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Lead in household dust
The Science of the Total Environment, 114 (1992) 1-6 Elsevier Science Publishers B.V., Amsterdam
Lead in household dust Hanne Jensen* Chemistry Department A, Building 207, Technical University of Denmark, DK-2800 Lyngby, Denmark (Received August 18th, 1990; accepted December 1st, 1990)
ABSTRACT The lead content of 55 samples of dust collected from vacuum cleaner bags from various parts of Denmark has been determined. The concentrations found ranged from 1.5-48.9 ppm lead in the dry dust, the geometric mean being 9 ppm which is comparable to the mean concentration of lead in Danish arable soil. No correlation was found between traffic density and concentration of lead in the dusts.
Key words: vacuum cleaner bags
INTRODUCTION
We all use our vacuum cleaners without really considering that we might be producing hazardous waste. The authorities in some Danish towns have decided that vacuum cleaner bags are to be treated, not as ordinary household waste, but together with paint, batteries and household chemicals, as hazardous waste. The view that the contents o f vacuum cleaner bags could be considered hazardous waste was based on an uncertainty about the lead content of the bags. In 1981 a paper was published [1] in which the results obtained from lead analyses of 17 vacuum cleaner bags, all collected in the greater Copenhagen area in 1979, were discussed. The geometric mean lead concentration found in the (dry) dust was 240 ppm which is about 16-times as high as the mean concentration found in Danish arable soil. To investigate whether or not the concentration o f lead in dust was still this high, dust from 55 vacuum cleaner bags was collected and analysed. *Present address: Danish Institute of Fundamental Metrology, Lundofteves 100, Building 307, DK-2800 Lyngby, Denmark. 0048-9697/92/$05.00
© 1992 Elsevier Science Publishers B.V. All rights reserved
2
H. JENSEN
The major source of lead emission in Denmark is the combustion of petrol. Bags were collected from households in areas (each with a 500 m radius) where the traffic density varies from < 1 0 0 - > 6 0 000 vehicles a day. METHOD The dust was dried at 105°C and then 2 g samples were digested with 50 ml 65% HNO3 (p.a.) and 1 ml 70% HC104 (p.a.). When the digestion was complete the samples were evaporated to dryness and diluted with 0.1 M HNO3. The solutions were analysed by the graphite oven technique (Perkin Elmer HGA72), with a Smith-Hieftje background correction (constructed in the Department). The same procedure was used in the investigation in 1979, but with deuterium background correction instead of Smith-Hieftje. Several sub-samples were taken (a total of 187 samples) from each of the 55 bags which were collected all over Denmark (Fig. 1) during 1989.
/__/9
Fig. 1. Map of Denmark showing where the vacuum cleaner bags were collected. Key to the locations and their traffic densities (vehiclesper day): Sk, Skagen (< 100); T, Tvis (6000); B, Brande (9400); A, ,~,rhus(20 000-25 000); Bi, Birkerod (14 000); S, Slangerup (5000-8500); L, Lyngby (51 000); ¢~= Osterbro (12 300-67 300); F, Frederiksberg (17 800-32 100); V, Valby (61 700); A, Amager (17 700-49 800); K, Karlstrup (5000); St, Stensved (4200).
3
L E A D IN H O U S E H O L D D U S T
RESULTS A N D DISCUSSION
To take a representative dust sample from a vacuum cleaner bag is very difficult, if not impossible. To solve the problem vee analysed several samples taken from different parts of each bag. These analyses showed that the standard deviation within bags was comparable to the standard deviation between the 55 different bags which were analysed. The 187 results follow the same lognormal distribution and this was tested by use of a x2-test (Table 1). A plot of the cumulated proportional frequencies on normal probability paper is shown in Fig. 2. The distribution of the results obtained from the individual households are shown in Fig. 3. The geometric mean is 9 ppm. The results from 1979 also follow a lognormal distribution (Table 2) and there is no significant difference between the S.D.s
TABLE 1 Testing the hypothesis that the measured lead concentrations belong to a lognormal distribution. One hundred eighty-seven determinations (ppm in dry dust) of lead in vacuun cleaner bags collected in 1989 m
lnx = 2.12
exp(2.12) = 8.4
Upper limit
Observed numbers ai
xi
lnxi
3.0 4.0 4.9 6.0 7.8 9.4 12.8 17.4 22.7
1.10 1.39 1.59 1.79 2.05 2.24 2.55 2.86 3.12
18 18 16 19 19 19 20 17 19 22
oo
187
(a i -
bi) 2 -
bi
Expected numbers b i
18.7 18.7 18.7 18.7 18.7 18.7 18.7 18.7 18.7 18.7 187 X2 (95%) = 14.1
f=10-3=7
I~
a(lnx) = 0.81
1.3
<
14.1
Cumulated observed frequencies 10% 19% 28% 38% 48% 58% 69% 78% 88% 100%
4
H, JENSEN
Probability of lower lead content %
9 e. 95 90 80 70 60 50 40 30 20
f
J
7
10 5 ppm Pb
¼
5
6
"/ 8 9 I0 Illi I13 Ii5 18 2L0
indry
2'5
dust
=
Fig. 2. Cumulative frequency plot for the determination of lead in 187 dust samples from vacuum cleaner bags.
