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Water Hardness and Mortality in the Netherlands
35
WATER HARDNESS AND MORTALITY IN THE NETHERLANDS R.L. ZIELHUIS Coronel Laboratory for Occupational and Environmental Health, Faculty of Medicine University of Amsterdam, The Netherlands B.J.A. HARING National Institute for Water Supply, Laboratory for Inorganic Chemistry, Voorburg, The Netherlands ABSTRACT In 1975 central water softening was discouraged by the Public Health Council because of the statistical negative association found
in 23 communities between
the hardness of drinking water and death rate from Ischemic Heart Disease (I.H.D.) over the period 1958-1970. Further studies were carried out during the last decade by a specially assigned interdisciplinary Working Group of the Health Aspects of Central Water Softening. Recent studies showed that the release of metals (Pb and Cu) from household waterdistribution pipes was positively correlated with water calcium. Furthermore a significant negative correlation was found between hardness and pH for these types of water. The hypothesis that the Ca and Mg deficiency in areas with soft drinking water increases the risk of 1.H.D.death rate was supported by the finding that food looses more Ca and Mg when it is cooked in soft water as compared to cooking in hard water. In contrast with earlier statistical investigations no significant relations were found over the period 1970-1977 between I.H.D. mortality and hardness of drinking water in 30 municipalities. The disappearance of the statistical relation could not be attributed to changes in water hardness. However, investigation Of a group of 17 municipalities of which mortality and water quality data are known for three periods, 1958-1962, and 1971-1977,
1965-1970
showed that the inverse statistical relation between 1.H.D.mortality
and water hardness still existed but with decreasing significance of correlation coefficients. The provisional conclusion of the Working Group is that other factors than water hardness overrule to a large extent the potential effect on I.H.D. mortality. Central water softening down to 2-3 meq/l Ca probably will have no observable effect on mortality. Other studies are still continuing. In 1981 a final report will be presented to the Minister of Health and EnvironmentalProtection.
HISTORY I n 1971 The N e t h e r l a n d s Water Works A s s o c i a t i o n (VEWIN) proposed c e n t r a l s o f t e n inq
of t h e d r i n k i n g w a t e r i n The N e t h e r l a n d s , down t o a b o u t 2 meq Ca/1(40 mg C a / l ) .
However, t h i s p r o p o s a l was c r i t i c i z e d by p u b l i c h e a l t h e x p e r t s , b e c a u s e i n The N e t h e r l a n d s t w o s t u d i e s had shown a n e g a t i v e r e l a t i o n s h i p between w a t e r hardn e s s and m o r t a l i t y from c a r d i a c d i s e a s e s , p a r t i c u l a r l y i n women ( r e f . 1 , r e f . 2 ) . The M i n i s t e r o f H e a l t h and Environmental P r o t e c t i o n a s k e d t h e P u b l i c H e a l t h Council (PHC) t o c o n s i d e r t h i s m a t t e r .
In 1975 a commission of t h e PHC proposed t o d e l a y
c e n t r a l w a t e r s o f t e n i n g pending f u r t h e r r e s e a r c h . The r e s e a r c h s h o u l d t r y t o answer t h e f o l l o w i n g q u e s t i o n s : 1. Is t h e r e l a t i o n s h i p between c a r d i o v a s c u l a r m o r t a l i t y s t i l l o b s e r v e d when more r e c e n t and more a c c u r a t e w a t e r q u a l i t y d a t a a r e t a k e n i n t o a c c o u n t ?
2. Does such a r e l a t l o n s h i p r e f l e c t a g r a d i e n t i n h a r d n e s s o r i n m e t a l c o n t e n t i n d r i n k i n g w a t e r , which a g a i n c o u l d b e r e l a t e d t o a g r e s s i v i t y of s o f t w a t e r ? A Working Group on H e a l t h Aspects of Water S o f t e n i n g was founded w i t h r e p r e s e n -
t a t i v e s of v a r i o u s governmental and non-governmental i n s t i t u t e s from t h e f i e l d s o f w a t e r t e c h n o l o g y and o f p u b l i c h e a l t h ( s e e Annex). S i n c e 1975 s e v e r a l s t u d i e s have been c a r r i e d o u t . Data on t h e r e l a t i o n between m o r t a l i t y (1958-1977) and w a t e r q u a l i t y (1952-1977) can b e p r e s e n t e d . A d d i t i o n a l s t u d i e s a r e g o i n g o n . The s t u d i e s were s u p p o r t e d by g r a n t s from t h e M i n i s t r y of P u b l i c H e a l t h and Environm e n t a l P r o t e c t i o n and t h e Dutch P r e v e n t i o n Fund, and from t h e EEC ( c o n t r a c t 2 73- 77- 1-ENV-N)
.
RESEARCH OBJECTIVES Aspects of t h e r e l a t i o n s h i p between m o r t a l i t y and w a t e r h a r d n e s s , which t h e Working Group d e c i d e d t o i n v e s t i g a t e were i n t e r a l i a : 1. t h e q u a l i t y o f d r i n k i n g w a t e r i n 1977 and 1979 p a r t i c u l a r l y w i t h r e s p e c t t o h a r d n e s s (Ca, Mg) and a g r e s s i v i t y (pH, m e t a l s ) , comparing t h e 1977 and 1979 d a t a w i t h t h o s e from 1952 a s f a r a s a v a i l a b l e . 2.
t h e t r e n d of m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e ( I C D 410-414, c e r e b r o v a s c u l a r m o r t a l i t y ( I C D 430-438)
428) and of
i n males and females > 30 y r o f a g e ,
o v e r t h e p e r i o d s 1958-1962, 1963-1970 and 1971-1977.
3. t h e r e l a t i o n between m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e and/or c e r e b r o v a s c u l a r d i s e a s e and w a t e r q u a l i t y d a t a ( a t pumping s t a t i o n and a t t a p ) from 1952 and 1977.
