This article was downloaded by: [North Carolina State University] On: 06 March 2015, At: 00:02 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Archives of Environmental Health: An International Journal Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vzeh20
Umbilical Cord Blood Lead Levels in California a
a
Kenneth P. Satin Dr. P.H. , Raymond R. Neutra M.D., Dr. P.H. , Guirguis Guirguis a
Ph.D. & Peter Flessel Ph.D.
a
a
California Department , Health Services , Berkeley, California, USA Published online: 03 Aug 2010.
To cite this article: Kenneth P. Satin Dr. P.H. , Raymond R. Neutra M.D., Dr. P.H. , Guirguis Guirguis Ph.D. & Peter Flessel Ph.D. (1991) Umbilical Cord Blood Lead Levels in California, Archives of Environmental Health: An International Journal, 46:3, 167-173, DOI: 10.1080/00039896.1991.9937445 To link to this article: http://dx.doi.org/10.1080/00039896.1991.9937445
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
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Umbilical Cord Blood Lead Levels in California
KENNETH P. SATIN, Dr. P.H. RAYMOND R. NEUTRA, M.D., Dr. P.H. GUlRCUlS CUIRCUIS, Ph.D. PETER FLESSEL, Ph.D. California Department of Health Services Berkeley, California
ABSTRACT. During the fall of 1984, we conducted a survey of umbilical cord blood lead levels of 723 live births that occurred at 5 hospitals located in 5 cities in California. Historical ambient air lead levels were used as a qualitative surrogate of air and dust exposure. The area-specific cord blood means (all means approximately 5 pg/dl), medians, deciles, and distributions did not vary among locations. The California distributions included means that were lower than the 6.6 pg/dl reported in Needleman et al.'s Boston study in 1979. Indeed, the entire California distribution was shifted to the left of the Boston study distribution, even though 3% of the California cord lead levels exceeded 10 d d l - t h e level above which Needleman et al. have documented psychoneurological effects in children during the first few years of life. Fourteen percent of premature babies had cord blood lead levels above 10 pg/dl. The association between prematurity (i.e., < 260 d gestation) and elevated (> 5 &dl) cord blood lead was observed in all hospitals and yidded a relative risk of 2.9 (95% CI: .9, 9.2) and a population attributable risk of 47%. Further research is needed to confirm this association and to explore the roles of endogenous and exogenous sources of lead exposure to the mothers who give birth to premature infants.
LEAD IS UBIQUITOUS in the environment, and it is among the most studied elements. Although it is not required for any physiologic process, lead readily binds to cellular constituents. At low lead concentrations, such binding may not produce measurable physiologic effects; however, at increased concentrations, biochemical processes are influenced, which may, in turn, produce adverse effects. Low lead levels (i.e., < 16 pg/dl) disrupt enzyme systems, particularly heme synChildren whose blood lead levels exceed 20 pg/dl begin to exhibit deficits in neurologic performa n ~ e . ~Higher -~ blood lead levels (i.e., 80-100 pg/dl) can result in encephalopathies and death.6,7The fetus is also at high risk from lead exposure; in fact, lead has historically been used as an abortifacient. Bellinger et al.' demonstrated a measurable alteration in behavior Mayljune 1991 [Vol. 46 (No. 3)]
at 1 and 2 y of age in a cohort of infants whose average cord blood lead level was 14.6 pg/dl. They hypothesized an in utero effect of lead on the embryo's neurological development. Indeed, a recent report on lead poisoning in children, presented by the Agency for Toxic Substances Diseases Registries (ATSDR), concluded that prenatal exposures that result in blood lead levels of 10-15 pg/dl are associated with deficits in neurobehavioral development, aminolevulinic acid dehydratase inhibition, and reduced gestational age and weight at birth.' Current evidence indicates that lead may produce adverse health effects at levels below the Centers for Disease Control's (CDC) cutoff (i.e., 25 Ccg/dl") for a safe lead body burden. This coupled with the fact that these effects may begin during exposure in utero pro167
vide cause for concern. Therefore, this study was undertaken to (a) determine the distribution of cord blood lead levels in California, (b) estimate the magnitude of the population at risk, and (c) identify high-risk subgroups.