(of the logarithmic values) found in 1979 and in 1989. This permits a comparison between the geometric mean values (both tests on the 5% significance level). The geometric mean of the determinations carried out in 1979 is 240 ppm Pb which is a significantly higher value than the mean (9 ppm) found in 1989. This decrease in lead content is not surprising. Lead emissions in Denmark were considerably higher in 1979 than today, from 1977 to 1984 lead emis-
LEAD IN HOUSEHOLD DUST Number of Households
10 6 2 n 10
20
3'0
Zo
~b
Fig. 3. Lead in Danish household dust.
mg Pb/kg dry dust
LEAD IN HOUSEHOLD DUST
5
TABLE 2 Testing the hypothesis that the measured lead concentrations belong to a lognormal distribution. 17 determinations of lead (ppm in dry dust) in vacuum cleaner bags collected in 1979 lnx = 5.48
exp (548) = 239
Upper limit
Observed numbers a i
xi
lnxi
150 210 340
5.01 5.35 5.83 ~
4 5 4 4 17
o(lnx) = 0.68 Expected numbers b i
4.25 4.25 4.25 4.25
Cumulated observed frequencies 24% 53% 76% 100%
17 X2(95%) = 3.84
f=4-3=1 (a i - bi) 2 ~;
- 0.18 < 3.84 bi
sions dropped by 75% (Table 3). Today it is estimated to be even lower as the a m o u n t of lead added to petrol, the main source of lead emission in Denmark, has decreased substantially since then. Legislation has lowered the upper limit for lead in petrol from 0.4 g/1 to 0.15 g/l, the mean value now TABLE 3 Lead in Danish petrol Year
1977 1978 1981 1982 1983 1984 1985 1989
[2] [2] [3] [3] [3] [3] [3] [5]
Lead in super petrol
Lead in ordinary petrol
(g/l)
(g/l)
0.30 0.29 0.27 0.14 0.14
0.57 0.40 0.27 0.22 0.14 0.14 0.14
Petrol sold (1000m3)
1881 1847 1887 1954 2003
Lead emmited to the atmosphere (tons)
971 - 700 410 360 310 205 190 -113
6
LEAD 1N HOUSEHOLD DUST
being 0.14 g/1 in both normal and super petrol. The emission has further decreased as today [4] more than 50% of Danish cars use unleaded petrol. No correlation was found between traffic density and concentration of lead in the vacuum cleaner bags. However, the lowest concentration of lead (1.5 ppm) was found in the area with the lowest traffic density. CONCLUSION There does not seem to be any reason for treating vacuum cleaner bags as hazardous chemical waste on account of the lead content of the dusts. The geometric mean lead concentration found in vacuum cleaner bag dusts in this investigation was 9 ppm which is not significantly different from the mean lead concentration of 17 ppm found in Danish arable soil. REFERENCES 1 J.C. Tjell, A. Elmlund and J. Aa. Hansen, Source or central separation of household food waste, in A.V. Bridwater and K. Lidgren, (Eds.), Household Waste Management in Europe, Van Nostrand Reinhold Company, London, 1981, pp. 92-103. 2 Blyforurening. Redegarelse for blyforurening i Danmark. Milj~styrelsen, 1979 (in Danish). 3 Forbrug af og forurening med bly i Danmark. Miljcprojekt nr. 105, Miljostyrelsen, 1989 (in Danish). 4 J. Kampmann, MiljoDanmark, 1989, 5,2 (in Danish). 5 Miljesturelsen,The Environmental Agency.