31 WATER QUALITY DATA 1952-1977-1979 consistency of drinking water quality The Laboratory of the National Institute for Public Health (R.I.V.) examines water quality at pumping stations on a routine basis. The water quality data from 1952 and from 1977 for 17 communities showed a high Spearman ranking order coefficient of inter-correlation, except for pH: PH
:
r
=
0.41
K20
:
r
=
0.93
rCa
:
r
=
0.86
rMg
:
r
=
0.83
rC1
:
r
=
0.78
rS04
:
r
=
0.68
rHC03
:
r
=
0.84
The rather good consistency in ranking order of the parameters of water hardness, in addition to the fact that the average concentrations also did not differ considerably, allow to correlate water hardness with mortality over the whole period 1958-1977. There was no consistency in the pH. However, the pH was calculated on the basis of CO
- and HCO -concentrations. This may have been the reason for the 2 3 low coefficient of correlation. Therefore, in 1979 the National Institute for
Water Supply (NIWS) carried out accurate measurement of pH in 28 water supply areas; in addition a new calculation of the Langelier index of water agressivity was carried out. This study showed a negative correlation betwPen pH and Cacontent: r=-0.70 (n=28). Although in general natural soft waters are expected to be more agressive than natural hard waters, various measures taken by the Dutch water production companies to condition (de-acidification) the water in the last decennia have led to an increase of the pH of soft waters. It was not possible to establish fixed data for most water works with respect to the time of introduction of these conditioning measures, because many measures to improve
water quality were taken over a period of several years. Metals in water In Amsterdam a pilot study was carried out to establish the random sampling size of tapwaters in order to derive a valid estimate of metal intake through tapwater. At 200 taps proportional sampling (ref. 4) of water used for consumption was carried out. A sample size of 50 taps from an at random number of 200 taps proved to yield a valid estimate of the contribution of drinking water to the intake of metals (Cd, Pb, Cu, Zn, Fe). The concentrations of Mn, Si, Li, Sr, Ba, B, Al, Cr, V, No, Co, Ni, As and Sb were determined in composite samples. The concentrations of these elements were
not expected to change during distribution; they should therefore be determined in water at the pumping station. A study was carried out in 20 communities, with 40.000 inhabitants, and with
a reasonable consistency of water hardness over the last 25 years. In tapwater the lead and copper levels were positively related to Ca-levels: r
Ca-Pb
=
+0.43,
= +0.38 (n=20). The pH in these 20 water supply areas was negativellr
rca-Cu related to Ca-level (r=-0.66, n=20). These findings already suggest that a negative correlation between hardness and mortality will not be due to increased metal levels (ref. 6 ) . The effect of water hardness on the mineral (Ca, Mg and Pb) content of some food stuffs was investigated in a limited study by the National Institute for Water Supply (ref. 5 ) . Tapwater from 6 communities, varying in hardness from Ca
=
114 mg/l and Mg
=
19 mg/l to Ca = 17 mg/l and Mg = 2.2 mg/l, was used to
cook potatoes and vegetables. The results (Figure A, B,
C)
indicated that the
Ca-level in the food stuffs generally increased when cooked in hard water, whereas a decrease or only a slight increase was found when cooked in soft water; the Mg-content decreased both when cooked in hard and in soft water. The Pb-content generally increased in hard water and decreased in soft water; however, the hard waters contained higher Pb-levels than the soft waters. The results of these tests may support the hypothesis that an inverse relation between hardness and ischaemic heart disease mortality is due to a deficiency of Ca and/or Mg in soft water. Such a deficiency will further be increased by the extractions of Ca and Mg from food by soft water. This particularly may have consequences when the nutritional intake of Ca and/of Mg is low. The studies of water quality allow the following conclusions:
- over the last 25 years there was a good consistency in hardness of drinking water
- in 1979 there was a negative correlation between pH and hardness - in 1977/1978 lead and copper levels in tapwaters were positively related to calcium levels
- cooking vegetables in soft waters decreases the Ca- and Mg-content of these foods probably more than in case hard water was used for cooking.
39
*80%i potatoes
cauliflower
endive
carrots
5 5
t60%
+40%
.20%
-20%l 0%
-40 % A.
2
6
'u
PERCENTAGE OF THE CHANGE OF THE CALCIUM CONCENTRATION IN SOME FOODSTUFFS DURING COOKING WITH HARD AND SOFT DRINKING WATER
0%
20 %
40 % 60 ..%
B.
PERCENTAGE OF DECREASE OF THE MAGNESIUM CONTENTS IN SOME FOODSTUFFS DURING COOKING WITH HARD AND SOFT DRINKING WATER
*300% 1. THE HAGUE + 250%
2. WAGENINGEN
3. ZUTPHEN 4. ARNHEM
+ 200%
5. MAASTRICHT 6. KERKRADE
+
150%
100%
a
50%
C.
PERCENTAGE OF THE CHANGE OF THE LEAD CONCENTRATION I N SOME FOODSTUFFS DURING COOKING WITH HARD A N 0 SOFT DRINKING WATER
FIGURE A,B,C. CONCENTRATION CHANGES OF Ca,Mg AND Pb IN POTATOES, AND VEGETABLES BY COOKING THEM IN HARD (GREY BARS) AND SOFT ( OPEN B A R S ) DRINKING WATER TYPES
40 MORTALITY I N 1958
- 1977 IN 17
COMMUNITIES
C o r r e l a t i o n s t u d i e s between m o r t a l i t y and w a t e r q u a l i t y have been c a r r i e d o u t o v e r 1958/1962 ( r e f . l), 1963-1970 ( r e f . 2) and a g a i n o v e r 1971-1977. However, t h e Working Group doubted whether f o r 6 communities s t u d i e d o v e r 1958/1962 and
1963/1970 t h e w a t e r q u a l i t y d a t a used f o r 1952 were w e l l enough r e p r e s e n t a t i v e , b e c a u s e of admixture of w a t e r w i t h d i f f e r e n t q u a l i t y from o t h e r w a t e r works. The Group, t h e r e f o r e , s e l e c t e d o t h e r communities w i t h a number o f i n h a b i t a n t s
> 40.000, s e r v e d by one w a t e r works and w i t h no i n d i c a t i o n of change i n w a t e r q u a l i t y o v e r a b o u t 20 y e a r s . The Group s e l e c t e d 30 communities f o r t h e f i n a l s t u d y ; 17 communities o f t h e s e had been s t u d i e d a s w e l l o v e r 1958/1962 and
1963/1970. The m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e and c e r e b r o v a s c u l a r d i s e a s e i n males and females 2 30 y r o f age was compared o v e r t h e p e r i o d s 1958-1962,
1963-1970 and 1971-1977, a g e - s t a n d a r d i z e d on t h e p o p u l a t i o n - 1968 ( t a b l e 1 and t a b l e 2 ) ; 17 communities. TABLE
1
Ranking o r d e r c o r r e l a t i o n o f i s c h a e m i c h e a r t d i s e a s e m o r t a l i t y i n 1958-1962,
1963-1970 and 1971-1977 Males
2
30 y r o f age
1963/1970
1958/1962 1963/1970
1971/1977
0 . 4ZX
0.39O 0.74xx
0.7EXX
0 .6tjXx 0 . 83xx
Females 2 30 v r o f a a e
1958/1962 1963/1970 legenda:
o
P
<
0.10
x
P
<
0.05
xx
P
<
0.01
Over t h e p e r i o d 1958/1977 i n 17 communities t h e c o n s i s t e n c y of m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e i n females and
from c e r e b r o v a s c u l a r d i s e a s e i n males
was r e a s o n a b l y good. I n a c o r r e l a t i o n s t u d y w i t h w a t e r q u a l i t y d a t a o v e r t h e p e r i o d 1958-1977 p a r t i c u l a r a t t e n t i o n s h o u l d b e p a i d t o t h e s e two groups o f mortality.
