A National Survey for Cadmium, Chromium, Copper, Lead, Zinc, Calcium, and Magnesium in Canadian Drinking Water Supplies Jean C. Meranger", Kunnath S. Subramanian, and Chantal Chalifoux Environmental Health Centre, Health Protection Branch, Health and Welfare Canada, Tunney's Pasture, Ottawa, Ontario K1A OL2, Canada
A national survey was conducted t o determine the levels of Cd. Cr, Cu, P b , Zn, Ca, and Mg in Canadian drinking water supplies. Samples of raw, treated, and distributed water, obtained from 70 municipalities across Canada, were analyzed by atomic absorption spectrometry. T h e concentrations of trace metals found were essentially the same for all three types of water samples. The tnedian and range values for distributed water expressed as ng of metal/mL of water were found to be: Cd 5 0 . 0 1 (10.01-0.49); Cr 1 2 . 0 (52.0-8.0); Cu, 20 (5.0-620); Zn, 10 (15.0-380). Values for water P b 11.0(11.0-63.0); hardness, expressed as mg of CaCO:I/L, ranged from 1 in S t . ,John's, Newfoundland, to 554 in Selkirk, Manitoba. Contamination of the water supplies with these metals except copper was minimal during treatment and distribution. In all cases. the median values for the distributed water were well below the LVHO upper limit recommendations. Throughout the world, there is an increasing interest in the quality of drinking water. Recently, attempts have been made to relate the occurrence of certain cancers and cardiovascular diseases to t h e presence of trace metal pollutants such as Cd a n d P b ( I ) and hardness of the local water supplies in terms of Ca and Mg (2-5). The toxic effects oftrace metal pollutants are well documented ( 6 ) .Higher levels of such essential micronutrients as Cr anti Zn may also have detrimental effects on health (7). T h e efficiency of various treatment processes in removing toxic elements or excessive amounts of micronutrients and t h e intri:)duction of trace metals into drinking water during distribution (e.g.. introduction of Cu from t h e corrosion of copper. brass, and bronze pipes and fittings) must also be determined. Therefore, the Department of National Health and Lf,.elfare has initiated a comprehensive nationwide program to determine both the organic and inorganic contaminants in water supplies at various stages of the treatment a n d distribution system. This paper presents the results of analyses for Cd, Cr. C u , P b . Zn, Ca, and Mg in raw, treated, a n d distributed water. Water supplies of 70 municipalities covering the 10 provinces of Canada are included in the present survey.
Experimenta 1 Apparatus. T h e levels of Cd, Cr, and P b were determined using a Perkin-Elmer atomic absorption spectrophotometer, Model 603, equipped with a heated graphite atomizer (HGA-2100) and a deuterium background corrector. Determinations for Cu, Zn. Ca, and Mg were obtained using the same instrument in t h e flame mode with a 2-in. single slot burner. Single element hollow cathode lamps were used as narrow line sources for all the elements except Cd and P b ; electrodeless discharge lamps were used for these elements to increase the sensitivity of the determination. Reagents. High-purity water was obtained by passing t a p water through two mixed bed ion exchange columns followed by distillation in a Corning all-glass distillation system. Appropriate standard solutions of Cd, Cr, Cu, P b , Zn, Ca, a n d Mg were prepared in 1%HNO:j (Baker Ultrex) immediately before analysis by serial dilution of the 1000 mg/L stock solution (Fisher Scientific) stored in polyethylene bottles. 0013-936X/79/0913-0707$01.00/0
Selection of Sampling Locations. Seventy municipalities were selected which provided a mixture of river, lake, and ground water sources across Canada. Selection of sampling stations was based on factors such as provincial boundaries, drainage basin, population, ground water sources, and chemistry of water supply (e.g., p H , hardness, disinfection methods, water treatment methods, and dissolved organics). One station was selected for every 200 000 people in each province giving the following percentage population coverage: Alberta, 76; British Columbia, 53; Manitoba, 63; New Brunswick, 32; Newfoundland, 20; Nova Scotia, 25; Ontario, 37; Prince Edward Island, 16; Quebec, 53; and Saskatchewan, 37. This represents 38%of the Canadian population. The total number of unfiltered raw, treated, and distributed drinking water supplies sampled was 70 (50 surface and 20 ground waters)! 