which coincide with the period when ambient air lead levels approach their peak in California (Table 1). Within each area, a target hospital was selected on the basis of having the largest number of births each month and the likelihood that women of low-socioeconomic status (SES) would deliver there (e.g., county facilities). The latter criterion was used because low SES is associated with increased lead exposure, especially from sources other than air, e.g., occupation, soil, residential paint. Lead samples were requested, and birth certificate information was abstracted for all deliveries for the months of October and November 1984. Delivery logs were also reviewed, and a list was made of all births that occurred in each hospital during the study period. In the hospital in Los Angeles, samples were collected for only a 3-wk period in November because such a large number of infants was delivered there each month. Because the catchment area for each hospital extended beyond the geographic area in the general vicinity of the hospital and ambient air monitoring station, "core" areas were designated for each hospital to reduce the potential for exposure misclassification. The core areas were defined as follows: (a) UkiahMendocino and Lake county zip codes, (b) San Francisco-San Francisco zip codes, (c) Fresno-arbitrarily defined central Fresno (city) zip codes, (d) Santa Monica-"coastal" Santa Monica area zip codes restricted to the more affluent neighborhoods, and (el Los Angeles-zip codes from innercity low-SES areas that surrounded the hospital. Approximately 10 ml of cord blood were collected in a blue-topped, lead-free, heparinized Vacutainer (B-D,
Downloaded by [North Carolina State University] at 00:03 06 March 2015
Methods This study was designed to provide a profile of umbilical cord blood lead levels that included the extremes of environmental lead exposures. The major sources of concern were food, water, and air. We assumed that there would be minimal regional variation among California study locations with respect to lead content of food. Even though lead levels in potable supplies can vary greatly in California, we were unable to evaluate this environmental source. Data on ambient air lead levels, however, are collected routinely. Moreover, several authors have shown that air lead levels directly relate to blood lead levels."-'4 Therefore, exposure areas were defined on the basis of (a) ambient air concentrations within specific locations, (b) hospitals within locations, and (c) the time of year to obtain blood samples that would result in the highest variation in airborne lead exposures. Historical air data were used to select Los Angeles and Fresno counties as the high-lead exposure areas; San Francisco as the intermediate area; and Ukiah, a rural community approximately 161 km (100 mi) north of San Francisco, as the low-exposure area. Santa Monica, a coastal city west of Los Angeles, was also included in the study because it represented an urban, fairly affluent, low-exposure area. Umbilical cord blood samples were collected during October and November,
Table 1.-Lead Values (ccg/m3)of Air Samples Collected near Study Hospitals (Umbilical Cord Blood Lead Study, 1984) Hospital
Los Month and year
Fresno
September 1984 Monthly mean Highest value
,344 .53
.360
October 1984 Monthly mean Highest value Monthly mean Highest value Monthly mean Highest value November 1984 Monthly mean Highest value Monthly mean Highest value Distance from collection station to hospital (km)
.53
San Francisco
Santa Monica
,433 .77
.298 .56
-
.420* .42* .448t .56t
,254 .37
-
Angeles
Ukiah
,104
.12
.088 .11
.44a* .56S
,240 .32
3.2
.818t 1.26t .783$
.88* 2.0*
1.73 .19
-
5.0
-
.m .11
32.0
15.3t 16.2$ ~
*North Main collection station (sample missing for November). tLynwood collection station. SPico Rivera collection station.