41 TABLE 2
Ranking o r d e r c o r r e l a t i o n of c e r e b r o v a s c u l a r m o r t a l i t y i n 1958-1962, 1963-1970 and 1971-1977 Males > 30 y r of age
1963/1970
1971/1977
0 . aoxx
1958/1962 1963/1970 Females >
30 y r of age
0.57xx 0.79xx
1963/1970
1958/1962 1963/1970
1971/1977
- 0.00
0.35O
0.66xx
legenda:
o < P
x < P
xx < P
0.10 0.05 0.01
RANKING ORDER CORRELATION BETWEEN MORTALITY AND WATER HARDNESS
The age-standardized m o r t a l i t i e s from ischaemic h e a r t d i s e a s e and from cerebrov a s c u l a r d i s e a s e i n males and females
>, 30 y r of age, were c o r r e l a t e d with
Ca- and Mg-content of water-1952 and -1977 i n 17 communities ( t a b l e 3 ) . TABLE
3
Ranking o r d e r c o r r e l a t i o n between c a r d i o v a s c u l a r m o r t a l i t y over 1958-1977 and water hardness i n 1952 and 1977 i n 17 communities
Males
2
water 1952
water 1977
Ca
Ca
Mg
M9
30 y r of age
mortality
-0.31
+0.12
19581’1962
-0.05
1963/1970
-0.48x -O.4lx
-0.45x -0.4fjX
1971/1977
-0.36O -0.45x
-0.36x
-0.33O
1958/1962
-0.38O -0.17
-0.28
-0.16
1963/1970
-0.67xx -0.42x
-0.56xx -0.54x
1971/1977
-0.4Sx
-0.36O
Females
legenda:
-0.08
>I 30 y r of age
o
P (one s i d e d )
<
X
P
< 0.05
xx
P
<
0.10 0.01
-0.30
-0.37’
42 For c e r e b r o v a s c u l a r m o r t a l i t y no s i g n i f i c a n t c o r r e l a t i o n s e x i s t e d . From t h i s study on m o r t a l i t y i n 17 communities over 1952-1977 it could be concluded that:
-
t h e n e g a t i v e c o r r e l a t i o n e s t a b l i s h e d over 1958/1962 f o r IHD-females with hardness-
1952 ( r = 0.49, P CO.05, n = 2 3 ) , based upon s t a n a r d i s a t i o n on t h e
Segi-population, was n o t f u l l y confirmed f o r 17 communities, a f t e r s t a n d a r d i s a t i o n on population-1968:
r=-0.38; 0.05 < P < 0.10; n=17);
-
t h e ranking o r d e r c o r r e l a t i o n s f o r m o r t a l i t y 1971/77 g e n e r a l l y was lower than
-
t h e ranking o r d e r c o r r e l a t i o n w i t h t h e Ca-content of water was h i g h e r than Ca with t h e Mg-content; t h e r e was no c o r r e l a t i o n with t h e quotient;
-
t h e ranking o r d e r c o r r e l a t i o n only e x i s t e d f o r ischaemic h e a r t d i s e a s e
-
t h e ranking o r d e r c o r r e l a t i o n s were h i g h e r f o r females than f o r males, b u t
f o r 1963/1970, b o t h i n r e l a t i o n t o water-1952 and water-1977;
MCJ
and n o t f o r c e r e b r o v a s c u l a r d i s e a s e ;
a l s o f o r males a n e g a t i v e c o r r e l a t i o n was r e p e a t e d l y observed. The Working Group f i n a l l y s t u d i e d t h e r e l a t i o n between ischaemic h e a r t d i s e a s e m o r t a l i t y and c e r e b r o v a s c u l a r m o r t a l i t y i n 30 c a r e f u l l y s e l e c t e d comm u n i t i e s , with
>40.000 i n h a b i t a n t s and with no apparent change i n hardness
o v e r l a s t 20-30 y r , and t h e hardness o f water i n 1977 ( t a b l e 4 ) . TABLE 4
Ranking o r d e r c o r r e l a t i o n between ischaemic h e a r t d i s e a s e ( I H D ) and cerebrov a s c u l a r m o r t a l i t y (CNS) i n males and females
>30 y r of age w i t h Ca- and
Mg-content of water i n 1977 i n 30 communities Males
30 v r of aqe
IHD CNS
Females IHD CNS
Ca
Mg
-0.01 -#O.14
-0.19 -0.02
-0.11 -0.12
-0.10
30 y r of age
-0.07
There d i d n o t e x i s t any r e l a t i o n s h i p between w a t e r hardness and m o r t a l i t y from ischaemic h e a r t and from c e r e b r o v a s c u l a r d i s e a s e i n 30 c a r e f u l l y s e l e c t e d communities, although t h e 17 communities i n which a r e l a t i o n between cardiov a s c u l a r m o r t a l i t y had been observed, were included. I n f a c t , f o r t h e o t h e r 13 communities t h e r e e x i s t e d a p o s i t i v e c o r r e l a t i o n . I n 16 communities f o r which t h e metal (Pb, C u , zn) c o n t e n t of tapwater was known, no c o r r e l a t i o n between m o r t a l i t y and metal c o n t e n t could be e s t a b l i s h e d .
43 I n 23 communities no c o r r e l a t i o n was observed between m o r t a l i t y and t h e L i - o r t h e SiO - c o n t e n t of d r i n k i n g w a t e r . 2 The Working Group concluded from t h e s e s t u d i e s t h a t a t t h e p r e s e n t moment a n e g a t i v e r e l a t i o n s h i p between m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e and h a r d n e s s
of d r i n k i n g w a t e r c a n n o t be f u l l y r e j e c t e d , b u t a p p a r e n t l y many o t h e r f a c t o r s which c o n t r i b u t e t o t h i s m o r t a l i t y may c o m p l e t e l y overshadow such a r e l a t i o n s h i p . DISCUSSION AND CONCLUSION The s t u d i e s c a r r i e d o u t i n The N e t h e r l a n d s s i n c e 1975 have made i t c l e a r t h a t The N e t h e r l a n d s i s n o t a s u i t a b l e c o u n t r y t o e l u c i d a t e t h e "water s t o r y " f o r t h e following reasons:
-
t h e number of communities w i t h >40.000 i n h a b i t a n t s s e r v e d by one w a t e r works, and w i t h an e x p e c t e d c o n s i s t e n c y i n w a t e r q u a l i t y i s s m a l l ( n = 3 0 ) ;
-
t h e range i n w a t e r h a r d n e s s i s l i m i t e d (Ca 16-117 mg/l; Mg 1-15 mg/l) i n comparison t o e . g .
t h e U.K.
(Ca 4 mg/l t o 160 m g / l ) . I n t h e 30 communities
s t u d i e s i n The N e t h e r l a n d s 46 3
-
%
%
had a C a - l e v e l < 60 mg/l,
33 % < 40 mg/l and
< 20 mg/l i n 1977;
t h e r e i s a c o n s i d e r a b l e m o b i l i t y w i t h i n t h e c o u n t r y ; t h i s would s e v e r e l y hamper a l o n g i t u d i n a l s t u d y ;
-
some communities have an a g e - d i s t r i b u t i o n which v e r y much d e v i a t e s from t h e c o u n t r y a v e r a g e , because of e . g . aged s u b j e c t s ; s u c h
i n s t i t u t i o n s f o r o l d i n v a l i d s , and
a d e v i a t i o n c a n n o t be a d e q u a t e l y overcome by age-
standardisation;
-
i n The N e t h e r l a n d s community b a s e d d a t a on f a c t o r s which may c o n t r i b u t e t o c a r d i o v a s c u l a r m o r t a l i t y do n o t e x i s t ; t h e r e f o r e , i t i s n o t p o s s i b l e t o a d j u s t t h e mortality data f o r e.g. Pocock e t a l .
socio-economic c o n d i t i o n s a s done by
(ref. 7).