70, and 140, respectively. Duplicate filtered samples were also collected a t each of t h e above locations. Sample Collection. All water samples were collected in the day time, during t h e period November 1976-January 197'7. Nalgene (linear polyethylene), 1000-mL screw-cap bottles were used as containers for t h e samples. Prior to use, t h e bottles were cleaned sequentially as follows: a detergent wash, t a p water rinse, soaking in 1%HNO:j for 24 h, and high-purity water rinse (10 times). After t h e cleaning operation, blanks for each bottle were prepared using high-purity water in 1% Baker Ultrex HNO:+ Any bottles having detectable concentrations of t h e trace metals of interest were rejected. T h e bottles to be used for collection were then dried a t 103 "C for 1 h. cooled to room temperature, capped, and labeled. T o check t h e effect of suspended solids on trace metal concentrations, filtered and unfiltered samples were obtained from the same location. Filtration was done on location by passing water samples through a 0.45-pm Millipore membrane filter placed in a n all-glass Millipore filtering system. T h e membrane filters had been washed with 1% HNO:3 followed by rinsing in high-purity water prior to filtration. Each Nalgene bottle was filled to the brim with the water sample to avoid any air space after adding 1%"0:) (Baker Ultrex) to the partly filled bottles. Samples were obtained from the following four locations in each municipality: (i) raw water intake prior to disinfection treatment; (ii) treated water immediately after all forms of treatment; (iii) distributed water from a public building about half a mile from the plant; and (iv) same as iii, hut about 1 mile from the plant. Before we collected samples from locations iii and iv, the taps were run a t their maximum flow rate for a t least 3 min. T h e samples were transported by air in heavy plastic coolers containing gel-type freezer packs. Immediately upon receipt in the laboratory, they were refrigerated a t 4 "C until analyzed. The consistency in sample collection was ensured by keeping the number of technologists conducting the sampling to a minimum. One person was chosen for Ontario and Western Canada, a second for Quebec a n d t h e Maritimes, and a third for Newfoundland. T h e specific sampling procedures were reviewed in detail with t h e technologists and the municipality personnel involved in the study. Analytical Procedure. The concentrations of Cd, Cr, and P b in the water samples were determined by graphite furnace atomic absorption spectrometry (GFAAS). T h e GFAAS technique was chosen because it has the extremely high sen-
Published 1979 American Chemical Society
Volume 13, Number 6, June 1979
707
Table 1. Optimized Parameters for the Determination of Cd, Cr, and Pb by Graphite Furnace Atomic Absorption Spectrometry (GFAAS) parameters
Cd
line, nm slit, nm charring temp, a OC charring time, s atomization temp, a OC atomization time, s sensitivity, 1 X l o v i 2 g detection limit, ng/mL linear working range, ng/mL
228.8 0.7 300 10 1400 5 0.9 0.01 0- 1
element Cr
Pb
357.9 0.7 600 10 2600 10 28.0 2.0 0-60
283.3 0.7 400 10 2100 7 24.0 1.o 0-10
a Temperatures represent the meter settings on the control panel of the HGA-2100 temperature programmer. Mass for 0.0044 absorbance with the nitrogen purge gas flow in the interrupt mode for Cd and Pb, and with the argon purge gas flow (50 mL/min) normal mode for Cr.
sitivity required for the direct determination of the above metals a t very low levels (0-50 ng of metal/mL). The technique also has the high selectivity and precision required for reliable analytical results. For the determination of a particular metal, 20-pL volumes of the samples were introduced into the graphite furnace with a n Eppendorf pipet fitted with disposable polypropylene tips. Prior to use, the tips were decontaminated from traces of the metals by soaking them for 24 h in 1%HNO,3 (Baker Ultrex), followed by 4 rinses with high-purity water. Parameters for the sequential dry, char, and atomize program of the HGA2100 were optimized in this laboratory and are shown in Table I. The peak absorbance mode was used to determine Cr and
P b , while Cd was determined in the concentration mode at a scale expansion of ten. Determinations of Cu, Zn, Ca, and Mg were made in the flame mode as described in Environment Canada’s “Analytical Methods Manual” (8).In the analysis of Ca and Mg, a solution of 0.2% lanthanum oxide in 0.4% HCl and 0.2% HNO:I was added prior to the measurement to mask matrix interferences. Working curves were prepared for each element using standard solutions in 1%HNO?. T h e concentration of each element was obtained in triplicate for each of the three types of filtered and unfiltered water samples by direct comparison with these linear working curves. T o correct for variations in sensitivity, standard solutions were injected every 15 min. The method of standard addition and the ammonium pyrrolidine carbodithioate (APCD)-methyl isobutyl ketone (MIBK) extraction procedure developed in this laboratory were used on all samples showing any significant amount of metal by the direct method.