Lead in household dust Hanne Jensen* Chemistry Department A, Building 207, Technical University of Denmark, DK-2800 Lyngby, Denmark (Received August 18th, 1990; accepted December 1st, 1990)
ABSTRACT The lead content of 55 samples of dust collected from vacuum cleaner bags from various parts of Denmark has been determined. The concentrations found ranged from 1.5-48.9 ppm lead in the dry dust, the geometric mean being 9 ppm which is comparable to the mean concentration of lead in Danish arable soil. No correlation was found between traffic density and concentration of lead in the dusts.
Key words: vacuum cleaner bags
INTRODUCTION
We all use our vacuum cleaners without really considering that we might be producing hazardous waste. The authorities in some Danish towns have decided that vacuum cleaner bags are to be treated, not as ordinary household waste, but together with paint, batteries and household chemicals, as hazardous waste. The view that the contents o f vacuum cleaner bags could be considered hazardous waste was based on an uncertainty about the lead content of the bags. In 1981 a paper was published [1] in which the results obtained from lead analyses of 17 vacuum cleaner bags, all collected in the greater Copenhagen area in 1979, were discussed. The geometric mean lead concentration found in the (dry) dust was 240 ppm which is about 16-times as high as the mean concentration found in Danish arable soil. To investigate whether or not the concentration o f lead in dust was still this high, dust from 55 vacuum cleaner bags was collected and analysed. *Present address: Danish Institute of Fundamental Metrology, Lundofteves 100, Building 307, DK-2800 Lyngby, Denmark. 0048-9697/92/$05.00
© 1992 Elsevier Science Publishers B.V. All rights reserved
2
H. JENSEN
The major source of lead emission in Denmark is the combustion of petrol. Bags were collected from households in areas (each with a 500 m radius) where the traffic density varies from < 1 0 0 - > 6 0 000 vehicles a day. METHOD The dust was dried at 105°C and then 2 g samples were digested with 50 ml 65% HNO3 (p.a.) and 1 ml 70% HC104 (p.a.). When the digestion was complete the samples were evaporated to dryness and diluted with 0.1 M HNO3. The solutions were analysed by the graphite oven technique (Perkin Elmer HGA72), with a Smith-Hieftje background correction (constructed in the Department). The same procedure was used in the investigation in 1979, but with deuterium background correction instead of Smith-Hieftje. Several sub-samples were taken (a total of 187 samples) from each of the 55 bags which were collected all over Denmark (Fig. 1) during 1989.
/__/9
Fig. 1. Map of Denmark showing where the vacuum cleaner bags were collected. Key to the locations and their traffic densities (vehiclesper day): Sk, Skagen (< 100); T, Tvis (6000); B, Brande (9400); A, ,~,rhus(20 000-25 000); Bi, Birkerod (14 000); S, Slangerup (5000-8500); L, Lyngby (51 000); ¢~= Osterbro (12 300-67 300); F, Frederiksberg (17 800-32 100); V, Valby (61 700); A, Amager (17 700-49 800); K, Karlstrup (5000); St, Stensved (4200).
3
L E A D IN H O U S E H O L D D U S T
RESULTS A N D DISCUSSION
To take a representative dust sample from a vacuum cleaner bag is very difficult, if not impossible. To solve the problem vee analysed several samples taken from different parts of each bag. These analyses showed that the standard deviation within bags was comparable to the standard deviation between the 55 different bags which were analysed. The 187 results follow the same lognormal distribution and this was tested by use of a x2-test (Table 1). A plot of the cumulated proportional frequencies on normal probability paper is shown in Fig. 2. The distribution of the results obtained from the individual households are shown in Fig. 3. The geometric mean is 9 ppm. The results from 1979 also follow a lognormal distribution (Table 2) and there is no significant difference between the S.D.s
TABLE 1 Testing the hypothesis that the measured lead concentrations belong to a lognormal distribution. One hundred eighty-seven determinations (ppm in dry dust) of lead in vacuun cleaner bags collected in 1989 m
lnx = 2.12
exp(2.12) = 8.4
Upper limit
Observed numbers ai
xi
lnxi
3.0 4.0 4.9 6.0 7.8 9.4 12.8 17.4 22.7
1.10 1.39 1.59 1.79 2.05 2.24 2.55 2.86 3.12
18 18 16 19 19 19 20 17 19 22
oo
187
(a i -
bi) 2 -
bi
Expected numbers b i
18.7 18.7 18.7 18.7 18.7 18.7 18.7 18.7 18.7 18.7 187 X2 (95%) = 14.1
f=10-3=7
I~
a(lnx) = 0.81
1.3
<
14.1
Cumulated observed frequencies 10% 19% 28% 38% 48% 58% 69% 78% 88% 100%
4
H, JENSEN
Probability of lower lead content %
9 e. 95 90 80 70 60 50 40 30 20
f
J
7
10 5 ppm Pb
¼
5
6
"/ 8 9 I0 Illi I13 Ii5 18 2L0
indry
2'5
dust
=
Fig. 2. Cumulative frequency plot for the determination of lead in 187 dust samples from vacuum cleaner bags.