One o f t h e q u e s t i o n s which c o u l d n o t be answered i n 1971 was whether h a r d n e s s o r a g r e s s i v i t y of d r i n k i n g w a t e r was t h e d e c i s i v e f a c t o r f o r t h e n e g a t i v e c o r r e l a t i o n between i s c h a e m i c h e a r t d i s e a s e m o r t a l i t y and w a t e r h a r d n e s s . The s t u d i e s have b r o u g h t forward e v i d e n c e t h a t
-
a t l e a s t i n The N e t h e r l a n d s a t t h e p r e s e n t t i m e
-agreSSiVity(pH, m e t a l c o n t e n t ) does n o t p l a y a r o l e . I f t h e r e would appear t o b e a c a u s a t i v e r e l a t i o n s h i p between w a t e r q u a l i t y and ischaemic h e a r t d i s e a s e mortal i t y , t h e n t h i s s h o u l d probably be r e l a t e d t o t h e h a r d n e s s of w a t e r , p a r t i c u l a r l y t h e Ca-content. S t u d i e s i n t h e UK s t r o n g l y s u g g e s t t h a t p a r t i c u l a r l y s o f t w a t e r w i t h Ca c o n t e n t below 40 t o 60 mg/l may c o n t r i b u t e t o c a r d i o v a s c u l a r m o r t a l i t y . The EEC a l s o recommended ( r e f . 3 ) t h a t C a - l e v e l s s h o u l d n o t be lower t h a n 60 mg/l. The t o t a l number o f 30 communities was t o o s m a l l t o d i v i d e t h e s e i n t o subcategor i e s o f w a t e r h a r d n e s s ; t h e r e f o r e , t h e B r i t i s h s u g g e s t i o n c o u l d n e i t h e r b e con-
f i r m e d , nor b e r e j e c t e d .
In 1971 p u b l i c h e a l t h e x p e r t s s t r o n g l y opposed t h e p r o p o s a l f o r c e n t r a l w a t e r s o f t e n i n g . However, i n view of t h e d a t a g a t h e r e d s i n c e 1975, t h e p r e l i m i n a r y c o n c l u s i o n of t h e Working Group i s t h a t , a l t h o u g h a c o n t r i b u t i o n from w a t e r s o f t n e s s t o m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e cannot b e r e j e c t e d , a p a r t i a l s o f t e n i n y of d r i n k i n g w a t e r down t o say 60 mq/l p r o b a b l y w i l l have no measurable e f f e c t on i s c h a e m i c h e a r t d i s e a s e m o r t a l i t y i n The N e t h e r l a n d s a t t h e p r e s e n t monien t . We s t i l l p r e s e n t t h i s c o n c l u s i o n a s p r e l i m i n a r y . Small s c a l e a d d i t i o n a l s t u d i e s a r e s t i l l g o i n g on ( T a b l e 5 ) . Most s t u d i e s w i l l be completed i n 1980 o r 1981. The Working Group w i l l submit t h e i r f i n a l c o n c l u s i o n , b a s e d upon a l l
s t u d i e s , i n 1981 t o t h e M i n i s t e r of
H e a l t h and Environmental P r o t e c t i o n . TABLE 5
Small s c a l e s t u d i e s on t h e r e l a t i o n between w a t e r h a r d n e s s and p a r a m e t e r s of h e a l t h ( h a z a r d s ) , c a r r i e d o u t by t h e Working Group on H e a l t h Aspects of Water Hardness : -
r e l a t i o n between b l o o d l e v e l s of Pb, Cu, Zn and L i i n aged males
-
a n a l y s i s of m e t a l l e v e l s i n a u t o p s y t i s s u e s
-
p e r i n a t a l m o r t a l i t y from a n e n c e p h a l i a and w a t e r h a r d n e s s
-
c a r d i o v a s c u l a r p a r a m e t e r s i n workers
and c a r d i o v a s c u l a r p a r a m e t e r s
-
a n a l y s i s of m e t a l s i n h a i r of s c h o o l c h i l d r e n
animal e x p e r i m e n t s on r e s o r p t i o n of m e t a l s from d i f f e r e n t t y p e s of d r i n k i n g water.
REFERENCES 1 K . B i e r s t e k e r , Hardness of d r i n k i n g w a t e r and m o r t a l i t y ( i n D u t c h ) . T . Soc. Geneesk. 45 (1967) p p . 658-661. 2 K . B i e r s t e k e r and R . L . Z i e l h u i s , Hard o r s o f t d r i n k i n g w a t e r ? ( i n D u t c h ) . TI. SOC. Geneesk. 53 (1975) pp. 3-9. 3 European Economic Community ( E E C ) . E . C . D i r e c t i v e of t h e C o u n c i l o f M i n i s t e r s on t h e q u a l i t y of w a t e r d e s t i n e d f o r human consumption, J u l y 1 5 t h 1980. 4 B.J.A. Haring, Human exposure t o m e t a l s r e l e a s e d from w a t e r d i s t r i b u t i o n s y s t e m s . La Tribune du CEBEDEAU 4 1 9 (1978) p p . 349-355. 5 B.J.A. Haring and W. van D e l f t , Changes i n t h e m i n e r a l composition of food a s a r e s u l t of cooking i n "hard" and " s o f t " w a t e r s . I n p r e s s , 1980b. H a r i n g and B.C.J. Zoeteman, I s c o r r o s i v e n e s s o f d r i n k i n g w a t e r a p o s s i b l e 6 B.J.A. c a u s e of t h e s t a t i s t i c a l a s s o c i a t i o n between w a t e r h a r d n e s s and c a r d i o v a s c u l a r d i s e a s e m o r t a l i t y ? I n p r e s s , 1980a. 7 S.J. Pocock, A . G . S h a p e r , D . G . Cook, R.F. Packham, R.F. Lacey, P. Powell and P . F . R u s s e l l , B r i t i s h Regional Heart Study: g e o g r a p h i c v a r i a t i o n s i n c a r d i o v a s c u l a r m o r t a l i t y , and t h e r o l e o f w a t e r q u a l i t y . B r i t . Med. J . 24 May 1980, pp. 1243-1249.
45
ANNEX
Composition of t h e Working Group i n H e a l t h Aspects of C e n t r a l Water S o f t e n i n g R . L . Z i e l h u i s ( c h a i r m a n ) , Coronel L a b o r a t o r y f o r O c c u p a t i o n a l and Environmental H e a l t h , U n i v e r s i t y of Amsterdam. B.J.A. Haring ( s e c r e t a r y ) , N a t i o n a l I n s t i t u t e f o r Water Supply, Voorburg B.C.J. Zoeteman, N a t i o n a l I n s t i t u t e f o r Water Supply , Voorburg K . B i e r s t e k e r , A g r i c u l t u r a l U n i v e r s i t y , Wageningen E . H . G r o o t , A g r i c u l t u r a l U n i v e r s i t y , Wageningen C.H.J. E l z e n g a , The N e t h e r l a n d s Waterworks T e s t i n g and Research I n s t i t u t e , R i j s w i j k A. B o e s , The N e t h e r l a n d s Waterworks A s s o c i a t i o n , R i j s w i j k G . J . BOS, Medical man, Leiden L.M. Dalderup, Labour I n s p e c t i o n , Amsterdam R.F.M. Herber, Coronel L a b o r a t o r y f o r O c c u p a t i o n a l and Environmental H e a l t h , U n i v e r s i t y of Amsterdam A.A.E. Wibowo, Coronel L a b o r a t o r y f o r O c c u p a t i o n a l and Environmental H e a l t h , U n i v e r s i t y o f Amsterdam A.W. Fonds, N a t i o n a l I n s t i t u t e f o r P u b l i c H e a l t h , B i l t h o v e n J.J.M. de G o e i j , I n t e r u n i v e r s i t y Reactor I n s t i t u t e , D e l f t T . Trouwborst, M i n i s t r y of P u b l i c H e a l t h and Environmental PrOteCtiOn,Leidschendam J.J.L. P i e t e r s , M i n i s t r y of P u b l i c H e a l t h and Environmental P r o t e c t i o n , Leidschendam P.van Leeuwen, N a t i o n a l I n s t i t u t e f o r P r e v e n t i v e Medicine, Leiden.
