/ag ml- 1 (Zoeterman & Metal contamination of drinking water from pipe corrosion 175

Brinkmann, 1976). In the United States, 2100 municipal water supplies were evaluated for sodium concentrations and 20 #g ml-1 was reported as the median value (NRC, 1977). The water samples analyzed in this study contained much higher levels of sodium than the literature values reported above. Concentrations of lead in the drinking water samples were below the analytical detection limit, i.e. < 0.005 ktg ml- 1, and are not included in Table 2. This level of lead was below the maximum permissible limit (0-05 #g ml- 1) suggested by WHO (1971). The office building location 16 has a distilled water facility and distilled water distribution pipes are of brass coated with tin. During transportation, lead in the distilled water increased to several/~g ml- 1 as shown on Fig. 3. Analysis of the pipe material revealed.that lead was a major component of the tin coating. Lead entered distilled water as a result of corrosion of the tin coating (chemical analysis showed that tin coating was actually tin-lead solder). This was further verified by analyzing the white precipitate formed inside the tube. Although distilled water was not used for drinking, it indicated that wrong selection of distribution pipe material could contaminate drinking water. The concentrations of zinc in the drinking water samples varied between < 0.005 and 0.77/~g ml- 1. Zinc in the finished water at the treatment plants and groundwater was < 0.01 and 0.045 ~g ml- 1, respectively. The results of the study indicated a build-up of zinc at locations which had galvanized pipes. This build-up was due to pipe corrosion at these locations. WHO (1971) proposed 5 and 15/~g ml-1 of zinc in drinking water as the highest desirable and the maximum permissible limits, respectively. All the water samples contained much less zinc than the highest desirable levels.

2.80

"7 2.~0

2.00

1.60 ////////) ~/////// 1.20 ~///////,

0.00

OAO

0.00 i i i i i Drinking Lab 6,313 Lab 6,315 DLab~317 Feed Ground Water SampLes Fig. 3. Distribution of lead in distilled water. 176 lbrahim A. Alam, Muhammad Sadiq

Zinc is essential for normal human growth, and drinking water is considered to contribute significantly to daily requirement. Desalinated water low in zinc could induce zinc deficiency (WHO, 1978b). The concentrations of aluminum, barium, cadmium, chromium, molybdenum, cobalt, manganese, nickel, titanium and vanadium were also determined in the drinking water samples. Most of these metals were below the detection limits of the instrument and certainly below the maximum permissible limits as proposed by WHO (1971). The analytical results of these metals are not reported. To evaluate corrosion of appliances and faucets, the first 50 ml of water taken from the faucets in the morning was analyzed for metal concentrations. The mean concentrations of copper and zinc in the S 1 and $2 samples are compared with SO samples in Fig. 4. In general, the concentrations of copper and zinc were higher in the first water sample (SO) compared to the concentrations found in the water samples collected after flushing for 5 or 15 min. It is evident that faucet corrosion increased copper and zinc concentrations. Similar conclusions can be drawn regarding iron concentrations. The concentrations of calcium, sodium, potassium, magnesium and strontium were not affected by overnight storage in the faucets and appliances. The results of this study indicate that corrosion of the distribution pipes and appliances could contaminate drinking water. Careful consideration must be given to the pipe materials used in drinking water distribution networks. Emphasis must be placed on monitoring water quality at the consumers' end, as well as at the treatment facilities. 7

5 % E ~4

I I I ! I I I I I I 1 2 3 4 5 6 ? 12 13 1~, 15 16 17 18 19 20 23 26 Sampling Locations

Copper in SO ~-~JCopper in S1.S2 ~ Zinc in SO I~--'~Zinc in S1.$2 Fig. 4. Copper and zinc concentrations in SO and SI + $2 water samples. Metal contamination of drinking waterfrom pipe corrosion 177

ACKNOWLEDGEM ENTS

The authors acknowledge the support of the Research Institute at the King Fahd University of Petroleum and Minerals, Dhahran, during the course of this study. The technical support of Messrs T. H. Zaidi, Hasan AI-Mohanna, and Aarif A. E1-Mubarek is also gratefully appreciated.