168
Archives of Environmental Health
Downloaded by [North Carolina State University] at 00:03 06 March 2015
presented in Table 2. These levels are based on the readings obtained at the monitoring station nearest each hospital. Our a priori classification of areas was based on historical data for this study period, but the range of lead levels was narrower than expected, i.e., 0.1-0.8 pg/m3 monthly average. The Santa Monica location was not as lead-free as expected; rather, the air lead profile was more characteristic of the intermediate lead exposure areas. Demographic characteristics of the study population are shown in Table 3. A total of 1680 births occurred across all hospitals. The mean maternal age was 26.4 y; mothers in Fresno tended to be slightly younger (24.4 y), whereas those in Santa Monica were older than average (29.8 y). Most of the infants were Hispanic or white. Only the hospital in San Francisco had an appreciable number of black infants (about 31%), and no hospital had more than 8% Asian births. Approximately 40-60% of the women lived outside the core area that surrounded the target hospital (Table 3). Approximately 60% of the blood samples could not be analyzed because of clotting (Table 3). However, regardless of the study area, characteristics (i.e., sex, racelethnicity, mother's age) of the infants who were not analyzed were similar to those of infants whose blood lead was determined. Also, no differences were found in the proportions of birth certificate-based reports of congenital malformations. One difference, however, was that mothers of infants for whom blood samples could be analyzed had fewer complications during pregnancy and delivery. Also, more blood samples obtained from infants who were born during the initial weeks of the study were useable. Blood lead levels did not vary by core area status and, therefore, subsequent analyses are based on the combined areas (Table 4). Blood lead levels were very
Rutherford, N]) from each infant born during the study period. Ethylene oxide was used in the hospitals that required sterilized collection tubes. Samples were collected after the umbilical cord had been severed. Collection tubes, which were refrigerated, were transported to the laboratory no later than 2 wk after a sample was collected. Refrigeration was not maintained during transportation. Samples were frozen in the laboratory until analysis. All samples were analyzed for total lead concentration by the California Department of Health Services, Air and Industrial Hygiene Laboratory (AIHL), using a heated furnace atomic absorption method described previou~ly.'~ Blood samples were diluted (1:SO) with distilled water prior to analysis, and bovine blood samples were used.15 The lowest bovine blood standard contained 7 pg lead/dl. To obtain sample concentrations below this value, the standard curve was extrapolated linearly to 0. Accuracy of the blood lead results was determined through AIHL's successful participation in the two ongoing blood lead proficiency testing programs: (1) the monthly CDC program (as a reference laboratory), and (2) the quarterly program of the New York State Department of Health. Approximately every tenth sample was analyzed in duplicate. The agreement between split samples was determined by calculating an intraclass correlation (ICC),'6 the value of which was 0.46 (on a scale of -1 [no agreement] to + 1 [complete agreement]), which indicated a high degree of concordance.
Results Blood lead levels generally reflect recent exposure, i.e., during the past 30 d." Location-specific ambient air concentrations for the relevant study periods are
Table I.-Ambmt Air Lead Levels (rslrnl) of Air Samples Collected near Study Hospitals (Umbilical Cord Blood Lead Study, 1984
I
Average lead concentration Study hospital/ air station Ukiah* Lakeport Fort Bragg San Franciscot 23rd St. Fresno Olive St. Santa Monica VA Robertson Blvd. Los Angeles North Main
Sept. 1984
Study period Oct. 1984
Nov. 1984
1st.
Annual summary (by quarter) 2nd. 3rd. 4th. 1st. (1985)
.09 .07
.09
.10 .08
.06 .06
.08
.07
.07
.08 .07
.09 .08
.05 .05
.30
.25
.17
.43
.20
.19
.22
.26
.34
.36
.24
.60
.24
.29
.41
.37
.32 .30
.38 .28
.37 .49
.59
.16 .20
.24 .24
.40 .40
.27 .42
.43
.42
-
.72
.37
.41
.56
.a
*There was no lead monitoring station in Ukiah. However, the communites of Lakeport and Fort Bragg are similar to Ukiah. Lakeport is located approximately 32 km (20 mi) inland, and Fort Bragg, a coastal area, is approximately 57 km (35 mi) from Ukiah. tAmbient air monitoring stations were located the following distances from the hospital: 5 km (3 mi), 3.2 km (2 mi), 4 km (2.5 mi), and 2 km (1.25 mi).
May/June1991 [Vd. 46 (NO.3)]
169
Table 3.-Demographic
Characteristics by Hospital (Umbilical Cord Blood Lead Study, 1984) Hospitallarea
Downloaded by [North Carolina State University] at 00:03 06 March 2015
Los Characteristic
Fresno
Total births (n) Sex (%) Male Female Missing Mother's age (3 Child's race (%) White* Hispanic Black Asian Other Missing Core areat ("10) Within core Out of area Births with lead sample n
439
010
Angeles
712
San Francisco
180
Santa Monica
255
Ukiah
142
Total
1 728
27.6
52.6 46.3 1.2 29.8
47.1 50.7 2.1 26.5
51 .O 47.0 2.0 26.4
3.1 91 .o 3.0 2.0 0.4 0.6
39.4 10.6 31.7 7.8 2.2 8.3
60.0 28.2 4.3 5.1 .4 2.0
77.5 15.5 0.0 1.4 4.2 1.4
21.9 61.5 5.7 4.2 1.2 5.6
44.2 55.8
32.2 67.8
63.3 36.7
38.4 61.6
76.1 23.9
43.1 56.9
259.0 59.0
601.O 84.5
94.0 52.2
50.0 19.6
69.0 48.6
1073.0 62.1
172.0 39.1
406.0
52.0 28.9
37.0 14.5
56.0 39.4
723.0 40.1
53.1 42.4 4.6 24.4
48.8 50.0 1.1 26.0
55.6 44.4
5.0 68.5 2.3 6.8 1.4 16.0
0.0
Births with usable lead sample+
n 010
57.0
*Does not include individuals who are Hispanic. tCore area included residences that were closest to hospital where delivery occurred (see text for explanation). *Cord blood sample not clotted or broken.