WATER HARDNESS AND MORTALITY IN THE NETHERLANDS R.L. ZIELHUIS Coronel Laboratory for Occupational and Environmental Health, Faculty of Medicine University of Amsterdam, The Netherlands B.J.A. HARING National Institute for Water Supply, Laboratory for Inorganic Chemistry, Voorburg, The Netherlands ABSTRACT In 1975 central water softening was discouraged by the Public Health Council because of the statistical negative association found
in 23 communities between
the hardness of drinking water and death rate from Ischemic Heart Disease (I.H.D.) over the period 1958-1970. Further studies were carried out during the last decade by a specially assigned interdisciplinary Working Group of the Health Aspects of Central Water Softening. Recent studies showed that the release of metals (Pb and Cu) from household waterdistribution pipes was positively correlated with water calcium. Furthermore a significant negative correlation was found between hardness and pH for these types of water. The hypothesis that the Ca and Mg deficiency in areas with soft drinking water increases the risk of 1.H.D.death rate was supported by the finding that food looses more Ca and Mg when it is cooked in soft water as compared to cooking in hard water. In contrast with earlier statistical investigations no significant relations were found over the period 1970-1977 between I.H.D. mortality and hardness of drinking water in 30 municipalities. The disappearance of the statistical relation could not be attributed to changes in water hardness. However, investigation Of a group of 17 municipalities of which mortality and water quality data are known for three periods, 1958-1962, and 1971-1977,
1965-1970
showed that the inverse statistical relation between 1.H.D.mortality
and water hardness still existed but with decreasing significance of correlation coefficients. The provisional conclusion of the Working Group is that other factors than water hardness overrule to a large extent the potential effect on I.H.D. mortality. Central water softening down to 2-3 meq/l Ca probably will have no observable effect on mortality. Other studies are still continuing. In 1981 a final report will be presented to the Minister of Health and EnvironmentalProtection.
HISTORY I n 1971 The N e t h e r l a n d s Water Works A s s o c i a t i o n (VEWIN) proposed c e n t r a l s o f t e n inq
of t h e d r i n k i n g w a t e r i n The N e t h e r l a n d s , down t o a b o u t 2 meq Ca/1(40 mg C a / l ) .
However, t h i s p r o p o s a l was c r i t i c i z e d by p u b l i c h e a l t h e x p e r t s , b e c a u s e i n The N e t h e r l a n d s t w o s t u d i e s had shown a n e g a t i v e r e l a t i o n s h i p between w a t e r hardn e s s and m o r t a l i t y from c a r d i a c d i s e a s e s , p a r t i c u l a r l y i n women ( r e f . 1 , r e f . 2 ) . The M i n i s t e r o f H e a l t h and Environmental P r o t e c t i o n a s k e d t h e P u b l i c H e a l t h Council (PHC) t o c o n s i d e r t h i s m a t t e r .
In 1975 a commission of t h e PHC proposed t o d e l a y
c e n t r a l w a t e r s o f t e n i n g pending f u r t h e r r e s e a r c h . The r e s e a r c h s h o u l d t r y t o answer t h e f o l l o w i n g q u e s t i o n s : 1. Is t h e r e l a t i o n s h i p between c a r d i o v a s c u l a r m o r t a l i t y s t i l l o b s e r v e d when more r e c e n t and more a c c u r a t e w a t e r q u a l i t y d a t a a r e t a k e n i n t o a c c o u n t ?
2. Does such a r e l a t l o n s h i p r e f l e c t a g r a d i e n t i n h a r d n e s s o r i n m e t a l c o n t e n t i n d r i n k i n g w a t e r , which a g a i n c o u l d b e r e l a t e d t o a g r e s s i v i t y of s o f t w a t e r ? A Working Group on H e a l t h Aspects of Water S o f t e n i n g was founded w i t h r e p r e s e n -
t a t i v e s of v a r i o u s governmental and non-governmental i n s t i t u t e s from t h e f i e l d s o f w a t e r t e c h n o l o g y and o f p u b l i c h e a l t h ( s e e Annex). S i n c e 1975 s e v e r a l s t u d i e s have been c a r r i e d o u t . Data on t h e r e l a t i o n between m o r t a l i t y (1958-1977) and w a t e r q u a l i t y (1952-1977) can b e p r e s e n t e d . A d d i t i o n a l s t u d i e s a r e g o i n g o n . The s t u d i e s were s u p p o r t e d by g r a n t s from t h e M i n i s t r y of P u b l i c H e a l t h and Environm e n t a l P r o t e c t i o n and t h e Dutch P r e v e n t i o n Fund, and from t h e EEC ( c o n t r a c t 2 73- 77- 1-ENV-N)
.
RESEARCH OBJECTIVES Aspects of t h e r e l a t i o n s h i p between m o r t a l i t y and w a t e r h a r d n e s s , which t h e Working Group d e c i d e d t o i n v e s t i g a t e were i n t e r a l i a : 1. t h e q u a l i t y o f d r i n k i n g w a t e r i n 1977 and 1979 p a r t i c u l a r l y w i t h r e s p e c t t o h a r d n e s s (Ca, Mg) and a g r e s s i v i t y (pH, m e t a l s ) , comparing t h e 1977 and 1979 d a t a w i t h t h o s e from 1952 a s f a r a s a v a i l a b l e . 2.
t h e t r e n d of m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e ( I C D 410-414, c e r e b r o v a s c u l a r m o r t a l i t y ( I C D 430-438)
428) and of
i n males and females > 30 y r o f a g e ,
o v e r t h e p e r i o d s 1958-1962, 1963-1970 and 1971-1977.
3. t h e r e l a t i o n between m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e and/or c e r e b r o v a s c u l a r d i s e a s e and w a t e r q u a l i t y d a t a ( a t pumping s t a t i o n and a t t a p ) from 1952 and 1977.