REFERENCES

Andermann, J. B. & Shapir, M. A. (1975). Changes in trace element concentrations in water treatment systems. In Trace Substances in Environmental Health, ed. D. D. Hemphill. University of Missouri, Columbia, pp. 87-91. Baccini, P. & Roberts, P. V. (1976). Die belastung der gewasser durch matalle. Beil. Forsch. Tech. Neue Zurcher Z., 18, 57-8. Bostrom, H. & Wester, P. A. (1967). Trace elements in drinking water and death rates in cardiovascular disease. Acta Med. Scand., 181, 465-73. CEC (1976). Commission for European Communities; Hardness of Drinking Water and Public Health. Pergamon Press, Oxford. Crawford, M. D., Gardner, M. J. & Morris, J: N. (1968). Mortality and hardness of local water supplies. Lancet, 1, 827-33. Dangel, R. A. (1975). Study of corrosion products in the Seattle Water Department distribution system. Environmental Protection Series, EPA-670/2-75-036. Durum, W. H. (1974). Occurrence of some trace elements in surface and groundwaters. Proc. 16th Water Quality Conference: Occurrence, Significance, and Control. University of Illinois, Urbana. Harris, R. W. & Elsea, W. R. (1967). Ceramic glaze as a source of lead poisoning. J. Am. Med. Assoc., 21}2, 544-6. Moore, M. R., Meredith, P. A., Goldberg, A., Carr, K. E., Tonner, P. G. & Lawrie, T. D. V. (1975). Cardiac effects of lead in drinking water. Clinc. Sci. Mole. Med., 49, 337-41. NRC (1977). National Research Council. Drinking Water and Health. The National Academy of Sciences, Washington, DC, pp. 205-488. Sakaki, N. (1964). The relation of salt intake to hypertension in Japanese. Geriatrics, 19, 735-41. Schroeder, H. A. (1960). Relation between hardness of water and death rates from certain chronic and degenerative diseases in the US. J. Chron. Dis., 12, 568-73. Semple, A. B., Parry, W. H. & Phillips, D. E. (1960). Acute copper poisoning, an outbreak traced to contaminated water from corroded geyser. Lancet, 2, 700-1. Shaper, A. G., Wright, D. H. & Kyobe, J. (1969). Environmental effects on the body build, blood pressure and blood chemistry in nomadic warriors serving in the army in Kenya. East Afri. Med. J., 46, 274-81. Sonneborne, M., Schon, D., Hoffmeister, H. & Mandelkow, J. (1983). Health effects of inorganic drinking water constituents, including hardness, iodide, and fluoride. CRC Crit. Rev. Environ. Control, 13, 1-22. Underwood, E. J. (1971). Trace Elements in Humans and Animals (3rd edn). Academic Press, New York. 178 Ibrahim A. Alam, Muhammad Sadiq

Walker-Smith, J. & Blomfield, J. (1973). Wilson's disease or chronic copper poisoning. Archiv. Dis. Child., 48, 476-9. WHO (1971). World Health Organization. International Standards for Drinking Water, (3rd edn). Geneva. WHO (1973). World Health Organization. Trace Elements in Human Nutrition. Tech. Rept. Ser. 352, 38-9. WHO (1978a). World Health Organization. Arterial Hypertension. Tech. Rept. Ser. 628, 1978a. WHO (1978b). World Health Organization. Health Effects of the Removal of Substances Occurring Naturally in Drinking Water. EURO Report and Studies 16. Zoeterman, B. C. J. & Brinkmann, F. J. J. (1976). Human intake of minerals from waters in the European communities. In Hardness of Drinking Water and Human Health. Pergamon Press, Oxford.