Table 4.--Mean, Range, and Percentile of Lead Values W d l ) , by Hospital (Umbilical Cord Blood Study, 1984) Hospitallarea San Santa Francisco Monica
Lead values
Fresno
Los Angeles
Mean Range Percentiles 99 90 75 50 25 10
4.7 .5-15
5.1 1-13
4.5 1-11
14.3 8.0 6.0 4.0 3.0 2.0
10.0 8.0 6.0 5.0 4.0 3.0
11.0 8.0 5.0 4.0 3.0 2.3
Ukiah
Total Boston*
4.8 2-1 2
5.2 1-13
4.9 .5-15
6.6 0-37
12.0 8.4 6.0 4.0 3.0 3.0
13.0 8.0 7.0 5.0 4.0 2.0
12.8 8.0 6.0 5.0 3.0 2.0
17.0 10.5 8.5 6.5 4.5 3.5
*Values extracted from Rabinowitz MB and Needleman HL.18
similar in all parts of California (Table 4). The overall mean cord blood lead level among all hospitals was 4.9 pgldl (range = .5-15 pg/dl). A one-way ANOVA showed that the area-specific mean blood lead levels were not different (p = .24). The area-specific distributions for blood lead levels were also very similar. Blood lead levels were also viewed in terms of factors related to pregnancy. Prematurity and complications of pregnancy or delivery were associated with slightly higher blood lead levels, but the differences were relatively small and contained a high degree of variation 170
resulting from the modest number of cases involved when these factors were stratified. The association between prematurity and blood lead level was observed in all four hospitals for which data were available to determine the length of gestation (Table 5). A cord blood lead level that exceeded 5 pg/dl (the median level) yielded a relative risk for prematurity of 2.9 (95% CI: 0.9-9.2) and a population attributable risk of 46.8%. N o association was observed between low birthweight (< 2 500 g) and cord blood lead levels (Table 6). Blood lead levels were not related to ethnicity or gender. Archives of Environmental Health
Table S.--Gestational Time, by lead Levels (rcsldl) (Umbilical Cord lead Study, 1984)
20 18
Hospital/ gestational days
X
n
Cord blood lead SE Range
16 14
pvalue
All hospitals*
2 260*
< 260
303 14
4.7 6.5
f
.135 .5-15 f1.004 2 -14
.007$
165 7
4.6 6.6
f
.187 .5-15 f2.021 2 -14
.37
2 260
2 260
< 260
48 4
4.3 6.3
4 2
35 2
4.6 6.5
55 1
5.3 7.0
0
,301 f .946
1 -11 5 - 9
.08
.403
2 -12 6 - 7
.30
f .500
*+ O .308
1 -13 7
-
f
.-Boston
8
Data not collected
Los Angeles San Francisco
-California
8
Fresno
< 260
12 10
5
0
10
20
15
25
30
40
35
CORD BLOOD LEAD LEVELS (uddl)
Santa Monica
2 260
< 260 Downloaded by [North Carolina State University] at 00:03 06 March 2015
Ukiah
2 260
< 260
f
Fig. 1. Percentage frequency, California and Boston lead levels. Umbilical Cord Lead Study, 1984.
100 -4
~~
*Excluding LosAngies (data not collected). tDays since last menstrual cycle. *p value from t test in which 2 2606 gestation period compared with < 260-d gestation period.