31 WATER QUALITY DATA 1952-1977-1979 consistency of drinking water quality The Laboratory of the National Institute for Public Health (R.I.V.) examines water quality at pumping stations on a routine basis. The water quality data from 1952 and from 1977 for 17 communities showed a high Spearman ranking order coefficient of inter-correlation, except for pH: PH
:
r
=
0.41
K20
:
r
=
0.93
rCa
:
r
=
0.86
rMg
:
r
=
0.83
rC1
:
r
=
0.78
rS04
:
r
=
0.68
rHC03
:
r
=
0.84
The rather good consistency in ranking order of the parameters of water hardness, in addition to the fact that the average concentrations also did not differ considerably, allow to correlate water hardness with mortality over the whole period 1958-1977. There was no consistency in the pH. However, the pH was calculated on the basis of CO
- and HCO -concentrations. This may have been the reason for the 2 3 low coefficient of correlation. Therefore, in 1979 the National Institute for
Water Supply (NIWS) carried out accurate measurement of pH in 28 water supply areas; in addition a new calculation of the Langelier index of water agressivity was carried out. This study showed a negative correlation betwPen pH and Cacontent: r=-0.70 (n=28). Although in general natural soft waters are expected to be more agressive than natural hard waters, various measures taken by the Dutch water production companies to condition (de-acidification) the water in the last decennia have led to an increase of the pH of soft waters. It was not possible to establish fixed data for most water works with respect to the time of introduction of these conditioning measures, because many measures to improve
water quality were taken over a period of several years. Metals in water In Amsterdam a pilot study was carried out to establish the random sampling size of tapwaters in order to derive a valid estimate of metal intake through tapwater. At 200 taps proportional sampling (ref. 4) of water used for consumption was carried out. A sample size of 50 taps from an at random number of 200 taps proved to yield a valid estimate of the contribution of drinking water to the intake of metals (Cd, Pb, Cu, Zn, Fe). The concentrations of Mn, Si, Li, Sr, Ba, B, Al, Cr, V, No, Co, Ni, As and Sb were determined in composite samples. The concentrations of these elements were
not expected to change during distribution; they should therefore be determined in water at the pumping station. A study was carried out in 20 communities, with 40.000 inhabitants, and with
a reasonable consistency of water hardness over the last 25 years. In tapwater the lead and copper levels were positively related to Ca-levels: r
Ca-Pb
=
+0.43,
= +0.38 (n=20). The pH in these 20 water supply areas was negativellr
rca-Cu related to Ca-level (r=-0.66, n=20). These findings already suggest that a negative correlation between hardness and mortality will not be due to increased metal levels (ref. 6 ) . The effect of water hardness on the mineral (Ca, Mg and Pb) content of some food stuffs was investigated in a limited study by the National Institute for Water Supply (ref. 5 ) . Tapwater from 6 communities, varying in hardness from Ca
=
114 mg/l and Mg
=
19 mg/l to Ca = 17 mg/l and Mg = 2.2 mg/l, was used to
cook potatoes and vegetables. The results (Figure A, B,
C)
indicated that the
Ca-level in the food stuffs generally increased when cooked in hard water, whereas a decrease or only a slight increase was found when cooked in soft water; the Mg-content decreased both when cooked in hard and in soft water. The Pb-content generally increased in hard water and decreased in soft water; however, the hard waters contained higher Pb-levels than the soft waters. The results of these tests may support the hypothesis that an inverse relation between hardness and ischaemic heart disease mortality is due to a deficiency of Ca and/or Mg in soft water. Such a deficiency will further be increased by the extractions of Ca and Mg from food by soft water. This particularly may have consequences when the nutritional intake of Ca and/of Mg is low. The studies of water quality allow the following conclusions:
- over the last 25 years there was a good consistency in hardness of drinking water
- in 1979 there was a negative correlation between pH and hardness - in 1977/1978 lead and copper levels in tapwaters were positively related to calcium levels
- cooking vegetables in soft waters decreases the Ca- and Mg-content of these foods probably more than in case hard water was used for cooking.
39
*80%i potatoes
cauliflower
endive
carrots
5 5
t60%
+40%
.20%
-20%l 0%
-40 % A.
2
6
'u
PERCENTAGE OF THE CHANGE OF THE CALCIUM CONCENTRATION IN SOME FOODSTUFFS DURING COOKING WITH HARD AND SOFT DRINKING WATER
0%
20 %
40 % 60 ..%
B.
PERCENTAGE OF DECREASE OF THE MAGNESIUM CONTENTS IN SOME FOODSTUFFS DURING COOKING WITH HARD AND SOFT DRINKING WATER
*300% 1. THE HAGUE + 250%
2. WAGENINGEN
3. ZUTPHEN 4. ARNHEM
+ 200%
5. MAASTRICHT 6. KERKRADE
+
150%
100%
a
50%
C.
PERCENTAGE OF THE CHANGE OF THE LEAD CONCENTRATION I N SOME FOODSTUFFS DURING COOKING WITH HARD A N 0 SOFT DRINKING WATER
FIGURE A,B,C. CONCENTRATION CHANGES OF Ca,Mg AND Pb IN POTATOES, AND VEGETABLES BY COOKING THEM IN HARD (GREY BARS) AND SOFT ( OPEN B A R S ) DRINKING WATER TYPES
40 MORTALITY I N 1958
- 1977 IN 17
COMMUNITIES
C o r r e l a t i o n s t u d i e s between m o r t a l i t y and w a t e r q u a l i t y have been c a r r i e d o u t o v e r 1958/1962 ( r e f . l), 1963-1970 ( r e f . 2) and a g a i n o v e r 1971-1977. However, t h e Working Group doubted whether f o r 6 communities s t u d i e d o v e r 1958/1962 and
1963/1970 t h e w a t e r q u a l i t y d a t a used f o r 1952 were w e l l enough r e p r e s e n t a t i v e , b e c a u s e of admixture of w a t e r w i t h d i f f e r e n t q u a l i t y from o t h e r w a t e r works. The Group, t h e r e f o r e , s e l e c t e d o t h e r communities w i t h a number o f i n h a b i t a n t s
> 40.000, s e r v e d by one w a t e r works and w i t h no i n d i c a t i o n of change i n w a t e r q u a l i t y o v e r a b o u t 20 y e a r s . The Group s e l e c t e d 30 communities f o r t h e f i n a l s t u d y ; 17 communities o f t h e s e had been s t u d i e d a s w e l l o v e r 1958/1962 and
1963/1970. The m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e and c e r e b r o v a s c u l a r d i s e a s e i n males and females 2 30 y r o f age was compared o v e r t h e p e r i o d s 1958-1962,
1963-1970 and 1971-1977, a g e - s t a n d a r d i z e d on t h e p o p u l a t i o n - 1968 ( t a b l e 1 and t a b l e 2 ) ; 17 communities. TABLE
1
Ranking o r d e r c o r r e l a t i o n o f i s c h a e m i c h e a r t d i s e a s e m o r t a l i t y i n 1958-1962,
1963-1970 and 1971-1977 Males
2
30 y r o f age
1963/1970
1958/1962 1963/1970
1971/1977
0 . 4ZX
0.39O 0.74xx
0.7EXX
0 .6tjXx 0 . 83xx
Females 2 30 v r o f a a e
1958/1962 1963/1970 legenda:
o
P
<
0.10
x
P
<
0.05
xx
P
<
0.01
Over t h e p e r i o d 1958/1977 i n 17 communities t h e c o n s i s t e n c y of m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e i n females and
from c e r e b r o v a s c u l a r d i s e a s e i n males
was r e a s o n a b l y good. I n a c o r r e l a t i o n s t u d y w i t h w a t e r q u a l i t y d a t a o v e r t h e p e r i o d 1958-1977 p a r t i c u l a r a t t e n t i o n s h o u l d b e p a i d t o t h e s e two groups o f mortality.