Results and Discussion The coefficient of variation of each point on the calibration curve used in the direct method of analysis for Cd, Cr, and P b by GFAAS was f3-4%. Although the validity of using direct calibration in GFAAS has been endorsed by several researchers (9-12), care should be exercised when applying this method to a wide variety of sample matrices. As a result, the APCD-MIBK extraction procedure developed in our laboratory and the method of standard addition were also used on a selected number of water samples representing a wide range of hardness and concentration of the above metals. There was good agreement among methods. These results along with a detailed study of the APCD-MIBK extraction procedure for the determination of a wide range of elements in the water
Table 11. Median and Range Values for the Cd, Cr, and Pb Content of Raw, Treated, and Distributed Waters throughout Canada as Determined by GFAAS Cd, nglrnL
province
Alberta
British Columbia Manitoba
New Brunswick Newfoundland
Nova Scotia
Ontario
Quebec
Saskatchewan
Prince Edward Island a
R (7)a T (7) D (14) R (8) T (9) D (18) R (5) T (5) D (10) R (4) T (4) D (8) R (3) T (3) D (6) R (4) T (4) D (8) R (11) T (1 1) D (22) R (19) T (21) D (40) R (5) T (5) D (10) R (1) T (1) D (2)
Cr, nglrnL
2.0 (2.0-3.0) 2.0 (2.0-3.0) 2.5 (12.0-3.0) 2.5 (2.0-3.0) 3.0 (2.0-4.0) 2.0 (12.0-5.0) 2.0 (12.0-5.0) 7.0 (12.0-9.0) 6.5 (12.0-9.0) 2.0 (52.0-2.0) 2.0 (12.0-2.0) 2.0 (52.0-2.0) 1 2 . 0 (12.0-2.0) 2.0 (2.0-3.0) 2.0 (2.0-3.0) 2.0 (12.0-2.0) 2.0 (2.0-4.0) 2.0 (2.0-3.0) 2.0 (52.0-6.0) 2.0 (12.0-7.0) 2.0 (52.0-5.0) 3.0 (12.0-68.0) 2.0 (12.0-8.0) 2.0 (12.0-8.0) 2.0 (12.0-2.0) 2.0 (2.0-3.0) 2.0 (2.0-3.0) 4.0 2.0 2.0
Pb, ng/rnL
1 1 . 0 (11.0-1.0) 11.0(11.0-1.0) 1 1 . 0 (11.0-1.0) 1 1 . 0 (11.0-3.0) 5 1.o ( 51.o-2.0) 1 1 .O (11.O-3.0) 1 1 . 0 (51.0-1.0) 11.0(11.0-1.0) 1 1 . 0 (51.0-1.0) 11.o (11.0-1.0) 1 1 . 0 (11.0-1.0) 1 1 . 0 (11.0-4.0) 6.0 (1.0-8.0) 1.0 (11.0-2.0) 1.5 (51.0-23.0) 1 1.o ( 51.o-2.0) 1 1.O (11 .O-95.0) 3.0 (11 .O-5.0) 1 1 .o ( 51.o-2.0) 11.0(51.0-1.0) 1 1.O (51.O-46.0) 1.0 (11.0-3.0) 1.0 (11.0-3.0) 1.O ( 51.O-8.0) 1 1 . 0 (11.0-1.0) 1 1 . 0 (11.0-1.0) I 1 .O ( 51 .O-65.0) 3.0 11.0 1.o
R = raw water: T = treated water: D = distributed water. The numbers in parentheses give the number of sampling locations for the corresponding type of No range is given since there was only one sample location in Prince Edward Island.
water.