Table 6.-Birthweight, by Lead levels (pg/dt) (Umbilical Cord Lead Study, 1984)
Hospital/ birthweight (g) ~
X
n ~~~
Cord blood lead SE Range
90
Eu
80
-
-
70-
5 I PI
60:
$
50-
California
+Boston
j" ::; 20-
p value
-
I01
18
~
0
All hospitals
22500
Archives of Environmental Health: An International Journal Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vzeh20
Umbilical Cord Blood Lead Levels in California a
a
Kenneth P. Satin Dr. P.H. , Raymond R. Neutra M.D., Dr. P.H. , Guirguis Guirguis a
Ph.D. & Peter Flessel Ph.D.
a
a
California Department , Health Services , Berkeley, California, USA Published online: 03 Aug 2010.
To cite this article: Kenneth P. Satin Dr. P.H. , Raymond R. Neutra M.D., Dr. P.H. , Guirguis Guirguis Ph.D. & Peter Flessel Ph.D. (1991) Umbilical Cord Blood Lead Levels in California, Archives of Environmental Health: An International Journal, 46:3, 167-173, DOI: 10.1080/00039896.1991.9937445 To link to this article: http://dx.doi.org/10.1080/00039896.1991.9937445
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Downloaded by [North Carolina State University] at 00:03 06 March 2015
Umbilical Cord Blood Lead Levels in California
KENNETH P. SATIN, Dr. P.H. RAYMOND R. NEUTRA, M.D., Dr. P.H. GUlRCUlS CUIRCUIS, Ph.D. PETER FLESSEL, Ph.D. California Department of Health Services Berkeley, California
ABSTRACT. During the fall of 1984, we conducted a survey of umbilical cord blood lead levels of 723 live births that occurred at 5 hospitals located in 5 cities in California. Historical ambient air lead levels were used as a qualitative surrogate of air and dust exposure. The area-specific cord blood means (all means approximately 5 pg/dl), medians, deciles, and distributions did not vary among locations. The California distributions included means that were lower than the 6.6 pg/dl reported in Needleman et al.'s Boston study in 1979. Indeed, the entire California distribution was shifted to the left of the Boston study distribution, even though 3% of the California cord lead levels exceeded 10 d d l - t h e level above which Needleman et al. have documented psychoneurological effects in children during the first few years of life. Fourteen percent of premature babies had cord blood lead levels above 10 pg/dl. The association between prematurity (i.e., < 260 d gestation) and elevated (> 5 &dl) cord blood lead was observed in all hospitals and yidded a relative risk of 2.9 (95% CI: .9, 9.2) and a population attributable risk of 47%. Further research is needed to confirm this association and to explore the roles of endogenous and exogenous sources of lead exposure to the mothers who give birth to premature infants.
LEAD IS UBIQUITOUS in the environment, and it is among the most studied elements. Although it is not required for any physiologic process, lead readily binds to cellular constituents. At low lead concentrations, such binding may not produce measurable physiologic effects; however, at increased concentrations, biochemical processes are influenced, which may, in turn, produce adverse effects. Low lead levels (i.e., < 16 pg/dl) disrupt enzyme systems, particularly heme synChildren whose blood lead levels exceed 20 pg/dl begin to exhibit deficits in neurologic performa n ~ e . ~Higher -~ blood lead levels (i.e., 80-100 pg/dl) can result in encephalopathies and death.6,7The fetus is also at high risk from lead exposure; in fact, lead has historically been used as an abortifacient. Bellinger et al.' demonstrated a measurable alteration in behavior Mayljune 1991 [Vol. 46 (No. 3)]
at 1 and 2 y of age in a cohort of infants whose average cord blood lead level was 14.6 pg/dl. They hypothesized an in utero effect of lead on the embryo's neurological development. Indeed, a recent report on lead poisoning in children, presented by the Agency for Toxic Substances Diseases Registries (ATSDR), concluded that prenatal exposures that result in blood lead levels of 10-15 pg/dl are associated with deficits in neurobehavioral development, aminolevulinic acid dehydratase inhibition, and reduced gestational age and weight at birth.' Current evidence indicates that lead may produce adverse health effects at levels below the Centers for Disease Control's (CDC) cutoff (i.e., 25 Ccg/dl") for a safe lead body burden. This coupled with the fact that these effects may begin during exposure in utero pro167
vide cause for concern. Therefore, this study was undertaken to (a) determine the distribution of cord blood lead levels in California, (b) estimate the magnitude of the population at risk, and (c) identify high-risk subgroups.