41 TABLE 2
Ranking o r d e r c o r r e l a t i o n of c e r e b r o v a s c u l a r m o r t a l i t y i n 1958-1962, 1963-1970 and 1971-1977 Males > 30 y r of age
1963/1970
1971/1977
0 . aoxx
1958/1962 1963/1970 Females >
30 y r of age
0.57xx 0.79xx
1963/1970
1958/1962 1963/1970
1971/1977
- 0.00
0.35O
0.66xx
legenda:
o < P
x < P
xx < P
0.10 0.05 0.01
RANKING ORDER CORRELATION BETWEEN MORTALITY AND WATER HARDNESS
The age-standardized m o r t a l i t i e s from ischaemic h e a r t d i s e a s e and from cerebrov a s c u l a r d i s e a s e i n males and females
>, 30 y r of age, were c o r r e l a t e d with
Ca- and Mg-content of water-1952 and -1977 i n 17 communities ( t a b l e 3 ) . TABLE
3
Ranking o r d e r c o r r e l a t i o n between c a r d i o v a s c u l a r m o r t a l i t y over 1958-1977 and water hardness i n 1952 and 1977 i n 17 communities
Males
2
water 1952
water 1977
Ca
Ca
Mg
M9
30 y r of age
mortality
-0.31
+0.12
19581’1962
-0.05
1963/1970
-0.48x -O.4lx
-0.45x -0.4fjX
1971/1977
-0.36O -0.45x
-0.36x
-0.33O
1958/1962
-0.38O -0.17
-0.28
-0.16
1963/1970
-0.67xx -0.42x
-0.56xx -0.54x
1971/1977
-0.4Sx
-0.36O
Females
legenda:
-0.08
>I 30 y r of age
o
P (one s i d e d )
<
X
P
< 0.05
xx
P
<
0.10 0.01
-0.30
-0.37’
42 For c e r e b r o v a s c u l a r m o r t a l i t y no s i g n i f i c a n t c o r r e l a t i o n s e x i s t e d . From t h i s study on m o r t a l i t y i n 17 communities over 1952-1977 it could be concluded that:
-
t h e n e g a t i v e c o r r e l a t i o n e s t a b l i s h e d over 1958/1962 f o r IHD-females with hardness-
1952 ( r = 0.49, P CO.05, n = 2 3 ) , based upon s t a n a r d i s a t i o n on t h e
Segi-population, was n o t f u l l y confirmed f o r 17 communities, a f t e r s t a n d a r d i s a t i o n on population-1968:
r=-0.38; 0.05 < P < 0.10; n=17);
-
t h e ranking o r d e r c o r r e l a t i o n s f o r m o r t a l i t y 1971/77 g e n e r a l l y was lower than
-
t h e ranking o r d e r c o r r e l a t i o n w i t h t h e Ca-content of water was h i g h e r than Ca with t h e Mg-content; t h e r e was no c o r r e l a t i o n with t h e quotient;
-
t h e ranking o r d e r c o r r e l a t i o n only e x i s t e d f o r ischaemic h e a r t d i s e a s e
-
t h e ranking o r d e r c o r r e l a t i o n s were h i g h e r f o r females than f o r males, b u t
f o r 1963/1970, b o t h i n r e l a t i o n t o water-1952 and water-1977;
MCJ
and n o t f o r c e r e b r o v a s c u l a r d i s e a s e ;
a l s o f o r males a n e g a t i v e c o r r e l a t i o n was r e p e a t e d l y observed. The Working Group f i n a l l y s t u d i e d t h e r e l a t i o n between ischaemic h e a r t d i s e a s e m o r t a l i t y and c e r e b r o v a s c u l a r m o r t a l i t y i n 30 c a r e f u l l y s e l e c t e d comm u n i t i e s , with
>40.000 i n h a b i t a n t s and with no apparent change i n hardness
o v e r l a s t 20-30 y r , and t h e hardness o f water i n 1977 ( t a b l e 4 ) . TABLE 4
Ranking o r d e r c o r r e l a t i o n between ischaemic h e a r t d i s e a s e ( I H D ) and cerebrov a s c u l a r m o r t a l i t y (CNS) i n males and females
>30 y r of age w i t h Ca- and
Mg-content of water i n 1977 i n 30 communities Males
30 v r of aqe
IHD CNS
Females IHD CNS
Ca
Mg
-0.01 -#O.14
-0.19 -0.02
-0.11 -0.12
-0.10
30 y r of age
-0.07
There d i d n o t e x i s t any r e l a t i o n s h i p between w a t e r hardness and m o r t a l i t y from ischaemic h e a r t and from c e r e b r o v a s c u l a r d i s e a s e i n 30 c a r e f u l l y s e l e c t e d communities, although t h e 17 communities i n which a r e l a t i o n between cardiov a s c u l a r m o r t a l i t y had been observed, were included. I n f a c t , f o r t h e o t h e r 13 communities t h e r e e x i s t e d a p o s i t i v e c o r r e l a t i o n . I n 16 communities f o r which t h e metal (Pb, C u , zn) c o n t e n t of tapwater was known, no c o r r e l a t i o n between m o r t a l i t y and metal c o n t e n t could be e s t a b l i s h e d .
43 I n 23 communities no c o r r e l a t i o n was observed between m o r t a l i t y and t h e L i - o r t h e SiO - c o n t e n t of d r i n k i n g w a t e r . 2 The Working Group concluded from t h e s e s t u d i e s t h a t a t t h e p r e s e n t moment a n e g a t i v e r e l a t i o n s h i p between m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e and h a r d n e s s
of d r i n k i n g w a t e r c a n n o t be f u l l y r e j e c t e d , b u t a p p a r e n t l y many o t h e r f a c t o r s which c o n t r i b u t e t o t h i s m o r t a l i t y may c o m p l e t e l y overshadow such a r e l a t i o n s h i p . DISCUSSION AND CONCLUSION The s t u d i e s c a r r i e d o u t i n The N e t h e r l a n d s s i n c e 1975 have made i t c l e a r t h a t The N e t h e r l a n d s i s n o t a s u i t a b l e c o u n t r y t o e l u c i d a t e t h e "water s t o r y " f o r t h e following reasons:
-
t h e number of communities w i t h >40.000 i n h a b i t a n t s s e r v e d by one w a t e r works, and w i t h an e x p e c t e d c o n s i s t e n c y i n w a t e r q u a l i t y i s s m a l l ( n = 3 0 ) ;
-
t h e range i n w a t e r h a r d n e s s i s l i m i t e d (Ca 16-117 mg/l; Mg 1-15 mg/l) i n comparison t o e . g .
t h e U.K.
(Ca 4 mg/l t o 160 m g / l ) . I n t h e 30 communities
s t u d i e s i n The N e t h e r l a n d s 46 3
-
%
%
had a C a - l e v e l < 60 mg/l,
33 % < 40 mg/l and
< 20 mg/l i n 1977;
t h e r e i s a c o n s i d e r a b l e m o b i l i t y w i t h i n t h e c o u n t r y ; t h i s would s e v e r e l y hamper a l o n g i t u d i n a l s t u d y ;
-
some communities have an a g e - d i s t r i b u t i o n which v e r y much d e v i a t e s from t h e c o u n t r y a v e r a g e , because of e . g . aged s u b j e c t s ; s u c h
i n s t i t u t i o n s f o r o l d i n v a l i d s , and
a d e v i a t i o n c a n n o t be a d e q u a t e l y overcome by age-
standardisation;
-
i n The N e t h e r l a n d s community b a s e d d a t a on f a c t o r s which may c o n t r i b u t e t o c a r d i o v a s c u l a r m o r t a l i t y do n o t e x i s t ; t h e r e f o r e , i t i s n o t p o s s i b l e t o a d j u s t t h e mortality data f o r e.g. Pocock e t a l .
socio-economic c o n d i t i o n s a s done by
(ref. 7).