708
1 0 . 0 1 (10.01-0.01) 1 0 . 0 1 (10.01-0.01) 10,0 1 (50.0 1-0.30) 1 0 . 0 1 (50.01-0.13) 1 0 . 0 1 (10.01-0.06) 1 0 . 0 1 (50.01-0.49) 0.02 (10.01-0.12) 0.03 (10.01-0.04) 1 0 . 0 1 (10.01-0.19) 1 0 . 0 1 (10.01-0.14) 1 0 . 0 1 (10.01-0.01) 1 0 . 0 1 (10.01-0.01) 0.38 (0.09-0.54) 0.06 (0.05-0.13) 0.07 (0.04-0.28) 1 0 . 0 1 (10.01-0.01) 5 0 . 01 (10.01-0.02) 5 0 . 0 1 (50.01-0.04) 0.02 (10.01-0.04) 0.01 (10.01-0.26) 1 0 . 0 1 (10.01-0.08) 1 0 . 0 1 (10.01-1.13) 5 0 . 0 1 (10.01-0.06) 50.01 (10.01-0.17) 1 0 . 0 1 (10.01-0.01) 10.01 (10.0 1-0.04) 10.01 (10.01-0.01) 0.10 50.01 10.01
Environmental Science & Technology
Table 111. Median and Range Values for the Cu, Zn, Ca, and Mg Content of Raw, Treated, and Distributed Waters throughout Canada as Determined by Flame Atomic Absorption Spectrometry (FAAS) Cu, nglmL
province
Alberta
R (7)a T (7) D (14)
British Columbia Manitoba
New Brunswick Newfoundland
Nova Scotia
Ontario
Quebec
Saskatchewan
Prince Edward Island
R (8) T (9) D (18) R (5) T (5) D (10) R (4) T (4) D (8) R (3) T (3) D (6) R (4) T (4) D (8) R (1 1) T(11) D (22) R (19) T (21) D (40) R (5) T (5) (10) f? (1) T (1) D (2)
Zn, nglmL
15.0(15.0-10.0) 15.0(15.0-5.0) 15.0(15.0-80.0) 1 5 . 0 (1 5.0- 140.0) 15.0(15.0-40.0) 15.0 (15.0-380.0) 15.0 (15.0-20.0) 15.0(15.0-10.0) 15.0(15.0-40.0) 15.0 (15.0-5.0) 15.0(15.0-5.0) 15.0(15.0-10.0)
15.0(55.0-80.0) 5.0 (5.0-10.0) 10.0 (15.0-480.0) 15.0(15.0-40.0) 20.0 (15.0-100.0) 40.0 (15.0-140.0) 10.0 (15.0-10.0) 5.0 (15.0-70.0) 10.0 (15.0-230.0) 58.0 (15.0-1 10.0) 5.0 (15.0-50.0) 50.0 (55.0-430.0) 60.0 (40.0-530.0) 40.0 (15.0-50.0) 115.0 (10.0-620.0) 15.0(15.0-5.0) 20.0 (10.0-90.0) 70.0 (20.0-220.0) 10.0 (15.0-20.0) 10.0 (55.0-40.0) 10.0 (15.0-140.0) 20.0 (15.0-330.0) 5.0 (15.0-100.0) 25.0 (15.0-240.0) 15.0(15.0-70.0) 10.0 (15.0-10.0) 15.0 (15.0-140.0)
10.0 (15.0-10.0) 10.0 (15.0-50.0) 23.0 (15.0-40.0) 7.5 (15.0-10.0) 7.5 (15.0-10.0) 7.5 (15.0-20.0) 15.0(15.0-20.0) 15.0(15.0-20.0) 15.0(15.0-80.0) 1 5 . 0 (15.0-330.0) 15.0(15.0-30.0) 10.0 (15.0-60.0) 15.0(15.0-5.0) 1 5 . 0 (15.0-5.0) 15.0(15.0-5.0)
15.0 15.0
15.0 15.0 (15.0-25.0)
(40.0-21 0.0)
Ca, mg/L
Mg, mg/L
33.7 (13.0-43.4) 33.0 (6.4-40.3) 29.2 (4.6-38.9) 1.8 (0.4-42.3) 2.2 (0.4-14.7) 2.2 (0.4-14.9) 60.2 (20.6-90.0) 21.3 (15.2-61.1) 22.6 (17.3-79.5) 8.6 (2.9-19.0) 8.7 (2.5-19.7) 8.7 (2.7-20.0) 1.8 (1.3-2.7) 9.8 (1.4-18.2) 2.5 (1.4-7.8) 3.5 (2.0-5.5) 5.8 (2.7-17.0) 3.6 (1.8-6.1) 28.3 (9.1-71.8) 25.6 (1 1.7-72.5) 28.3 (1 1.5-72.0)