which coincide with the period when ambient air lead levels approach their peak in California (Table 1). Within each area, a target hospital was selected on the basis of having the largest number of births each month and the likelihood that women of low-socioeconomic status (SES) would deliver there (e.g., county facilities). The latter criterion was used because low SES is associated with increased lead exposure, especially from sources other than air, e.g., occupation, soil, residential paint. Lead samples were requested, and birth certificate information was abstracted for all deliveries for the months of October and November 1984. Delivery logs were also reviewed, and a list was made of all births that occurred in each hospital during the study period. In the hospital in Los Angeles, samples were collected for only a 3-wk period in November because such a large number of infants was delivered there each month. Because the catchment area for each hospital extended beyond the geographic area in the general vicinity of the hospital and ambient air monitoring station, "core" areas were designated for each hospital to reduce the potential for exposure misclassification. The core areas were defined as follows: (a) UkiahMendocino and Lake county zip codes, (b) San Francisco-San Francisco zip codes, (c) Fresno-arbitrarily defined central Fresno (city) zip codes, (d) Santa Monica-"coastal" Santa Monica area zip codes restricted to the more affluent neighborhoods, and (el Los Angeles-zip codes from innercity low-SES areas that surrounded the hospital. Approximately 10 ml of cord blood were collected in a blue-topped, lead-free, heparinized Vacutainer (B-D,
Downloaded by [North Carolina State University] at 00:03 06 March 2015
Methods This study was designed to provide a profile of umbilical cord blood lead levels that included the extremes of environmental lead exposures. The major sources of concern were food, water, and air. We assumed that there would be minimal regional variation among California study locations with respect to lead content of food. Even though lead levels in potable supplies can vary greatly in California, we were unable to evaluate this environmental source. Data on ambient air lead levels, however, are collected routinely. Moreover, several authors have shown that air lead levels directly relate to blood lead levels."-'4 Therefore, exposure areas were defined on the basis of (a) ambient air concentrations within specific locations, (b) hospitals within locations, and (c) the time of year to obtain blood samples that would result in the highest variation in airborne lead exposures. Historical air data were used to select Los Angeles and Fresno counties as the high-lead exposure areas; San Francisco as the intermediate area; and Ukiah, a rural community approximately 161 km (100 mi) north of San Francisco, as the low-exposure area. Santa Monica, a coastal city west of Los Angeles, was also included in the study because it represented an urban, fairly affluent, low-exposure area. Umbilical cord blood samples were collected during October and November,
Table 1.-Lead Values (ccg/m3)of Air Samples Collected near Study Hospitals (Umbilical Cord Blood Lead Study, 1984) Hospital
Los Month and year
Fresno
September 1984 Monthly mean Highest value
,344 .53
.360
October 1984 Monthly mean Highest value Monthly mean Highest value Monthly mean Highest value November 1984 Monthly mean Highest value Monthly mean Highest value Distance from collection station to hospital (km)
.53
San Francisco
Santa Monica
,433 .77
.298 .56
-
.420* .42* .448t .56t
,254 .37
-
Angeles
Ukiah
,104
.12
.088 .11
.44a* .56S
,240 .32
3.2
.818t 1.26t .783$
.88* 2.0*
1.73 .19
-
5.0
-
.m .11
32.0
15.3t 16.2$ ~
*North Main collection station (sample missing for November). tLynwood collection station. SPico Rivera collection station.