One o f t h e q u e s t i o n s which c o u l d n o t be answered i n 1971 was whether h a r d n e s s o r a g r e s s i v i t y of d r i n k i n g w a t e r was t h e d e c i s i v e f a c t o r f o r t h e n e g a t i v e c o r r e l a t i o n between i s c h a e m i c h e a r t d i s e a s e m o r t a l i t y and w a t e r h a r d n e s s . The s t u d i e s have b r o u g h t forward e v i d e n c e t h a t
-
a t l e a s t i n The N e t h e r l a n d s a t t h e p r e s e n t t i m e
-agreSSiVity(pH, m e t a l c o n t e n t ) does n o t p l a y a r o l e . I f t h e r e would appear t o b e a c a u s a t i v e r e l a t i o n s h i p between w a t e r q u a l i t y and ischaemic h e a r t d i s e a s e mortal i t y , t h e n t h i s s h o u l d probably be r e l a t e d t o t h e h a r d n e s s of w a t e r , p a r t i c u l a r l y t h e Ca-content. S t u d i e s i n t h e UK s t r o n g l y s u g g e s t t h a t p a r t i c u l a r l y s o f t w a t e r w i t h Ca c o n t e n t below 40 t o 60 mg/l may c o n t r i b u t e t o c a r d i o v a s c u l a r m o r t a l i t y . The EEC a l s o recommended ( r e f . 3 ) t h a t C a - l e v e l s s h o u l d n o t be lower t h a n 60 mg/l. The t o t a l number o f 30 communities was t o o s m a l l t o d i v i d e t h e s e i n t o subcategor i e s o f w a t e r h a r d n e s s ; t h e r e f o r e , t h e B r i t i s h s u g g e s t i o n c o u l d n e i t h e r b e con-
f i r m e d , nor b e r e j e c t e d .
In 1971 p u b l i c h e a l t h e x p e r t s s t r o n g l y opposed t h e p r o p o s a l f o r c e n t r a l w a t e r s o f t e n i n g . However, i n view of t h e d a t a g a t h e r e d s i n c e 1975, t h e p r e l i m i n a r y c o n c l u s i o n of t h e Working Group i s t h a t , a l t h o u g h a c o n t r i b u t i o n from w a t e r s o f t n e s s t o m o r t a l i t y from i s c h a e m i c h e a r t d i s e a s e cannot b e r e j e c t e d , a p a r t i a l s o f t e n i n y of d r i n k i n g w a t e r down t o say 60 mq/l p r o b a b l y w i l l have no measurable e f f e c t on i s c h a e m i c h e a r t d i s e a s e m o r t a l i t y i n The N e t h e r l a n d s a t t h e p r e s e n t monien t . We s t i l l p r e s e n t t h i s c o n c l u s i o n a s p r e l i m i n a r y . Small s c a l e a d d i t i o n a l s t u d i e s a r e s t i l l g o i n g on ( T a b l e 5 ) . Most s t u d i e s w i l l be completed i n 1980 o r 1981. The Working Group w i l l submit t h e i r f i n a l c o n c l u s i o n , b a s e d upon a l l
s t u d i e s , i n 1981 t o t h e M i n i s t e r of
H e a l t h and Environmental P r o t e c t i o n . TABLE 5
Small s c a l e s t u d i e s on t h e r e l a t i o n between w a t e r h a r d n e s s and p a r a m e t e r s of h e a l t h ( h a z a r d s ) , c a r r i e d o u t by t h e Working Group on H e a l t h Aspects of Water Hardness : -
r e l a t i o n between b l o o d l e v e l s of Pb, Cu, Zn and L i i n aged males
-
a n a l y s i s of m e t a l l e v e l s i n a u t o p s y t i s s u e s
-
p e r i n a t a l m o r t a l i t y from a n e n c e p h a l i a and w a t e r h a r d n e s s
-
c a r d i o v a s c u l a r p a r a m e t e r s i n workers
and c a r d i o v a s c u l a r p a r a m e t e r s
-
a n a l y s i s of m e t a l s i n h a i r of s c h o o l c h i l d r e n
animal e x p e r i m e n t s on r e s o r p t i o n of m e t a l s from d i f f e r e n t t y p e s of d r i n k i n g water.
REFERENCES 1 K . B i e r s t e k e r , Hardness of d r i n k i n g w a t e r and m o r t a l i t y ( i n D u t c h ) . T . Soc. Geneesk. 45 (1967) p p . 658-661. 2 K . B i e r s t e k e r and R . L . Z i e l h u i s , Hard o r s o f t d r i n k i n g w a t e r ? ( i n D u t c h ) . TI. SOC. Geneesk. 53 (1975) pp. 3-9. 3 European Economic Community ( E E C ) . E . C . D i r e c t i v e of t h e C o u n c i l o f M i n i s t e r s on t h e q u a l i t y of w a t e r d e s t i n e d f o r human consumption, J u l y 1 5 t h 1980. 4 B.J.A. Haring, Human exposure t o m e t a l s r e l e a s e d from w a t e r d i s t r i b u t i o n s y s t e m s . La Tribune du CEBEDEAU 4 1 9 (1978) p p . 349-355. 5 B.J.A. Haring and W. van D e l f t , Changes i n t h e m i n e r a l composition of food a s a r e s u l t of cooking i n "hard" and " s o f t " w a t e r s . I n p r e s s , 1980b. H a r i n g and B.C.J. Zoeteman, I s c o r r o s i v e n e s s o f d r i n k i n g w a t e r a p o s s i b l e 6 B.J.A. c a u s e of t h e s t a t i s t i c a l a s s o c i a t i o n between w a t e r h a r d n e s s and c a r d i o v a s c u l a r d i s e a s e m o r t a l i t y ? I n p r e s s , 1980a. 7 S.J. Pocock, A . G . S h a p e r , D . G . Cook, R.F. Packham, R.F. Lacey, P. Powell and P . F . R u s s e l l , B r i t i s h Regional Heart Study: g e o g r a p h i c v a r i a t i o n s i n c a r d i o v a s c u l a r m o r t a l i t y , and t h e r o l e o f w a t e r q u a l i t y . B r i t . Med. J . 24 May 1980, pp. 1243-1249.
45
ANNEX
Composition of t h e Working Group i n H e a l t h Aspects of C e n t r a l Water S o f t e n i n g R . L . Z i e l h u i s ( c h a i r m a n ) , Coronel L a b o r a t o r y f o r O c c u p a t i o n a l and Environmental H e a l t h , U n i v e r s i t y of Amsterdam. B.J.A. Haring ( s e c r e t a r y ) , N a t i o n a l I n s t i t u t e f o r Water Supply, Voorburg B.C.J. Zoeteman, N a t i o n a l I n s t i t u t e f o r Water Supply , Voorburg K . B i e r s t e k e r , A g r i c u l t u r a l U n i v e r s i t y , Wageningen E . H . G r o o t , A g r i c u l t u r a l U n i v e r s i t y , Wageningen C.H.J. E l z e n g a , The N e t h e r l a n d s Waterworks T e s t i n g and Research I n s t i t u t e , R i j s w i j k A. B o e s , The N e t h e r l a n d s Waterworks A s s o c i a t i o n , R i j s w i j k G . J . BOS, Medical man, Leiden L.M. Dalderup, Labour I n s p e c t i o n , Amsterdam R.F.M. Herber, Coronel L a b o r a t o r y f o r O c c u p a t i o n a l and Environmental H e a l t h , U n i v e r s i t y of Amsterdam A.A.E. Wibowo, Coronel L a b o r a t o r y f o r O c c u p a t i o n a l and Environmental H e a l t h , U n i v e r s i t y o f Amsterdam A.W. Fonds, N a t i o n a l I n s t i t u t e f o r P u b l i c H e a l t h , B i l t h o v e n J.J.M. de G o e i j , I n t e r u n i v e r s i t y Reactor I n s t i t u t e , D e l f t T . Trouwborst, M i n i s t r y of P u b l i c H e a l t h and Environmental PrOteCtiOn,Leidschendam J.J.L. P i e t e r s , M i n i s t r y of P u b l i c H e a l t h and Environmental P r o t e c t i o n , Leidschendam P.van Leeuwen, N a t i o n a l I n s t i t u t e f o r P r e v e n t i v e Medicine, Leiden.