(of the logarithmic values) found in 1979 and in 1989. This permits a comparison between the geometric mean values (both tests on the 5% significance level). The geometric mean of the determinations carried out in 1979 is 240 ppm Pb which is a significantly higher value than the mean (9 ppm) found in 1989. This decrease in lead content is not surprising. Lead emissions in Denmark were considerably higher in 1979 than today, from 1977 to 1984 lead emis-
LEAD IN HOUSEHOLD DUST Number of Households
10 6 2 n 10
20
3'0
Zo
~b
Fig. 3. Lead in Danish household dust.
mg Pb/kg dry dust
LEAD IN HOUSEHOLD DUST
5
TABLE 2 Testing the hypothesis that the measured lead concentrations belong to a lognormal distribution. 17 determinations of lead (ppm in dry dust) in vacuum cleaner bags collected in 1979 lnx = 5.48
exp (548) = 239
Upper limit
Observed numbers a i
xi
lnxi
150 210 340
5.01 5.35 5.83 ~
4 5 4 4 17
o(lnx) = 0.68 Expected numbers b i
4.25 4.25 4.25 4.25
Cumulated observed frequencies 24% 53% 76% 100%
17 X2(95%) = 3.84
f=4-3=1 (a i - bi) 2 ~;
- 0.18 < 3.84 bi
sions dropped by 75% (Table 3). Today it is estimated to be even lower as the a m o u n t of lead added to petrol, the main source of lead emission in Denmark, has decreased substantially since then. Legislation has lowered the upper limit for lead in petrol from 0.4 g/1 to 0.15 g/l, the mean value now TABLE 3 Lead in Danish petrol Year
1977 1978 1981 1982 1983 1984 1985 1989
[2] [2] [3] [3] [3] [3] [3] [5]
Lead in super petrol
Lead in ordinary petrol
(g/l)
(g/l)
0.30 0.29 0.27 0.14 0.14
0.57 0.40 0.27 0.22 0.14 0.14 0.14
Petrol sold (1000m3)
1881 1847 1887 1954 2003
Lead emmited to the atmosphere (tons)
971 - 700 410 360 310 205 190 -113
6
LEAD 1N HOUSEHOLD DUST
being 0.14 g/1 in both normal and super petrol. The emission has further decreased as today [4] more than 50% of Danish cars use unleaded petrol. No correlation was found between traffic density and concentration of lead in the vacuum cleaner bags. However, the lowest concentration of lead (1.5 ppm) was found in the area with the lowest traffic density. CONCLUSION There does not seem to be any reason for treating vacuum cleaner bags as hazardous chemical waste on account of the lead content of the dusts. The geometric mean lead concentration found in vacuum cleaner bag dusts in this investigation was 9 ppm which is not significantly different from the mean lead concentration of 17 ppm found in Danish arable soil. REFERENCES 1 J.C. Tjell, A. Elmlund and J. Aa. Hansen, Source or central separation of household food waste, in A.V. Bridwater and K. Lidgren, (Eds.), Household Waste Management in Europe, Van Nostrand Reinhold Company, London, 1981, pp. 92-103. 2 Blyforurening. Redegarelse for blyforurening i Danmark. Milj~styrelsen, 1979 (in Danish). 3 Forbrug af og forurening med bly i Danmark. Miljcprojekt nr. 105, Miljostyrelsen, 1989 (in Danish). 4 J. Kampmann, MiljoDanmark, 1989, 5,2 (in Danish). 5 Miljesturelsen,The Environmental Agency.