168
Archives of Environmental Health
Downloaded by [North Carolina State University] at 00:03 06 March 2015
presented in Table 2. These levels are based on the readings obtained at the monitoring station nearest each hospital. Our a priori classification of areas was based on historical data for this study period, but the range of lead levels was narrower than expected, i.e., 0.1-0.8 pg/m3 monthly average. The Santa Monica location was not as lead-free as expected; rather, the air lead profile was more characteristic of the intermediate lead exposure areas. Demographic characteristics of the study population are shown in Table 3. A total of 1680 births occurred across all hospitals. The mean maternal age was 26.4 y; mothers in Fresno tended to be slightly younger (24.4 y), whereas those in Santa Monica were older than average (29.8 y). Most of the infants were Hispanic or white. Only the hospital in San Francisco had an appreciable number of black infants (about 31%), and no hospital had more than 8% Asian births. Approximately 40-60% of the women lived outside the core area that surrounded the target hospital (Table 3). Approximately 60% of the blood samples could not be analyzed because of clotting (Table 3). However, regardless of the study area, characteristics (i.e., sex, racelethnicity, mother's age) of the infants who were not analyzed were similar to those of infants whose blood lead was determined. Also, no differences were found in the proportions of birth certificate-based reports of congenital malformations. One difference, however, was that mothers of infants for whom blood samples could be analyzed had fewer complications during pregnancy and delivery. Also, more blood samples obtained from infants who were born during the initial weeks of the study were useable. Blood lead levels did not vary by core area status and, therefore, subsequent analyses are based on the combined areas (Table 4). Blood lead levels were very
Rutherford, N]) from each infant born during the study period. Ethylene oxide was used in the hospitals that required sterilized collection tubes. Samples were collected after the umbilical cord had been severed. Collection tubes, which were refrigerated, were transported to the laboratory no later than 2 wk after a sample was collected. Refrigeration was not maintained during transportation. Samples were frozen in the laboratory until analysis. All samples were analyzed for total lead concentration by the California Department of Health Services, Air and Industrial Hygiene Laboratory (AIHL), using a heated furnace atomic absorption method described previou~ly.'~ Blood samples were diluted (1:SO) with distilled water prior to analysis, and bovine blood samples were used.15 The lowest bovine blood standard contained 7 pg lead/dl. To obtain sample concentrations below this value, the standard curve was extrapolated linearly to 0. Accuracy of the blood lead results was determined through AIHL's successful participation in the two ongoing blood lead proficiency testing programs: (1) the monthly CDC program (as a reference laboratory), and (2) the quarterly program of the New York State Department of Health. Approximately every tenth sample was analyzed in duplicate. The agreement between split samples was determined by calculating an intraclass correlation (ICC),'6 the value of which was 0.46 (on a scale of -1 [no agreement] to + 1 [complete agreement]), which indicated a high degree of concordance.
Results Blood lead levels generally reflect recent exposure, i.e., during the past 30 d." Location-specific ambient air concentrations for the relevant study periods are
Table I.-Ambmt Air Lead Levels (rslrnl) of Air Samples Collected near Study Hospitals (Umbilical Cord Blood Lead Study, 1984
I
Average lead concentration Study hospital/ air station Ukiah* Lakeport Fort Bragg San Franciscot 23rd St. Fresno Olive St. Santa Monica VA Robertson Blvd. Los Angeles North Main
Sept. 1984
Study period Oct. 1984
Nov. 1984
1st.
Annual summary (by quarter) 2nd. 3rd. 4th. 1st. (1985)
.09 .07
.09
.10 .08
.06 .06
.08
.07
.07
.08 .07
.09 .08
.05 .05
.30
.25
.17
.43
.20
.19
.22
.26
.34
.36
.24
.60
.24
.29
.41
.37
.32 .30
.38 .28
.37 .49
.59
.16 .20
.24 .24
.40 .40
.27 .42
.43
.42
-
.72
.37
.41
.56
.a
*There was no lead monitoring station in Ukiah. However, the communites of Lakeport and Fort Bragg are similar to Ukiah. Lakeport is located approximately 32 km (20 mi) inland, and Fort Bragg, a coastal area, is approximately 57 km (35 mi) from Ukiah. tAmbient air monitoring stations were located the following distances from the hospital: 5 km (3 mi), 3.2 km (2 mi), 4 km (2.5 mi), and 2 km (1.25 mi).
May/June1991 [Vd. 46 (NO.3)]
169
Table 3.-Demographic
Characteristics by Hospital (Umbilical Cord Blood Lead Study, 1984) Hospitallarea
Downloaded by [North Carolina State University] at 00:03 06 March 2015
Los Characteristic
Fresno
Total births (n) Sex (%) Male Female Missing Mother's age (3 Child's race (%) White* Hispanic Black Asian Other Missing Core areat ("10) Within core Out of area Births with lead sample n
439
010
Angeles
712
San Francisco
180
Santa Monica
255
Ukiah
142
Total
1 728
27.6
52.6 46.3 1.2 29.8
47.1 50.7 2.1 26.5
51 .O 47.0 2.0 26.4
3.1 91 .o 3.0 2.0 0.4 0.6
39.4 10.6 31.7 7.8 2.2 8.3
60.0 28.2 4.3 5.1 .4 2.0
77.5 15.5 0.0 1.4 4.2 1.4
21.9 61.5 5.7 4.2 1.2 5.6
44.2 55.8
32.2 67.8
63.3 36.7
38.4 61.6
76.1 23.9
43.1 56.9
259.0 59.0
601.O 84.5
94.0 52.2
50.0 19.6
69.0 48.6
1073.0 62.1
172.0 39.1
406.0
52.0 28.9
37.0 14.5
56.0 39.4
723.0 40.1
53.1 42.4 4.6 24.4
48.8 50.0 1.1 26.0
55.6 44.4
5.0 68.5 2.3 6.8 1.4 16.0
0.0
Births with usable lead sample+
n 010
57.0
*Does not include individuals who are Hispanic. tCore area included residences that were closest to hospital where delivery occurred (see text for explanation). *Cord blood sample not clotted or broken.