17.7 (11.9-38.2) 17.8 (10.0-35.5) 17.0 (9.3-18.2) 1.1 (0.2-19.1) 1.1 (0.3-18.2) 1.3 (0.2-18.8) 52.5 (6.9-81.7) 24.3 (6.9-38.7) 22.9 (6.7-38.3) 1.0 (0.8-2.7) 1.6 (0.7-2.5) 1.6 (0.7--2.6) 0.8 (0.6- 1.0) 1.0 (0.6-21.0) 0.8 (0.6--0.9) 1.2 (0.7--1.5) 1.2 (0.7--1.3) 1.2 (0.9--1.5) 7.3 (2.4--24.9) 6.3 (2.5--24.9) 6.9 (2.3-27.5)
9.4 (2.9-30.8) 12.9 (2.8-31.7) 13.5 (2.7-33.0) 32.2 (28.6-59.5) 31.6 (13.3-59.3) 36.1 (11.9-62.2) 15.3 14.8 (9.2-9.5)
3 . 1 (0.8--8.3) 3.3 (0.8--12.7) 3.2 (0.8--12 9) 23.7 (14.7-55.3) 28.6 (1 1.2-54.5) 28.3 (10.0-54.8) 12.2 11.7 (12.7-13.7)
R = raw water: T = treated water: D = distributed water. The numbers in parentheses give the number of sampiing locations for the corresponding type of water. No range is given since there was only one sample location in Prince Edward Island. a
Table IV. Comparison of the Concentration of Copper in Treated and Distributed Waters from Selected Canadian Cities province
British Columbia
Manitoba New Brunswick Newfoundland Nova Scotia Ontario
Quebec
sampling point
PH
hardness, mg/L CaC03
Kelowna Prince George North Vancouver Winnipeg Swan River Fredericton Moncton St. John's Clarenville Dartmouth Truro Sudbury Thunder Bay Barrie Quebec Riviere du Loup Shawinigan
7.9 7.5 6.3 7.7 7.2 7.2 6.8 6.0 6.0 7.0 7.0 6.6 7.5 7.8 7.2 9.0 7.0
115 175 6 74 452 100 22 1 10 6 15 50 48 200 24 30 20
samples will be t h e subject of a further publication. T h e operating and analytical parameters for t h e determination of Cd, Cr, and P b using GFAAS are presented in Table I. Although the optimum atomization temperature for Cd was found to lie in the range 1600-1800 "C, a temperature of 1400 "C was chosen to eliminate chemical interference. T h e results of GFAAS analysis for Cd, Cr, and P b are shown in Table 11. The median and range values are given for raw (Le., lake, river, or well as the source of drinking water), treated (Le., the raw water after treatment a t the purification plant but before reaching the distribution system), and distributed (Le.,a t the
Cu content, nglmL treated distribum
20 40
15 10 70
15 50 5
15 10 90
15 10
55
15 10
15
40 140 40 160 110 260 200 560 50 110 220 20 110 90 120 150 100
consumer's tap) water supplies for each Canadian province. In general, the waters sampled contained Cd. Cr, and Ph a t or below the detection limit. However, raw water obtained from blagog in the province of Quebec showed values of 1.1, 68.0, and 235.0 ng/mL for Cd, Cr, and Ph. respectively. These values fell below the detection limit in treated waters from the same location. Treated water from Halifax. Nova Scotia, contained 95 ng/mL P h compared to