Table 4.--Mean, Range, and Percentile of Lead Values W d l ) , by Hospital (Umbilical Cord Blood Study, 1984) Hospitallarea San Santa Francisco Monica
Lead values
Fresno
Los Angeles
Mean Range Percentiles 99 90 75 50 25 10
4.7 .5-15
5.1 1-13
4.5 1-11
14.3 8.0 6.0 4.0 3.0 2.0
10.0 8.0 6.0 5.0 4.0 3.0
11.0 8.0 5.0 4.0 3.0 2.3
Ukiah
Total Boston*
4.8 2-1 2
5.2 1-13
4.9 .5-15
6.6 0-37
12.0 8.4 6.0 4.0 3.0 3.0
13.0 8.0 7.0 5.0 4.0 2.0
12.8 8.0 6.0 5.0 3.0 2.0
17.0 10.5 8.5 6.5 4.5 3.5
*Values extracted from Rabinowitz MB and Needleman HL.18
similar in all parts of California (Table 4). The overall mean cord blood lead level among all hospitals was 4.9 pgldl (range = .5-15 pg/dl). A one-way ANOVA showed that the area-specific mean blood lead levels were not different (p = .24). The area-specific distributions for blood lead levels were also very similar. Blood lead levels were also viewed in terms of factors related to pregnancy. Prematurity and complications of pregnancy or delivery were associated with slightly higher blood lead levels, but the differences were relatively small and contained a high degree of variation 170
resulting from the modest number of cases involved when these factors were stratified. The association between prematurity and blood lead level was observed in all four hospitals for which data were available to determine the length of gestation (Table 5). A cord blood lead level that exceeded 5 pg/dl (the median level) yielded a relative risk for prematurity of 2.9 (95% CI: 0.9-9.2) and a population attributable risk of 46.8%. N o association was observed between low birthweight (< 2 500 g) and cord blood lead levels (Table 6). Blood lead levels were not related to ethnicity or gender. Archives of Environmental Health
Table S.--Gestational Time, by lead Levels (rcsldl) (Umbilical Cord lead Study, 1984)
20 18
Hospital/ gestational days
X
n
Cord blood lead SE Range
16 14
pvalue
All hospitals*
2 260*
< 260
303 14
4.7 6.5
f
.135 .5-15 f1.004 2 -14
.007$
165 7
4.6 6.6
f
.187 .5-15 f2.021 2 -14
.37
2 260
2 260
< 260
48 4
4.3 6.3
4 2
35 2
4.6 6.5
55 1
5.3 7.0
0
,301 f .946
1 -11 5 - 9
.08
.403
2 -12 6 - 7
.30
f .500
*+ O .308
1 -13 7
-
f
.-Boston
8
Data not collected
Los Angeles San Francisco
-California
8
Fresno
< 260
12 10
5
0
10
20
15
25
30
40
35
CORD BLOOD LEAD LEVELS (uddl)
Santa Monica
2 260
< 260 Downloaded by [North Carolina State University] at 00:03 06 March 2015
Ukiah
2 260
< 260
f
Fig. 1. Percentage frequency, California and Boston lead levels. Umbilical Cord Lead Study, 1984.
100 -4
~~
*Excluding LosAngies (data not collected). tDays since last menstrual cycle. *p value from t test in which 2 2606 gestation period compared with < 260-d gestation period.
Table 6.-Birthweight, by Lead levels (pg/dt) (Umbilical Cord Lead Study, 1984)
Hospital/ birthweight (g) ~
X
n ~~~
Cord blood lead SE Range
90
Eu
80
-
-
70-
5 I PI
60:
$
50-
California
+Boston
j" ::; 20-
p value
-
I01
18
~
0
All hospitals
22500
